heterosis and combining ability studies in

HETEROSIS AND COMBINING ABILITY STUDIES IN ONION (Allium cepa L.)

Thesis submitted to the University of Agricultural Sciences, Dharwad in partial fulfillment of the requirement for the

Degree of

MASTER OF SCIENCE (AGRICULTURE)

In

HORTICULTURE

By

NINGADALLI MALLIKARJUN

DEPARTMENT OF AGRICULTURAL ECONOMICS COLLEFE OF AGRICULTURE, DHARWAD

UNIVERSITY OF ARGICULTURAL SCIENCES, DHARWAD – 580 005

DECEMBER, 2006

ADVISORY COMMITTEE

DHARWAD

(P. R. DHARMATTI) DECEMBER, 2006 MAJOR ADVISOR

Approved by:

Chairman : ______________________ (P. R. DHARMATTI) Members : 1.______________________

(R. V. PATIL) 2._____________________ (S. GANGAPRASAD)

3._____________________

(K. S. NAIK)

CONTENTS

Chapter No.

Title

I. INTRODUCTION

II. REVIEW OF LITERATURE

III. MATERIAL AND METHODS

IV. EXPERIMENTAL RESULTS

V. DISCUSSION

VI. SUMMARY

VII. REFERENCES

APPENDIX

LIST OF TABLES

Table No.

Title

1. Genotypes used for evaluation and their sources

2. Genotypes used for hybridization and their source and features

3. Distribution of 34 genotypes in to different cluster

4. Per cent contribution of characters towards divergence in 34 genotypes of onion

5. Average intra and intercluster D2 values of Onion genotypes

6. The nearest and farthest cluster from each cluster based on D2 value

7. Clusters mean for 12 characters in onion

8. Analysis of variance (mean sum of square) for 12 characters in onion

9. Per se performances of parents and hybrids and magnitude of heterosis for number of leaves at 60 DAT

10. Per se performances of parents and hybrids and magnitude of heterosis for plant height 60 DAT

11. Per se performances of parents and hybrids and magnitude of heterosis for number of leaves at 90 DAT

12. Per se performances of parents and hybrids and magnitude of heterosis for plant height 90 DAT

13. Per se performances of parents and hybrids and magnitude of heterosis for neck thickness

14. Per se performances of parents and hybrids and magnitude of heterosis for length of bulb

15. Per se performances of parents and hybrids and magnitude of heterosis for width of bulb

16. Per se performances of parents and hybrids and magnitude of heterosis for shape index

17. Per se performances of parents and hybrids and magnitude of heterosis for bulb weight

18. Per se performances of parents and hybrids and magnitude of heterosis for total soluble solids

19. Per se performances of parents and hybrids and magnitude of heterosis for storage loss

20. Per se performances of parents and hybrids and magnitude of heterosis for bulb yield

21. Analysis of variance (mean sum of squires) for combining ability for 12 characters in onion

22. Estimation of GCA effect of parents for 12 characters in onion (L × T)

23. Estimation of SCA effect of parent for 12 characters in onion (L × T)

24. Best combiner gca for important economic characters

25. Per se performance and combining ability effects of top 5 hybrids for higher yield and their corresponding bulb weight

26. Per se performance of top 5 hybrids for higher yield and their corresponding TSS and storage loss

LIST OF FIGURES

Figure No.

Title

1. Per se performances of parents and hybrids for total soluble solids (0Brix)

2. Per se performances of parents and hybrids for storage loss (%)

3. Per se performances of parents and hybrids for bulb yield (g)

LIST OF PLATES

Plate No.

Title

1. Best genotypes (White)

2. Best genotypes (Red)

3. Best genotypes (Red)

4. Superior hybrid and their parents

5. Superior hybrid and their parents

LIST OF APPENDICES

Appendix No.

Title

I. Monthly meteorological data for experiment year 2004-05 of Main Agricultural Research Station, University of Agricultural Sciences, Dharwad

I. INTRODUCTION

Onion (Allium cepa var. cepa L.), 2n = 16 is the most important species of the Allium group belonging to family Alliaceae. It can be regarded as the single important vegetable species in the world after tomatoes.

Onion is known to have many important medicinal and therapeutic effects such as blood sugar lowering, antiplatelet aggregation, fibrinolytic effects. Bulb juice is used as smelling agent an hysterical convulsions and faintness. The nutritive values of onion varies among the varieties and generally 100 g of edible bulb contains moisture (86.8 g), carbohydrates (11.0 g), protein (1.2 g), fibre (0.6 g), minerals (0.4 g), calcium (180 mg), phosphorus (50 mg), vitamin C (11 mg), iron (0.7 mg), nicotinic acid (0.4 mg) and a little of thiamine. Although, onion has low nutritional value (average nutritional value = 2.06), it is one of the most widely used vegetable due to its flavouring and seasoning the food, both at mature and immature bulb stage. Besides, it is being used as salad and pickle. To a lesser extent, it is used by processing industry for dehydration in the form of onion flakes and powder, which are in great demand in the world market.

In the world, India ranks first in total area and second in production after China and third after Netherlands and Spain in export. Indian onions is being exported to Malaysia, Singapore, Gulf Countries, Sri Lanka, Bangladesh, Pakistan and Nepal. At present, in the world, onion occupies an area of 297 million ha with the production of 51.91 million tonnes and average productivity is 17.47 tonnes per ha (Anon., 2005). In our country, it is being grown on an area of 0.52 million ha with a production of 6.5 million tonnes and the productivity is 12.50 tonnes per ha. Most of the onion produced in India comes from Maharashtra, Gujarat, Karnataka, Orissa, Uttara Pradesh and Andhra Pradesh. Karnataka alone occupies an area of 1.24 lakh ha with a production of 6.93 lakh tonnes with an average productivity of 5.60 tonnes per ha (Anon., 2005). The major onion producing districts of Karnataka are Dharwad, Bijapur, Gadag, Chitradurga, Haveri, Davanageri and Bellary.

According to Vavilov (1951) the primary centre of origin lies in Central Asia. The near east and Mediterranean are the secondary centres of origin. It is an ancient crop having been utilized in medicine, rituals and as a food in Egypt and in India since 600 B. C. Reference of onion as a food was also found in Bible and Quran. The genus Allium is very large with more than 500 species, which are perennial and mostly bulbous plants. Out of these, only seven species are in cultivation. However, Allium cepa (onion) and Allium sativum (Garlic) are the two major cultivated species grown all over the world.

Onion is an outstanding diploid biennial vegetable that shows severe inbreeding depression. Crossing among divergent groups shows significant improvement in traits. The discovery the cytoplasmic male sterility in onion (Jones and Clarke, 1943) enabled for commercial hybrid seed production and at present hybrid onions have dominated over the conventional varieties in the western countries owing to improved yield and quality of bulb. There is a growing interest on use of onions in food industries for canning and dehydration. Hence, there is a urgent need to develop cultivars suitable for processing industry.

The onion breeders must develop more sophisticated and efficient approaches in selecting and testing the parents, which will produce superior hybrids or varieties. Genetic diversity plays an important role in plant breeding either to exploit heterosis or to generate productive recombinants. The choice of parents is of paramount importance in breeding programme. Assessment of a large number of genotypes for a genetic diversity is the first step in this direction. In heterosis breeding programme, large number of hybrids produced and evaluated to exploit hybrid vigour, which usually requires more resources and manpower. It is possible to select parents/inbreds based on morphological diversity with good combining ability for economic traits and producing superior hybrids. The analysis of general combining ability (GCA) and specific combining ability (SCA) helps in identifying potential line/inbreeds for the production of superior hybrids for yield and yield attributing characters.

The line × tester analysis (Kempthrone, 1957) is one of the simplest and efficient method of evaluating large number of inbreds for their combining ability and per se performance. Analysis of GCA and SCA also helps to know the type of gene action controlling various characters and in the development of suitable breeding strategies. At present, onion hybrids are not predominantly cultivated in India. There is a need to develop hybrids in onion for obtaining uniform size bulbs with more shelf life and higher yield. In this background, the present study on onion was initiated with the following objectives.

1. To assess the genetic divergence in onion genotypes.

2. To estimate the best heterotic combination for bulb yield and its attributes and

3. Identification of productive F1 combinations.

II. REVIEW OF LITERATURE

Onion is one of the most important vegetables and grown worldwide under outdoor condition. It has become an important commercial crop because of its area, production and consumption. During the past few decades tremendous developments have contributed to the knowledge and understanding of various aspects of crop production and various literature has been generated. The main aim of any breeding programme is the improvement of both qualitative and quantitative characters of the plant. The information on genetic architecture of various quantitative traits, particularly of those that contribute to the bulb yield, disease resistance and quality would be the most useful in planing the breeding programmes and make effective selections. The purpose of this section is to give comprehensive upto date information on the various aspects of genetic divergence, heterosis and combining ability of onion. The review pertaining to present investigation is presented under following headings.

2.1 Genetic diversity

2.2 Heterosis

2.3 Combining ability

2.1 GENETIC DIVERSITY

Genetically diverse parents are expected to give hybrid vigour (Harrigton, 1940) and hence, it necessitates to assess the genetic divergence among the existing varieties and germplasm collection for identification of parents for hybridization.

D2 statistics developed by Mahalanobis (1936) actually provides a measures of

magnitudes of divergence between two groups and individually under comparison. It considers the variation produced by any characters and their consequent effect that it bears on other character. The technique was first used by Mahalanobis is an anthropometric survey of the united province in India. Its application to the field of botany was started with the work of Nair and Mukharji (1960) who applied this method in classifying the natural population and plantation teak. Latter, its application was extended to field crops. Murthy and Pavate (1962) observed that D

2 analysis can be extended to the situations where overlapping species need

to be discriminated and also to the fact that discrimination at subspecies level is needed. They used it for testing the genetic divergence among 13 flue cured tobacco varieties, which could be classified into four clusters considering four characters together. Following this study the technique has been applied in several vegetable crops.

Patil (1983) applied Mahalanobis D2 statistics to data for 20 bulb character in 37

cultivars of onion collected from different parts of India. Based on this, they grouped cultivars into 18 clusters. The largest cluster had five varieties and there were 10 solitary clusters. The clustering pattern was not directly associated with the geographical distribution.

Lokhande et al. (1987) based on D2 values obtained from analysis of agronomic

traits, 33 divergent varieties of garlic were grouped into 14 cluster. The clustering patterns were not correlated with geographical diversity.

Patil et al. (1987) grouped 45 varieties of onion into 12 clusters on the basis of bulb, biochemical and storage character.

Hwang (1993) carried out multivariate analysis to study 10 quantitative characters in 64 local (Korea) and 32 exotic cultivars of garlic (Allium sativum). Based on bolting habit of varieties the cultivars the groups were corresponded with the geographical distribution.

Leecultai and Chungdonghee (1996) applied Euclidan D2 statistics to measure the

distances among 60 onion varieties and were grouped into four groups. These groups were

not associated with geographical origin and yield and bulb weight contributed largely to the D2

statistics.

Patil (1997) D2 analysis indicated enormous diversity among the collections. Twenty

five onion genotypes were assigned to seven clusters. The clustering pattern obtained in the present investigation revealed that geographic diversity did not seen to have a direct association with genetic diversity.

Mohanty et al. (2001) reported the genetic diversity among 12 garlic cultivars for yield and yield components. Based on genetic affinity, the cultivars were grouped into five clusters. The clustering pattern indicated the lack of significant correlation between geographic origin and genetic divergence.

Tanikawa et al. (2002) examined 22 onion (A. cepa) cultivars by using randomly amplified polymorphic DNA (RAPD) markers. Cluster analysis reveals six clusters. Comparison between cluster and various characteristics did not demonstrated any relationship.

Mota et al. (2004) have conducted experiment to determine the genetic diversity of 11 garlic cultivars, the cultivars were divided into noble (requires vernelization for bulb formation) and half noble (does not require vernelization for bulb formation). These groups showed 57.1 and 54.2 per cent similarity, respectively.

Kambiz (2006) observed cluster analysis on morphological and phytochemical characters arranged the 24 garlic ecotypes in five main groups, but did not indicate significant relationship between genetic diversity and geographical origins.

Panthee et al. (2006) studied the diversity in garlic genotypes collected from different places of Nepal. Data were analysed by using principal component and cluster analysis procedure to reveal three major clusters. Four principal components were identified explaining more than 85 per cent of total variation. Major contributing characters were bulb weight, diameter, yield and number of cloves per bulb.

2.2 HETEROSIS

Heterosis refers to superiority of F1 hybrids in general vigour, yield and adoption. The magnitude of heterosis depends on accumulation of favourable dominant alleles in the F1 population. If parental population differ from each other for more favourable dominant alleles the magnitude of heterosis will also be proportionately higher. This relationship is evidenced in the basic formula for heterosis (Falconer, 1981).

Heterosis in F1 = Σdy2

Where,

‘d’ is magnitude of dominance and ‘y’ is difference between the parental populations for allelic frequencies at the locus.

Onion was the first vegetable crop to exploit heterosis commercially (Jones and Clarke, 1943), when they found out cytoplasmic genetic male sterility “Italian red” since, the classic paper by Jones and Davis (1944) demonstrating inbreeding depression and recovery of vigour of hybrids after crossing among inbred lines, there has been constant efforts to develop hybrid onion cultivated in the public and private sectors. Heterosis has been exploited in onion breeding for the past four decades except in India where very little research has been done. An attempt has been made to present information available on heterosis for individual character.

2.2.1 Plant height

Vadivel et al. (1982) evaluated 30 hybrids and 13 parents of Allium cepa L. aggregatum and the significant positive heterosis over mid parent was observed in fourteen hybrids and over better parent in 12 hybrids, whereas only two hybrids having positive significant heterosis over best parent. Aghora (1985) observed significant positive heterosis for plant height in four crosses over better parent.

Madalageri (1983) studied heterosis in onion a 9 × 9 complete diallel crosses and observed significant heterosis over mid parent in F1s. Only one hybrid was distinct with a favourable significant heterotic value on both mid and better parent.

Netrapal et al. (1988) reported significant heterosis for plant height over the better

and best parent in 8 × 8 diallel cross.

Veeregowda (1988) observed significant heterosis for four and three over mid parent, respectively. Among all crosses, only one cross over mid, better and best parent, respectively.

Divakar (2001) observed the positive heterosis for 41 and 40 crosses over mid and

better parent, respectively in 10 × 10 half diallel cross of onion.

Borgaonkar et al. (2005) studied heterosis in okra and found positive heterosis for this character over the standard check.

2.2.2 Number of leaves per plant

Madalageri (1983) recorded significant positive heterosis over mid parent in six

crosses and two crosses have exceeded their better parental value in a 9 × 9 diallel analysis.

Aghora (1985) reported significant positive heterosis for number of leaves over mid parent in five crosses, whereas only one F1 recorded significant positive heterosis over the better parent. Similar results also expressed the positive heterosis for the total bulb yield.

Netrapal et al. (1988) noticed heterosis only in seven crosses out of 28 cross combination over better parent and the study concluded that the at least one parent having more leaves contributed to increase in leaves in F1s of onion.

Veeregowda (1988) recorded significant positive heterosis only for three crosses and remaining all crosses were having negative heterosis out of 55 crosses of onion.

Sayed et al. (1999) evaluated the parents and F1 hybrids from a half diallel cross of onion for earlyness, bulb ratio (neck diameter/bulb diameter), number of leaves per plant and bulb height. They observed the highly significant additive and non-additive gene effects which were involved in the inheritance of all the characters.

Divakar (2001) has noticed in his study that positive heterosis in 28 crosses out of 45 F1s were for leaf numbers over mid parent, whereas 18 and 11 crosses recorded positive heterosis over better parent and standard check, respectively.

2.2.3 Bulb weight

Bulb weight is an important character directly related to bulb yield. Joshi and Tandon (1976) noted heterosis to the extent of 72 per cent over the mid parent value and upto 37 per cent over the better parent in onion hybrids.

Hosfield et al. (1977) have observed a significant heterosis for bulb weight based on the mid parent. However, the heterosis over better parent was significant but comparatively low.

Vadivel et al. (1982) have evaluated 30 hybrids and their parents. The results showed that both positive and negative heterosis for bulb weight. Whereas, one cross recorded significant heterosis for yield and most yield components.

Aghora (1985) observed that the seven crosses of onion were having significant heterosis over better parent and 13 crosses over mid parent.

Veeregowda (1988) also observed significant positive heterosis for onion bulb weight in seven crosses out of 55 crosses over better parent.

Doruchowsk (1986) crossed eight male sterile line with 8 pollen parents and heterosis was observed only for bulb weight in onion.

Divakar (2001) in his study involving 10 × 10 half diallel observed that out of 45 crosses, 8 crosses were found to be significant positive heterosis over mid parent, 30 crosses over better parent and 15 crosses found significant over standard check for bulb weight.

2.2.4 Neck thickness

Veeregowda (1988) revealed that out of 55 crosses of onion, 22, 10 and 2 crosses were recorded negative heterosis over mid, better and best parent, respectively.

Divakar (2001) observed that 15 crosses had negative heterosis for neck thickness over mid parent, six crosses found negative heterosis over better parent and though the 35 crosses had negative heterosis over check for neck thickness but only one has found significant towards negative.

2.2.5 Bulb dimensions and shape index

There is no sufficient literature to discuss the bulb length, bulb diameter and bulb shape individually, hence, these three traits are presented together.

Madalageri (1983) reported three crosses with favourable effects for bulb length and

four crosses for bulb diameter over the best parent in a 8 × 8 diallel crosses. The studies also revealed significant mid parental heterosis for globulor bulbs with shape index around 1.00, but this was observed only in three crosses out of 72 hybrids. Studies on heterosis by Vadivel et al. (1982) also revealed the presence of heterosis over mid parent for shape index of onion bulb.

Aghora (1985) observed majority of crosses with negative significance and there were only 12 crosses with positively significant heterosis for the polar diameter.

Dorucjowsk (1986) observed heterosis for bulb diameter over better parent. Similarly,

Netrapal et al. (1988) in a 8 × 8 diallel cross noticed heterosis for bulb diameter (horizontal and vertical) over better parent and best parent.

Veeregowda (1988) recorded significant positive heterosis for polar diameter in two crosses for equatorial diameter an in nine crosses.

Divakar (2001) in an experiment with 10 × 10 half diallel among 45 crosses he observed seven crosses which shown significant positive heterosis for shape index over mid parent, five crosses over better parent and two crosses over standard check.

Borgaonkar et al. (2005) studied heterosis 28 F1 from eight parents crossed in 8 × 8 diallel manner and they found that the higher degree of heterobeltiosis for fruit yield. The

cross No. 129 × JNDO-5 exhibited the highest heterobeltiosis (52.22%).

2.2.6 Total soluble solids

Soluble solid is an important quality attribute of onion. The genotypes with high total soluble solids store better than others. McCollum (1968) and Padda et al. (1973) obtained a high heterosis for total soluble solids in onions.

Madalageri (1983) reported non-significant heterosis in a large number of crosses over mid parent. Only two crosses with positive significant heterosis and nine crosses with negative significance were found. None of the crosses had the significance level in the favourable direction over better parent.

Netrapal et al. (1988) observed only one hybrid with heterosis over both the better and best parent among 29 crosses.

Aghora (1985) reported positive heterosis over mid parent in four crosses. Heterosis

over better parent was not observed in any of the crosses for total soluble solids in a line × tester analysis of onions.

Veeregowda (1988) reported positive heterosis over mid parent in 16 crosses, over better parent in 4 crosses for total soluble solids in bulbs of onion.

Divakar (2001) noticed that among 45 crosses, 21 crosses exhibited significant positive heterosis for total soluble solid over mid parent, 12 crosses over better parent and ten crosses exhibited over standard check in onion hybrids.

Arun et al. (2005) studied heterosis in tomato for the total soluble solid. Their findings

revealed that crosses CLN-5915-206D4-2-2-0 × CLN-13511E and CLN-1462A x FT-5 recorded highest heterosis over check (Noween).

2.2.7 Storage status

The storage losses in onion could be accounted for three reasons.

1. The loss in weight of the bulb

2. The spoilage due to sprouting and

3. The loss due to rotting of whole bulbs

Hosfield et al. (1977b) reported significant negative heterosis over mid parent for storage loss in weight whereas in none of the crosses better parental heterosis was noticed.

Madalageri (1983) reported that in none of the hybrids significant level of negative heterosis was observed but few crosses had fairly high heterotic values.

Netrapal et al. (1988) observed significant negative heterosis over better parent and best parent. Further, they noticed that the best performing parents played a greater role in its hybrids for better quality in storage.

Suciv et al. (1988) associated the effect of heterosis on yield in onion, the study indicated that high yielding hybrids showed good vegetative growth, uniform bulb size and good storage quality.

Divakar (2001) observed that two crosses of onion had negatively significant heterosis over mid parent and better parent for storage loss due to rotting.

2.3 COMBINING ABILITY

The genetic values of parents are expressed in terms of combining abilities. Spargue and Tatum (1942) defined general combining ability (gca) as the average performance of the progeny of an individual when it is mated to a number of other individuals in a population. Specific combining ability (sca) which is a term that refers to the average performance of the progeny of a cross between two specific parents that are different from what would be expected on the basis of their general combining ability alone. Estimation of combining abilities provide quite relevant and vital information that is of direct utility to plant breeding programmes. Hybridization is one of the means of obtaining increased yield and choice of parents in such a programme is difficult owing to the differential behaviour of the inbreds in relation to combining ability. A measures of general and specific combining ability of the parents in terms of additive and non-additive portions of genetic variance would be of immense value in the choice of parents and of effective crosses for plant improvement.

Generally, general combining ability is associated with genes, which are additive in their effects, while specific combining ability is attributed to deviation from the additive scheme caused by dominance and epistasis. General combining ability involves both additive

effects as well as additive × additive, additive × dominance and dominance × dominance type of interactions (Griffing, 1956).

The extent of hybrid vigour is dependent on the combining ability of the lines used as parents. If a line with an outstanding combining ability could be found, it might be used as a

common parent for obtaining superior combinations. Generally, ‘top crossing’, ‘line × tester’ analysis and ‘diallel crossing technique’ are employed for this purpose. Following review presents the available genetic information on combining ability for different characters in onion.

Srivastava et al. (2005) studied combining ability in 45 crosses along with 18 chilli (Capsicum annuum L.) for eight characters. The ratio of 5/8 suggested that non-additive gene has greater role in the inheritance of all the characters except for fruit length and ripe fruit yield per plant, where additive gene action played an important role.

2.3.1 Plant height

Madalageri (1983) in his study observed the significant variance for gca and sca in onion and magnitude of gca was higher, indicating the predominant additive effects.

Divakar (2001) observed that the variance of GCA and SCA were significant and magnitude of GCA was higher indicating the predominant additive genetic variances. The gca effects were positive and significant for three parents and sca effects were positively significant for 22 crosses.

Sundari et al. (2003) noticed that analysis of variance for combining ability indicated significant differences among parents. The estimated components of variance due to sca were greater than those due to gca for all characters. The estimates of effects of general combining ability among the lines L-2 proved to be a good combiner for the plant height. The

cross L-3 × T-12 has shown good sca for plant height.

Srivastava et al. (2005) studied combining ability in 45 crosses along with 18 parents of chilli (Capsicum annuum L.) for eight characters. The ratio of 5/8 suggested that non-additive gene has greater role in the inheritance of plant height.

2.3.2 Number of leaves per plant

Sayed et al. (1999) observed the magnitude of mean square of the specific combining ability appeared to be small in comparison with that of the general combining ability indicating that additive genetic variance is more important in determining these characters. A pronounced hybrid vigour was detected for most of the traits studied, indicating that non-

additive gene effects which were also have a significant role in the inheritance of these characters.

Madalageri (1983) evaluated forty five hybrids and parents for their sca and gca effect in which, he found the significance of gca and sca variance revealed additive and non-additive effect playing a role in the inheritance of this trait.

Divakar (2001) studied combining ability effect. For number of leaves per plant and found that magnitude of GCA variance was higher than SCA variance for the trait indicating the major influence of additive genetic variance. Significant and positive sca effect was found in 29 crosses.

Sundari et al. (2003) observed the components of variance due to sca were greater than those due to gca for number of leaves per plant was found to be the good general

combiner and the cross L-3 × T-14 is found to be good specific combiner for this character.

2.3.3 Bulb weight

Hostfield et al. (1976) found that both general combining ability and specific combining ability were highly significant at all the locations in diallel crosses of onion.

Madalageri (1983) found that the variances of gca, sca and reciprocals were significant. The gca variance were much higher than sca suggesting high portion of additive effects in onion hybrids.

Divakar (2001) noticed the variance of GCA and SCA were significant. The GCA variances were much higher than SCA suggesting high proportion of additive genetic variance parent 10 was found to be a good general combiner. Three crosses had significant and

positive sca effect. High sca effect was found in cross 4 × 8 involving one parent having positive and another parent having negative gca effect.

Sundari et al. (2003) noticed that variance due to sca effect were greater than those due to sca effect. Among the tester T-6 was found to be good general combiner and cross L-2

× T-8 found good specific combiner for bulb weight.


Although, gca and sca variance were significant (Madalageri), the greater magnitude

of sca might be due to epistatic effect of additive × additive type.

Divakar (2001) observed the variance due to gca was found to be significant and sca variance was non-significant indicating the importance of additive genetic variance in the inheritance of the trait. The significant negative gca effects were found in two parents and none of the crosses had negative and significant sca effect.

Sundari et al. (2003) have noticed the estimated components of variance due to sca were greater than those due to gca for all the characters, among the tester T-19 was found good general combiner for this trial.

2.3.5 Bulb dimensions and shape index

Madalageri (1983) found that the variances of gca and sca for popular and equatorial diameter were significant, suggesting the importance of additive and non-additive effects in the inheritance of these characters. Even the variance for gca and sca were low but it was significant indicating both additive and non-additive gene controlling the inheritance of shape index.

Divakar (2001) noticed that the variance for GCA and SCA were low but significant, indicating both additive and non-additive genes controlling the inheritance of shape index.

Generally, the parents with tapedo (very high shape index) and flat (very low index) shape have exhibited. Significantly positive and negative gca effects, respectively.

Sundari et al. (2003) have noticed the estimated components of variance due to sca were greater than those due to gca for shape index.

Arun et al. (2005) in his study of heterosis for qualitative characters observed that the cross CLN1462A x FT-5 has recorded highest significant value over the check (Noween).


Singh and Nandapuri (1975) analysed the total soluble solids in tomato and indicated that the estimates of sca and gca were of the same order suggesting the importance of non-additive and additive gene effects.

Madalageri (1983) observed that the gca, sca and reciprocal variances were significant. The gca/sca value was suggestive of higher magnitude of additive effects than dominance effects.

Hays and Randle (1996) have conducted the factorial mating design using three male sterile F1 lines in test crosses with a sample of open pollinated onion population to estimate combining ability and heterosis the results were significant for heterosis for soluble solids.

Divakar (2001) found that the variance for combining ability revealed significant variance due to SCA and GCA indicating importance of both additive and non-additive genetic variance in the inheritance of this trait.

Sundari et al. (2003) have reported the combining ability variance components receals that relative magnitude on non-additive component for all the characters except vertical bulb diameter was greater than additive component indicating predominance of non-additive gene action governing these characters.

2.3.7 Storage losses

The studies on combining ability (Hosfield et al., 1976 and 1977a, b) analysis indicated that GCA and SCA variances were highly significant at all locations in all experiments.

In general, GCA were in larger magnitude than SCA (Hosfield et al., 1976 and 1977a, b). According to them, although, most of the differences noted among crosses for storage losses in weight were due to genes with primarily additive effects, the small but significant non-additive variances present can not be overlooked, for the non-additive variances for storage losses in weight is ample for use in specific hybrid combinations.

Divakar (2001) reported that the combining ability estimates revealed significant estimates for both GCA and SCA variances. Indicating the importance of both additive and non-additive genetic variances of the inheritance of this character. However, estimates of variance due to GCA were higher than SCA indicating predominance of additive variances.

Sundari et al. (2003) have reported that the estimated sca were greater than those due to gca. The combining ability variance components reveal that relative magnitude on non-additive component for storage loss.

III. MATERIAL AND METHODS

The study on heterosis and combining ability in onion was undertaken during the year 2004-06 at the Olericulture Unit, Department of Horticulture, University of Agricultural Sciences, Dharwad. The details of material and methods used for the divergence studies, development of F1 hybrids and their evaluation, experimental designs adopted and statistical procedures followed are revealed in this chapter.

3.1 EXPERIMENTAL SITE AND LOCATION

The experiment was conducted in the red clay soils (Inceptisols) of the Olericulture Unit, Department of Horticulture, University of Agricultural Sciences, Dharwad.

Geographically, Dharwad is located at 15026' North latitude, 76

007' east longitude at

an altitude of 678 m above the mean sea level. Dharwad is situated in the agro-climatic zone-VIII.

The mean monthly maximum and minimum temperature during hot months (March and April) and cold months (December and January) ranges from 36.30

0C to 18.90

0C and

29.900C to 12.90

0C, respectively. The annual rainfall of 1006.30 mm was received during the

month of May to October. The details of the weather data are presented in Appendix I.

EXPERIMENT-I

3.3 EVALUATION OF GENOTYPES AND SELECTION OF PARENTS

Totally, 34 genotypes of both red and white coloured were collected from various sources like National Research Centre on Onion and Garlic (NRCOG) at Rajagurunagar (Pune, Maharashtra), Arka series from IIHR, Hesarghatta, Bangalore and local varieties. The list and sources of the 34 genotypes are presented in Table 1. Out of 34 genotypes, only superior genotypes of both red and white types were selected for further study, whereas for present research work only red types were choosen (Plate 1, 2 and 3).

3.3.1 Nursery raising

Raised nursery beds of 3.0 × 1.2 m size with 15 cm in height were prepared and sterilized. Each bed was applied with 500 g of 15:15:15 NPK complex fertilizer and was mixed thoroughly. The seeds of 34 genotypes were sown in rows spaced at 10 cm apart on 18

th

November, 2004. The beds were watered regularly. The plant protection measures were taken to protect the seedlings from soil borne diseases. The seedlings were ready for transplanting in 40 days and were transplanted on 29

th December, 2004 in the main field with

34 entries in randomized block design with three replications. The space between the plants was 10 cm and between the row was 30 cm. The plants were fertilized with 120 kg of N, 50 kg of P2O5 and 60 kg of K2O per ha and were grown under irrigation.

Details of the experiment

Number of genotypes : 34

Design : Randomized Block Design (RBD)

Replications : 3

Spacing : 30 × 10 cm

Fertilizer dose : 120:50:120 kg NPK

Table 1. Genotypes used for evaluation and their sources

Sl. No. Genotype Source

1. Arka Pitamber IIHR, Hesarghatta

2. Telagi Red Collections from Bijapur

3. PBR-5 Germplasm unit

4. RHRO White Olericulture section, UAS, Dharwad

5. Local White UAS, Dharwad

6. PRO-6 NRCOG Rajagurunagar

7. NRCOG-W-217 ------ " ------

8. NRCOG-W-130 ------ " ------

9. NRCOG-W-149 ------ " ------

10. NRCOG-W-395 ------ " ------

11. NRCOG-155 ------ " ------

12. NRCOG-659 ------ " ------

13. NRCOG-W-102 ------ " ------

14. Phule Safed ------ " ------

15. Pusa White round IARI

16. NRCOG-W-416 NRCOG Rajagurunagar

17. NRCOG-W-272 ------ " ------

18. NRCOG-W-208 ------ " ------

19. NRCOG-536 ------ " ------

20. NRCOG-596 ------ " ------

21. NRCOG-642 ------ " ------

22. NRCOG-934 ------ " ------

23. NRCOG-937 ------ " ------

24. NRCOG-205 ------ " ------

25. NRCOG-608 ------ " ------

26. NRCOG-327 ------ " ------

27. NRCOG-588 ------ " ------

28. Rose onion ------ " ------

29. N-53 UAS, Dharwad

30. Royal selection Seminis

31. Arka Bindu IIHR, Hesarghatta

32. Arka Kalyan ------ " ------

33. Arka Pragati ------ " ------

34. Bellary Red UAS, Dharwad

Plate 1: Best genotypes (White)

Plate 2: Best genotypes (Red)

Plate 3: Best genotypes (Red)

The experiment was carried out during 2004-06 and the recommended package of practices were followed.

3.4 OBSERVATIONS RECORDED

The following observations were recorded and used for genetic diversity study and evaluation of hybrids. The five randomly selected plants from each entry and the average from these five plants was worked out for the purpose of statistical computation. The details of observations recorded in each experiment and techniques adopted for recording the observations were as follows.

The observations for plant height, number of functional leaves and neck thickness were collected on 60 days after transplanting.

The data on remaining characters were collected after the harvest from the total bulbs harvested. Five competitive bulbs were selected randomly for recording the bulb weight, bulb dimension, total soluble solids. Another lot of 10 bulbs were kept for storage studies. These bulbs were initially weighed and bagged in a cloth bag. They were kept for 30 days in a room. After 30 days, the observations on loss in weight was recorded.

3.4.1 Leaf number per plant

The number of fully grown, green functional leaves were recorded from five randomly selected plants at 60 and 90 days after transplanting and average number of leaves per plant was calculated.

3.4.2 Plant height (cm)

The maximum plant height was measured from ground level to tip of longest leaf (when held vertically) at 60 and 90 days after transplanting. The mean of the five plants in a treatment was worked out.

3.4.3 Neck thickness (cm)

The neck thickness was measured with the help of Vernier calipers and the measurement was made in centimeters below the joint of leaf lamina, the observations recorded on five plants were averaged to get a mean value.

3.4.4 Bulb weight (g)

Five competitive bulbs were weighed individually on an electronic balance and then mean value was worked out.

3.4.5 Bulb length (cm)

The length between two polar ends was recorded with the help of a Vernier caliper. The mean length of bulb was calculated.

3.4.6 Bulb diameter (cm)

The bulb diameter at the middle of the bulb across the polar length was measured with the help of a Vernier caliper and the mean was calculated.

3.4.7 Shape index

The bulb shape index was determined by dividing the bulb length with bulb diameter. The bulb with 1.00 index was considered as globular, those with less than 1.00 as flat and those with more than 1.00 as tarpedo types.

3.4.8 Total soluble solids (0B)

Total soluble solids was recorded with the help of Refractometer and average was computed.

3.4.9 Colour of the bulbs

Colour of the bulbs were assigned based on the visual observation.

3.4.10 Yield per ha (t/ha)

Total yield obtained from the plot was used to calculate the yield of bulbs in tonnes per ha.

3.4.11 Storage loss in weight (%)

The loss in weight was obtained by taking difference between the weight of the bulbs prior to storage and weight after storage. The per cent reduction in the initial weight was computed.

3.5 CROSSING PROGRAMME

Among 34 genotypes, best 12 genotypes were selected based on divergence study (Table 2).

The bulbs of the selected parents were planted in a crossing block on 30th August,

2005 and started flowering in October and ended in November.

3.5.1 Emasculation and pollination

The individual flower umbels were covered with butter paper bags of appropriate size with fine holes prior to opening of buds. About 15 to 20 fully developed flower buds were bagged. Next day morning between 7.00 am to 9.00 am the anthers were removed before their dehiscence. Those flowers which did not open by then were also removed to avoid selfing. The emasculated flowers were bagged again and labelled indicating the parent and the date of emasculation. After exactly, four days when the style had fully grown to a length of about 4 mm and stigma with shinning sticky surface (stigma was receptive) flowers were pollinated with the pollens of desired and bagging was done again to prevent the visit of bees and the flies. Umbels were harvested after the seeds become black colour.

3.6 EXPERIMENT-II : EVALUATION OF F1 HYBRIDS

The experiment was carried out by using RBD design with three replications. The seeds of all the 36 hybrids were sown in a seed bed on 16

th March 2006. Since some of the

hybrids did not germinate only 15 hybrids were taken for further study and were transplanted in a main field after one month of sowing.

3.7 CULTURAL PRACTICES

Recommended package of practices were followed for raising onion crop.

Table 2. Genotypes used for hybridization and their source and features

Sl. No.

Genotypes Source Features

Lines

1. Bellary red UAS, Dharwad Light red, medium size, 30-40 g weight

2. PRO-6 4-5 cm in size, red colour, 30-35 g

3. Telagi red UAS, Dharwad Light red, medium sized, 46 kg/bulb

4. NRCOG-937 NRCOG-Rajagurnagar

Medium sized bulb, average yield 30 t/ha, red colour

5. NRCOG-155 ------"------ Dark red, medium size, 20 t/ha

6. NRCOG-659 ------"------ Average size, light pink, 22 t/ha

Testers

NRCOG-588 ------"------ Medium sized bulbs, average yield 30 t/ha, red in colour

NRCOG-205 ------"------ Light red, medium to large bulbs, 20 t/ha

NRCOG-327 ------"------ Red colour, medium sized, flat to stobular, red in colour

NRCOG-642 ------"------ 50-70 g, 20 t/ha, red in colour

Arka Pragati IIHR, Hesarghatta Medium sized bulb, average yield 20 t/ha, red in colour

Arka Kalyan IIHR, Hesarghatta Bulbs 4-6 cm across, 33 t/ha, red in colour

3.8 STATISTICAL ANALYSIS

3.8.1 Mahalanobis D2 anaflysis

Mahalanobis (1936) D2 statistics was used for assessing the genetic divergence

between populations. The generalized distance between any two population is given by formula.

D2 = ΣΣ λij σai σaj

Where,

D2 : Square of generalized distance

λij : Reciprocal of the common dispersal matrix

σai : (µi2 - µi2)

σaj : (µi1 - µi1)

µ : General mean

Since the formula for computation requires inversion of higher order determinant, transformation of the original correlated unstandardized character mean (Xs) to standardized uncorrelated variable (Ys) was done to simplify the computational procedure. The D

2 values

were obtained as the corresponding uncorrelated (Ys) values of any two uncorrelated genotypes (Rao, 1952).

3.8.1.2 Clustering of D2 values

All the (n-1)/2 D2 values were clustered using Tocher’s methods as described by Rao

(1952).

3.8.1.2.1 Intracluster distance

The intracluster distance were calculated by formula given by Singh and Choudhary (1977).

Square of the intra cluster distance =

ΣD2i is the sum of distance between all possible combinations of the entries included

in the cluster.

n - number of possible combinations

3.8.1.2.2 Inter cluster distance

The inter cluster distance were calculated by the formula described by Singh and Choudhary (1977).

Square of intra cluster distance =

Where,

ΣD2i is the sum of distance between all possible combinations (ninj) of the entries

included in the cluster study.

ΣD2i

n

ΣD2i

ninj

ni : Number of entries in cluster i

nj : Number of entries in cluster j

3.8.2 Line × Tester analysis

3.8.2.1 Analysis of variance (ANOVA)

Mean values of the five random plants selected from each parent (genotypes) for yield and yield attributing parents. The analysis of variance was carried out and format of ANOVA is given below.

Sources of variance d.f. MSS

Replications (r-1) -

Lines (1-1) M1

Tester (t-1) M2

Line × Tester (lt-1) -

Error (l-1) (t-1) -

Total (ltr-1)

Where,

r = Number of replications

l = Number of lines

t = Number of tester

3.8.2.2 Estimation of heterosis

The magnitude of heterosis was estimated in relation to mid parental and better parental values. They were thus calculated as percentage increase or decrease of F1s over the mid parent value (MP) and better parental value (BP).

a. Heterosis over mid parent

MP = × 100

Where,

MP =

b. Heterosis over better parent (BP)

BP = × 100

F1 – MP

MP

F1 – BP

BP

P1 + P2

2

Where,

BP = Value of better parent

F1 = Value of hybrid

The significance of F1 heterosis value were tested by comparing them with CD values obtained separately for MP and BP employing the formula given below.

CD for MP = 3/2 × × ‘t’ value

Where,

eMSS = Error mean sum of squares

r = Number of replications

t = Table ‘t’ value at error degree of freedom of freedom

3.8.2.3 Combining ability analysis

The variation among the hybrids was further partitioned in to genetic components attributes to general combining ability (gca) and specific combining ability (sca) following the method suggested by Kempthrone (1957).

Estimation of combining ability effects

The combining ability effects were estimated as follows.

X . . .

µ = ltr

^ Xi . . X . . . gi = - tr ltr

^ X.j. X . . . gj = - lr ltr

^ Xij. Xi . . X.j. X . . . Sij = - - + r tr lr ltr

Where,

X. . .: Total of all hybrids

Xi. . : Total of ith line over all testers and replications

X.j. : Total of jth tester over all lines and replications

Xij. : Total of ijth cross over all the replications

eMSS

r √

Standard errors of the effects

The variance of the estimates were calculated following formula given below.

The standard error of the estimates are the square of their variances.

M4 ½ i. S.E. (gca for line) =

rt M4 ½ ii. S.E. (gca for testers ) =

rl

M4 ½ iii. S.E. (sca effect) =

r

The critical differences were calculated by multiplying the standard error with table ‘t’ value at 5 and 1 per cent levels of probabilities for error degrees of freedom.

The analysis was based on the following mathematical model.

YijK = µ + gi + gj + Sij + rK + eijK

Where,

YijK : Any characters measured of the cross (i × j) in the kth replication

µ : Population mean

gi : gca effect of ith parent

gj : gca effect of jth parent

Sij : sca effect of (i × j)th

cross

rk : Effect due to kth replication

eijK : Random error effect associated with (ijk)th observation in k

th replication

i : Number of female parent

j : Number of male parent

k : Number of replications

ANOVA for combining ability

Source of variation

d.f. MSS Expectations

Replication (r-1) - -

Hybrids (lt-1) - -

Lines (l-1) M1 σ²e + r [Cov(FS) - 2Cov(HS) + rt [Cov(HS)]

Testers (t-1) M2 σ²e + r [Cov(FS) - 2Cov(HS) + rl [Cov(HS)]

Line × tester (l-1) (t-1) M3 σ²e + r [Cov(FS) - 2Cov(HS)]

Error (r-1) (lt-1) M4 σ²e

IV. EXPERIMENTAL RESULTS

The results of experiment conducted during 2004-06 at Olericulture Unit, Department of Horticulture, University of Agricultural Sciences, Dharwad on “Heterosis and combining ability studies in onion” is presented in this chapter under the following captions.

EXPERIMENT I:

4.1 GENETIC DIVERSITY

Genetic divergence along with variability are of greatest interest to plant breeders as they play a vital role in forming a successful breeding programme. Analysis of genetic divergence has been used to quantify the genetic distance between the genotypes and to identify the promising types to initiate crossing programme.

4.1.1 Group constellations

A method suggested by Tocher (Rao, 1952) was used to group the genotypes into different clusters based on the D

2 value. Thirty four genotypes were grouped into nine

clusters. Among nine clusters, cluster II was the biggest cluster with 10 genotypes followed by cluster I with six genotypes. Whereas, the clusters IV, V, VI, VII, VIII having three genotypes each, the cluster III has two genotypes and cluster IX has solitary genotype (Table 3).

4.1.2 Mahalanobis generalized distance (D2) analysis

D2 analysis was carried out using all the 12 characters and generalized distance (D

2)

was calculated for each pair genotypes.

4.1.3 Per cent contribution of characters towards divergence

The per cent contribution of each character towards divergence is presented in Table 4. It was observed that bulb yield was the single highest contributor (76.83%) towards divergence followed by bulb weight (12.30%), number of leaves at 60 days (4.46%), number of leaves at 30 days after transplanting (0.53%) and neck thickness (0.18%).

The remaining characters viz., height of plant, length of the bulb, width of the bulb, shape index and total soluble solids did not contribute significantly to the total divergence.

4.1.4 Intra and interrelationship between clusters

The average D2 values of intra and inter cluster distances are given in Table 5.

Maximum differences among the genotypes within the intra cluster was shown by cluster I (4.56) followed by cluster II (3.81), cluster VIII (3.76), cluster VI (3.16), cluster, cluster VIII (2.53), cluster V (2.22), cluster IV (1.91) cluster III (1.00) and cluster IX showed zero.

Diversity among the clusters varied from 6.00 to 137.63 inter cluster distances. Cluster III and V has shown maximum inter cluster distance (137.63) followed by II and V (134.80). The lowest inter cluster distance was noticed between cluster IV and IX (6.31) followed by cluster II and III (6.00).

As indicated by the inter cluster D2 values, cluster VIII is nearest to the cluster I

(22.33), while cluster III is farthest from cluster I (103.12) (Table 6).

Cluster III is nearest to the cluster II (6.31) and the cluster V (137.49) is farthest and for cluster III. Cluster II (6.31) is nearest and cluster V is farthest (137.63).

Table 3. Distribution of 34 genotypes in to different cluster

Cluster Number of genotypes

Name of genotypes

I 6 NRCOG-W-102, NRCOG-W-208, NRCOG-W-416, NRCOG-W-272, Phule safed and Pusa white round.

II 10 PBR-5, RHRO-White, Local white, PRO-6, NRCOG-W-217, NRCOG-W-130, NRCOG-W-149, NRCOG-W-395, NRCOG-155 and NRCOG-659.

III 2 Arka Pitamber and Telagi Red.

IV 3 NRCOG-536, NRCOG-596 and NRCOG-642.

V 3 Arka Bindu, Arka Kalyan and Arka Pragati.

VI 3 NRCOG-608, NRCOG-327 and NRCOG-588.

VII 3 NRCOG-934, NRCOG-937 and NRCOG-205.

VIII 3 Rose onion, N-53 and Royal selection.

IX 1 Bellary Red.

Table 4. Per cent contribution of characters towards divergence in 34 genotypes of onion

Characters Per cent contribution Rank

Number of leaves at 60 DAT 3.03 IV

Height of plant at 60 DAT (cm) 0.53 VI

Number of leaves at 90 DAT 4.46 III

Height of plant at 90 DAT (cm) 0.00 -

Neck thickness (cm) 0.18 VIII

Length of the bulb (cm) 0.00 -

Width of the bulb (cm) 0.00 -

Shape index 0.00 -

TSS (OB) 0.00 -

Storage loss (%) 2.67 V

Bulb weight (gm) 12.30 II

Yield (t/ha) 76.83 I

Table 5. Average intra and intercluster D

2 values of Onion genotypes

Cluster I II III IV V VI VII VIII IX

I

4.564

102.90

103.12

44.87

42.25

42.66

34.53

22.33

40.12

II

3.819

6.00

136.13

137.49

134.66

120.29

113.79

130.23

III

1.00

136.30

137.63

134.80

120.52

113.89

130.42

IV

1.91

8.63

8.12

21.86

29.39

6.32

V

2.22

10.43

23.36

28.35

10.01

VI

3.16

18.85

24.96

9.30

VII

2.53

15.81

18.13

VII

3.76

24.18

IX

00.00

♦ Diagonal value indicates intra cluster distance

♦ Above the diagonal values indicates inter cluster distance

For cluster IV, cluster IX (6.00) has shown nearest value and the farthest was cluster III (136.30). To the cluster V nearest cluster was IV cluster (8.63) and farthest cluster was III cluster (137.63). For the cluster VI, cluster IX (9.00) was nearest, whereas cluster III (134.80) was farthest. Cluster VII showed minimum cluster distance with cluster VIII (15.81) and maximum distance with III cluster (120.52). For VIII and IX cluster, the cluster IX (18.00) and cluster IV (6.00), respectively have shown minimum difference whereas cluster III (113.89) and I (130.00), respectively have shown highest difference.

The cluster means in respect of 12 characters and over all characters were score across the nine clusters are presented in Table 7.

In case of number of leaves at 60 DAT, the genotypes of cluster IX exhibited the highest mean leaf number (10.26) followed by cluster VIII (10.24). Cluster V compared of lowest number of leaves (9.18). The mean values of remaining cluster were intermediate. The number of leaves thus ranged from lowest in cluster V to 9.18 to highest in cluster IX (10.26).

With regard to height of plant at 60 DAT, cluster means ranged from 56.80 cm (cluster I) to 45.80 cm in cluster V. The highest height of plants at 30 DAT was observed in cluster I (56.80 cm) followed by cluster IX (53.66 cm). The lowest plant height at 60 DAT was observed in cluster V (45.80 cm).

Cluster mean for number of leaves at 90 DAT ranged from as low as 8.46 to as high as 11.20. Cluster V gas given the highest numbers of leaves at 90 DAT (11.20) followed by cluster IV (10.23), whereas the cluster VII has shown least number of leaves at 90 DAT (8.46). Remaining clusters shown intermediate cluster mean.

Again for height of plant at 90 DAT, the cluster mean ranged from 58.05 to 48.98 cm. The cluster VII has shown lowest height of plant at 90 DAT (48.90) and the highest height was shown by cluster IV (58.05) followed by cluster VI (57.98).

Cluster means for length of the bulb ranged from as low as 3.3 (cluster IX) and as high as 4.42 in cluster I, followed by the cluster VIII (4.20). Remaining clusters have shown intermediate value of cluster mean.

With regard to width of the bulb, cluster means ranging from 2.86 to 4.37 cm was observed. The highest width of bulb was observed in the cluster I (4.37 cm) followed by the cluster V (4.24 cm). However, the lowest width of bulb was observed in cluster IV (2.86 cm).

For shape index, the cluster mean ranged from 1.15 to 0.94. The genotypes comprising of cluster V shown lowest shape index (0.94). The highest shape index was observed in cluster IX (1.15) followed by cluster II (1.08).

With regard to total soluble solids, cluster means ranging from 11.79 to 6.02 was observed. The highest total soluble solids was observed in the cluster V (11.79

0B) comprising

of three genotypes followed by cluster IX (10.1) with one genotype. All other cluster means are having intermediate value except cluster VI, which is having lowest cluster mean (11.79

0B).

Range of value varied from 1.10 to 0.79 cm in case of neck thickness of bulbs. The highest neck thickness of bulb obtained in the cluster VI (1.01 cm) and lowest neck thickness of bulb obtained in cluster VIII (0.79).

Cluster mean varied from highest of 20.81 to 19.40 per cent in case of storage loss of onion bulbs. Cluster VI exhibited highest cluster mean value (20.81%). The lowest storage loss was observed in cluster IX (19.40) followed by cluster III (19.61%).

In case of bulb weight, the mean cluster value ranging from 117.33 to 66.27 g. The highest value of 117.33 g was observed in cluster IV followed by cluster VI (107.22). The lowest value in cluster III (66.27 g). Remaining cluster showed intermediate results.

Table 6. The nearest and farthest cluster from each cluster based on D

2 value

Cluster No. Nearest cluster with D2 value

Farthest cluster with D2

value

I VIII (22.33) II (103.12)

II III (6.00) V (137.49)

III II (6.00) V (137.63)

IV IX (6.31) III (136.30)

V IV (8.63) III (137.63)

VI IX (9.00) III (134.80)

VII VIII (15.81) III (120.52)

VIII IX (18.00) III (113.89)

IX IV (6.00) III1 (30.42)

Table 7. Clusters mean for 12 characters in onion

Sl. N

o

Clu

ste

r

No

Of

En

trie

s

No

of

leav

es

60 D

AT

Ht

of

pla

nt

60

DA

T

(cm

)

No

of

leav

es

60 D

AT

Ht

of

pla

nt

90

DA

T

(cm

)

Len

gth

of

bu

lb

(cm

) 6

Wid

th

Of

Bu

lb

Sh

ap

e

Ind

ex

8

TS

S

Of

Bu

lb

(0B

) N

eck

thic

kn

ess

(c

m)

Sto

rag

e

Lo

ss

(%)

Yie

ld

(t/h

a)

Bu

lb

Weig

ht

(gr)

Overa

ll

Sco

re

Ran

k

1 I 6 9.50

(7)

56.80

(1)

9.20

(8)

54.83

(5)

4.42

(1)

4.37

(1)

1.01

(6)

9.96

(3)

1.04

(8)

19.67

(3)

16.33

(7)

92.20

(7) 57 5

2 II 10 9.69

(6)

50.01

(7)

9.36

(7)

50.60

(8)

3.76

(7)

3.46

(7)

1.08

(2)

9.27

(4)

0.97

(3)

19.68

(4)

16.65

(6)

95.65

(6) 67 7

3 III 2 10.10

(4)

52.10(

(5)

9.90

(5)

52.4

(7)

3.43

(8)

3.33

(8)

1.03

(5)

8.09

(7)

1.00

(5)

19.61

(2)

12.05

(8)

66.27

(9) 73 8

4 IV 3 9.73

(5)

53.10

(3)

10.23

(2)

58.05

(1)

3.90

(6)

3.62

(6)

1.07

(3)

8.30

(6)

0.99

(4)

20.40

(5)

24.38

(1)

117.33

(1) 43 1

5 V 3 9.18

(9)

45.80

(9)

11.20

(1)

54.60

(6)

3.99

(3)

4.24

(2)

0.94

(9)

11.79

(1)

0.96

(2)

20.50

(7)

24.02

(2)

97.37

(5) 56 4

6 VI 3 10.20

(3)

50.23

(6)

10.12

(3)

57.98

(2)

3.91

(5)

4.00

(4)

0.97

(8)

6.02

(9)

1.10

(9)

20.81

(9)

17.66

(5)

107.22

(2) 65 6

7 VII 3 9.35

(8)

46.40

(8)

8.46

(9)

48.90

(9)

4.20

(2)

3.99

(5)

1.05

(4)

7.81

(8)

1.02

(7)

20.46

(6)

11.44

(9)

86.33

(8) 83 9

8 VIII 3 10.24

(2)

52.75

(4)

9.74

(6)

57.63

(3)

3.96

(4)

4.02

(3)

0.98

(7)

8.88

(5)

0.79

(1)

20.51

(8)

21.68

(3)

105.33

(3) 49 3

9 IX 1 10.26

(1)

53.66()

(2)

10.03

(4)

55.30

(4)

3.31

(9)

2.86

(9)

1.15

(1)

10.1

(2)

1.01

(6)

19.40

(1)

20.05

(4)

97.96

(4) 47 2

In case of bulb yield the range varied from 11.44 to 24.38 t per ha. The cluster IV comprising of three genotypes recorded highest value (24.38 t/ha) followed by cluster V (24.02 t/ha). The lowest value was recorded by cluster VII comprising of three genotypes (11.44 t/ha).

While, characteristics scoring for cluster means, the most desirable magnitude of the trait is given score one and the least desirable as nine. Hence, the cluster with least desirable score across 12 characters gets first rank and that the cluster with highest overall score gets the ninth rank.

EXPERIMENT II : EVALUATION OF F1 HYBRIDS

4.2 ANALYSIS OF VARIANCE

The analysis of variance for 12 characters are presented in Table 8. It is clear from the table that all the entries comprising parents showed significant difference for most of the characters except for width of the bulb and storage loss. Among the parents, lines (females) exhibited significant differences for the many of the characters viz., number of leaves at 60 DAT and 90 DAT, neck thickness, length of the bulb, bulb weight, TSS and bulb yield. Testers (males) also differed significantly for half of the characters except for plant height at 60 DAT, neck thickness, length and width of the bulb, shape index and storage loss. The contribution of female Vs males showed highly significant variation for six characters viz., number of leaves at 60 DAT and at 90 DAT, plant height 90 DAT, TSS and bulb yield. The variance for hybrids was highly significant for almost all characters except for plant height at 60 DAT. The variance due to parents Vs hybrids was also significant for most of the characters except for plant height at 90 DAT, neck thickness, width and shape of the bulb.

4.2.1 Magnitude of heterosis

The mean per se values of the parents and hybrids and magnitude of heterosis over mid parent and better parent are presented separately for each characters in Table 9 to 20.

4.2.1.1 Number of leaves at 60 DAT (Table 9)

A range of variation for number of leaves per plant at 60 DAT was observed among females. The female parent PRO-6 showing lowest (7.20) and NRCOG-659 the highest (13.20) per se values. The male parent it was ranged between 8.16 (Arka Kalyan) to 10.27

(NRCOG-327). Among the F1s, the lowest mean value (7.00) was recorded in PRO-6 ×

NRCOG-327 and highest (14.00) was recorded in Bellary red × Arka Pragati.

The heterosis over mid parent ranged between –27.56 (NRCOG-659 × NRCOG-327)

to 51.62 (Bellary red × Arka Pragati). As many as seven crosses showed significant mid parent heterosis in positive direction. While, five crosses exhibited significant heterosis in

negative direction. The range for better parent heterosis was from –35.61 (NRCOG-659 × NRCOG-327). With respect to heterosis over better parent, five crosses showed significant heterosis towards negative direction and six crosses exhibited significant heterosis towards positive direction. The maximum heterosis over better parent was manifested by the cross

NRCOG-937 × Arka Pragati.

4.2.2 Plant height at 60 DAT (Table 10)

The range of variation for this trait among the female parents was 38.00 (Bellary red) to 50.73 cm (NRCOG-937) and among male parents, it was ranged from 40.00 (Arka Pragati) to 44.00 (Arka Kalyan). Among the hybrids, the lowest and highest plant height was recorded

by Bellary red × Arka Pragati (42.00 cm) and NRCOG-937 × NRCOG-327 (57.00 cm), respectively.

Table 8. Analysis of variance (mean sum of square) for 12 characters in onion

Source of variance

d.f.

No of leaves 60 DAT

Ht of plant

60DAT (cm)

No of leaves 60 DAT

Ht of plant

90 DAT (cm)

Neck thicknes

s (cm)

Length of bulb

(cm)

Width Of

Bulb (cm)

Shape Index

Bulb

Weight (gr)

TSS of Bulb (0B)

Storage

loss (%)

Yield (t/ha)

Replication

2

0.1875

12.7164

0.0441

6.3030

0.0065

0.0329

0.4365

0.0017

12.5273

0.3374

0.0041

0.1413

Parents

7

10.6680*

*

68.315**

8.8179**

106.7305*

0.0248

0.3447*

0.4403

0.0248

*

253.7177**

9.3206**

1.7971

42.9201*

*

Lines

4

15.3707*

*

78.5827

9.5510**

83.7793

0.0425*

0.4647**

0.6618

0.0246

** 278.9540

4.8091**

3.0377

59.1394*

*

Testers

2

4.3411**

12.000

10.9200**

142.1544*

0.0014

0.2007

0.1674

0.0161

271.3822**

16.3819*

*

0.1233

63.1495*

*

Lines Vs. Testers

1

4.5114**

139.876*

*

1.6810*

127.6871*

0.0008

0.1525

0.1000

0.0427

117.4433

13.2442*

*

0.1823

77.9154*

*

Crosses

14

10.923**

53.4802*

*

5.3404**

57.2662*

0.0595**

0.5458**

2.5910

*

0.0996

**

177.7556**

15.1176*

*

23.0504*

*

30.1383*

*

Parents Vs. Crosses

1

4.4977**

80.8595*

1.9726*

0.1565

0.0011

1.0948**

0.0700

0.0085

914.4749**

83.8533*

*

35.2565*

*

81.5329*

*

Error

44

0.4685

11.6500

0.5498

23.6035

0.0119

0.1220

0.7350

0.0106

49.0831

0.5609

1.7841

3.3109

* and ** indicates significant at 5 and 1% respectively

Table 9. Per se performances of parents and hybrids and magnitude of heterosis for number of leaves at 60 DAT

The range of mid parent heterosis varied from –8.59 (NRCOG-659 × Arka Kalyan) to

36.67 (NRCOG-937 × NRCOG-327) per cent. Out of 15 hybrids, four crosses showed significant positive heterosis and none of them showed significant negative heterosis.

Heterosis in F1s over their better parent ranged from –15.24 (NRCOG-659 × NRCOG-

327) to 18.75 per cent (NRCOG-937 × NRCOG-327). Four crosses exhibited significant negative heterosis and three of them showed significant positive heterosis.

4.2.3 Number of leaves per plant at 90 DAT (Table 11)

The highest number of leaves in the female was observed with NRCOG-659 (11.83) and the lowest was PRO-6 (7.60). Among the males range of variation was 8.60 (Arka

Pragati) to 11.8 (Arka Kalyan). Among the hybrids Bellary red × NRCOG-327 and PRO-6 ×

Arka Kalyan were observed minimum (8.13) and maximum (12.30) by NRCOG-659 × Arka Kalyan for number of leaves per plant.

The range of mid parent heterosis varied from –17.15 (Bellary red × NRCOG-327) to

41.03 per cent (NRCOG-937 × Arka Pragati). Out of 15 hybrids, only three crosses have shown significant negative heterosis and only three crosses showed significant positive

heterosis. Heterosis in F1s over their better parent ranged between –21.41 (NRCOG-659 ×

Arka Pragati) to 37.50 per cent (NRCOG-937 × Arka Pragati). Among the 15 hybrids, seven hybrids showed significant negative heterosis and only two crosses showed significant positive heterosis. The maximum heterosis over better parent was manifested by the cross

NRCOG-937 × Arka Pragati.

4.2.4 Plant height at 90 DAT (Table 12)

Among the parents, NRCOG-327 (62.80 cm) had recorded highest plant height and lowest was recorded by NRCOG-937 (43.40 cm). In hybrids, the range for plant height

varied from 48.00 (Bellary red × Arka Pragati) to 64.90 cm (NRCOG-937 × Arka Kalyan).

The magnitude of heterosis over mid parent ranged between –17.09 (NRCOG-659 ×

NRCOG-327) to 30.85 per cent (NRCOG-937 × Arka Kalyan). Out of 15 hybrids, only two hybrids exhibited significant negative heterosis and only two hybrids exhibited significant positive heterosis over mid parent.

The range for better parent heterosis varied from –21.97 (NRCOG-659 × NRCOG-

327) to 16.31 per cent (NRCOG-937 × Arka Kalyan) and only five crosses showed significant

negative heterosis and only one cross (NRCOG-937 × Arka Kalyan) has showed positive heterosis for plant height at 90 DAT.

4.2.5 Neck thickness (Table 13)

PRO-6 female parent has a neck thickness of 0.83 cm. While, Telagi red shown a

neck thickness of 1.17 cm. Whereas, crosses Bellary red × NRCOG-327 showed least neck thickness (0.68 cm) among the hybrids.

The heterosis over mid parent ranged between –32.01 (Bellary red × NRCOG-327)

to 30.35 per cent (PRO-6 × Arka Pragati). The range for heterosis over better parent varied

from –32.34 per cent (Bellary red × NRCOG-327) to 21.95 per cent (PRO-6 × Arka Pragati). Only one cross shown significant negative heterosis over mid parent and only three crosses showed significant negative heterosis over better parent. The maximum heterosis over better

parent toward negative direction was given by Bellary red × NRCOG-327.

Table 10. Per se performances of parents and hybrids and magnitude of heterosis for plant height 60 DAT

Plant height (cm) at 60 DAT

Per se value Heterosis percentage over Sl. No.

Entries

F1s Mid parent Better parent

Lines

1. Bellary Red 38.00 - -

2. PRO-6 49.20 - -

3. Telagi Red 49.00 - -

4. NRCOG-659 50.73 - -

5. NRCOG-937 48.00 - -

Testers

1. NRCOG-327 42.00 - -

2. Arka Pragati 40.00 - -

3. Arka Kalyan 44.00 - -

F1 hybrids

1. Bellary Red × NRCOG-327 47.00 17.50 ** 12.90 *

2. Bellary Red × Arka Pragati 42.00 9.40 6.67

3. Bellary Red × Arka Kalyan 49.48 20.67** 12.45*

4. PRO-6 × NRCOG-327 47.00 0.88 -6.50

5. PRO-6 × Arka Pragati 46.00 3.14 -6.50

6. PRO-6 × Arka Kalyan 49.00 5.15 -0.41

7. Telagi Red × NRCOG-327 45.30 -0.37 -1.48

8. Telagi Red × Arka Pragati 47.00 5.62 -4.08

9. Telagi Red × Arka Kalyan 55.00 18.28 ** 12.24*

10. NRCOG-659 × NRCOG-327 43.00 -7.26 -15.24**

11. NRCOG-659 × Arka Pragati 43.07 -5.07 -15.11*

12. NRCOG-659 × Arka Kalyan 43.30 -8.59 -14.65*

13. NRCOG-937 × NRCOG327 57.00 26.67 ** 18.75**

14. NRCOG-937 × Arka Pragati 50.00 13.64 4.17

15. NRCOG-937 × Arka Kalyan 47.00 2.17 -2.08

SEm+ 1.97 2.41 2.79

CD at 5% 5.60 6.66 5.53

CD at 1% 7.46 8.78 10.11


Table 11. Per se performances of parents and hybrids and magnitude of heterosis for number of leaves at 90 DAT

Number of leaves


Entries


Lines


2. PRO-6 7.60 - -

3. Telagi Red 9.20 - -

4. NRCOG-659 11.83 - -

5. NRCOG-937 7.60 - -

Testers

1. NRCOG-327 9.60 - -



F1 hybrids

1. Bellary Red × NRCOG-327 8.13 -17.15 ** -18.94 **

2. Bellary Red × Arka Pragati 12.20 35.30 ** 21.59 **

3. Bellary Red × Arka Kalyan 9.97 -8.70 -15.54 **

4. PRO-6 × NRCOG-327 8.30 -3.49 -13.54 *

5. PRO-6 × Arka Pragati 8.90 14.10 * 11.25

6. PRO-6 × Arka Kalyan 8.13 -16.15 ** -31.07 **

7. Telagi Red × NRCOG-327 10.00 6.38 4.17


9. Telagi Red × Arka Kalyan 9.30 -11.43 * -21.19 **

10. NRCOG-659 × NRCOG-327 11.00 2.64 -7.04

11. NRCOG-659 × Arka Pragati 9.30 -6.22 -21.41 **

12. NRCOG-659 × Arka Kalyan 12.30 4.09 3.94

13. NRCOG-937 × NRCOG327 10.00 16.28 * 4.17

14. NRCOG-937 × Arka Pragati 11.00 41.03 ** 37.50 **

15. NRCOG-937 × Arka Kalyan 9.77 0.69 -17.23 **

SEm+ 0.428 0.5243 0.6054

CD at 5% 1.220 1.053843 1.216854

CD at 1% 1.629 1.405124 1.622472


Table 12. Per se performances of parents and hybrids and magnitude of heterosis for plant height 90 DAT

Plant height (cm) at 90 DAT


Entries


Lines


2. PRO-6 47.87 - -

3. Telagi Red 53.73 - -

4. NRCOG-659 55.40 - -

5. NRCOG-937 43.40 - -

Testers

1. NRCOG-327 62.80 - -



F1 hybrids

1. Bellary Red × NRCOG-327 52.67 -10.71 -16.14 *

2. Bellary Red × Arka Pragati 48.00 -7.87 -12.99

3. Bellary Red × Arka Kalyan 50.00 -9.88 -10.39

4. PRO-6 × NRCOG-327 50.33 -9.04 -19.85 **

5. PRO-6 × Arka Pragati 56.00 15.58 * 14.21

6. PRO-6 × Arka Kalyan 52.00 0.32 -6.81

7. Telagi Red × NRCOG-327 50.00 -14.19 * -20.38 **

8. Telagi Red × Arka Pragati 56.00 8.98 4.22

9. Telagi Red × Arka Kalyan 51.00 -6.88 -8.60

10. NRCOG-659 × NRCOG-327 49.00 -17.09 ** -21.97


12. NRCOG-659 × Arka Kalyan 50.00 -10.07 -10.39

13. NRCOG-937 × NRCOG327 52.00 -2.07 -17.20 **


15. NRCOG-937 × Arka Kalyan 64.90 30.85 ** 16.31 *

SEm+ 2.805 3.4354 3.9668

CD at 5% 7.993 6.905154 7.973268

CD at 1% 10.67 9.206872 10.631024


Table 13. Per se performances of parents and hybrids and magnitude of heterosis for neck thickness

Neck thickness (cm)


Entries


Lines


2. PRO-6 0.83 - -


4. NRCOG-659 0.98 - -

5. NRCOG-937 0.97 - -

Testers

1. NRCOG-327 1.00 - -



F1 hybrids

1. Bellary Red × NRCOG-327 0.68 -32.01 ** -32.34 **


3. Bellary Red × Arka Kalyan 1.17 17.06 * 15.51

4. PRO-6 × NRCOG-327 0.80 -12.73 -20.00 *

5. PRO-6 × Arka Pragati 1.17 30.35 ** 21.95 *

6. PRO-6 × Arka Kalyan 0.92 1.28 -6.44

7. Telagi Red × NRCOG-327 1.10 1.54 -5.71


9. Telagi Red × Arka Kalyan 0.95 -11.63 -18.57 *

10. NRCOG-659 × NRCOG-327 1.11 11.93 11.00



13. NRCOG-937 × NRCOG327 0.95 -3.39 -5.00



SEm+ 0.063 0.0770 0.0889

CD at 5% 0.179 0.15477 0.178689

CD at 1% 0.239 0.20636 0.238252


Table 14. Per se performances of parents and hybrids and magnitude of heterosis for length of bulb

Length of bulb (cm)


Entries


Lines


2. PRO-6 3.28 - -


4. NRCOG-659 4.22 - -

5. NRCOG-937 3.66 - -

Testers

1. NRCOG-327 3.78 - -



F1 hybrids

1. Bellary Red × NRCOG-327 3.27 -7.89 -13.58


3. Bellary Red × Arka Kalyan 4.03 10.91 1.85

4. PRO-6 × NRCOG-327 3.20 -9.35 -15.34 *

5. PRO-6 × Arka Pragati 4.10 21.84 ** 18.84 *

6. PRO-6 × Arka Kalyan 3.80 4.97 -4.04

7. Telagi Red × NRCOG-327 3.70 3.64 -2.12

8. Telagi Red × Arka Pragati 4.17 22.37 ** 20.77 *

9. Telagi Red × Arka Kalyan 4.97 35.70 ** 25.42 **

10. NRCOG-659 × NRCOG-327 3.90 -2.46 -7.51

11. NRCOG-659 × Arka Pragati 3.76 -1.91 -10.83


13. NRCOG-937 × NRCOG327 4.17 12.06 10.23



SEm+ 0.202 0.2469 0.2851

CD at 5% 0.575 0.496269 0.57305

CD at 1% 0.767 0.661692 0.764068


4.2.6 Length of the bulb (Table 14)

The mean value of this trait indicated that the females varied from 3.31 cm (Bellary red), Arka Kalyan had the highest (3.96 cm) bulb length and lowest was with Arka Pragati

(3.45 cm). The mean value for hybrids was in the range of 3.20 cm (PRO-6 × NRCOG-327) to

4.97 cm (Telagi red × Arka Kalyan).

Out of 15 cross combinations, only three crosses exhibited significantly positive

heterosis over the mid parent values. The range was from 9.35 per cent (PRO-6 × NRCOG-

327) to 35.70 per cent (Telagi red × Arka Kalyan) though three hybrids showed significant

positive heterosis over better parent. The higher value was exhibited by the cross Telagi red × Arka Kalyan for the length of the bulb.

4.2.7 Width of bulb (Table 15)

Among parents, NRCOG-937 (4.17 cm) recorded the highest bulb width. The per se

performance of hybrids was in the range of 2.18 cm (Bellary red × NRCOG-327) to 5.07 cm

(NRCOG-659 × Arka Kalyan).

heterosis over mid parent exhibited by the hybrids for width of bulb was in the range of –41.39 (Bellary red x NRCOG-327) to 39.02 per cent (PRO-6 x NRCOG-327). Only two crosses showed significantly positive heterosis over mid parent and none of the crosses have shown significant heterosis over better parent.

4.2.8 Shape index (Table 16)

Parent displayed variation for this trait, which fell between 0.97 in line NRCOG-659 to 1.15 in line Bellary red. Among hybrids, the range was between 0.78 in PRO-6 x NRCOG-327 to 1.44 in cross Telagi red x Arka Kalyan.

Out of 15 hybrid crosses, four crosses showed significant negative heterosis and three crosses showed significant positive heterosis over mid parent and highest value was showed by cross Telagi red x Arka Kalyan (48.29%). The extent of heterosis over better parent was from –34.10 (Bellary red x Arka Pragati) to 39.23 per cent. Totally, nine crosses showed significant heterosis over better parent, among them only two crosses showed towards positive direction. The highest 39.23 per cent was given by the cross Telagi red x

Arka Kalyan followed by the cross NRCOG-659 × NRCOG-327 (23.47%).

4.2.9 Bulb weight (Table 17)

The magnitude of variation among the parents with respect to bulb weight was 67.63 (Bellary red) to 89.67 g (Arka Kalyan). The cross combination of Talagi x Arka Kalyan recorded highest bulb weight (111.19 g) compared to other crosses.

Mid parent heterosis exhibited by the F1s for bulb weight varied from –13.14 (PRO-6

× Arka Kalyan) to 37.11 per cent (NRCOG-937 × NRCOG-327). Totally, six crosses showed

significant positive heterosis over mid parent, the highest was by NRCOG-937 × NRCOG-327. With respect to better parent, five crosses showed positive heterosis. The highest was

recorded again by NRCOG-937 × NRCOG-327 (34.74%).

4.2.10 Total soluble solids (Table 18)

The TSS among the parents was ranged between 7.38 (Telagi red) to 12.480B (Arka Kalyan), while in hybrids the range was found between 8.30 (NRCOG-659 x NRCOG-327) to 17.000B (Bellary red x NRCOG-327) (Fig. 1).

Table 15. Per se performances of parents and hybrids and magnitude of heterosis for width of bulb

Width of bulb (cm)


Entries


Lines


2. PRO-6 3.02 - -


4. NRCOG-659 3.71 - -

5. NRCOG-937 4.17 - -

Testers 3.55

1. NRCOG-327 3.67 - -


3. Arka Kalyan - -

F1 hybrids

1. Bellary Red × NRCOG-327 2.18 -41.39 * -44.02 *



4. PRO-6 × NRCOG-327 4.57 39.02 * 28.64

5. PRO-6 × Arka Pragati 3.37 0.60 -8.35

6. PRO-6 × Arka Kalyan 3.97 12.90 -1.00

7. Telagi Red × NRCOG-327 3.17 -6.86 -10.80

8. Telagi Red × Arka Pragati 4.80 38.66 * 30.67


10. NRCOG-659 × NRCOG-327 3.83 5.55 3.23

11. NRCOG-659 × Arka Pragati 2.27 -38.54 * -38.87 *


13. NRCOG-937 × NRCOG327 2.90 -24.84 -30.40



SEm+ 0.496 0.6062 0.7000

CD at 5% 1.412 1.218462 1.407

CD at 1% 1.886 1.624616 1.876


Table 16. Per se performances of parents and hybrids and magnitude of heterosis for shape index

Shape index


Entries


Lines


2. PRO-6 1.01 - -


4. NRCOG-659 0.97 - -

5. NRCOG-937 1.18 - -

Testers

1. NRCOG-327 0.98 - -



F1 hybrids


2. Bellary Red × Arka Pragati 0.76 -31.22 ** -34.10 **


4. PRO-6 × NRCOG-327 0.75 -24.83 ** -25.83 **

5. PRO-6 × Arka Pragati 1.24 20.52 ** 17.67 *

6. PRO-6 × Arka Kalyan 1.05 9.91 4.64

7. Telagi Red × NRCOG-327 0.91 -9.75 -12.22

8. Telagi Red × Arka Pragati 1.01 -3.82 -4.73


10. NRCOG-659 × NRCOG-327 1.21 23.89 ** 23.47 **



13. NRCOG-937 × NRCOG327 0.97 -10.36 -17.85 *

14. NRCOG-937 × Arka Pragati 0.92 -17.31 * -21.53 **

15. NRCOG-937 × Arka Kalyan 0.85 -18.21 * -27.48 **

SEm+ 0.059 0.0727 0.0839

CD at 5% 0.168 0.146127 0.168639

CD at 1% 0.224 0.194836 0.224852


Table 17. Per se performances of parents and hybrids and magnitude of heterosis for bulb weight

Bulb weight (g)


Entries


Lines


2. PRO-6 85.33 - -

3. Telagi Red 74.00 - -

4. NRCOG-659 88.59 - -

5. NRCOG-937 68.54 - -

Testers

1. NRCOG-327 71.00 - -



F1 hybrids

1. Bellary Red × NRCOG-327 89.00 28.40 ** 25.53 **


3. Bellary Red × Arka Kalyan 82.00 4.26 -8.55

4. PRO-6 × NRCOG-327 81.67 4.48 -4.30

5. PRO-6 × Arka Pragati 81.67 -3.26 -4.30

6. PRO-6 × Arka Kalyan 76.00 -13.14 * -15.24*

7. Telagi Red × NRCOG-327 89.67 23.68 ** 21.17 **

8. Telagi Red × Arka Pragati 98.00 24.44 ** 17.36 *


10. NRCOG-659 × NRCOG-327 76.00 -4.76 -14.21 *



13. NRCOG-937 × NRCOG327 95.67 37.11 * 34.74 **

14. NRCOG-937 × Arka Pragati 81.00 6.55 -3.00

15. NRCOG-937 × Arka Kalyan 92.50 16.30 * 2.60

SEm+ 4.04 4.95 5.72

CD at 5% 11.49 13.68 15.80

CD at 1% 15.33 18.00 20.80


Table 18. Per se performances of parents and hybrids and magnitude of heterosis for total soluble solids

Total soluble solids (0Brix)


Entries


Lines


2. PRO-6 10.58 - -


4. NRCOG-659 10.15 - -

5. NRCOG-937 9.27 - -

Testers

1. NRCOG-327 8.32 - -



F1 hybrids


2. Bellary Red × Arka Pragati 13.66 22.88 ** 11.72 *

3. Bellary Red × Arka Kalyan 14.00 24.48 ** 12.15 *

4. PRO-6 × NRCOG-327 10.73 13.58 * 1.42

5. PRO-6 × Arka Pragati 13.10 14.83** 7.08

6. PRO-6 × Arka Kalyan 14.10 22.25 ** 12.95 *

7. Telagi Red × NRCOG-327 12.26 56.33 ** 47.49 **

8. Telagi Red × Arka Pragati 13.03 32.93 ** 6.54

9. Telagi Red × Arka Kalyan 14.00 40.99 ** 12.1 *

10. NRCOG-659 × NRCOG-327 8.30 -10.09 -18.20 **

11. NRCOG-659 × Arka Pragati 11.16 -3.19 -11.44 *

12. NRCOG-659 × Arka Kalyan 9.83 -13.09 ** -21.23 **

13. NRCOG-937 × NRCOG327 9.30 5.78 0.36

14. NRCOG-937 × Arka Pragati 12.16 13.18 * -0.54

15. NRCOG-937 × Arka Kalyan 13.16 21.07 ** 5.47

SEm+ 0.423 0.5296 0.6115

CD at 5% 1.205 1.064496 1.229115

CD at 1% 1.610 1.419328 1.63882


0

2

4

6

8

10

12

14

16

18

To

tal s

olu

ble

so

lid

s (

0B

rix

)

Bellary Red NRCOG-

659

NRCOG-

327

Bellary Red

x Arka

Kalyan

PRO-6 x

Arka Kalyan

Telagi Red x

Arka Kalyan

NRCOG-

659 x Arka

Kalyan

NRCOG-

937 x Arka

Kalyan

Entries

Fig. 1 : Per se performances of parents and hybrids for total soluble solids (0Brix)

Lines Testers

F1s

Fig. 1: Per se performances of parents and hybrids for total soluble solids (0Brix)

The heterosis was ranged from –13.09 (NRCOG-659 × Arka Kalyan) to 85.52 per

cent (Bellary red × NRCOG-327) over mid parent. Among the 15 hybrids, 11 crosses showed significant positive heterosis, while only one cross had significant negative heterosis over mid parent,

With respect to better parent, the variation of per cent of heterosis was from –18.20

(NRCOG-659 × NRCOG-327) to 69.83 (Bellary red × NRCOG-327). Among the total hybrids,

six crosses have shown the positive significant heterosis. The cross Bellary red × NRCOG-327 has shown highest value over better parent for TSS of bulb.

4.2.11 Storage loss of bulb (Table 19)

Among the parents, lowest storage loss was shown by the Bellary red (19.40%) and

highest was by NRCOG-937 (20.50%) and among hybrids the cross NRCOG-659 × NRCOG-

327 showed highest storage loss whereas lowest by the cross Bellary red × NRCOG-327 (18.07%) (Fig. 2).

The variation in the magnitude of heterosis percentage over the mid parent was from

–9.14 (Bellary red × NRCOG-327) to 23.98 per cent (NRCOG-937 × NRCOG-327). Though, the six hybrids have shown negative heterosis but none of them had significant value towards

negative direction. In case of better parent, the range varied from –11.29 (Bellary red ×

NRCOG-327) to 23.58 per cent (NRCOG-937 × NRCOG-327). Among 15 crosses, only one

cross (Bellary red × NRCOG-327) showed significant negative heterosis for storage loss over better parent.

4.2.12 Yield (Table 20)

A wide range of variation was observed among parents from 11.93 (NRCOG-937) to 25.80 t per ha (Arka Kalyan). Among the hybrids, the highest yield of 29.53 t per ha was

recorded in Telagi red × Arka Kalyan followed by Bellary red × Arka Pragati (26.70 t/ha),

Bellary red × NRCOG-327 (25.20), PRO-6 × Arka Kalyan (25.03) and NRCOG-659 × Arka Pragati (24.93 t/ha) (Fig. 3).

Mid parent heterosis for yield ranged between –15.98 (NRCOG-659 × Arka Kalyan)

to 62.22 per cent in NRCOG-937 × NRCOG-327). There were four cross showing significant positive heterosis over mid parent. With respect to better parent the range was much but only three crosses were showing the significant positive heterosis over better parent for yield. The

highest per cent heterosis towards positive direction was given by the cross NRCOG-937 ×

NRCOG-327 followed by Bellary red × NRCOG-327 and Telagi red × Arka Kalyan.

4.3 ANALYSIS OF VARIANCE FOR COMBINING ABILITY STUDIES

Analysis of variance with respect to 12 characters are presented in Table 21. Differences in female (lines) were significant for the characters viz., number of leaves at 60 DAT, plant height at 60 DAT and TSS. Males (testers) differed significantly only for number of leaves at 60 DAT. The differences were significant for most of the character in female Vs males (lines Vs testers) variance except for plant height at 90 DAT and length of bulb.

Female × male (line × tester), contribution was of higher magnitude for all the characters. Females (lines) contribution was more for all the characters except for width of the bulb, while male (tester) contributed more for character width of the bulb.

The GCA and SCA variance was less than one for all the characters indicating the preponderance of non-additive gene effects.

Table 19. Per se performances of parents and hybrids and magnitude of heterosis for storage loss

Storage loss (%)


Entries


Lines


2. PRO-6 20.13 - -

3. Telagi Red 20.10 - -

4. NRCOG-659 22.10 - -

5. NRCOG-937 20.50 - -

Testers

1. NRCOG-327 20.37 - -



F1 hybrids



3. Bellary Red × Arka Kalyan 23.40 18.68 ** 16.81 **

4. PRO-6 × NRCOG-327 23.33 15.23 ** 14.57 **

5. PRO-6 × Arka Pragati 19.23 -5.10 -5.72

6. PRO-6 × Arka Kalyan 21.67 7.88 7.62

7. Telagi Red × NRCOG-327 23.37 15.49 ** 14.73 **



10. NRCOG-659 × NRCOG-327 26.00 22.45 ** 17.65 **

11. NRCOG-659 × Arka Pragati 24.50 15.29 ** 10.86 *

12. NRCOG-659 × Arka Kalyan 23.00 9.18 * 4.07

13. NRCOG-937 × NRCOG327 25.33 23.98 ** 23.58 **

14. NRCOG-937 × Arka Pragati 24.47 19.64 ** 19.35 **

15. NRCOG-937 × Arka Kalyan 19.63 -3.12 -4.23

SEm+ 0.771 0.0445 1.0906

CD at 5% 2.197 1.898445 2.192106

CD at 1% 2.934 2.53126 2.922808


Table 20. Per se performances of parents and hybrids and magnitude of heterosis for bulb yield

Bulb yield (t/ha)


Entries


Lines


2. PRO-6 22.73 - -

3. Telagi Red 22.80 - -

4. NRCOG-659 19.46 - -

5. NRCOG-937 11.93 - -

Testers

1. NRCOG-327 17.82 - -



F1 hybrids


2. Bellary Red × Arka Pragati 26.70 16.64 ** 3.62

3. Bellary Red × Arka Kalyan 21.50 -6.15 -16.56 **

4. PRO-6 × NRCOG-327 23.10 13.92 * 1.61

5. PRO-6 × Arka Pragati 24.20 -0.21 -6.08

6. PRO-6 × Arka Kalyan 25.03 3.23 -2.85

7. Telagi Red × NRCOG-327 19.00 -6.45 -16.67


9. Telagi Red × Arka Kalyan 29.53 21.62 ** 14.62 *

10. NRCOG-659 × NRCOG-327 18.30 -1.82 -5.96

11. NRCOG-659 × Arka Pragati 24.93 10.26 -3.23

12. NRCOG-659 × Arka Kalyan 19.00 -15.98 ** -26.26 **

13. NRCOG-937 × NRCOG327 24.13 62.22 ** 35.43 **

14. NRCOG-937 × Arka Pragati 21.27 12.82 -17.46 **

15. NRCOG-937 × Arka Kalyan 20.11 6.68 -21.95 **

SEm+ 1.051 1.2866 1.4857

CD at 5% 2.993 2.586066 2.986257

CD at 1% 3.997 3.448088 3.981676


0

5

10

15

20

25

30

Sto

rag

e lo

ss (

%)

Bellary Red NRCOG-

659

NRCOG-

327

Bellary Red

x Arka

Kalyan

PRO-6 x

Arka Kalyan

Telagi Red x

Arka Kalyan

NRCOG-

659 x Arka

Kalyan

NRCOG-

937 x Arka

Kalyan

Entries

Fig. 2 : Per se performances of parents and hybrids for storage loss (%)

Lines Testers

F1s

Fig. 2 : Per se performances of parents and hybrids for storage loss (%)

0

5

10

15

20

25

30

Bu

lb y

ield

Bellary Red NRCOG-

659

NRCOG-

327

Bellary Red

x Arka

Kalyan

PRO-6 x

Arka Kalyan

Telagi Red x

Arka Kalyan

NRCOG-

659 x Arka

Kalyan

NRCOG-

937 x Arka

Kalyan

Entries

Fig. 3 : Per se performances of parents and hybrids for bulb yield (g)

Lines Testers

F1s

Fig. 3: Per se performances of parents and hybrids for bulb yield (g)

Table 21. Analysis of variance (mean sum of squires) for combining ability for 12 characters in onion

Source of variation

Df No of leaves 60 DAT

Ht of plant 60

DAT (cm)

No of leaves 60

DAT

Ht of plant 90

DAT (cm)

Length of bulb

(cm)

Width of Bulb (cm)

Shape Index

TSS Of Bulb (

0B)

Neck thickness (cm)

Storage loss (%)

Bulb weight

(gr)

Yield (t/ha)

Replication 2 0.2334 17.2486 4.4282 6.1447 0.1672 0.3727 0.0034 0.3020 0.0023 0.0647 18.6889 1.8545

Cross 14 10.9230**

19.3789 53.48.02 ** 57.2662 0.5458** 2.5910 * 0.0996 ** 15.1176 ** 0.0505 ** 23.0504 ** 177.7556* 30.1383 *

Female 4 17.6025 * 37.4582* 85.2660 ** 43.4272 0.6050 0.7792 0.0869 33.7561 ** 0.0386 32.8947 136.3111 25..3484

Male 2 22.8453 * 13.3230 34.8092 45.7260 1.0062 1.7722 0.0556 8.8580 0.0507 20.2007 26.6222 19.7395

Female Vs. male

1 4.6028 * *

11.8533 42.2551 * 67.0707 0.4011 3.7016** 0.1169 ** 7.3633 ** 0.0721 ** 18.8407 ** 236.7611* 35.1330**

Error 28 0.5692 22.0682 15.4668 36.6609 0.1344 0.9521 0.0150 0.8618 0.0080 2.1992 76.2365 4.5916

GCA 0.2234 0.2661 0.3968 -0.3466 0.0051 -0.0393 -0.0006 0.2741 -0.0004 0.1488 -2.0861 -0.1766

SCA 1.3445 -3.4050 8.9294 10.1366 0.0889 -0.9165 0.0340 2.1672 0.0214 5.5472 51.5082 10.1790

GCA/SCA 0.1161 -0.0781 0.0444 0.0341 0.0573 -0.428 0.0176 0.1264 0.0186 0.0268 0.0839 0.0173

Contribution of

females

46.04 55.23 45.54 21.67 31.67 8.59 24.93 63.80 18.53 40.77 21.91 24.03

Contribution of males

29.88 9.82 9.30 11.41 26.34 9.77 7.98 8.37 12.17 12.52 1.98 9.36

Contribution of F X M

24.08 34.95 46.15 66.93 41.99 81.64 67.09 27.83 69.30 46.71 76.19 66.61


4.4 COMBINING ABILITY EFFECTS

Estimation of general combining ability (gca) and specific combining ability (sca) effects for all the characters are presented in Table 22 and 23, respectively.

4.4.1 Number of leaves at 60 DAT

The lines (females), which possessed significant sca effects were Bellary red (1.23) and NRCOG-937 (1.53). Among the tester, only Arka Pragati (1.28) showed positive gca effect. The highest negative gca effect was exhibited by the tester PRO-6 (-1.84).

A total of four crosses showed significant sca effects of which only the cross Bellary

red × Arka Pragati (1.52) was in positive direction and rest three were in negative direction.

4.4.2 Plant height at 60 DAT

Among all the parents and hybrids, one showed significant positive gca and one showed sca effect, respectively. The parent NRCOG-937 (3.90) and the hybrid NRCOG-937

× NRCOG-327 (5.39) recorded the highest non-significant gca and sca effect, respectively.

4.4.3 Number of leaves at 90 DAT

Two out of five lines had significant gca effect with one (NRCOG-659) in desired direction and the other one (PRO-6) in non-desired direction. Among the tester, none of them showed significant sca effect at either of the sides. While, Arka Pragati showed highest non-significant gca value towards positive direction.

Out of 15 crosses, significant gca effects were observed for five crosses of which three crosses were positive and other two crosses were in negative direction. Among them,

highest significant positive and negative sca effect were observed in Bellary red × Arka

Pragati (1.85) and NRCOG-659 × Arka Pragati (-1.81), respectively.

4.4.4 Plant height at 90 DAT

All the parents had non-significant gca effect, but the line NRCOG-937 showed highest non-significant gca effect towards positive direction.

Among the 15 hybrids, only one cross (NRCOG-937 × Arka Kalyan) showed positive significant sca effect, rest all showed significant among them five crosses showed towards positive direction.


Among the eight parents, only two parents had significant negative gca effect, but none of them showed positive significant gca value. The highest negative gca effect was noticed in Bellary red (-0.10) followed by the NRCOG-327 (-0.07).

Out of 15 hybrids, only two crosses showed significant negative sca effect. The

highest value was given by the cross Bellary red × NRCOG-327.

4.4.6 Length of the bulb

Among the eight parents, significant gca effects were observed for four parents, of which half were positive and other half were in negative direction. The highest significant positive and negative gca were observed in Telagi red and Bellary red, respectively.

Table 22. Estimation of GCA effect of parents for 12 characters in onion (L ×××× T)

Table 23. Estimation of SCA effect of parent for 12 characters in onion (L ××××T)

Out of 15 hybrids, only one cross had significant positive sca effect and that was

NRCOG-937 × NRCOG-327 and none of the hybrid showed significant negative sca effect.

4.4.7 Width of the bulb

None of the parents had significant gca value either in positive or negative direction, but the parent NRCOG-937 showed highest positive non-significant value for gca.

For the sca effect also, none of the crosses had heterosis in positive direction and only one cross showed significant sca effect towards negative direction and that was

NRCOG-659 × Arka Pragati (-1.65).

4.4.8 Shape index

Among eight parents, five parent had significant gca effect of which three had towards positive direction and rest towards negative direction. The parent Telagi red had highest (0.11) towards positive and highest negative significant gca was given by both the Bellary red and NRCOG-937 (-0.10).

With respect to sca effect only three hybrids had significant positive value and highest

value was with cross Telagi red × Arka Kalyan (0.26) and only two crosses had significant

value towards negative direction and higher value was with PRO-6 × NRCOG-327 (-0.22).

4.4.9 Bulb weight

The parent NRCOG-937 showed highest but non-significant gca value towards positive direction (3.38), the one parent showed significant values towards negative direction and that was PRO-6 (-6.40).

Among the hybrids, one cross had negative significant sca effect and one cross

NRCOG-65a × Arka Kalyan (10.82) to show positive effect for sca and that was cross.


Among the parents, three crosses each had significant negative gca effect and again three crosses to show significant positive gca effect. The parents Bellary red and NRCOG-659 had highest positive (2.52) and negative (-2.71), respectively.

For sca effect, three crosses showed significant negative effect and the only one

cross (Bellary red × NRCOG-327) showed significant positive sca effect to the extent of 2.96.

4.4.11 Storage loss

Among the total parents, five had the significant gca effect. Three parents had their value towards positive side and only two parents had towards negative direction and highest value was with Bellary red (-1.94).

Out of the total hybrids, only four hybrids had significant sca effect, two had positive side and another two for negative side and highest negative sca effect given by the cross

(Bellary red × NRCOG-327) was –3.22.

4.4.12 Bulb yield

Only two parents had significant gca effect and one had positive effect (Arka Pragati), 1.17) and another one towards negative direction (NRCOG-659, -2.33).

For sca effect, two crosses had negative significant value, highest value was showed

by cross Telagi red × NRCOG-327 (-4.08) towards positive direction, the significant values

was given by three crosses. Highest value was with cross Telagi red × Arka Kalyan (5.36)

followed by the cross NRCOG-937 × NRCOG-327 (3.42) and cross NRCOG-659 × Arka Pragati (3.02).

V. DISCUSSION

Onion (Allium cepa L.) is one of the most important commercial vegetable crop grown and exported from India. Many varieties of onion have been released, yet 70 per cent of production is from local types which are inferior in quality and yield. The released varieties also lack in qualities such as uniformity in shape and colour, high per cent of bolting and splits, susceptibility to diseases and poor shelf life. In recent years single cross hybrids are gaining greater importance owing to their high yield and uniformity of the product.

The utilization of heterosis in plant breeding depends upon valuable genetic stock, evaluation of the stock and finding out diverse ones and identifying suitable cross combinations, which helps in predicting the promising hybrids. Therefore, development of high yielding superior quality hybrids is very much essential to improve the productivity of onion crop. In this chapter, results of genetic diversity, heterosis and combining ability studies have been discussed.

5.1 GENETIC DIVERGENCE

Selection of genetically distant parents for hybridization is a basic need for generation of genotypes with desirable characters. Genetic diversity between genotypes indicate difference in the gene frequencies. Mahalanobis generalized distance is the most widely used technique in plant breeding to know the distance between the genotypes. This statistical tool has been employed widely to resolve genetic divergence at their varietal and species level in classifying crop plants. This is possible by clustering the entries based on D

2 values, as it

represents the index of genetic diversity among genotypes and clusters.

Based on the D2 values, 34 genotypes were grouped into nine clusters. There were

six genotypes in the cluster I and 10 genotypes were present in cluster II. In cluster III, two genotypes were present, three genotypes were present in each cluster IV to VIII, while cluster IX was solitary one.

The formation of solitary cluster may be due to total isolation preventing the gene flow or intensive natural/human selection for diverse adoptive complexes. The intra cluster distance varies from 1.00 in cluster III to maximum distance of 4.564 in cluster I. This reveals the presence of divergent genotypes within different clusters. The inter cluster D

2 values also

ranged widely with minimum value of 6.12 between cluster IV and cluster IX and maximum values of 137.63 between cluster III and cluster V indicating high diversity among the genotypes. Cluster III with two genotypes and cluster V with three genotypes were the most divergent groups with a maximum inter cluster distance (137.63). It is desirable to select accessions from clusters showing high inter cluster distance (cluster III and cluster V) and also with high bulb yields as parents in heterosis breeding programme for obtaining desirable crosses.

The most divergent genotypes are Arka Pitambar and Talagi Red from cluster III and Arka Bindu, Arka Kalyan and Arka Pragati from cluster V.

Among the 12 characters studies, the most important character contributing to the divergence was yield of bulbs. This was followed by bulb weight, number of leaves, storage loss, height of the plant and neck thickness of the bulb. Similar results were noticed by Panthee (2006) in garlic, where bulb weight, diameter and yield were the major contributor to the genetic diversity.

5.2 HETEROSIS BREEDING

Heterosis is the superiority of F1 hybrid over both of its parents in terms of yield and or other characters. Utilization of hybrids vigour as a means of improving the yield of horticultural crops has become one of the most important technique in vegetable breeding. The advent of onion hybrids in India has less impact. In many of the places local varieties have been substituted by some varieties, which are not enough potential in yield and quality parameters. In view of this it is essential to identify the parents which can produce better hybrids, which perform better than local varieties grown in the particular areas. By keeping

this objective in view the diverse selected parents are crossed in a L × T manner and F1s are evaluated.

Combining ability analysis helps in diagnosing the additive and non-additive gene action which inturn leads to identification of suitable parents and cross combination that could be exploited for crop improvement. The results of this experiment on heterosis and combining ability have been discussed here.

There were five and three crosses which showed significant heterosis over mid parent and better parent, respectively suggesting dominant gene action. The highest

heterosis for bulb yield was noticed in crosses over better parent are NRCOG-937 × NRCOG-

327 (35.43%) (Plate 4) followed by Bellary Red × NRCOG-327 (25.66%) (Plate 5) and Telagi

Red × Arka Kalyan (14.62%). This might be due to higher bulb weight was noticed in the above crosses. The per cent heterosis for bulb weight in these hybrids was 34.74 per cent

(NRCOG-937 × NRCOG-327), 25.35 per cent (Bellary Red × NRCOG-327) and the cross

Telagi Red × Arka Kalyan has shown 24.00 per cent of heterosis. Similar results were also recorded by Veeregouda (1988), Vinutha (2000), Divakar (2001).

The plant height and number of leaves recorded higher value in the above crosses. These growth parameters directly helped for increased bulb weight and yield. These results were confirmative with Madalageri (1983), Vadivel et al. (1982), Aghora (1985) and Vinutha (2000).

The negative heterosis is welcoming in the quality parameters like neck thickness and storage loss. There were only three crosses, which showed negative significant heterosis for

neck thickness. The highest value (-32.34%) was given by the cross (Bellary Red × NRCOG-

327) followed by the cross PRO-6 × NRCOG-327 (-20.00%) and NRCOG-659 × NRCOG-327

(-18.57%). For the storage loss only one cross (Bellary Red × NRCOG-327) showed

significant negative heterosis (-11.29%) and the cross Bellary Red × Arka Pragati and Telagi

Red × Arka Kalyani showed highest non-significant negative heterosis of the value (-9.97%) and (-8.79%), respectively. The negative heterosis for these characters were also observed by Hosfield et al. (1977) and Divakar (2001).

Shape index is also the important quality parameter. The highest heterosis value for

this trait was observed in the cross Telagi Red × Arka Kalyan (39.23%) followed by NRCOG-

659 × NRCOG-327 (23.47%) and PRO-6 × Arka Pragati (17.67%). Similarly, Vadivel (1982) and Vinutha (2000) observed heterosis over mid parent and better parent for shape index in onion.

For the character TSS, among the hybrids there were six hybrids to show positive

and significant heterosis. The highest value was showed by the cross Bellary Red × NRCOG-

327 (69.83%). The cross Telagi Red × NRCOG-327 and PRO-6 × Arka kalyan showed the value 47.49 and 12.95 per cent, respectively. Haey and Randle (1996), Vinutha (2000) observed significant positive heterosis for total soluble solids.

Plate 4: Superior hybrid and their parents

Plate 5: Superior hybrid and their parents

Table 24. Best combiner gca for important economic characters

Sl. No.

Characters Cross combination Values

1. Yield (t/ha) Bellary Red 1.39

Arka Pragati 1.17

Telagi Red 1.14

2. Bulb weight (g) NRCOG-937 3.38

NRCOG-659 2.04

Telagi Red 1.82

3. Total soluble solids (0B) Bellary Red 2.52

Arka Kalyan 0.65

Telagi Red 0.73

4. Storage loss (%) Bellary Red -1.94

Telagi Red -1.48

Arka Kalyan -0.67

Arka Pragati -0.67

Table 25. Per se performance and combining ability effects of top 5 hybrids for higher yield and their corresponding bulb weight

Bulb weight (g) Yield (t/ha)

Combining ability effect Combining ability effect Per se

performance GCA

Per se performance

GCA

Sl. No. Crosses

Line Tester SCA

Line Tester SCA

1. NRCOG-937 × NRCOG-327 95.67 3.38 -0.22 5.89 24.13 -1.24 -1.13 3.42

2. Bellary Red × NRCOG-327 89.00 -0.84 -0.22 3.44 25.20 1.39 -1.13 1.86

3. Telagi Red × Arka Kalyan 111.19 1.82 -1.38 -10.29 29.53 1.14 -0.04 5.36

4. Bellary Red × Arka Pragati 85.00 -0.84 1.16 -1.96 26.70 1.39 1.17 -2.93

5. PRO-6 × NRCOG-327 81.67 -6.40 0.22 1.67 23.10 1.04 -1.13 0.12

Table 26. Per se performance of top 5 hybrids for higher yield and their corresponding TSS and storage loss

Sl. No. Crosses TSS (0B) Bulb weight (g) Yield (t/ha) Storage loss (%)

1. NRCOG-937 × NRCOG-327 9.30 95.67 24.13 25.33

2. Bellary Red × NRCOG-327 17.00 89.00 25.20 18.07

3. Telagi Red × Arka Kalyan 14.00 111.19 29.53 18.33

4. Bellary Red × Arka Pragati 13.66 85.00 26.70 18.37

5. PRO-6 × NRCOG-327 10.73 81.67 23.10 23.33

Combining ability studies

The tester Arka Pragati was the only parent to show good gca effect significantly for

bulb yield and the highest gca effect for this trait was shown by cross Telagi Red × Arka

Kalyan followed by NRCOG-937 × NRCOG-327. For the important yield attributing character i.e., bulb weight, the line NRCOG-937 and the tester Arka Kalyan were the parents to show

highest gca effect and the cross Telagi Red × Arka Pragati was the highest to show the gca value. For the number of leaves and plant height, the highest gca value was shown by the line NRCOG-937 and highest sca for number of leaves and plant height was given by the cross

Bellary Red × Arka Pragati and NRCOG-937 × NRCOG-327, respectively. Similar study was done by Divakar (2001) and Sundari (2003).

We are interested in parents and hybrids which show the least GCA and SCA, respectively for the characters like storage loss and neck thickness. The parents to show the least GCA effect were Bellary Red among the line and Arka Kalyan and Arka Pragati among

the tester. The cross to show least SCA effects were Bellary Red × NRCOG-327 followed by

NRCOG-937 × Arka Kalyan. Bellary Red has shown least gca effect for neck thickness and among the tester it was NRCOG-327. The cross to show least sca effect for neck thickness was shown least sca effect for storage loss also. Similar findings were observed by Divakar (2001) and Sundari (2003).

For shape index the highest gca effect was shown by Telagi Red (line) and Arka

Kalyan (tester). The highest sca effect was given by the cross Telagi Red × Arka Kalyan

followed by PRO-6 × Arka Pragati, while for TSS highest gca effect was given by Bellary Red (line) and among test Arka Kalyan and highest sca effect for this trait was shown by Bellary

Red × NRCOG-327. The results were in confirmative with the results of Sundari (2003).

FUTURE LINE OF WORK

Based on the present study, the following hints are proposed to try at one’s best for further improvement of the crop in the same line.

♦ Some more genotypes have to be tested for higher yield and least storage loss.

♦ The best performing hybrids have to be tried across different locations to test their stability and confirm their performance.

♦ Use wild species as donar parent to reduce storage loss.

VI. SUMMARY

Studies on “Heterosis and combining ability studies in onion” was undertaken during 2004-06 in Olericulture Unit, Department of Horticulture, University of Agricultural Sciences, Dharwad. The study was mainly contemplated to develop best hybrids and also to find the best general and specific combiner for higher yield and other yield attributing characters.

The study was initiated with a total of 34 genotypes collected from different sources and were evaluated for their performance and genetic divergence during 2004.

In continuation of that study a total of 12 genotypes were selected as parents for

hybridization programme. These selected genotypes were crossed in line × tester method by using six as lines and six as testers but only 15 hybrids were got from five line and three testers.

Genotypes viz., Bellary Red, PRO-6, Telagi red, NRCOG-659 and NRCOG-937 were used as lines. NRCOG-327, Arka Pragati and Arka Kalyan were used as testers and have given hybrids.

Fifteen hybrids were evaluated along with eight parents during 2006 for estimation of heterosis and combining ability.

Genetic divergence

Using Mahalanobis D2 statistics method, 34 genotypes were grouped into nine

clusters. There were six genotypes in the cluster I and 10 genotypes were present in cluster II. In cluster III, two genotypes were present. Three genotypes were present in each cluster IV to VII, while cluster IX was solitary cluster. The intra cluster distance varies from 1.00 in cluster III to maximum distance of 4.564 in cluster I. The inter cluster D

2 values ranged from

minimum value of 6.123 between cluster IV and cluster IX and maximum value of 137.630 between cluster III and cluster V. Cluster III with two genotypes and cluster V with three genotypes were the most divergent groups with maximum intercluster distance (137.630). It is desirable to select accessions from cluster showing high intercluster distance.

Based on D2 analysis and group clustering, the genotype Arka Pitamber and Telagi

red from cluster III and from cluster V Arka Bindu, Arka Kalyan and Arka Pragati were most divergent genotypes.

Among the 12 characters studied, the most important contributing to the divergence was yield of bulbs followed by bulb weight.

Heterosis

Significant heterosis was observed for the hybrids Bellary Red × Arka Pragati and

NRCOG-937 × Arka Pragati over mid and better parent respectively for the traits number of leaves and plant height, but none of them were significant. For the number of leaves at 90

DAT, the cross NRCOG-937 × Arka Pragati showed highest significant value. The cross

NRCOG-937 × Arka Kalyan was the only one hybrid to show significant heterosis for the character plant height at 90 DAT.

As we are more interested in negative heterosis for the neck thickness as the bulb

character. Bellary Red × NRCOG-327 showed highest negative heterosis over better parent.

For length of the bulb, Telagi red × Arka Kalyan cross showed highest significant positive heterosis over better parent and for the width of the bulb though no one hybrid have shown

significant heterosis the highest non-significant heterosis was given by Telagi red × Arka Pragati shape index is also important characters of the bulb hence this has been also studied.

For this, the cross Telagi red × Arka Kalyan showed highest significant heterosis.

For bulb weight character, the cross Telagi red × NRCOG-327 showed highest significant heterosis over mid parent but no cross showed heterosis over better parent.

Since processing industries are more interested in TSS of bulb this character also

studied. The cross Bellary Red × NRCOG-327 showed highest value over better parent.

For storage loss also, we are interested for negative heterosis the cross Bellary Red

× NRCOG-327 showed significant heterosis over better parent in favourable direction.

For bulb yield, the highest heterosis over better parent was noticed in cross NRCOG-

937 × Arka Pragati (35.34%).

Combining ability

Bellary Red was found to be a good general combiner for neck thickness, TSS of bulb and storage loss and Arka Pragati for number of leaves at 60 DAT. Telagi red was found good general combiner for length of the bulb, shape index and bulb weight whereas NRCOG-659 and Arka Pragati were found good general combiner for number of leaves at 90 DAT and for bulb yield, respectively.

With regard to specific combining ability which is more important for exploitation of

heterosis. The Bellary Red × Arka Pragati showed highest positive SCA for number of leaves at 60 DAT, plant height at 60 DAT and number of leaves at 90 DAT. For plant height at 90

DAT, the cross NRCOG-937 × Arka Kalyan showed highest sca effect.

For neck thickness as we need a cross which show negative sca effect and that was

found to be Bellary Red × NRCOG-327. The cross NRCOG-937 × NRCOG-327 showed highest sca effect for length of the bulb. Whereas, for width of the bulb the cross NRCOG-937

× Arka Kalyan showed highest sca value. For the shape index, Telagi red × Arka Kalyan was found to be the best specific combiner.

For bulb weight and TSS the cross Telagi red × NRCOG-327 and Bellary Red ×

NRCOG-327 showed highest sca value, respectively. The Bellary Red × NRCOG-327 was

the cross to show highest negative sca effect and finally for the yield Telagi red × Arka Kalyan were found to be good specific combiners.

VII. REFERENCES

AGHORA, T. S., 1985, The heterosis and combining ability studies in onion (Allium cepa L.)

using × tester analysis. M. Sc. (Agri.) Thesis, University of Agricultural Sciences, Dharwad.

ANONYMOUS, 2005, Horticultural Crop Statistics of Karnataka State at a Glance 2002-03.

ANONYMOUS, 2005, The Hindu Survey of Indian Agriculture, The Hindu Publications.

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Appendix I. Monthly meteorological data for experiment year 2004-05 of Main Agricultural Research Station, University of Agricultural Sciences, Dharwad

Temperature (0C)

Months Rainfall (mm) No. of rainy days Mean maximum Mean minimum

Relative humidity (%)

December, 2004 - - 29.4 12.5 45

January, 2005 4.80 1 30.7 15.0 49

February, 2005 Trace - 33.2 16.3 43

March, 2005 - - 36.0 18.9 42

April, 2005 75.00 5 36.3 21.3 53

May, 2005 29.40 3 37.0 21.5 55

June, 2005 151.00 10 30.9 21.5 76

July, 2005 290.20 19 27.4 21.5 83

August, 2005 138.80 15 27.1 20.4 81

September, 2005 194.50 14 27.5 20.3 85

October, 2005 89.40 9 29.6 19.1 70

November, 2005 38.00 1 29.4 14.9 51

December, 2005 Trace - 28.9 13.1 53

Total 1006.3

HETEROSIS AND COMBINING ABILITY STUDIES IN ONION (Allium cepa L.)

NINGADALLI MALLIKARJUN 2006 Dr. P. R. DHARMATTI MAJOR ADVISOR

ABSTRACT

An investigation was taken to decipher the magnitude of diversity, heterosis and combining ability in onion. The material for the study consisted of 34 genotypes. These were collected from National Research Center on Onion and Garlic (NRCOG) Rajaguru nagar, IIHR Hesarghatta and local varieties maintained at Olericulture section, Department of Horticulture, UAS Dharwad were evaluated in randomized block design with three replications during 2004-05 to study the diversity, magnitude of heterosis and combining ability using Line X Tester analysis.

Genetic diversity for yield and yield contributing traits was carried out involving 34 genotypes. Based on D

2 value the total genotypes assigned in to 9 clusters indicating the

presence of appreciable amount of diversity. The cluster III with two genotypes and cluster V with three genotypes were most divergent groups with maximum inter cluster distance (137.63). Out of 12 characters, bulb yield contributed maximum to the divergence The study on heterosis revealed that, significant heterosis was found for all the characters studied. For yield five hybrids exhibited significant positive heterosis over mid parent. Three crosses viz., NRCOG-937 x NRCOG-327, Bellary Red x NRCOG-327 and Telagi Red x Arka Kalyan have exhibited significant positive heterosis over better for yield. The Bellary Red proved as good general combiner for TSS and storage loss. For yield, Arka Pragati has found to be good general combiner for yield the crosses Telagi Red x Arka Kalyan and NRCOG-937 xNRCOG-327 were found specific combiners for bulb yield.

heterosis and combining ability studies in

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