genetic diversity and correlated response to selection of grain yield and associated characters in...

_____________________________________________________________________________________________________ *Corresponding author: Email: [email protected];

Original Research Article

Journal of Basic and Applied Research International

13(1): 56-61, 2016 ISSN: 2395-3438 (P), ISSN: 2395-3446 (O)

International Knowledge Press www.ikpress.org

GENETIC DIVERSITY AND CORRELATED RESPONSE TO SELECTION OF GRAIN YIELD AND ASSOCIATED

CHARACTERS IN MAIZE ( Zea mays L.)

J. O. AGBOLADE1, O. J. OLAWUYI 2, O. B. BELLO3*, O. D. OLUSEYE1 AND R. J. 1. KOMOLAFE 1

1Department Plant Science and Biotechnology, Federal University, Oye Ekiti, Nigeria. 2Department of Botany, University of Ibadan, Ibadan, Oyo State, Nigeria.

3Department of Biological Sciences, Fountain University, Osogbo, Osun State, Nigeria.

AUTHORS’ CONTRIBUTIONS This work was carried out in collaboration among all authors. Author JOA designed the study, wrote the

protocol and interpreted the data. Author ODO anchored the field study, gathered the initial data and performed preliminary data analysis. Author OBB, the corresponding author and authors OJO and RJA managed the

literature searches and produced the initial draft. All authors read and approved the final manuscript.

Received: 22nd July 2015 Accepted: 20th August 2015 Published: 3rd October 2015 __________________________________________________________________________________

ABSTRACT

Sixteen genotypes of maize were evaluated for genetic variability and character associations in the Research Farm of the Department of Botany, University of Ibadan, Nigeria for 90 days in the 2012, 2013 and 2014 cropping seasons. Perforated polythene bags (18 × 9 cm) were filled with 6kg sandy-loam soil and were spaced at a distance of 10 cm apart between rows. Three seeds from each genotype were then planted per bag without treatment in three replicates. Data on plant and stem height, leaf width, leaf length and number of leaves were collected after planting at 14 days interval on each replicate for a particular genotype. The plant height of EVDT.Y200STRQPM genotype was significantly (p < 0.05) different from other genotypes, while genotype pairs; TZE-OR2DTSTRQPM and 2009TZE-ORIDTSTRQPM, TZEI 22, TZEI 98 and OBANTAPA, TZEI 4, TZEI 161, BODIJA as well as EVDT-W99STR, OJO, 98SYNWECSTRQPM were similar to each other. The result of correlation coefficient shows that stem height was highly significant and positively correlated with the plant height (p < 0.01; r = 0.91). The genotype is negative and non-correlated with plant height, stem height, leaf width and number of leaves, but positive and non-significantly associated with leaf length, replicate and week after planting. Keywords: Maize genotype; character; variability; morphology; genetic diversity; germplasm. 1. INTRODUCTION Maize (Zea mays L.) is one of the most widely grown grain crops domesticated by indigenous peoples in prehistoric times with 332 million metric tons

annually in the United States of America [1,2]. The leafy stalk produces ears which contain grains called kernels consisting of an endosperm, embryo, pericarp and tip cap. The kernels are used in cooking as a vegetable or starch [3]. Sugar-rich varieties called

Agbolade et al.; JOBARI, 13(1): 56-61, 2016

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sweet corn are usually grown for human consumption, while field corn varieties are used as chemical feed stocks [1,2]. Maize also plays an important role in the prevention of digestive ailments, and can be processed for a range of uses both as an ingredient in food or drinks, such as corn syrup in soft drinks or maize meal and for industrial purposes [4]. The starch part of the kernel is used in foods and many other products such as adhesives, clothing, pharmaceutical tablets, paper production, and can be converted into sweeteners, and used in products such as sweets, bakery products and jams. The oil from the embryo is used in cooking oils, margarine and salad dressings, while the protein, hulls and soluble part of the maize kernel are used in poultry feed [5]. The applications of genetics in correlation studies are used in evaluating variability in maize through character association [5,6]. Environmental changes across locations and years due to climatic conditions, disease and pest pressures, soil fertility and socio-economic factors affect the yield performance of maize [5,7]. [4] emphasized the need to select genotypes that outperform the local commercial varieties in their 'safety-first screening approach. Yield stability measures the ability of a variety to maintain high yields across environments [8.9]. A stable responsive genotype is one that is able to utilize resources available in the high yielding environment while maintaining above average performance in all other environments. It is only the high yielding, stable and responsive variety that will satisfy the needs of farmers in their diverse and changing farming environments [9]. The morphological characters of maize which include plant height, stem height, leaf length, leaf width, tassel arrangement, number of leaves, ear length, cob diameter and yield may vary depending on the genotype and environment in which they are grown [5]. Therefore, this study examined the contribution of genotypes and growth stages on variations in morphological characters of maize germplasm.

2. MATERIALS AND METHODS 2.1 Experimental Site and Sources of Planting

Materials This study was carried out in an open field at the Research Farm of the Department of Botany, University of Ibadan, Ibadan, Nigeria between March and May, 2012, 2013 and 2014. A total of sixteen genotypes of maize were evaluated in this study. Fourteen genotypes were collected from the germplasm of the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and they include: TZEI 161, TZEI 98, TZEI 25, TZEI 22, TZEI, TZEI

4, TZEOR2DTSTRQPM, DMRESRWQPM, EVDTY2000STRQPM, TZEYDTSTRQPM, EVDTW99STR, 98SYNWECST-RQPM, 2009TZEORIDTSTSTRQPM, OBANTAPA and TZEYBPDTSTRQPM. Two varieties were also obtained from Ojo and Bodija markets.

2.2 Research Design and Method of Planting The experiment was laid out factorially in a complete randomized design (CRD) with three replicates in each polythene bag without treatments. Perforated polythene bags (18 × 9 cm) were filled with 6 kg sandy-loam soil, and were spaced at a distance of 10cm apart between the rows. Three seeds from each genotype were then planted per bag without in three different rows. Thinning was later carried out to leave one healthy plant per pot at two weeks after planting. Standard cultural practices such as proper weeding and watering of plants were also carried out.

2.3 Data Collection and Analysis Data were collected after planting at 14days interval on each replicate for a particular genotype. Data on the following growth characters were taken: Plant height, Stem height, Leaf width, Leaf length and Number of leaves. These were measured using a meter rule in centimeter (cm), except number of leaves which was determined by counting. Data collected were subjected to analysis of variance (ANOVA) using SPSS, version 16.0. The model for analyses of variance included genotype, replicate, weeks after planting. The means were separated by Duncan's multiple range test at 5% level of probability, while Pearson correlation co-efficient was also done to establish relationship among the characters.

3. RESULTS

3.1 Mean Square of Genotype, Replicate and Different Growth Stages for Morphological Characters of Maize

The results from Table 1 shows that the weeks after planting was highly significant (p<0.01) for plant height, stem height and number of leaves but non-significant for leaf width and leaf length, while the genotypic effect was highly significant for plant height, stem height, leaf width and leaf length and number of leaves.

3.2 Effect of Growth Stages on Morphological Characters of Maize

The plant height and stem height are significantly higher at 8 weeks after planting (WAP) with 71.06 cm


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and 48.03 cm, respectively than other growth stages (Table 2). The leaf length (50.86 cm) was the highest at 2 WAP, while the highest number of leaves (8.21) and leaf width (3.97 cm) were recorded at 4 WAP. The 4, 6 and 8 WAP for plant height, stem height, leaf width and number of leaves were not significantly different from one another, while the leaf length at 2 WAP was significantly different from other weeks, but significant differences did not exist between 6 and 8 WAP. The leaf width was not significantly different from each other for all the weeks. 3.3 Genotypic Variation in Morphological

Characters of Maize The plant height and stem height of EVDT.Y200STRQPM were significantly (p<0.05) higher and different from other genotypes (Table 3). TZE-QR2DTSTRQPM and 2009TZE-ORIDTSTRQPM genotypes were not significantly (p>0.05) different from each other, but different from TZEI 22, TZEI 98 and OBANTAPA, as well as TZEI 4, TZEI 161, BODIJA and EVDT-W99STR, OJO, 98SYNWECSTRQPM which were not different from one another, but significantly different from TZYBPDTSTRQPM. The stem height for TZE-QR2DTSTRQPM, 2009TZEORIDTSTRQPM, TZEI 22, TZEI 98, OBANTAPA and TZEI 161 genotypes were not significantly different from each other, but different from TZEI 25, TZEI 4 and BODIJA which are not significantly different from each other. EVDT-W99STR, OJO and 98SYNWECSTRQPM did not produce significant effect from each other, but significantly different from TZYBPDTSTRQPM. The TZEI 98, 2009TZEORIDTSTRQPM and EVDT.Y200STRQPM genotypes were significantly higher but different for leaf width, leaf length and number of leaves than other genotypes. There is no genotypic difference among EVDT.Y2000STRQPM, TZEYDTSTRQPM, TZE-QR2DTSTRQPM and TZEI-22 as well as OBANTAPA, TZEI 25 and TZEI 4 for leaf width, while similar effect was observed for

BODIJA and OJO markets. The leaf length of TZEYDTSTRQPM, TZE-QR2DTSTRQPM, TZEI 98, TZEI 25, TZEI 4, BODIJA and OJO produced similar genetic effect different from TZEI 161, EVDT-W99STR and 98SYNWECSTRQPM as well as EVDT.Y2000STRQPM and OBANTAPA. The genotypic effect for number of leaves per plant was not significantly different in nine genotypes, while TZEI 161 and OJO as well as EVDT-W99STR and 98SYNWECSTRQPM had genetic similarities. 3.4 Correlation Co-efficient of Five

Morphological Characters, Genotypes and Growth Stages of Maize

The results in Table 4 show that stem height was highly significant and positively correlated with the plant height (p<0.01; r = 0.91). The leaf length was highly significant and positively associated with plant height (r = 0.72), stem height (r = 0.53) and leaf width (r = 0.83), while the number of leaves was positively related with plant height (r = 0.87), stem height (r = 0.75), leaf width (r = 0.87) and leaf length (r = 0.73). The plant height was positive and strongly correlated with stem height, leaf width, leaf length and number of leaves with (p<0.01; r = 0.91, 0.87 and 0.72). There was no association between plant height and genotypes. Again, the leaf length and number of leaves were strongly related with leaf width (p<0.01; r = 0.83 and 0.87) respectively. The genotype was negative and non-significantly related with plant height (r = -0.22), stem height (r = -0.15), leaf width (r = -0.24), leaf length (r = -0.17), number of leaves (r = -0.19) and growth stages. 4. DISCUSSION The growth stages and genotypes which recorded high significant effect on most of the morphological characters is an indication of variability which is a key to crop improvement. This conforms to [4] who had reported significant amount of variability for different morphological traits in maize genotypes and also reported significant genetic differences for

Table 1. Mean square of genotype, replicate, weeks after planting of five morphological characters of

maize

Source of variation Df PH SH LWD LL NL Year 2 10.11 ns 3.21 ns 1.17ns 8.31ns 1.22 ns Replicate 2 307.49ns 153.85ns 0.17ns 88.02ns 4.26ns

Weeks after planting 3 4210.96** 9034.21** 2.27ns 938.51ns 71.31** Genotype 15 4069.67** 2933.30** 8.20** 1046.31** 29.81**

Error 171 619.47 421.40 1.88 264.74 6.67 Total 192 700.22 833.67 4.92 300.19 23.64

PH-Plant height, SH-Stem Height, LW-Leaf width, LL-Leaf length, NL-Number of leaves ** P< 0.01 highly significant,*P< 0.05 significant


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Table 2. Effect of growth stages on five morphological characters of maize

Weeks after Planting PH(cm) SH(cm) LW(cm) LL(cm) NL 2 50.89b 19.56b 3.49a 50.86a 5.48b 4 69.19a 46.57a 3.97a 45.67ab 8.21a

6 68.13a 46.27a 3.71a 40.40b 7.50a

8 71.06a 48.03a 3.92a 43.34b 7.83a

PH-Plant height, SH-Stem Height, LW-Leaf width, LL-Leaf length, NL-Number of leaves Means with the same letter in the same column are not significantly different at P< 0.05 using Duncan’s Multiple Range

Test (DMRT)

Table 3. Genotypic variation in five morphological characters of maize

Genotypes PH(cm) SH(cm) LW(cm) LL(cm) NL 1. EVDT.Y2000STRQPM 1.01a 75.04a 4.52abc 51.58abc 9.17a 2. TZEYDTSTRQPM 86.26ab 68.38ab 4.48abc 50.92abcd 6.92abc

3. DMRESRWQPM 85.19abc 56.28bc 4.70ab 53.64ab 8.5ab 4. TZE-OR2DTSTRQPM 77.74bcd 39.85cd 4.18abc 44.94abcd 8.17ab

5.2009 TZE-ORIDTSTRQPM 74.06bcd 40.39cd 4.07abcd 58.69a 8.5ab

6. TZEI 22 71.44bcde 44.29cd 4.50abc 42.73bcd 8.00ab

7. TZEI 98 66.23bcde 37.30cd 4.85a 46.45abcd 8.33ab

8. OBANTAPA 64.02bcde 43.43cd 3.83abcde 51.73abc 7.67ab

9. TZEI 25 62.39cde 34.72d 3.93abcde 47.43abcd 7.58ab

10. TZEI 4 61.74de 34.38d 3.73abcde 45.20abcd 8.75ab

11.TZEI 161 61.43de 39.51cd 3.28cde 36.00cd 6.58bc

12. BODIJA 56.78de 33.02d 3.45bcde 49.21abcd 7.83ab

13. EVDT-W99STR 48.83e 29.22de 2.72ef 37.50cd 5.25cd 14. OJO MARKET 48.43e 27.40de 3.49bcde 49.68abcd 6.42bc

15. 98SYNWECSTRQPM 47.68e 25.78de 2.84def 36.00cd 5.00cd

16. TZYBPDTSTRQPM 23.73f 12.71e 1.78f 19.55e 3.42e

PH-Plant height, SH-Stem Height, LW-Leaf width, LL-Leaf length, NL-Number of leaves per plant Means with the same letter in the same column are not significantly different at P> 0.05 using Duncan’s Multiple Range

Test (DMRT) Table 4. Correlation co-efficient of five morphological characters, genotypes and growth stages of maize

PH(cm) SH(cm) LW(cm) LL(cm) NL REP WAP SH(cm) 0.91** LW(cm) 0.87** 0.73**

LL(cm) 0.72** 0.53* 0.83**

NL 0.87** 0.75** 0.87** 0.73**

WAP 0.22ns 0.35* 0.08ns -0.17ns 0.231ns 0.00ns Genotype -0.22ns -0.15ns -0.24ns 0.005ns -0.19ns 0.00ns 0.00ns

PH-plant height, SH-stem height, LW-leaf width, LL-leaf length, NL-number of leaves, REP-replicate, WAP-week after planting *, ** significant at P < 0.05 and P < 0.01respectively ns= non-significant

morphological characters of maize genotypes. The reason for the observed differences in the morphological characters at different weeks after planting might be due to the variation in their genetic makeup [4,10]. These results are in agreement with those obtained by [4] who had reported significant amount of variability for different morphological traits in maize genotypes. [4] also reported increased performance of heterogeneous populations over those resulted from selfing. Therefore, the differences observed for morphological characters in maize

genotypes might be due to genetic variations among the hybrids. This supported the findings of [11] who observed similar results on genetic differences for plant height among different maize hybrids. The morphological variation in the expression of the characters however, could be due to the contributions of genotype, environment and their interactions. The genotypic variation measures the extent of genetic variability in a crop species, and also quantifies the extent of variability in different characters [12].


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Correlations studies revealed the positive associations of plant height with stem height, leaf length and leaf width, and contributed significantly to the production of number of leaves as similarly observed by [13-16]. The variation in morphological characters is essential for selection in maize breeding [15,17]. The maize improvement programme is dependent not only on the amount of genetic variability present in the population, but also on the extent to which it is heritable, which sets the limit of progress that can be achieved through selection [4,18-21]. 5. CONCLUSION The maize genotypes evaluated exhibited variability for most of the traits. The morphological characters could be encouraged for further selection in improvement of maize breeding in Nigeria. The findings from this research show genetic variability among the studied germplasm. Values and data recorded are representatives of these genetic variants, and could be used as reference in similar studies. However, further investigation is needed to examine the contributions of environmental interaction to the performance of maize genotypes. COMPETING INTERESTS Authors have declared that no competing interests exist. REFERENCES 1. Food and Agriculture Organization of the

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