Euphytica 23 (1974) 219-224

A STUDY ON HETEROSIS IN RICE (ORYZA SATIVA L.)’

S. S. SAINI, ISH KUMAR and M. R. GAGNEJA

Department of Plant Breeding, Punjab Agricultural University, Ludhiana, India

Received 8 September 1973

SUMMARY

Heterosis for yield and four yield components, viz. panicle number per plant, panicle length, spikelet per panicle and lOOO-grain weight, was studied in fifteen crosses involving six varieties of rice, Uryza sutiva L. Positive and significant heterosis for yield was observed in 11 and 8 crosses, over the mid- parent and the better parent, respectively. Hamsa x Hybrid 27 gave the highest heterosis both over the mid-parent (156.23 %) and the better parent (136.38%) followed by Jaya x Norin 18 with respec- tive values of 155.18 and 56.29%.

As compared with the average yield of 36.54 g per plant of the high yielding commercial variety, viz. Jaya hybrids in 8 crosses gave significant higher yield and four crosses, viz. Hamsa x Hybrid 27, Hybrid 27 x Jhona 349, Jaya x Palman 579 and Jaya x Hybrid 27, gave 80.51, 66.56, 57.11 and 56.30 g per plant, recording an increase of 120.33,82.13,56.29 and 54.08 %, respectively. The heterosis for yield was due to simultaneous heterosis for a number of yield components. The possibility of hybrid crop production as compared with the recently developed high yielding rice varieties has also been discussed.

INTRODUCTION

Although heterosis for yield in rice has been reported to vary from 9.0 to 186 % (NAGAI, 1958), the difficulties involved in hybrid seed production had till recently impeded the utilisation of this phenomenon. The recent discoveries of cytoplasmic male sterility and a genie fertility restoration system in rice (SHINJYO & OMURA, 1966; SHINJYO, 1969; ERICKSON, 1969; ATHWAL & VIRMANI, 1972)supportthe economical production of hybrid seed. This has stimulated the interest of rice breeders for the ex- ploitation of hybrid vigour. Before undertaking the commercial production of a hybrid crop, against the recently developed high yielding varieties, like IR 8 and Jaya, with a yield potential of over 10 tons per hectare, it is necessary to determine the maximum degree of heterosis attainable and the specific combination of parents for this purpose. The present study reports on the extent of hybridvigour for yield and yield compo- nents in 15 crosses involving four short statured high yielding varieties and two tall indigenous varieties of rice.

MATERIALS AND METHODS

Six rice varieties were crossed in all possible combinations. The characteristic features of the varieties are:

1 Contribution No. 73.15 from the Department of Plant Breeding, Punjab Agricultural University, Ludhiana, India.

Euphytica 23 (1974) 219

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Table 1. Mean performance of mid-parent (P), better parent (BP), FIs and expression of heterosis (per cent) for yield and yield components in crosses of six rice varieties.

Cross Panicles per plant

P BP Fl heterosis percentage

Jaya x Hamsa Jaya x Pal. 579 Jaya x Norin 18 Jaya x Hyb. 27 Jaya x Jh. 349 Hamsa x Pal. 579 Hamsa x Norin 18 Hamsa x Hyb. 27 Hamsa x Jh. 349 Pal. 579 x Norin 18 Pal. 579 x Hyb. 27 Pal. 579 x Jh. 349 Norin 18 x Hyb. 27 Norin 18 x Jh. 349 Hyb. 27 x 349

CD. 5% C.D. 1%

12.60 13.51 8.68

12.83 14.35 13.12 8.29

12.44 13.95 9.20

13.35 14.86 8.52

10.03 14.18

P BP

13.00 15.39 22.86 19.08 14.03 18.68 38.27** 33.14** 13.00 16.70 92.40** 28.46* 13.00 13.83 7.79 6.38 15.70 14.33 -0.14 -8.73 14.03 21.37 62.88** 52.32** 12.21 15.23 83.72** 24.73 12.67 20.75 66.80** 63.77** 15.70 18.12 29.89** 15.41 14.03 24.11 162.07** 71.85** 14.03 20.89 56.48** 48.90** 15.70 23.37 57.27** 48.85** 12.67 17.70 107.75** 39.70** 15.70 16.73 66.80** 6.56 15.70 18.25 28.70** 16.24

2.90 3.35 3.82 4.41

Crosc lOOO-grain weight

P BP F1 heterosis percentage

P BP

Jaya x Hamsa 26.55 27.93 28.92 8.93** 3.54 Jaya x Pal. 579 24.99 27.93 27.80 11.24** -0.46 Jaya x Norin 18 27.76 27.93 23.35 -15.89** -16/W** Jaya x Hyb. 27 27.14 27.93 32.08 18.20** 14.86** Jaya x Jh. 349 26.09 27.93 32.12 23.11 ** 15.00** Hamsa x Pal. 579 23.61 25.17 26.08 10.46** 3.62 Hamsa x Norin 18 26.38 27.58 27.78 5.31* 0.72 Hamsa x Hyb. 27 25.76 26.35 29.81 15.72** 13.13** Hamsa x Jh. 349 24.71 25.17 29.02 17.44** 11.53** Pal. 579 x Norin 18 24.82 27.58 25.28 1.85 -8.34** Pal. 579 x Hyb. 27 24.20 26.35 27.17 12.27** 1.031 Pal. 579 x Jh. 349 23.15 24.25 27.98 20.86** 11.54** Norin 18 x Hyb. 27 26.96 27.58 29.28 8.60** 6.16** Norin 18 x Jh. 349 25.92 27.58 30.07 16.01** 9.03** Hyb. 27 x Jh. 349 25.30 26.35 28.37 12.13** 10.77**

-- C.D. 5 % 1.18 1.35 C.D. 1% 1.55 1.78

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Panicle length Spikelet number -

P BP F1 heterosis percentage P BP FI heterosis percentage

24.16 24.49 26.20 8.44** 8.44** 185.31 207.20 219.20 18.49** 5.97 24.01 24.19 27.29 13.66** 12.82** 196.46 207.20 237.60 20.49** 14.67** 21.95 23.83 26.28 15.17** 6.08** 149.21 207.20 247.96 65.96** 19.67** 23.66 23.23 26.30 11.16** 13.22** 207.41 207.62 239.08 15.27** 15.15** 24.07 24.30 27.03 12.30** 11.23** 193.36 207.20 211.90 9.65 2.27 24.34 24.49 27.30 12.16** 11.47** 174.58 185.72 211.86 21.35** 14.07** 22.28 24.49 25.13 12.79** 2.61 127.53 185.72 202.50 58.79** 9.04* 23.99 24.49 26.93 12.26** 9.96** 185.52 207.62 237.75 28.15** 14.51** 24.40 24.49 24.65 1.02 0.65 171.48 179.52 194.88 13.64** 8.56 22.14 24.19 27.21 22.90** 12.48** 138.68 185.72 193.90 39.82** 4.40 23.84 24.19 26.88 12.75** 11.12** 196.67 207.62 199.31 1.55 -3.81 24.25 24.30 26.18 7.96** 7.74** 182.62 185.72 210.73 15.39** 14.47** 21.79 23.49 26.82 23.08** 14.18** 149.62 207.62 216.77 44.88** 4.41 22.19 24.30 26.69 20.28** 9.84** 135.58 179.52 197.79 45.89** 10.18* 23.90 24.30 26.12 9.29** 1.49** 193.57 207.62 195.21 0.85 -5.98

P BP P BP

0.84 0.98 14.35 16.56 1.11 1.29 18.89 21.80

Yield per plant

P BP F: heterosis percentage

32.60 36.54 50.43 54.69** 38.01** 38.01 31.08 36.54 53.54 72.27** 46.52** 46.52 22.38 36.54 57.11 155.18** 56.29** 56.29 35.30 36.54 56.30 59.49** 54.08** 54.08 35.94 36.54 35.38 -1.56 -3.17 -3.17 27.13 28.66 55.10 103.10** 92.25** 33.68 18.44 28.66 34.67 88.02** 20.97 -5.12 31.36 34.06 80.51 156.73** 136.38** 120.33 32.00 35.35 2.99 -90.66** -91.54** -122.21 16.91 25.61 34.22 102.37** 33.62 -6.35 29.83 34.06 40.66 36.31; 19.38 11.28 30.41 35.35 33.77 10.79 4.47 -7.59 21.14 34.06 45.69 116.13** 34.15** 25.04 21.78 35.35 26.76 22.87 -24.30 -26.76 34.70 35.35 66.55 91.81** 68.26** 82.13

P BP

increase in yield over ‘Jaya’ (in %)

8.35 8.82 10.99 11.61

Euphytica 23 (1974) 221

S. S. SAINI, ISH KUMAR AND M. R. GAGNEJA

Jaya- Evolved a<Hyderabad (India) from a cross T(N)1 x T 141. It is a semi-dwarf high yielding variety with short, bold grains and has a yield potential of more than 10 tons per hectare. Hamsa - Evolved in Andhra Pradesh (India) from a cross HR12 x T(N)I. It is a semi- dwarf variety with fine, long, slender grains. Palman 579-Evolved at IRRI (Philippines) from a crossIR8 x Tadukan and acclima- tised in Punjab. It is a short statured variety with long, slender grains. It has good tillering capacity. Norin 18-A juponica variety introduced in the Kangra Hills of erstwhile Punjab in 1951. Hybrid 27-Evolved in-Punjab from an in&a x Juponica cross, Jhona 349 x Rikku 132. It has tall plants with somewhat stiff straw. Jhona 349-A tall indigenous variety developed by pure line selection.

Twenty-one entries including six parents and 15 F,s were grown in a randomized block design with three replications. Each plot consisted of one row of 10 single plants, transplanted at 40 cm and 30 cm between and within rows, respectively. A non- experimental strip of 4 rows was transplanted all round the experimental area of to prevent border effects. The crop was grown under high level of fertility, i.e. 100: 50: 50 NPK kg/ha. Observations were recorded on all the 10 experimental plants in a row for yield and four yield components, viz. panicle number per plant, length of the leading panicle (cm), number of spikelets on the leading panicle and 1000 grain weight (g). The plant yield and lOOO-grain weight were recorded after drying the grains to 14% moisture. To test the performance of F1 hybrids, heterosis was calculated over both the mid parent and the better parent.

RESULTS

Mean values of mid parent (‘p>, better parent (BP), F,s, heterosis over mid parent and better parent are presented in Table 1. The yield of the F,s was also compared with that of Jaya and the increase in yield (%) is given in the last column under yield in the same table. 1. Panicle number per plant. In 12 combinations F, hybrids produced significantly more panicles per plant than their mid parents. The extent of heterosis varied from -0.14 % (Jaya x Jhona 349) to 162.07 % (Palman 579 x Norin 18). In eight crosses the F1 hybrids significantly exceeded their better parent, with a maximum increase of 71.85% in Palman 579 x Norin. 2. Panicle length. In 14 cross combinations the panicle length significantly outdid the mid parent and in 13 cases the better parent. The maximum increase over mid parent and better parent was 23.08 and 14.18 %, respectively, both in Norin 18 x Hybrid 27. 3. Spikelets per panicle. Significant heterosis over mid parent and better parent was observed in 12 and 8 cross combinations respectively. The range of heterosis was from 0.85 to 65.96 % over the mid parent and from -5.98 to 19.67 % over the better parent. The highest heterosis was observed in Jaya x Norin 18 over both mid parent and better parent. 4. IOOO-grain weight. In 13 cross combinations the F1 hybrids exhibited significant increase over their mid parent. The highest value (23.11%) was in Jaya x Jhona 349. The only cross in which there was significant decrease in lOOO-grain weight was Jaya x

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Norin 18. In eight crosses significant increase over better parent was observed, and the highest increase of 15.0 % was in Jaya x Jhona 349, followed by Jaya x Hybrid 27 with 14.87 ‘A increase. 5. YieZd per plant. Significant heterosis over mid parent was observed in 11 cases in a positive direction and in one case in a negative direction. The maximum heterosis of 156.73 % was observed in Hamsa x Hybrid 27 followed by Jaya x Norin 18 with 155.18 % heterosis. The F, hybrids also excelled their better parent in eight cross com- binations. The highest increase over better parent was again observed in Hamsa x Hybrid 27, to the extent of 136.38%. In the cross, Hamsa x Jhona 349, a significant decrease of 9 1.54 % in yield was noticed.

The comparison of F1 hybrids with the highest yielding commercial variety, Jaya, was also made to assess the actual superiority of F, hybrids. The values given in the last column under yield in Table 1 indicate that nine cross combinations exhibited con- siderable increase over Jaya and the highest increase of 120.33 % was in Hamsa x Hybrid 27, followed by Hybrid 27 x Jhona 349 (82.13 %) and Jaya x Norin 18 (56.29 %).

DISCUSSION

Although rice has some advantages over wheat in hybrid breeding as its seed rate is lower, and it can be transplanted, ratooned and propagated by tiller separation (RICHHARIA, 1962), still heterosis in this crop could not be exploited commercially. The recent discoveries of a cytoplasmic male sterility and genie fertility restoration system in rice, reported by several workers (Shinjyo & OMURA, 1966; SHINJYO, 1969; ERICKSON, 1969; ATHWAL & VIRMANI, 1972) seem to solve this problem and producing hybrid seed on commercial basis at reasonably low costs may be feasible. Earlier ex- periments on heterosis in rice were conducted for academic studies, and their results are of limited practical value.‘Although, heterosis for yield was reported to be as high as 186.0 per cent over the better parent (KADAM et al., 1937), a new assessment of the phenomenon is necessary, especially when we possess varieties like IR 8 and Jaya with a yield potential of over ten tons per hectare. The results obtained in the present studies reveal that the increase in yield of F1 hybrids over the best commercial variety, Jaya, was in some combinations as high as 120.37 %, which suggests the feasibility of commercial hybrid crop production in rice.

The heterosis for yield was positive and significant in 11 and 8 combinations over the mid parent and the better parent respectively. Cross Hamsa x Hybrid 27 gave the highest heterosis of 136.38 % over the mid parent and 120.37 % over the better parent. The actual yield in this cross was the highest, i.e. 80.51 g per plant as compared with 36.54 g per plant in the case of highest yielding varieties, viz. Jaya. The next best cross was Hybrid 27 x Jhona 349, with a yield of 66.55 g per plant, which was higher than that of Jaya by 80.51%. Other crosses which out-yielded Jaya by over 50 % were Jaya x Norin 18 (56.29) and Jaya x Hybrid 27 (54.08).

The heterosis for yield in most of the cases was due to simultaneous heterosis for one or more components of yield, either over the mid parent or over both mid parent and better parent. Out of 15 crosses, the heterosis over the mid parent was positive and significant in 11, 14, 12 and 13 cases for panicle number per plant, panicle length, spikelet per panicle and lOOO-grain weight respectively. The corresponding figures for

Euphytica 23 (1974) 223

S. S. SAINI, ISH KUMAR AND M. R. GAGNEJA

heterobeltioses were 7, 13,8 and 8. In the case of Hamsa x Hybrid 27, which gave the highest yield per plant and also the highest heterotic values, there was significant heterosis for all four yield components studied even over the better parent. In the second best cross, i.e. Hybrid 27 x Jhona 349, significant heterosis was observed for panicle number, panicle length and lOOO-grain weight, over the mid parent, and for the last two characters also over the better parent. Heterosis for yield and yield com- ponents in rice has been reported by several workers (JONES, 1926; KADAM et al., 1937; CAPINPIN~PUNYASINGH, 1938; BROWN, 1953; ALIM&SEN, 1957; PILLAI, 1961; RAO, 1965; IRRI 1970).

Inspite of positive heterosis for the yield components, there was negative heterosis for yield in two cases over the mid parent and in four cases over the better parent and it was significant in the case of Hamsa x Jhona 349. This may be due to hybrid sterility, which may vary from cross to cross. In Hamsa x Jhona 349 which recorded the highest negative heterosis for yield 95% of the spikelets were sterile, and the average yield was only 2.99 g per plant as compared with 32.00 g and 35.35 g per plant in the case of mid parent and the better parent respectively.

With the introduction of efficient plant type varieties like IR 8, Jaya, IR 5, IR 20 etc. a breakthrough in rice production has been reported in some of the Asian countries (ATHWAL, 1970). The present studies indicate the possibility of another similar break- through in hybrid crop production, providing the hybrids reported to be the best, especially those of Hamsa x Hybrid 27 and Hybrid 27 x Jhona 349, maintain their yield potential under commercial conditions. Further, before releasing the rice hybrids their adaptability and quality should be tested and the economics of hybrid seed pro- duction worked out.

REFERENCES

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Philipp. Agric. 27 : 253-277. ERICKSON, J. R., 1969. Cytoplasmic male sterility in rice (Oryza sativa L.). Agron. Abstr. 1969:6. IRRI (Int. Rice Res. Inst.), 1970. Annual Report 1969. Los Batios Leguna. Philippines: 266 p. JONES, J. W., 1926. Hybrid vigour in rice. J. Amer. Sot. Agron. 18: 423. KADAM, B. S., G. G. PAUL & V. K. PATANKAR, 1937. Heterosis in rice. Ind. J. agr. Sci. 7: 118-125. NAGAI, I., 1959. Japonica rice - Its breeding and culture. Yokendo Ltd., Tokyo 843 pp. PILLAI, M. S., 1961. Hybrid vigour in rice. Rice News Letter 9(l): 15-17. RAO, G. M., 1965. Studies on hybrid vigour in inter-racial hybrids of rice (Oryza sativa L.) Andhra

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