Studies On The Combining Ability And Herbitability Of Agronomic Characters In Early Hybrid Rice

Two Dual-purpose Genie Male Sterile (DGMS) Lines, i. e., Zhu 1 S and 810S , Six Cytoplasmic genie Male sterile(CMS) lines, i. e., XinxiangA , Jin23A, FengyuanA, V20A, 316A and T98A and 12 Restorer Lines, i. e., R29, R402, R404, D34, D68, T0463, T0974, R28, R33, Zaohuil, ZaoSOO and Y055 were used. 96 early hybrid rice were made by way of incomplete diallete cross (NCII) design , 12 agronomic characters of the parents and their hybrids , i. e, Plant height .Panicle length .Productive tillers per plant, Maxium tillers per hill, Ratio of tillers to productive tillers, Filled spikelets per panicle, Spikelets per panicle, Seed setting rate, 1000-grain weight, Days to heeding, Theoretical grain yield per plant and Practical grain yield per plant were studied for evaluating the combining ability and heridity of these traits. The distinctness of combining ability between the DGMS lines and the CMS lines was characterized . Based on the study the value on utilization of the newly-bred seed parents and pollen parents was estimated so as to facilitate the development of early hybrid rice and its parents in the future. Via this study the following conclusions were obtained:1. General combining ability (GCA) and specific combining ability (SCA) were highly statistically significant as shown by variance analysis of all combinations, and GCA was greater than SCA, which showed the additive effect was more important than the non-additive effect for all of the agronomic characters. All characters were influenced greater by restorer line than by female sterile line except panicle length.2. There existed a positive correlation between GCA and parental values except maxium fillers per plants and seed-setting rate. However, correlationship between GCA and parental phenotypic value of only 2characters( spikelets per panicle and 1000-grain weight) was statistically significant, which indicated the relationship between GCA and parental phenotypic value was complex.3. The analysis on the relationship between GCA and SCA effects indicated that SCA had no bearing on GCA. And the correlations between GCA or SCA and F1 heterosis were statistically significant, but high SCA could not mean strong heterosis of combinations.4. The broad heritability of all characters analysed was high except spikelets per plant and seed-setting rate. The estimates of narrow heritability were descending in such order: 1000-grain weight, plant height, panicle length, productive tillers per panicle, seed-setting rate , spikelets per panicle, days to heading, theoretical grain yield per plant, practical grain yield per plant, panicle per plant, ratio of tillers to productive tiller , maxiurn tillers per plant.5. The phenotypic correlation coefficient, correlative heritability and relative selection efficiency of seed-setting rate, filled spikelets per panicle, plant height, ratio of tillers to productive tillers, panicle per plant were high with grain yield per plant. The genetic advance of comprehensive selection index equation constructed with filled spikelets per panicle and grain yield per plant was greatest, and all the relative efficiencies of selection index equation constructed with filled spikelets per panicle were high , which indicated filled spikelets per panicle was the important character in various indices for selecting grain yield per plant.6. Zhu 1 S, T98A and V20A were better than the other female sterile lines and R402, R404, T0463, T0974 and Y055 were the best among the restorer lines. The improved female sterile lines and restorers whose superior characters could compensate each other or with many superior characters should be chosen in early hybrid rice breeding.