Comparisons Of Individual Heterosis And Population Heterosis Of Three Hybrid Rice Combinations In Rice (Oryza Sativa L.)

Rice hybrid heterosis phenomenon was mentioned firstly by Jones(1926)who used the plant density 30cm×90cm which was large for rice growing.So the hybrid heterosis was considered individual heterosis.Because of tillers in rice,high yield in rice was obtained by utilizing the population heterosis rather than the large individual heterosis.In this study,we used the split plot method of three factors including different water management(A factor,two levels),different density(B factor,four levels)and genotype(C factor,nine levels namely three F1 combinations and parents)to detect the individual and population heterosis of three combinations and ten traits of each combination and parents and compare the difference between population and individual heterosis in three hybrid F1 combinations.The main results are summarized as follows:1.The plant height,panicles number per plant,panicle length,number of spikelet per panicles,number of filled grains per panicles,setting rate,heading days,grain yield,biological yield and 1000-grain weight of the three hybrid rice combinations in parched field and normal field were not different significantly.2.Among the different densities,the changes of panicle number,grain number per panicle,full grain number per panicle and setting rate were decreaed as the increasing density.When the density was 30cm×90cm,the panicle length was longest,the plant height,1000 grain weight,grain yield and biomass production was smallest,respectively.And the heading days were shortest.When the density was 30cm×13cm,the plant height,1000 grain-weight,grain yield and biomass production were largest,respectively.3.For the mid-parent heterosis in individual heterosis,the mid-parent heterosis of panicle number and grain yield were affected significantly by different density.The mid-parent heterosis of grain number per panicle and full grain number per panicle were affected notably by different density.While the mid-parent heterosis of plant height,panicle length,setting rate,heading days,biomass yield and 1000 grain weight were not affected notable.When the density was 30cmx90cm,the mid-parent heterosis of plant height,panicle number,setting rate,1000 grain weight,grain yield and biomass yield was largest.When the density was 30cmx30cm,the mid-parent heterosis of grain number per panicle,full grain number per panicle and panicle length was largest.When the density was 20cm×17cm,the mid-parent heterosis of plant height,panicle number,grain number per panicle,full grain number per panicle,grain yield and biomass yield was smallest.For the over-parent heterosis in individual,the over-parent heterosis of panicle number was only affected significantly by different density and the other 9 traits were not affected significantly.When the density was 3 0cm x 90cm,the over-parent heterosis of panicle number,panicle length,setting rate,1000 grain-weight,grain yield and biomass yield was largest.When the density was 30cm×13cm,the over-parent heterosis of plant height,grain number per panicle,full grain number per panicle was largest.When the density was 20cm×17cm,the over-parent heterosis of plant height,grain number per panicle,full grain number per panicle,setting rate,1000-grain weight,grain yield and biomass production was smallest.4.For the maternal heterosis in the population,the maternal heterosis of grain yield was affected significantly by the different density and the maternal heterosis of biomass production was affected notably by the different density.For the maternal heterosis of grain yield in the differnert combination and the density in the population,the heterosis was largest but the density was smallest and the grain yield was not high.When the density was 30cm×13cm,the grain yield was largest in the three combinations but the maternal heterosis of grain yield was not highest.These results suggested that the high maternal heterosis of grain yield with large phenotype was valuable in the fact production.The maternal heterosis of grain yield was high but the utilization value was not always large.For the paternal heterosis in the population heterosis,the paternal heterosis of grain yield and biomass production were not affected notably by the different density.