Analysis Of Heterosis And Combining Ability On Indica-compatible Japonica Lines In Rice

In order to explore the inheritance of major agronomic traits in indica-compatible japonica lines, provided supportion of the breeding of indica-compatible japonica rice at the domain of yangzi river, and provide reference for hybrid rice breeding, hybrids made from 4 different photo-thermo- -sensitive genetic male sterile lines(PTGMS)and 15 different indica-compatible japonica lines(ICJL) in 4×15 incomplete diallel pattern were used in field trials in 2003 and 2005 respectively, to evaluate their plant height (PH), panicles per plant (PP), panicle length(PL), filled grains per panicle (FGP), spikelets per panicle (SP), seed setting rate (SSR), 1000-grain weight (GW), grains weight per plant (GWP)and pollen fertility(PF). The compatibility of 15 different ICJL was evaluated, and analysis was made on heterosis, simple correlation, combining ability and heritability of these traits. The main results were as follows:1. The compatibility between GX17, GX24, GX 35 and W9593S, GX 09, GX16, GX43 and GD-8S, and GX39, GX41 and japonica PGMS lines were relatively good. And the hybrids of ICJL with better compatibility often had higher heterosis. For example, W9593S/GX 35 showed exceptionally high heterosis.2. The average value of the F₁s showed (highly) significant positive heterobeltiosis in PH, PP, SSR, GW and GWP, and (significant) negative heterobeltiosis in the other characters. The highest heterobeltiosis appeared in PP and GWP. The GWP heterobeltiosis of GX07, GX09, GX35 and GX43 were positively significant at 1%level, and that of GX10 and GX13 were also positively significant at 5% level. While the GWP heterobeltiosis of GX16, GX17, GX24 and GX38 were negative but insignificant.3. Except for PH and PP, the average value of other traits showed significant or highly significant negative competitive heterosis. The lowest negative competitive heterosis appeared in FGP and SP. GX35 showed positive heterosis in GWP but did not reached 5% significant level. GWP competitive heterosis of GX7, GX17, GX38 and GX43 were negative and significant at 1%level, while GX39 and GX41 were negative and significant at 5% level.4. All the coefficients between PH and PL; PP and GWP; FGP and SP, SSR, GWP; GWP and SP, SSR were positively significant at 1% level, while the coefficients between PP and FGP, SSR; FGP and PL, GW, PF; GW and SSR, PF; GWP.and PF were positively significant at 5% level.5. GCA of GX09, GX10, GX35, GX24, GX19, GX25, GX38 and GX41 were relatively high, while the GCA of GX16 and GX43 were the lowest. Combinations of W9593S/GX35, N5088S/GX41, W9593S/GX24, N537S/GX39, GD-8S/GX13, GD-8S/GX07, N5088S/GX39, W9593S/GX19, N5088S/GX10, N537S/GX13, N5088S/GX38 and W9593S/GX16 showed high SCA in GWP.6. The three traits PH, PL and GW were mainly determined by GCA, which indicated the additive effect of genes, while the other traits, PP, FGP, SP, GWP, SSR and PF were greatly affected by SCA, which showed the non-additive effect.7. The correlation between GCA effect value and phenotypic value of parents was positive. Correlation of total GCA effect value of parents and phenotypic value of hybrid progeny was positively significant at 1%level. And correlation of SCA effect value and phenotypic value of hybrid progeny was also positively significant at 1%level.8. GCA and SCA are independent to each other. All the traits in hybrid rice are affected by both of GCA and SCA. Only those hybrids with high SCA and high GCA in both or one of the parents had high yield potential. Therefore, in hybrid rice breeding, to have parents with good GCA is the foundation, and the key is to develop new combinations with high SCA.9. The h_B² of seven traits PL, FGP, SR GW, GWP, SSR and PF were generally high, which means they were main determined by genotype effects. The order of the h_N² from high to low was as follows: GW＞PL＞SP＞PH＞SSR＞PP＞FGP＞GWP＞PF.