Relationship Among Specific Combining Ability And Genetic Distance And Heterosis In Hybrid Rice

The studying and utilization of heterosis are the foundations of hybrid rice development. With the widespread application of crop heterosis, the point of how fast and accurate to predict heterosis has become the focus for breeders to care about and devotes to. But the traditional study methods have a lot of limitations, which make it difficult to predict heterosis. The development of molecular markers provides a new means to predict heterosis, and have effectively improved the efficiency of breeding. In this study, the hybrid rice heterosis were studied based on special combining ability (SCA) and yield-related SSR markers of functional genes, respectively; the correlations of heterosis with SCA and genetic distance (GD) were analyzed; and the possibility of forecast rice heterosis by SCA and GD were discussed. The results summarized as follows:1.Correlations of specific combining ability with heterosis and genetic distance in hybrid riceThe genetic difference of nine three-line hybrid rice were analyzed based on SSR molecular markers, the correlation of SCA with heterosis and GD were studied combined with yield performance of 20 hybrid crosses (5X4 NCII). The results indicated that the correlation of yield SCA with control heterosis (r1=0.5609*) and average heterosis (r2=0.541*) were significant, but insignificant between SCA and GD (r=0.2143). Thus, the heterosis can be reflected by SCA; the hybrid parents selected in this study can be used to breed strong superiority combinations; but the SCA can not be reflected by GD, the correlation of which needs further study.2. Correlation between genetic distance of SSR markers of functional gene and heterosis in riceThe genetic distance of 29 rice parents was tested based on 41 yield-related SSR markers of functional gene. The correlation between GD and heterosis of 47 crosses was studied. The results showed that:A total of 105 alleles gene among 29 materials were detected using 41 SSR markers of functional gene. The number of alleles per locus ranged from 2 to 4, with an average of 2.56 alleles per locus. The PIC changes from 0.12 (RM262) to 0.66 (RM252) and the average was 0.40. Cluster analysis indicated that all of the 29 materials could be divided into two classes at GD 0.60, which was coincident with the results of the genealogist analysis. The results indicated that the PIC of 41 SSR markers of functional gene selected in this study was higher and the genetic diversity of 29 materials was bigger. So, SSR markers could be efficiently used for measuring genetic diversity.The correlation between SSR genetic distance of functional gene and actual yield heterosis was significant(r=0.29*), but insignificant between GD and other heterosis (number of effective tiller per plant, NETP; seed setting percentage, SSP; 1000-grain weight, TGW; filled spikelets per panicle, FSPP; theoretical yield, TY; and actual yield, AY), which indicated the possibility of forecasting heterosis by SSR markers of functional gene. But the correlation coefficient obtained in this study was too small to predict heterosis, the correlation between genetic distance and heterosis needs further study.