Molecular Marker-Assisted Selection For Heterosis In Rice

The utility of heterosis is an efficient way to improve yield in rice. At present, however, the yield potential of rice new hybrid combinations is stagnant. The molecular marker-assisted breeding is an efficient way for making full use of genetic diversity, fine selection at molecular level and therefore, lead to higher yield potential of rice hybrids. The present research attempts to find out the relationship between parental genetic difference and heterosis of hybrids through molecular marker techniques, which provides help to molecular marker-assisted selection for rice heterosis.In this research, 12 indica rice parents were crossed by use of NCII design and 27 F1 hybrids were obtained, and Teyou 63, a most popular indica rice hybrid, was used as the control variety. Agricultural economic characters closely related with yield were recorded and analysed for their relationships with yields, and main factors contributing to yields were further analysed by partial correlation analysis and path coefficients analysis of hybrid performance and standard heterosis. The genetic differences among the parents were studied by RAPD and SSR molecular marker techniques. And the relationship between the closest factor related to yield and genetic distance was evaluated by partial correlation analysis. Results from the study showed filled seeds per panicle to be the most important factor among the major characters contributing to yield, followed by effect panicle number, and then the 1000-seed weight and panicle length. The correlation between filled seeds per panicle and RAPD marker genetic distance was not significant, while that between filled seeds per panicle and SSR marker genetic distance and that between filled seeds per panicle and RAPD-SSR genetic distance were very significant. The analysis of relationship between standard heterosis and parental genetic distance indicated the hybrids indicated positive increase of yield with parental genetic distances from 0.50 to 0.83 of SSRs or from 0.59 to 0.81 of RAPD-SSRs. These results showed that SSR molecular marker technique is superior to RAPD in parent selection for rice heterosis, and it is better to combine both RAPD and SSR molecular markers for the marker-assisted selection. The study results would provide valuable help to selection of hybrid parents by molecular marker-assisted selection in rice.