Zheng JiaKui

Correlations between specific combining ability,heterosis and genetic distance in hybrid rice

Hybrid rice breeding is the combining ability breeding. Screening hybrid rice combinations with high special combining ability (SCA) is able to breed strong superiority combinations with practical values. In this study, the genetic distances (GD) of nine three-line hybrid rice (5 CMS lines and 4 restorer lines) were examined using SSR markers. Based on yield performances of 20 hybrid crosses (5 x 4 NCII), the relationships between SCA, heterosis and GD were studied. The correlations of yield SCA with the control heterosis (r1=0.5609) and the average heterosis (r2=0.541) were significant, but not significant with GD (r=0.2143). Thus, the heterosis can be reflected by SCA; the hybrid parents selected in this study can be used to develop strong superiority combinations; but the SCA cannot be reflected by GD, which needs further study.

Effect of ecological environments on subspecies characteristics and economic traits in filial generations of cross between indica and japonica rice

Two recombinant inbred lines (RILs) populations, RILSA derived from the cross between “Zhongyouzao8” (indica) and “Toyonihiki” (japonica) rice cultivars, and RILSB derived from the cross between “Qishanzhan” (indica) and “Akihikari” (japonica) rice cultivars, were grown in Liaoning and Sichuan Provinces, China to understand the effects of ecological environments on the subspecies characteristics and economic traits in filial generations of cross between indica and japonica. The results showed that both the subspecies characteristics and economic traits changed significantly. The effects of ecological environments on Cheng’s index and six subspecies characteristics were different on the basis of populations or characteristics. The distribution of Cheng’s index in RILSA was japonicalinous in Liaoning and Sichuan. The distribution of Cheng’s index in RILSB approached to normal distribution in Liaoning, but it was japonicalinous in Sichuan. As a whole, the two populations were more japonicalious in Sichuan than in Liaoning. The panicle number, seed setting rate and per-thousand-grain weight were decreased significantly in Sichuan. The grain number per panicle showed no significant change. A significant positive correlation was found between Cheng’s index and the economic traits, including six subspecies traits. It suggested that the reason that the filial generation of cross between indica and japonica in northern China showed japonicanous subspecies characteristics might be the artificial selection by breeders on the economic traits. In addition, indica-japonica differentiation and the relationship with ecological environments were discussed.