Identification And Inheritance For Early Fixation In Hybrid Rice (Oryza Sativa L.)

Since rice breeding changed from the conventional to the hybrid, rice production and quality have been increasing greatly, and the green revolution was brought about. Rice hybrid breeding needs "CMS" or "PGMS/TGMS" system, seeds production is complicated, and hybrid seeds can only be used once. To breed a hybrid is time-and labour-consuming. Most breeders have taken great effects to explore a way to simplify the process of hybrid breeding, pajticularly in the study on apomixis, and some progresses have also been made, but the apomixis has not been utilized in rice breeding. It is likely that there will be a very long time for apomixis to be used in rice breeding. Stability in early generation (p2 or F1 generation) was observed recently in hybridization in rice. The early genotypes were fixed, and the true breeding hybrid can be used by farmers. So its mechanisms are important for breeders. This study mainly analyzed two early stable populations derived from the same maternal parent and the inheritance for early fixation of diploid rice 429, 430, 950, 942, 966 and 85-15. The main results are summarized as below1 The Analysis of the Two Early Stable Populations Derived from the Same Maternal ParentDB102, a spontaneously mutational triploid, was used as maternal parent to cross with two diploid rice Taiping 369 and Zhongzuo59 respectively. Two ? populations, 718 population and 736 population were obtained. The ? progenies of these two populations were uniform, and the coefficient of variation (CV) of plant heights, length of panicles, days to heading, numbers of productive panicle, 1000-grain weights of the two populations were smaller than or near to that of control variety Shanyou63. SSR analysis showed that both of the two populations inherieted from their parents, so both progenies were true hybrid. In addition, the genotype of F2 and F3 of the two populations were homozygous, and the two populations should be early stable populations.Although 718 and 736 populations were derived from the same maternal parent,their paternal were different. They had different genetic background from different paternal parent, and 24 SSR loci produced poplymorphic bands between them. The phenotype of the two populations were observed the same, as if they were from one combination, so gene silencing was prabable to have happened in the two populations, or these loci didn't affect the expression of genes nearby.2 The Analysis of Inherited Characteristics of Stability in Early Generation in Rice429, 430, 942, 966, 950 and 84-15 are all early stable diploid rice, they were used to cross with other common diploid rice. In according to the analysis of agronomic traits and SSR, it was found that only the F2 population of 429 9311 was stable in early generation,none of the other F2 populations were stable in early generation. The characteristics of stability in early generation was probably inherited in the cross of 429X 9311, but it was not probably inherited in other crosses. All these indicated that the phenomina of stability in early generation might be controlled by some genetic factors, and these factors were likely to be existed in some rice, but the factors were complex,...