Mapping Of Fertility-restoring Genes For Yinshui Cytoplasmic Male Sterility And Gold Hull And Internode Gene In Rice (Oryza Sativa L.)

Fertility-restoring genes are bases for application of rice heterosis and of great significance in breeding of three-line hybrid rice. Elucidation of the gold hull and internode gene will accelerate the mechanized production of three-line hybrid rice seeds and enhance quality rice breeding programs.R68 was an Yinshui cytoplasmic male sterility (CMS) restorer line with gold hull and internode trait developed by China National Rice Research Institute (CNRRI). A population consisting of three hundred and eighty nine plants obtained from more than 2000 F₂ population of the cross between Yinshui CMS line Zhong9A and restorer line R68, was used for inheritance study. A total of 82 excessive sterile lines were selected from Zhong9A/R68 F₂ population to map the fertility-restoring (Rf) gene by bulked-extremes and recessive class analysis method. Four hundred and thirteen pairs of SSR primers, which distributed on 12 chromosomes, were screened for polymorphisms between the parents and between two bulks. The result showed that RM283 on chromosome 1 and RM5756, RM258, RM6100, RM171 on chromosome 10 were found to be polymorphic between the parents and between the two gene bulks. Ten highly fertile and ten highly sterile lines were selected from F₂ population of Zhong9A/R68 to screen the gene bulks. The results indicated that the five SSR markers might be linked to fertility-restoring genes. Then a total of 82 excessive sterile lines were used to estimate the genetic distance between five SSR markers and fertility-restoring genes respectively. Genetic analyses were carried out for gold hull and internode gene with three hundred and sixteen plants selected from Zhong9A/R68 F₂ population. In addition, a total of 75 gold hull and internode plants were used as the mapping population,, Relying on simple sequence repeat (SSR) markers and bulked segregate analysis (BSA) method. Further four hundred and thirteen pairs of SSR primers, which distributed on 12 chromosomes, were screened for polymorphism between Zhong9A and R68, Using the SSR markers demonstrating polymorphism between the parents, a total of 75 gold hull and internode lines were screened for SSR marker that co-segregate with gold hull and internode phenotype, The genetic distance between SSR markers and gold hull and internode gene, respectively was estimated and the main results listed as follows:Classical genetic analysis revealed that two dominant genes in R68 control fertility restoration of Yinshui CMS line. Meantime, molecular mapping indicated that RM283 located on chromosome 1 was found linked to one Rf gene at a distance of 6.7 cM, and that the other Rf gene was mapped on the long arm of chromosome 10 flanked by RM 5756, RM258 and RM6100, RM171 at distances of 10.4, 8.0 and 2.4, 4.2 cM, respectively. Classical genetic analyses revealed that a recessive gene in R68 controls gold hull and internode trait, while the color of gold hull and internode plants from golden to light golden, indicated that some genes interact with gold hull and internode gene also control the trait. A gold hull and internode gene was mapped on rice chromosome 3 flanked by RM1230 and RM7000 on one side, as well as RM227 and RM514 on the other, at distances of 8.7 cM, 3.3 cM, 2.7 cM and 4.7 cM, respectively. Through contrast, the gene is different from the located gold hull and internode genes , it was believed that the gold hull and internode gene of R68 was the first mapped gold hull and internode gene on rice chromosome 3 and was designated tentatively as gh5. Elucidation of this gene laid a firm foundation for marker-assisted selection (MAS) and for further fine-scale mapping of this gene. Moreover, it will provide original materials for mechanized production of three-line hybrid rice seeds and functional rice breeding programs.