Dominance complementation of Hd1 and Ghd8 contributes to extremely late flowering in two rice hybrids

摘要

A rice hybrid is the product of a cross between two genetically distinct inbred lines. Owing to yield heterosis in rice hybrids, hybrid rice breeding has been developed and widely used in agriculture. In some cases, the hybrid F(1)lines show extremely late flowering. However, the genetic basis of the phenomenon is not very clear. In this study, two hybrids were found to have heading date of similar to 130 days, which was much later than their inbred parents. To elucidate the underlying mechanism, mapping populations consisting similar to 2000 F-2 individuals were developed, and eight pools were created based on the flowering time of the F-2 individuals. Whole genome deep sequencing of the parental lines and the eight pools enabled the identification of two major loci underlying heading date, on chromosome 6 and 8, respectively. Follow-up PCR amplification and Sanger sequencing showed Hd1 (Heading date1) and Ghd8/DTH8 (Grain number,plant height and heading date 8) were probably the causal genes on the two loci. The female parent had the genotypeHd1(WT)ghd8(1bp-del)while the male parents had the genotype hd1(4bp-del)Ghd8(WT). Furthermore, genotypes of F-2 individuals at Hd1 and Ghd8 were investigated to estimate the genetic effects of different genotype combinations. The result showed that dominance complementation effects of the two genes leaded to extremely late flowering in the F(1)hybrid crosses with the genotype Hd1(WT/4bp-del)Ghd8(WT/1bp-del). Taken together, this study lays a foundation for further functional validation and breeding utilization of important flowering genes in genetic improvements of hybrid rice.