Study of the effect of Hd1-harboring genomic region on heading date in rice

Transition from vegetative to reproductive stage in rice plays a vital role in regulation of timing of flowering and is one of its adaptation related traits to different cultivation areas or different cropping seasons. Several genes related to heading date were identified in rice, that Hd1 on the 6th rice chromosome is one of the most important ones. In this study, two rice cultivars including Sadri (as early flowering donor parent) and Neda (as late flowering recipient parent) were crossed to investigate the effect of Hd1-harboring genomic region on rice heading date, and BC2 generation was developed with two times of backcrossing. Then a single heterozygote plant in BC2 generation was self-pollinated to obtain BC2F2 population for conducting phenotypic and molecular studies. The studied population had a continuous phenotypic distribution in heading date and some individuals in the population showed transgressive segregation over late flowering parent. On the basis of an InDel region in first exon of Hd1 gene a functional specific marker was designed which produced a distinct different banding pattern among the cross parents. Hence, this marker was used toevaluate allelic pattern of Hd1 in BC2F2 population. Analysis of allelic segregation revealed that Hd1 locus in the studied population followed from the expected Mendelian segregation (with 1:2:1 ratios). Composite interval mapping (CIM) with microsatellite markers showed that genomic region at Hd1-RM527 interval had a high relationship (LOD>7.5) to heading date and explained nearly 28 percent of phenotypic variation of the trait. Additive effect of the donor parent allele on the trait was negative and was estimated nearly -3.4 days. Results of this investigation indicated that Hd1 had a significant effect on heading date in rice and it is possible to use the newly developed functional marker in this research for tracing the Hd in segregating populations and marker-assisted selection (MAS) for early maturity.