Assessment of Relationship of Hd5 and Hd6 with Heading Date in Local and Improved Rice Cultivars

In this research the relationship of functional SNP of Hd5 and Hd6 genes with heading date was investigated in rice. For this purpose, 45 local and improved rice cultivars were phenotypically evaluated in Gorgan condition, and were genotyped using primer pairs specific to the genes. Association analysis in total population showed that Hd5 SNP explained 4.8% of variations in heading date and its additive effect was estimated equal to 2.6 days. However, Hd6 SNP explained equal to 5.5 % of variations in heading date and its additive effect was estimated equal to -2.4 days. After subdividing the population into two local and improved groups association analysis showed that effect of Hd5 SNP on heading date of improved cultivars wasn’t significant. However, in local cultivars, the SNP explained a relatively high portion (16.2%) of variations in heading date and its additive effect was estimated equal to 4.4 days. Effect of Hd6 SNP on heading date wasn’t significant in local cultivars, but in improved cultivars the SNP explained a relatively high portion (17.6%) of variations in heading date and its additive effect was estimated equal to -3.8 days. On the basis of the results of this research it can be concluded that improving cultivars with earliness alleles of both Hd5 and Hd6 genes is possible.