Assessment of Impact of Ehd1 and Ehd3 Genes on Heading Date in Rice Cultivars

Flowering time control is one of the most important components of interactions between plants and their growth environment that is a crucial factor not only for yield rate but also for rice grain quality. In this research phenotypic and molecular studies were conducted in 45 local and improved rice cultivars. Firstly polymorphism of Ehd1 and Ehd3 genes between the cultivars was studied and then the association of the two genes with heading date was investigated. Results of phenotypic studies indicated the existence of higher variation of heading date in local cultivars than that of improved cultivars. Local cultivars had on average 8 days earliness relative to improved ones, with being significant difference between their heading dates. Specific primers designed based on multiple alignments could detect polymorphism between different cultivars. Association studies showed that pooled population Ehd1 had a higher association with heading date than Ehd3 (12.1 vs. 5.4%) and their additive effects were estimated, respectively, 3.4 and 2.2 days. Regarding to quantitative nature of the studied trait and minor effects of the two genes on heading date, it can be concluded that when improving early-mature cultivars utilizing the two genes breeders might consider the roll of other genes and their interactions.