Molecular Genetic Variation And Adaptation Mechanisms Of Long-day Surpression Genes For Heading Date In Rice(Oryza Sativa L.)

Cutivated rice(Oryza sativa L.)was domesticated from O.rufipogon Griff.and widely distributes around the world.Increasing crop yield has always been one of the most important goals of scientific research,and improvement in crop productivity requires optimal flowering time for various geographical conditions.Rice varieties are domesticated to grow widely between 53° N and 40° S.Due to the remarkable adaptability to various environments,rice varieties with diverse flowering times have been domesticated or improved from Oryza rufipogon.Detailed knowledge of the genetic factors controlling flowering time will facilitate understanding the adaptation mechanism in cultivated rice and enable breeders to design appropriate genotypes for distinct preferences.In this study,four genes(Hd1,DTH8,Ghd7 and OsPRR37)in a rice long-day suppression pathway were collected and sequenced in 154,74,69 and 62 varieties of cultivated ricerespectively.Under long-day conditions,the varieties with nonfunctional alleles flowered significantly earlier than those with functional alleles.However,the four genes have different genetic effects in the regulation of flowering time:Hdl and OsPRR37 are major genes that generally regulate rice flowering time for all varieties,while DTH8 and Ghd7 only regulate regional rice varieties.Geographic analysis and network studies suggested that the nonfunctional alleles of these suppression loci with regional adaptability were derived recently and independently.Alleles with regional adaptability should be taken into consideration for genetic improvement.The rich genetic variations in these four genes,which adapt rice to different environments,provide the flexibility needed for the breeding of rice varieties with diverse flowering times.