Control of Awn Length in Rice Breeding Programs in Hokkaido

Abstract Understanding genetic diversity is a primary goal of the molecular evolution of the genes. Awn length is a well-documented phenotype among domestication traits in rice, from long to short awn. In addition, awnlessness is favor for current rice farmers. Here, we identified the genetic basis of awn length during rice breeding programs in Hokkaido. We found variation of awn length ranging from 0.0 to 37.6 mm. Varieties with a short-awn or awnlessness have been selected under rice breeding programs. Genetic analysis on awn length identified that RAE1 and RAE2 on chromosomes 4 and 8, respectively, accounted for awning. These genes were well known to be significant during Asian rice domestication. Sequence variations of the genes would clarify the molecular evolution of the genes on awn length. Firstly, the loss-of-function allele in RAE1, rae1, was selected for short awn length. Then, alleles on RAE2, RAE2-H01 to RAE2-H04, were targeted for the selection of short-awn or awnlessness. The selections on awnlessness phenotype could diversify these alleles on the genes, RAE1 and RAE2, exhibiting the variation of awn length.