Domestication and breeding selection in rice has extremalized threshability in modem cultivars of different subspecies.Low threshability retains more grains on the panicles especially in japonica and high threshability make easier for harvesting in indica.Although in previous reports,this trait were commonly regarded as quality traits,moderate threshability is still important in certain cultivar type of some areas,e.g.medium-mature japonica from the Lower Yangtze River.The genetic mechanisms underlying the quantitative variations especially moderate threshability remains largely unclear.