Global rice production requires abundant fresh water consumption,but water shortage in many rice-growing areas is an everincreasing problem constraining rice production and causing significant yield loss.Based on their cultivation pattes and habits,rice varieties are classified into lowland and upland rice,which are cultivated in paddy fields and rain-fed regions without irrigation (e.g.,mountain areas),respectively.During long-term natural and human selection,upland rice has evolved with improved drought resistance for adaption to the drought-prone upland environments.However,the genetic and evolutionary mechanisms underlying the differentiation of upland rice from lowland rice,especially for drought resistance,remain unclear.