The use of alkaline salt lands for crop production is hindered by a scarcity of knowledge and breeding efforts for plant alkaline tolerance. Through genome association analysis of sorghum, a naturally high-alkaline-tolerant crop, we detected a major locus, (), specifically related to alkaline-salinity sensitivity. An allele with a carboxyl-terminal truncation increased sensitivity, whereas knockout of increased tolerance to alkalinity in sorghum, millet, rice, and maize. encodes an atypical G protein γ subunit that affects the phosphorylation of aquaporins to modulate the distribution of hydrogen peroxide (HO) These processes appear to protect plants against oxidative stress by alkali. Designing knockouts of homologs or selecting its natural nonfunctional alleles could improve crop productivity in sodic lands.