Improving crop phosphorus (P) uptake and use capabilities is needed to alleviatehunger and increase sustainability. The rice ( Oryza sativa L.) protein kinase P HOSPHORUS- S TARVATION TOL ERANCE 1 ( OsPSTOL1 ), which is absent from many modern varieties, increases root growth and stimulates yield under P deficient conditions. A biogeographic survey of genetic variation in OsPSTOL1 demonstrates its loss in a subset of japonica rice after the temperate-tropical split and typical absence in paddy varieties of east Asia. Additional loss-of-function alleles have accumulated in countries with high fertilizer use and irrigation control, suggesting that OsPSTOL1 may be less favorable or unnecessary in those conditions. OsPSTOL1 homologues are present in agronomic crop species. OsPSTOL1 is an unusual family member due to its presence of a kinase domain and loss of a transmembrane domain; a similarly truncated OsPSTOL1 -like gene is present in bread wheat ( Triticum aestivum L.). Overexpression of OsPSTOL1 in wheat confers an increase in shoot and root growth under low P conditions, as well as a more rapid induction of the core low P response pathway. This work suggests that OsPSTOL1 acts on an evolutionarily conserved mechanism in wheat that may be utilized for crop improvement.