Two strategies for achieving higher yield under phosphorus deficiency in winter wheat grown in field conditions

Under field conditions, phosphorus (P) deficiency reduces wheat yield by affecting different yield components. However, the physiological strategies by which wheat genotypes with different yield structures respond to low-P stress are not clear. In the present study, we investigated tiller, floret, and root biomass, and P uptake and remobilization at two levels of P under field conditions in three winter wheat genotypes with different yield structures and P-efficiencies. Results showed that P-efficient cultivars CA9325 and ND139 got higher yield and total P accumulation than P-inefficient ND3291 at low-P, but not at normal P treatment. However, both the P-efficient wheat cultivars tend to have the same advantageous yield components at both high P and low-P stress. CA9325, a large-eared genotype, developed more fertile florets, and therefore had more grains at low-P stress. Increasing the number of grains formed a large sink for P demand during the grain-filling stage. Correspondingly, this genotype developed large roots for sustaining post-anthesis P uptake. ND139, a multi-eared genotype, developed many more tillers at low-P stress, and formed more ears at maturity. P from infertile tillers was probably reutilized by the surviving tillers to ensure floret development. Correspondingly, the contribution of pre-anthesis P uptake in ND139 and subsequent remobilization of P to the grains was higher. It was found that larger root rather than higher root activity was the determinant factor in efficient pre-anthesis P uptake in ND3291 and efficient post-anthesis P uptake in CA9325. It is concluded that increasing wheat yield at low soil P availability can be realized by either increasing ears per plant or increasing grains per ear through crop management or breeding.