Rhizosphere phosphorus fractions controlled through P fertilization influence wheat infection by Heterodera avenae

Heterodera avenae (cereal cyst nematode, CCN) infects wheat and causes severe yield losses. CCN infestations can be decreased by applying phosphate fertilizer in wheat fields, but the underlying mechanisms are still largely unclear.

In this study, the relationships among CCN, wheat root morphological traits, soil P fractions, and soil phosphatase activity in the rhizosphere were investigated with single superphosphate (SSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), and ammonium polyphosphate (APP) application and without phosphate fertilizer (CK) application. APP most effectively inhibited the occurrence of CCN, with the number of cysts decreasing by 48.8%, and was decreased by 31.6%, 33.9%, and 16.4% in SSP, MAP, and DAP treatments, respectively. With APP, the concentrations of Resin-Pi and NaOH-Pi in rhizosphere soil increased significantly, and the proportional lengths of medium (1-3 mm) and coarse roots (> 3 mm) increased, while that of fine roots (0-1 mm diameter) decreased. Moreover, soil phosphatase activity decreased along with highest shoot P accumulation in APP treatment, suggesting that P nutrition provided by APP is more easily absorbed by wheat than the other tested fertilizers. Furthermore, negative relationships were observed between cyst numbers and shoot P accumulation (r = -0.87, p < 0.001), coarse root length proportion (r = -0.59, p < 0.01), Resin-Pi (r = -0.50, p < 0.05), and NaOH-Pi concentrations (r = -0.57, p < 0.01). SEM analysis indicated that the concentrations of Resin-Pi and NaOH-Pi increased by phosphate fertilizer additions, enhancing shoot P accumulation and inhibiting the occurrence of CCN in wheat.

As an effective P source that elevates rhizosphere Resin-Pi and NaOH-Pi, APP not only promotes wheat growth by enhancing P uptake, but also increases the resistance of wheat against CCN. These findings provide an in-depth understanding of the control of CCN through phosphate fertilization management, enabling sustainable agricultural development.