Potassium Sulphate Induces Resistance of Rice against the Root-Knot Nematode Meloidogyne graminicola

Background Potassium (K), an important nutrient element, can improve the stress resistance/tolerance of crops. The application of K in resisting plant parasitic nematodes shows that the K treatment can effectively reduce the occurrence of nematode diseases and increase crop yield. However, data on K2SO4 induced rice resistance to Meloidogyne graminicola are still lacking. To evaluate rice resistance against M. graminicola induced by K2SO4 and to further clarify its mechanism is essential for the rational use of K fertilizer to ensure the safety of rice production.Results In this work, K2SO4 treatment effectively reduced the numbers of both galls and nematodes in rice roots, and delayed the development of nematodes to the adult stage. Rather than by affecting the attractiveness of roots to nematodes and the morphological phenotype of giant cells at feeding sites, such effect was achieved by rapidly stimulating hydrogen peroxide (H2O2) accumulation, increasing callose deposition. Meanwhile, such induced resistance required the active participation of the potassium channel OsAKT1 and the potassium transporter OsHAK5. The numbers of both galls and nematodes were higher in both gene deficient plants than that in the wild-type plants, and the K2SO4-induced resistance showed weaker in the defective plants than in the wild-type plants.Conclusions K2SO4 treatment effectively induces rice resistance to root-knot nematode M. graminicola. The mechanism of inducing resistance is to prime the basic defense of rice, up-regulating the expression of resistance-related genes and with the involvement of K+ channel and transporter. These laid a foundation for further study on the mechanism of rice to defense against root-knot nematodes and the effective use of potassium fertilizer to improve rice resistance against nematodes in the field.