Purpureocillium lilacinum for plant growth promotion and biocontrol against root-knot nematodes infecting eggplant

Purpureocillium lilacinum is a biocontrol Ascomycota fungus against various plant pathogens. In the present study, the efficacy of P. lilacinum was evaluated against a root-knot nematode, Meloidogyne incognita that infects eggplants. We performed an in vitro experiment in which the direct effects of P. lilacinum on the second-stage juvenile survival and egg hatching of M. incognita were tested at different exposure times. The results showed that P. lilacinum significantly reduced the rates of egg hatching and juvenile survival in a dose-dependent manner. Microscopic observation demonstrated that P. lilacinum directly penetrated the eggs and contacted the juveniles, indicating how P. lilacinum parasitizes M. incognita. We also performed a pot assay in which soil-grown eggplants were treated with P. lilacinum followed by inoculation with M. incognita. The results indicated that P. lilacinum effectively reduced the nematode population and the number of galls in plant roots. Interestingly, application of P. lilacinum resulted in significant enhancements in plant growth and biomass, even under nematode infection, while it improved plant photosynthetic pigments, i.e., chlorophyll and carotenoids. Taken together, our study suggested that P. lilacinum can be used as a plant growth-promoting fungus and a biological nematicide for disease management of root-knot nematodes in eggplants.