Designing of nematode egg parasitic fungus, Purpureocillium lilacinum, nanoemulsion for management of Meloidogyne incognita infection in tomato

Summary Purpureocillium lilacinum is a potent biocontrol agent against Meloidogyne spp. and various other plant-parasitic nematodes in crops. However, existing commercial formulations of P. lilacinum suffer from drawbacks like short shelf life and inconsistent performance in different environmental conditions. To address these issues, a new nano-formulation of P. lilacinum was developed and tested against Meloidogyne incognita infecting tomatoes. Initially, edible oil-based emulsions were prepared using probe ultrasonication, with 40 formulations screened and 14 selected for further testing. Seven of these emulsions remained stable at room temperature (28 ± 4°C) for 8 weeks, with stability assessed based on particle size, zeta potential, and particle shape using particle size analysis and transmission electron microscopy (TEM). Among these, NE 8 (comprising 10 ml of 1% carboxyl methyl cellulose (CMC), 1.25 ml of Tween 80 and 5 ml of sunflower oil) exhibited superior characteristics, with an average particle size of 226.6 nm, a zeta potential of −54.80 mV, and a spherical morphology under TEM examination. The P. lilacinum nanoemulsion formulation was produced by homogenising NE 8 emulsion and spores at a 1:1 ratio, ensuring efficient spore dispersion and encapsulation without loss of viability. In vitro tests demonstrated 100% immobility of M. incognita second-stage juveniles (J2) and 100% parasitism of eggs at a concentration of 5.0 ml l −1 . Under glasshouse conditions, soil drenching with the nano-formulation at concentrations ranging from 0.5 to 5.0 ml l −1 resulted in enhanced tomato growth and significant suppression of M. incognita populations in soil and roots, with increased egg mass parasitism. Bio-safety tests confirmed that P. lilacinum nano-formulation at concentrations of 0.25 ml l −1 and 5.0 ml l −1 had no harmful effects on the earthworm Eudrilus eugeniae .