Oleic Acid and Linoleic Acid Enhances the Biocontrol Potential of Metarhizium rileyi

Metarhizium rileyiis a wide spread insect fungi with a good biocontrol potentiality to various pests, particularly noctuid insects. However, it is characterized by its slow growth, its sensitivity to abiotic stress, and the slow speed of kill to pests, which hinder its use compared with other entomopathogenic fungi. In this study, the responses ofM. rileyito eight types of lipids were observed; among the lipids, oleic acid and linoleic acid significantly promoted the growth and development ofM. rileyiand enhanced its stress tolerances and virulence. An additional mechanistic study demonstrated that exogenous oleic acid and linoleic acid significantly improved the conidial germination, appressorium formation, cuticle degradation, and cuticle infection, which appear to be largely dependent on the up-regulation of gene expression in growth, development, protective, and cuticle-degrading enzymes. In conclusion, exogenous oleic acid and linoleic acid enhanced the stress tolerances and virulence ofM. rileyivia protecting conidial germination and promoting cuticle infection. These results provide new insights for the biopesticide development ofM. rileyi.