Mutant Screening of Metarhizium lepidiotae for Increased UV-Tolerance and Virulence
Mutant Screening of Metarhizium lepidiotae for Increased UV-Tolerance and Virulence
Wenyou Huang1, Dan Yü1, Song Huang1,2, Jian Xiao2, Ping Qi2, Anhua Song2* and Zhen Huang1*
ABSTRACT
The ability of entomopathogenic fungi to be applied for pest control in field applications is often hampered by negatively active abiotic factors including high temperature, desiccation and UV irradiation. Selecting isolates with high UV tolerance and virulence is important in improving the efficacy and utility of fungal insect pathogens as insect biological control agents for use under field conditions. UV-irradiation of Metarhizium lepidiotae, coupled to growth selection, second metabolites change and insect bioassays using Plutella xylostella larvae as the host resulted in the isolation of a collection of mutants with increased virulence. One mutant, designated, MlUV-40b showed ＃3.3-fold increase in virulence as compared to the wild type parent, with an LC50 = 0.3 ×105 conidia/ml versus 1.1 × 105 conidia/ml, respectively and LT50 = 92 and 123.0 h for the MlUV-40b and wild type, respectively. The MlUV-40b mutant displayed increased UV tolerance, but decreased total conidial production. In addition, alterations in the secretome were seen in the mutant. Contact insect toxicity of cell-free culture supernatants and the EthOAc extracts derived from the MlUV-40b mutant were 1.2-3 times more potent than that of the wild type. A simple approach coupling mutagenesis and growth & second metabolites were used to isolate strains with increased stress resistance and virulence. Increased virulence in some of the mutants correlated with increased insecticidal activity in cell-free extracts that could potentially be used directly for insect control.
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June 2021
Vol. 53, Iss. 3, Pages 801-1200
