title: Screening of Metarhizium anisopliae UV-induced mutants for faster growth yields a hyper-virulent isolate with greater UV and thermal tolerances.
abstract: The insect pathogenic fungus Metarhizium anisopliae is an important insect biological control agent commercialized for use worldwide. Fungal infection is percutaneous, and rapid germination and growth has been linked to virulence. Using a simple in vitro growth screen to isolate mutants with increased virulence, M. anisopliae SM04 conidia were exposed to UV radiation for 20, 40, and 60 min, and mutants were subsequently screened for more rapid growth on standard potato dextrose agar. From a screen of >6,000 colonies, mutants were selected based on larger colony diameters as compared to the wild-type parent. Insect bioassays using the diamondback moth, Plutella xylostella, revealed one mutant, designated as MaUV-40.1 as displaying both more rapid growth and increased virulence. The mean lethal time to kill (LT50using 106conidia/ml) was 57.6 and 115.4 h for the MaUV-40.1 mutant and wild-type strains, respectively. Total conidial production, UV and thermal tolerances of the MaUV-40.1 strain were increased, but a reduced secretome was seen for the mutant compared to wild type. Analyses of culture supernatants indicated significant shifts in secondary metabolite production in the mutant. The insecticidal activity of EthOAc extracts derived from MaUV-40.1 mutant cell-free culture supernatants were ~20 times more potent that wild-type extracts. These data indicate that mutagenesis coupled to a growth screen can be a simple approach to isolate strains with greater stress resistance and virulence and that cell-free extracts may hold promise as an alternative to the living organism for insect control.
authors: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, College of Agriculture, South China Agricultural University, Guangzhou, 510642, China.
authors: Jing
authors: J
authors: Zhao
authors: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, College of Agriculture, South China Agricultural University, Guangzhou, 510642, China.
authors: Ruina
authors: R
authors: Yao
authors: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, College of Agriculture, South China Agricultural University, Guangzhou, 510642, China.
authors: Yun
authors: Y
authors: Wei
authors: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, College of Agriculture, South China Agricultural University, Guangzhou, 510642, China.
authors: Song
authors: S
authors: Huang
authors: Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Bldg. 981, Museum Rd, Gainesville, FL, 98195-2700, USA. keyhani@ufl.edu.
authors: Nemat O
authors: NO
authors: Keyhani
authors: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, College of Agriculture, South China Agricultural University, Guangzhou, 510642, China. hzscau@126.com.|Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Bldg. 981, Museum Rd, Gainesville, FL, 98195-2700, USA. hzscau@126.com.
authors: Zhen
authors: Z
authors: Huang
mesh_terms: D000818:Animals; D001681:Biological Assay; D003470:Culture Media / Q000737:chemistry; D007915:Lepidoptera / Q000382:microbiology* / Q000502:physiology*; D008403:Mass Screening; D052981:Metarhizium / Q000254:growth & development* / Q000528:radiation effects*; D050296:Microbial Viability; D009154:Mutation; D016019:Survival Analysis; D014466:Ultraviolet Rays; D014774:Virulence
chemical_list: D003470:Culture Media
keywords: Destruxin; Insecticidal activity; Metarhizium anisopliae; Plutella xylostella; Secretome; UV-induced mutation