Media Composition Influences Growth, Enzyme Activity and Virulence of the Entomopathogen Metarhizium anisopliae (Hypocreales: Clavicipitaceae)

Three isolates of Metarhizium anisopliae were cultured on six media having different compositions on the basis of chitin, carbon and nitrogen contents. The effect of nutrition on growth and virulence was studied by measuring colony growth, spore yield, germination rate, spore bound Pr1, lipase activity and virulence of inoculum produced by different media against 2 nd instar larvae of diamondback moth (Plutella xylostella). Chitin peptone nutrition media produced the highest colony growth but maximum conidial yield was observed for medium having high C/N ratio. Highest lipase activity (3.63 µmol/ml/min) was observed for spores produced by High C/N medium for isolates M408 while highest Pr1 activity (2.1µmol/ml/min) was observed on CPN medium for M460. Conidia from medium C/N ratio proved to be the most virulent for all the three isolates with Median survival time (ST50) values of 1.45, 1.62 and 1.72 days for M408, M440 and M460, respectively. Median survival time values for different nutrient media proved to be positively correlated with spore bound Pr1 and lipase activity having correlation coefficient values of 0.42 and 0.67, respectively.