Differentiation of the entomopathogenic fungus Metarhizium flavoviride (hyphomycetes)

The differentiation of a Brazilian isolate of Metarhizium flavoviride (CG 423), a promising candidate for the biocontrol of grasshoppers, was investigated. Conidia were spread onto solid medium (1% yeast extract, 2.8% agar, 96.2% distilled water), incubated at 28 degrees C and observed during 26 h. Germination initiated as conidia size increased from 5.3 (+/-0.6) x 3.1 (+/-0.3) mu m (0 h incubation) to 8.1 (+/-0.2) x 6.1 (+/-0.2) mu m (8 h incubation). Gen tubes started to appear after 10 h incubation showing a high degree of multipolarity. Twenty six hours after inoculation, hyphal differentiation and anastomosis among hyphae from adjacent conidia were recorded. Appressoria were formed only from conidia incubated in liquid medium containing minimum concentration of yeast extract (0.06%; w/v). Appressoria were firmly adhered to the bottom of plastic dishes.