Transformation of the entomopathogenic fungus Metarhizium flavoviride to high resistance to benomyl

A Brazilian isolate of Metarhizium flavoviride, which has been developed as a biocontrol agent against the grasshopper Rhammatocerus schistocercoides, was stably transformed to be resistant to benomyl (beta-tubulin gene). Hig hly resistant transformants were obtained which grew in benomyl concentrati ons greater than 30 times (200 mu g mL(-1)) the concentration that inhibits wild type proliferation. These transformants were mitotically stable after 20 successive transfers on non-selective media. No significant differences in conidia yield were observed between stably transformed strains and wild type (CG423). Chymoelastase (Prl) secretion was greater in some transforma nts than in the wild type. In the presence of benomyl, appressoria differen tiation occurred at similar rates in CG423 and transformants. However, the percentage of conidial germination in the transformants was higher than in the wild type, indicating the potential use of these transformants along wi th benomyl. Additionally, the resistance levels of the transformants observ ed in the present study demonstrate the potential use of these transformant s for assessing the persistence of a particular isolate in fields without t his fungicide.