Generation of benomyl resistant Beauveria bassiana strains and their infectivity against Helicoverpa armigera

Beauveria bassiana transformants were obtained by conventional protoplastin g and transformed by eletroporation and polyethylene glycol (PEG) treatment . These displayed mitotic stability in Beauveria bassiana. Strains transfor med with pSV50 harbouring the beta -tubulin gene of Neurospora crassa grew well on benomyl concentrations of 10 mug ml(-1) unlike the recipient strain . The transformants were mitotically stable on either selective or non-sele ctive medium. The efficiency of transformation by linear and circular pSV50 cosmid was 8 and 10 transformants per mug DNA per ml viable protoplast by electroporation, respectively, and 4 and 6 by the protoplast PEG method, re spectively. Southern blot and hybridization of undigested fungal DNA of wil d type and four transformants, probed with beta -tubulin sequence of pSV50, showed hybridization at high Mr region of genomic DNA in four transformant s, whereas in wild type genomic DNA, no homology of the sequence was observ ed. Digested genomic DNA, of four transformants gave a complex hybridizatio n pattern. Virulence tests of the transformants showed that there was no si gnificant loss in the pathogenicity toward Helicoverpa armigera third insta r larvae. This method of transformation should prove useful with entomopath ogenic fungal species in which a genetic transformation system has not yet been established.