- Gliocladium roseum and G. virens are saprophytic fungi with biological control activity against various plant pathogens, including those causing seedling diseases in cotton. Genetic transformation systems were developed to provide the potential for incorporating additional traits to improve the biocontrol efficacy of Gliocladium. Gliocladium roseum protoplasts were transformed with G. virens genomic DNA. The 6.7 kb plasmid pH1S containing a bacterial hygromycin B resistance gene, hygB, was used to transform G. virens. Up to ten methionine-independent G. roseum transformants were recovered per microgram of G. virens DNA. Transformation frequencies as high as 150 hygromycin B-resistant transformants per microgram of circular palsmid DNA were observed with electroporation at a field strength of 500 V/cm. Total DNA was isolated from G. virens transformants and hybridized to purified hygB or pBR322 (the vector used in the pH1S construct) DNA. The hygB DNA was integrated into genomic DNA. Precise excision of the plasmid by two different restriction endonucleases provided evidence for the presence of multiple tandem copies in some transformants. The presence of multiple bands in digests of other transformants suggested multiple sites of integration. 1989 Springer-Verlag.