A procedure is presented for transforming Colletotrichum gloeosporioides f. sp. aeschynomene to benomyl resistance by using a mutant beta-tubulin gene from Neurospora crassa. Hybridization between the N. crassa beta-tubulin gene and transformant DNAs digested with StyI indicated that the integration site in all transformants was in a specific region of the genome. Transformants tolerated up to 300 micrograms of benomyl per milliliter but differed in pigmentation, growth rate, and pathogenicity. All transformed strains remained benomyl resistant after repeated subculture on medium lacking benomyl. The authors speculate that the bias in the site of integration was due to selection against transformants with other configurations between the N. crassa beta-tubulin gene and C. g. aeschynomene genome, which were unstable, lethal, or unsuitable for expression of the benomyl phenotype. (Copyright (c) 1993 The American Phytopathological Society.)