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Molecular Plant Pathology

Biased DNA Integration in Colletotrichum gloeosporioides f. sp. aeschynomene Transformants with Benomyl Resistance. John L. Armstrong,U.S. EPA Environmental Research Laboratory, 200 S.W. 35th St., Corvallis, OR 97333; Deborah L. Harris, ManTech Environmental Technology, Inc., 200 S.W. 35th St., Corvallis, OR 97333. Phytopathology 83:328-332. Accepted for publication 15 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-328.

A procedure is presented for transforming Colletotrichum gloeosporioides f. sp. aeschynomene to benomyl resistance by using a mutant β-tubulin gene from Neurospora crassa. Hybridization between the N. crassa ?-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 μg 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. We speculate that the bias in the site of integration was due to selection against transformants with other configurations between the N. crassa β-tubulin gene and C. g. aeschynomene genome, which were unstable, lethal, or unsuitable for expression of the benomyl phenotype.