VIEW ARTICLE

Genetics

Genetics of Resistance to Benomyl in Venturia inaequalis Isolates from Israel and New York. Talma Katan, Division of Plant Pathology, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50 250, Israel; E. Shabi(2), and J. D. Gilpatrick(3). (2)Division of Plant Pathology, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50 250, Israel; (3)Department of Plant Pathology, Cornell University, NYS Agricultural Experiment Station, Geneva, NY. Phytopathology 73:600-603. Accepted for publication 8 December 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-600.

Fourteen single-spore cultures of Venturia inaequalis isolated from apple scab lesions at two sites in Israel and at three sites in New York state, United States, showed resistance to benomyl. Four levels of resistance were determined in vitro: five isolates with low resistance grew at 0.5 but not at 5 μg of benomyl per milliliter; one moderately resistant isolate grew at 5 but not at 50 μg/ml; three highly resistant isolates grew and sporulated at 50 μg/ml but more slowly than at 5 μg/ml; and five isolates with very high resistance grew and sporulated abundantly at benomyl concentrations higher than 50 μg/ml. In crosses between different resistant isolates and between sensitive wild-types and resistant isolates, the levels of benomyl resistance are controlled by a polymorphic series consisting of four allelic mutations, in a single Mendelian gene. No effect of modifying genes or cytoplasmic components on benomyl resistance was evident in the isolates from either country.