Detection and Characterization of Benomyl-Resistant Monilinia laxa on Apricots. J. M. Ogawa, Department of Plant Pathology, University of California, Davis 95616. B. T. Manji, R. M. Bostock, V. M. Caņez, and E. A. Bose, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 68:29-31. Accepted for publication 12 July 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-29.

In 1980, Monilinia laxa resistant to benomyl was isolated from decayed fruit and blighted twigs of apricots in California. Resistant isolates grew on Difco potato-dextrose agar (PDA) amended with 1 mg/L benomyl and one isolate grew at 2 mg/L benomyl. Colonies of benomyl-resistant isolates had typical scalloped margins on Difco PDA, except two single-spored benomyl-resistant subcultures that grew very rapidly with no scalloped margins and produced very few conidia. Conidia of three benomyl-resistant isolates germinated normally, but unlike the other benomyl-resistant isolates, were incapable of producing colonies on benomyl-free Difco PDA medium. A greater proportion of conidia of one of these isolates germinated and grew normally on PDA medium prepared with fresh potatoes than on media prepared with Difco PDA. Benomyl-resistant isolates failed to grow out from mycelial plugs when transferred to benomyl-free Difco PDA medium after extended exposure to 3 mg/ L benomyl. Benomyl-resistant isolates produced smaller cankers than benomyl-sensitive isolates on inoculated almond shoots.

Keyword(s): Monilinia fructicola.