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In Vitro Reactions of Cladosporium caryigenum with Pecan Condensed Tannins and Isoquercitrin. D. W. Laird, Graduate student, Mississippi State University, Mississippi State, Present address: Department of Plant Pathology, North Carolina State University, Raleigh, 27695; C. H. Graves, Jr., and P. A. Hedin. Professor, Mississippi State University, and research chemist, USDA, ARS, respectively, Mississippi State. Phytopathology 80:147-150. Accepted for publication 28 August 1989. Copyright 1990 The American Phytopathological Society.. DOI: 10.1094/Phyto-80-147.

In vitro growth of Cladosporium caryigenum, the pecan scab incitant, was significantly inhibited by condensed tannin and isoquercitrin, allelo-chemicals that had been extracted from freeze-dried pecan leaves (Carya illinoensis cv. Van Deman). Nine isolates of C. caryigenum varied in their responses to condensed tannin at a concentration of 4,000 ?g/ml. Even the most tolerant isolate was inhibited at concentrations of 4,000 ?g/ml and above. Isoquercitrin at 4,000 ?g/ml was about two to four times more inhibitory than tannin to growth of three isolates of C. caryigenum, and differences were found in the tolerance of the three isolates to isoquercitrin.

Additional keywords: disease resistance, pecan phenolics.