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Resistance

Association of Seed Coat Factors with Resistance to Rhizoctonia solani in Phaseolus vulgaris. Krishna Prasad, Research Assistant, Department of Horticulture, Iowa State University, Ames 50010, Present address of senior author: Department of Horticulture, University of Maryland, College Park 20742; Jack L. Weigle, Professor, Department of Horticulture, Iowa State University, Ames 50010. Phytopathology 66:342-345. Accepted for publication 27 August 1975. DOI: 10.1094/Phyto-66-342.

Black-seeded cultivars of Phaseolus vulgaris were resistant to Rhizoctonia solani (Thanatephorus cucumeris) infection, while most white-seeded cultivars were susceptible to both seed infection and preemergence damping-off. The seed coats of most white-seeded beans cracked readily before emergence. Extracts of white seed coats stimulated growth of R. solani. The seed coats of resistant black-seeded cultivars adhered tightly to the cotyledons. Extracts of black seed coats contained phenolic compounds that inhibited growth of R. solani.