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Disease Control and Pest Management

Colonization of Peanut Seed by Cylindrocladium crotalariae. D. M. Porter, Research plant pathologist, U.S. Department of Agriculture, Agricultural Research Service, Tidewater Agricultural Experiment Station, Suffolk, VA 23437; F. S. Wright(2), R. A. Taber(3), and D. H. Smith(4). (2)Agricultural engineer, U.S. Department of Agriculture, Agricultural Research Service, Tidewater Agricultural Experiment Station, Suffolk, VA 23437; (3)(4)Professors, Department of Plant Pathology and Microbiology, Texas A&M University, Texas Agricultural Experiment Station, College Station, 77995. Phytopathology 81:896-900. Accepted for publication 5 March 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991. DOI: 10.1094/Phyto-81-896.

Cylindrocladium crotalariae, the causal agent of Cylindrocladium black rot (CBR) of peanut (Arachis hypogaea), was isolated at a much higher frequency from peanut seed (retained by a screen 6.4 25.4 mm) shortly after curing than 7 mo after initial isolation assay, when the frequency decreased approximately 87%. The frequency of C. crotalariae in seed of the cultivars Florigiant, VA 81B, and NC 6 was 15.4, 23.4, and 21.8%, respectively, before storage, and 1.6, 4.0, and 5.6%, respectively, after storage at ambient conditions for 7 mo in an unheated building. Under similar disease pressure, seed of NC 8C, a peanut cultivar with resistance to C. crotalariae, was colonized less frequently than seed of cultivars Florigiant, VA 81B, and NC 6. Seed colonization was directly correlated to incidence of CBR in the field. Seed colonization increased as disease incidence increased. Significant differences were noted among cultivars of Florigiant, VA 81B, and NC 6 in the isolation frequency of C. crotalariae. Colonization by C. crotalariae was similar in seed stored at ambient and refrigerated (5 C) conditions. The fungus was not isolated from peanut seed treated with seed protectants. Hyphae of C. crotalariae ramified both intracellularly and intercellularly throughout the testae of discolored seed. In seed with dark brown testae, hyphae were observed in the cotyledonary tissues.

Additional keywords: seed transmission, seed treatment.