First Report of Sclerotium rolfsii on Kenaf in South Africa

Plant Disease
W J SwartJ Terblanche

Abstract

Kenaf, Hibiscus cannabinus L. (Malvaceae), is being planted commercially in South Africa for the high quality cellulose fibers that it produces. In a January 2001 survey of 3-month-old kenaf plants grown from seed in experimental plots near Rustenburg, Northwest Province, 30% of plants were observed with severe wilting. Stems at ground level of all infected plants had sunken tan lesions, white mycelial strands, and small, dark brown, 1 to 2 mm diameter sclerotia. Isolations from diseased stem tissue on malt extract agar (MEA) consistently yielded a fungus conforming to the description of Sclerotium rolfsii Sacc. (teleomorph Athelia rolfsii (Curzi) Tu & Kimbrough). Pathogenicity tests were conducted by applying toothpick tips (5 mm) colonized by S. rolfsii on MEA to the stems of 120-day-old potted plants of 10 kenaf cultivars in the greenhouse. Five plants of each cultivar were wounded once using a sharp dissecting needle, and a colonized toothpick tip was placed on top of each wound. Control treatments consisted of five plants per cultivar each wounded and inoculated with sterile toothpick tips. All inoculation points were wrapped using Parafilm, and the experiment was conducted twice. Lesions were measured after 10 days. Mean ...Continue Reading

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