Leaf blight of sorghum caused by drechslera australiensis--a new report from India

摘要

Foliar diseases of sorghum (Sorghum bicolor (L.) Moench] are potential yield reducers as they cause premature drying of leaves that results in considerable reduction in grain and fodder yields. The widely prevalent common leaf blight is incited by Exserohilum turcicum (Pass.) Leonard & Suggs (Frederiksen 2000). We have observed a leaf blight on grain sorghum cultivars in Rajasthan, India, caused by a different pathogen, Drechslera australiensis as described below. Severely blighted leaves of locallandrace cultivars grown in a farmers' field near Udaipur were collected in the rainy season, 2001. The characteristic symptoms were narrow (1-5 mm) lesions of varying (2-71 mm) length. The lesions had reddish brown margins and straw-colored centers, andcoalesced to cover the leaf lamina (Fig. 1). Isolation from the diseased leaves on potato dextrose agar (PDA) medium yielded a culture with brownish-grey mycelium and pale brown, small, 3-septate conidia resembling Drechslera sp. Pathogenicity of the purified culture was tested by spray inoculating (1 X 10~5 conidia mL~(-1)) on the leaves of 21-day old plants of known susceptible sorghum cultivar, Kekri local. The characteristic lesions developed within 7 days of inoculation.