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Report of Melampsora medusae on Populus deltoides in Southern Africa. T. N. Trench, University of Natal, Pietermaritzburg. A. P. Baxter, and H. Churchill. Plant Protection Research Institute, Pretoria; and The Lion Match Company, Greytown, Republic of South Africa. Plant Dis. 71:761. Accepted for publication 3 April 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0761D.

The South African match industry relic on a single clone of Populus deltoides Marsh. (match poplar). This clone has not shown marked susceptibility to Melampsora larici-populina Kleb. or M. aecidioides (DC.) Schroet., both reported on Populus spp. in South Africa (1). During 1985-1986. match poplar in large area of South Africa and Zimbabwe showed unusually severe rust symptoms. Branches were markedly defolialed, with only tufts of chlorotic leaves at the tips. The morphological characteristics distinguishing M. medusae Thum. from the above-mentioned species include urediniospores predominantly obovate. 18-39 x 12-21 (28 X 18) µm, the wall surface distantly and prominently echinulate with a distinct equatorial smooth patch; and paraphyses capitate. mostly with uniformly thickened walls and a large lumen. Our identification of M. medusae was confirmed by John Walker of the Biological and Chemical Research Institute, New South Wales, Australia, who found telia on the affected leaves. Specimens have heen deposited in Herb. PREM (Republic of South Africa) and Herb. DAR (Australia). No search ha been made yet for an alternate host in South Africa.

Reference: (1) G. C. A. van der Westhuizen et a1. Bothalia 10:83. 1969.