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.