Effects of Temperature and Light Intensity on Telia Development by Puerto Rico and Taiwan Isolates of Phakopsora pachyrhizi, the Soybean Rust Fungus. L. A. Dufresne, Department of Botany, University of Maryland, College Park 20742. G. A. Bean, M. R. Bonde, and R. W. Goth. Department of Botany, University of Maryland, College Park 20742; Plant Disease Research Laboratory, USDA, ARS, Frederick, MD 21701; and USDA, ARS, Beltsville, MD 20705. Plant Dis. 71:629-631. Accepted for publication 9 December 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0629.

Isolates of Phakopsora pachyrhizi, one from Taiwan and one from Puerto Rico, were cultured on the soybean cultivar Williams at two temperatures and three light intensities. The Taiwan isolate produced telia after 21 and 30 days and the Puerto Rico isolate produced telia after 34 and 35 days at 10 and 15 C, respectively. At low light intensity (3.9 µE/m²/sec), the Taiwan and Puerto Rico isolates produced telia after 29 and 33 days, respectively; at intermediate light intensity (5.3 µE/m²/sec) after 26 and 36 days, respectively; and at high light intensity (6.1 µE/ m²/sec) after 22 and 34 days, respectively. The Taiwan isolate produced larger lesions with a higher percentage of telia than the Puerto Rico isolate.