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Ecology and Epidemiology

Sporulation of Peronosclerospora sorghi, P. sacchari, and P. philippinensis on Maize. N. B. Duck, Federal fellow, U. S. Department of Agriculture, Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Ft. Detrick, Building 1301, Frederick, MD 21701; M. R. Bonde(2), G. L. Peterson(3), and G. A. Bean(4). (2)(3)Research plant pathologist, and biological laboratory technician, respectively, U. S. Department of Agriculture, Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Ft. Detrick, Building 1301, Frederick, MD 21701; (4)Professor of plant pathology, Department of Botany, University of Maryland, College Park 20742. Phytopathology 77:438-441. Accepted for publication 27 August 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987.. DOI: 10.1094/Phyto-77-438.

Nine isolates of Peronosclerospora sorghi, three of P. sacchari, and four of P. philippinensis were compared as to the number of conidiospores produced per square centimeter of surface of infected maize leaves. Systemically infected plants were induced to sporulate 21 days after inoculation by placing them in a dew chamber. All cultures of P. sorghi produced less than 3.0 103 conidia per square centimeter of infected leaf surface except two cultures from Thailand. The Thailand isolates produced more than 1.5 104 conidia per square centimeter of leaf area. Isolates of both P. sacchari and P. philippinensis produced 4.0 103 to 1.0 104 spores per square centimeter of infected leaf area. The large number of spores produced by the Thailand strain was atypical for P. sorghi and may represent a larger potential threat to maize production than other strains of P. sorghi. Isolates of P. sacchari and P. philippinensis were indistinguishable on the basis of sporulation, and five of six cultures produced significantly more spores per square centimeter of leaf area than the typical isolates of P. sorghi.

Additional keywords: corn, downy mildews, maize, sorghum, sugarcane.