Effects of Temperature and Relative Humidity on Germinability and Infectivity of Puccinia polysora Uredospores. C. A. Hollier, Former Graduate Research Assistant, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762. S. B. King, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, P.O. Drawer PG, Mississippi State, MS 39762. Plant Dis. 69:937-939. Accepted for publication 15 March 1985. 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, 1985. DOI: 10.1094/PD-69-937.

Uredospores of Puccinia polysora were maintained at temperatures of 4–36 C at four-degree increments and at relative humidities of 15, 35, 65, and 95% for 1, 3, 7, 28, and 56 days, then germinability and infectivity were evaluated. After treatment, germination was determined after a 24-hr incubation period on water agar. Germinability was best maintained at 12–20 C throughout the testing period, regardless of relative humidity. Germinability decreased from a level of 78–86% at all relative humidities (day 1) to 35% at 15% RH, 27% at 35% RH, and 0% at 65 and 95% RH (day 56). Infectivity, determined by inoculation of excised maize leaf tissue floated on a kinetin/sucrose solution, was directly related to germinability.