VIEW ARTICLE

Effects of Pregermination Environments on the Germinability of Uredospores of Two Wheat Rust Fungi. P. N. Sood, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Present address of senior author: Michigan State Department of Agriculture, Plant Industry Division, 1120 W. State Fair, Detroit 48203; M. V. Wiese, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 64:1244-1248. Accepted for publication 30 April 1974. DOI: 10.1094/Phyto-64-1244.

Newly produced uredospores of Puccinia graminis f. sp. tritici and Puccinia recondita f. sp. tritici, the stem rust and leaf rust pathogens of wheat, respectively, were exposed en masse to different environmental treatments for periods up to 48 h and subsequently tested for germinability. Germination was conducted under standard conditions in which nontreated spores routinely germinated at levels greater than 84%. Light, temp, relative humidity, and the duration of these parameters applied to uredospores, all influenced subsequent germination levels, but had only minor effects on germination rate. Germination was markedly reduced or did not occur after spores were exposed to temp above 25 C, especially in dark, water-saturated (hydration) atmospheres. The magnitude of such detrimental effects increased gradually with exposure time. With both fungi, germinability losses due to hydration were reduced or prevented if hydration was conducted in incandescent light. Light at 10,800 to 12,300 lx, that included wavelengths greater than 500 nm, was significantly effective. Germinability was inversely related to rates of spore respiration in pregermination environments.