Effects of Temperature and Light on Germination of Urediniospores of the Pearl Millet Rust Pathogen, <i>Puccinia substriata</i> var. <i>indica</i>

Abstract

Germination of urediniospores of Puccinia substriata var. indica was evaluated after 2, 4, 6, and 8 h of incubation in petri dishes containing 2% water agar under 10, 16, 20, 25, 30, and 35°C in light (1650 lux, cool white fluorescent), dark, alternate light-dark, and alternate dark-light. Less than 1% germination occurred at 35°C. At 30°C, percent germination did not significantly change after 4 h. At 10°C, percent germination increased with longer incubation. Under all illumination conditions, percent maximum germination after 4 to 8 h occurred at 20-25°C. Response surface analysis indicated that under all four illumination regimes, urediniospore germination greater than 90% occurs between 19 and 22°C after 6-7 h of incubation. Two hours of continuous light appeared to significantly delay germination, but exposure to light during the first hour of incubation was stimulatory when followed by 1 h dark.