Development of gray leaf spot from inoculated foci on two maize cultivars in Uganda

Abstract

The spatio-temporal spread of gray leaf spot on maize caused by Cercospora zeae-maydis was studied in two locations in central Uganda. Gray leaf spot development was assessed for three cropping seasons at 0.75 m to 5.25 m from inoculated foci on two open-pollinated maize varieties. In all the seasons, disease spread was adequately depicted by both power and exponential models. Distance from inoculum focus significantly (P<0.05) affected leaf damage but the effect of direction from inoculated focus was variable depending on the season, location and cultivar. Thus, depending on the location and seasonal variation, genotype effect greatly affects severity of gray leaf spot. Gradients for the two cultivars differed significantly (P<0.001) in intercept (a) but not slope (b) of the linearised power disease gradient for the number of lesion on the ear leaf. Our results indicate that maize genotypes affect both increase and spread of gray leaf spot. The rapid flattening of the disease gradient was indicative of long distance dispersal of C. zeae-maydis in tropical unlike in temperate environments.