Submitted to: Microbial Ecology International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/1998
Publication Date: N/A
Technical Abstract: We developed mathematical models for intra- and inter-strain competitive interactions among multiple localized infections of the biotrophic plant parasite Puccinia graminis in wheat leaves. In the infection model, the leaf is composed of a defined number of potential lesion sites, in which only one infection per site can mature and sporulate. In the sporulation model, all infections in a leaf compete for a pool of resources within the leaf for spore production. In inoculations with single parasite strains, we measured the following parameters: infection efficiency, maximum number of infections per leaf, parasite sporulation efficiency per lesion, and maximum sporulation supported by leaves. From mixed-strain inoculations, we determined competition coefficients for effects of each strain on the other during infection and spore production. Strain SR22 showed superior infection efficiency, carrying capacity for infections per leaf, and maximum sporulation supported per leaf in single-strain tests. The fitnes advantage of SR22 was tempered, however, by the greater competitive ability of strain SR41, which reduced both infection by SR22 spores and sporulation by SR22 infections in leaves with mixed parasite populations. Our methods of analyzing competitive ability are applicable to other plant parasites.