Competition and Distribution Studies of Genetically Marked Strains of Ustilago violacea in the Same Host Plant

Abstract

Four plants of Silene alba were inoculated with a suspension of cells of the anther smut fungus, Ustilago violacea, containing six genetically marked strains, three of each mating type; thus, nine possible dikaryons could form and compete within the plant. On average, 44 infected flower buds from each plant were sampled and analyzed for genotype of the infecting dikaryon using rapid screening techniques capable of identifying the nine possible dikaryons. Different dikaryons could penetrate and infect the same flower shoot, lateral branch, pedicel, or, even rarely, the same anther. Of 177 infected flower buds, 90 were infected by a wild-type + wild-type dikaryon, 86 with one of three wild-type + mutant dikaryons, and only two anthers of nine analyzed from one flower were infected with a mutant + mutant dikaryon Only two flowers of the 177 contained two different dikaryons, both of which could penetrate the same anther, sporulating together within it. Clearly, however, usually only one dikaryon comes to pre...