Genetics of Ustilago violacea. V. Outcrossing and Selfing in Teliospore Inocula

Abstract

Plants of Silene alba inoculated with a suspension of four haploid sporidial strains of U stilago violacea with different colony color and auxotrophic markers and mating types yielded teliospores with only one of the three possible auxotrophic genotypes. All of the tested buds from each plant had teliospores with the same genotype. Smutted buds from each plant inoculated with teliospores heterozygous for colony color markers usually gave teliospores with the same genotype. The frequency of outcrossing in a mixed inoculum of telespores with different colony color genotypes was 6.6%. Homozygous teliospores were obtained from 4.6% of the smutted plants inoculated with heterozygous teliospores for color markers. Spontaneous mutation for a color marker in the nuclei of infectious dikaryotic hyphae was detected by the genotype of sporidial clones in colonies from teliospores. These observations suggest that new physiological races in the species may result from spontaneous mutation in dikaryotic hyphae, yielding heterozygous teliospores which can eventually produce recombinant teliospores by selfing.