Genotypic variation within a phenotype as a possible basis for somatic hybridization in rust fungi

Abstract

It is generally considered that the production of new strains of rust by somatic hybridization cannot be adequately explained by hyphal anastomosis and nuclear exchange. Such a mechanism would account for the observed recombination if, as is proposed, the rust fungi in their dikaryophase carry multiple haploid genotypes within any one phenotype. Such hidden variation could arise through whole chromosome exchange between the nuclei of a dikaryotic cell. Possible ways of generating genotypic variation within a phenotype are suggested by the results of recent investigations of Puccinia graminis f. sp. tritici in axenic culture.