Genetic Dissection of T-DNA Insertional Mutants Reveals Uncoupling of Dikaryotic Filamentation and Virulence in Sugarcane Smut Fungus

The biotrophic basidiomycetous fungus Sporisorium scitamineum causing smut disease in sugarcane is characterized by a life cycle composed of a yeast-like nonpathogenic haploid basidiosporial stage outside the plant and filamentous pathogenic dikaryotic hyphae within the plant. Under field conditions, dikaryotic hyphae are formed after mating of two opposite mating-type strains. However, the mechanisms underlying genetic regulation of filamentation and its association with pathogenicity and development of teliospores are unclear. This study has focused on the characterization and genetic dissection of haploid filamentous mutants derived from T-DNA insertional mutagenesis. Our results support the existence of at least three genotypes among the six haploid filamentous mutants that differentially contribute to virulence and development of the whip and teliospore, providing a novel foundation for further investigation of the regulatory networks associated with pathogenicity and teliospore development in S. scitamineum.