Genotypic and phenotypic characterization of Cryptococcus flavescens, beneficial biocontrol agents for controlling Fusarium head blight of wheat

Cryptococcusflavescens strain OH182.9_3C (3C) previously displayed significant biological control activity against Fusarium head blight, a globally important disease of wheat; however, the diversity within C. flavescens has not been previously characterized. Multilocus sequence typing was performed on strain 3C and 12 other C. flavescens strains using six apparently unlinked loci: rDNA-ITS, β-tubulin, chitin Synthase 1, elongation factor 1, heat shock protein 70 kDa and a mostly anonymous region. The rDNA-ITS sequences were identical across all the 13 strains. The other five loci consistently revealed two genotypes, A (6 strains, including 3C and type strain NRRL Y-1401T) and B (7 strains), with high bootstrap support. This genotypic split was congruent to the mating type previously performed on some of the tested strains. Phenotypic variation noted using Biolog assays supported the grouping by genotype and revealed the slow assimilation of several carbon sources by two isolates of genotype A. In green-house bioassays, the strains of both genotypes showed biocontrol efficacy against Fusarium head blight, but genotype A as a whole showed slightly greater biocontrol efficacy than genotype B strains. This study provided insight into the phylogenetic relationships within C. flavescens species and resources for developing genetic and phenotypic markers to differentiate subspecies of C. flavescens.