Tracking native and applied populations of Cryptococcus flavescens in the environment

Cryptococcus flavescens OH182.9_3C (3C) is a beneficial yeast strain that expresses significant biological control efficacy against Fusarium head blight, a globally important disease of wheat. In this study, traditional and quantitative PCR (qPCR) assays targeting one copy of the hsp70 gene were developed and applied to monitor the population dynamics of beneficial 3C-like C. flavescens in wheat and barley fields and on harvested grains. The assay was found to be specific to 3C-like C. flavescens, though detection of a different genotype of C. flavescens can occur with 104-fold lower sensitivity. The utility of the assays to detect native C. flavescens populations and track an inoculant strain was demonstrated in different field experiments. Across ten wheat growing states, up to 25% of wheat heads harbored 3C-like C. flavescens. However, by harvest those populations were found on no >8% of dry wheat heads. Additional comparisons indicated that native populations of 3C-like C. flavescens preferentially colonized wheat heads, colonizing wheat foliage and barley heads at significantly (P