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Poster: Biology & Disease Mgmt: Biological Control


Characterization and distribution of natural populations of Cryptococus flavescens across the United States
K. PARK (1), J. Shin (1), K. Myeong (1), S. Lee (1), S. Lee (1), M. Kim (1), K. Kim (1) (1) National Institute of Horticultural and Herbal Science, South Korea

Fusarium head blight (FHB) is an important disease of small grains caused primarily by Fusarium graminearum. This disease causes grain yield and quality losses under conducive conditions. The yeast Cryptococcus flavescens is an effective biological control agent of FHB on wheat. In this study, the biogeography and genetic diversity of natural populations of C. flavescens across the United States were characterized. Wheat spikes samples were collected at flowering and at harvest and assayed for C. flavescens using specific PCR primers designed on the heat shock protein hps70KDa. This assay is 1,000 times more selective for C. flavescens than other Cryptococcus spp. Samples with > 106 cells/g of wheat tissue were subjected to microbial isolation, and colonies with C. flavescens-like morphology were selected and characterized using amplified ribosomal DNA restriction analysis (ARDRA) profiling and multilocus genotyping. The results showed that C. flavescens was widespread across the country, albeit at low incidence (approximately 10%, n = 320). Spikes were the preferred tissue of colonization. When present, populations of C. flavescens ranged from 105-107 cells/g of tissue. Plant growth stage influenced C. flavescens colonization. This work confirms that C. flavescens is found across a broad geographical area in close association with wheat. Further, it demonstrates that C. flavescens is a non-invasive biological control option for FHB in the regions sampled.