APS Homepage

Poster: Biology & Disease Mgmt: Oomycetes


Survey data reveals potential interactions between soil-borne fungi and oomycetes isolated in the midwest
E. LERCH (1), A. Fakhoury (2), M Chilvers (3), A Robertson (1); (1) Iowa State University, IA, USA, (2) Sourthern Illinois University, IL, USA, (3) Michigan State University, MI, USA

Root rot pathogens, such as Fusarium and Pythium species are frequently isolated together from damped-off soybean seedlings. Consequently, they are hypothesized to form a multi-species complex that infects soybean, however the interaction has not been extensively studied and is not well understood. The objective of this research was to identify potential interactions between fungi and oomycetes. Data from 2012 Midwest survey funded by the USDA-NIFA and USB/NCSRP was used. Data comprised species recovered from seedlings collected by soybean pathologists from fields with seedling disease or a history of disease. Hierarchical clustering was used to identify groups of isolates frequently recovered together from the same field. When data were analyzed including all fungi and oomycetes, regardless of pathogenicity, six distinct clusters were identified. Within each cluster were fungal and oomycete pathogens and non-pathogens. When data were reanalyzed with only pathogenic species, four distinct clusters were present. Cluster 3 contained only Fusarium species, while cluster 2 contained several Pythium species as well as Phytophthora sojae, Phytophthora sansomeanea and F. verticillioides. The remaining two clusters contained Fusarium and Pythium species. These data should allow soybean pathologists to identify potential interactions between specific species of soil-borne fungi and oomycetes that can be explored and used to enhance our understanding of root rot on soybean.