Identification and community dynamics of fungi associated with root,crown, and foot rot of field pea in western Canada

Fungal and oomycete communities in symptomatic roots, crowns and lower stem tissues of field pea plants from sites across the Canadian prairies were characterized using plate culture and sequence-based identification. Symptomatic plants were sampled at the mid-flowering stage from a total of 21 fields in 2014 and 2015. Fungi and oomycete species were isolated on agar medium and grouped into operational taxonomic groups (OTU) based on their morphology. From the OTUs, 40 fungal and oomycete species were identified according to translation elongation factor-1 alpha or ITS sequences. Fusarium spp. accounted for more than 60 % of total isolations. The fungal communities were similar in roots and crowns, but differed from communities in lower stems. In 2014, the most prevalent fungi isolated from roots were F. avenaceum, F. solani and F. redolens, but F. solani was dominant in 2015. In crown tissues, F. avenaceum was most prevalent in 2014 but F. solani was more prevalent in 2015. Stem tissues were primarily colonized by Peyronellaea spp. (= Ascochyta / Phoma spp.) and Alternaria spp. in 2014, but there was a drastic decrease in Peyronellaea spp. in 2015. This study indicated that climate, primarily precipitation levels, and local edaphic characteristics may play a profound role in the structure of phytopathogen communities associated with the root and foot rot diseases complex of field pea on the Canadian prairies.