Identification of Fungal Species Associated With Crown and Root Rots of Wheat and Evaluation of Plant Reactions to the Pathogens in North Dakota.

Common root rot (CRR) and crown rot (CR), caused by Bipolaris sorokiniana and Fusarium species, respectively, can cause significant yield losses in cereal crops. To assess the prevalence, incidence, and severity of these diseases in North Dakota, wheat samples were collected from spring wheat fields across the state in 2012, 2013, and 2014. Based on subcrown internode symptoms, a greater incidence and severity of CRR was observed in 2012 (warm and dry year) than in 2013 and 2014. Also, the Northwestern Glaciated Plains and Northwestern Great Plains ecoregions showed greater CRR incidence and severity compared with the Northern Glaciated Plains and Lake Agassiz Plains ecoregions in the state. B. sorokiniana and Fusarium species, including Fusarium acuminatum, Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, Fusarium equiseti, Fusarium pseudograminearum, Fusarium oxysporum, Fusarium redolens, Fusarium sporotrichioides, and Fusarium solani were isolated and identified from the root and crown tissues of the wheat samples. B. sorokiniana was isolated more frequently than other fungal species in all sampled years and ecoregions of North Dakota. F. acuminatum, F. avenaceum, F. culmorum, F. equiseti, F. graminearum, F. pseudograminearum, and F. redolens were pathogenic causing infections on seedlings of the two wheat genotypes (ND652 and Alsen), whereas isolates of F. oxysporum and F. solani were nonpathogenic and considered as secondary invaders associated with the root and CR diseases. Evaluation of some spring wheat genotypes for reactions to one B. sorokiniana isolate at seedling and adult plant stages, and one F. culmorum isolate at the seedling stage, indicated that susceptibility to these pathogens varied among different wheat genotypes tested. This study provides useful information on fungal species associated with CRR and CR of wheat in North Dakota and on resistant/susceptible reactions of some spring wheat lines to the different fungal isolates evaluated.