Survey of root diseases of wheat and barley in southeastern Idaho

Root diseases of wheat and barley in southeastern Idaho (Intermountain West area of the U.S.A.) have not been extensively studied. Surveys were conducted in 2001 and 2002 to assess root disease severity and to identify soilborne pathogens present in 81 wheat and 52 barley fields in 13 southeastern Idaho counties. Bipolaris sorokiniana and Fusarium culmorum were the most frequent pathogens isolated and also the most virulent in greenhouse pathogenicity tests. Other pathogenic fungi isolated from root lesions included Fusarium spp., Rhizoctonia solani, and Gaeumannomyces graminis var. tritici. Nematode soil assays revealed that 96% of the fields had lesion nematodes (mostly Pratylenchus neglectus) and 78% had stunt nematodes (Tylenchorhynchus spp.). Other nematode species were detected in less than 18% of the fields. The cereal cyst nematode (Heterodera avenae) was found in two fields. Greenhouse experiments with soil cores indicated that disturbing the soil to simulate disking reduced the severity of fusarium root rot. Plant breeders attempting to incorporate resistance to root rot into cereal crops in the Intermountain West should focus on screening with B. sorokiniana and F. culmorum isolates.