Identification of Diaporthe longicolla on dry edible pea, dry edible bean, and soybean in North Dakota.
Dry edible bean (Phaseolus vulgaris), dry edible pea (Pisum sativum) and soyabean (Glycine max) are important crops in North Dakota, USA. Soyabean production has expanded well beyond its traditional growing region in recent years, resulting in direct overlap with dry edible bean and pea production areas. Possible short rotations among these crops raise concerns about the increase of soil and/or residue-borne pathogens known to infect the crops, and give rise to the possibility of other pathogens developing overlapping host ranges. One pathogen of concern is D. longicolla [Phomopsis longicolla], the cause of Phomopsis seed decay and stem disease of soyabean. In July 2009, dry edible pea stems with red, elongated lesions were observed and collected from a commercial production field in northwest North Dakota. In September 2010, lower stems of soyabean and dry edible bean showing reddish brown lesions and small, black pycnidia were collected from field research plots in Fargo. Based on morphological characteristics, amplification and sequencing of the DNA ITS region, and pathogenicity tests, the pathogen was confirmed as D. longicolla. This is thought to be the first report of D. longicolla causing stem disease on dry edible beans and dry edible peas, and stem disease on soyabean in North Dakota.