Characterization of Fusarium oxysporum f.sp. pisi associated with root rot of field pea in North Dakota and the effects of temperature on aggressiveness

Abstract

Fusarium root rot is an important disease of field pea (Pisum sativum var. sativum L.) that occurs everywhere pea is grown, causing yield loss of up to 75%. Fusarium root rot is caused by a complex of Fusarium species, most notably Fusarium solani in the Pacific Northwest US and F. avenaceum in the northern Great Plains of the U.S. and Canada. F. oxysporum f.sp. pisi (Fop) was frequently isolated from peas exhibiting root rot symptoms in North Dakota during recent surveys. Fop causes wilt (races 1, 5 and 6) and near wilt (race 2) on pea. However, its contribution to pea root rot remains unclear. Fop race was determined for isolates from North Dakota pea root rot surveys. ND Fop isolates were evaluated for root rot pathogenicity and aggressiveness at standard and elevated temperatures. Results from greenhouse wilt assays indicated that all Fop races exist in North Dakota, with race 2 most prevalent among the 25 North Dakota isolates evaluated. Root rot evaluations conducted at 21/18℃ and 25/19℃ day/night temperatures demonstrated that most Fop isolates were as, or more aggressive than F. solani and F. avenaceum under both temperature regimes. Aggressiveness of Fop isolates tended to increase at elevated assay temperatures. Results from these experiments indicate that Fop may be an important contributor to the root rot complex of field pea in North Dakota and should be considered in integrated pest management strategies, including pea breeding efforts to improve resistance to Fusarium root rot.