First report of Fusarium root rot in soybean caused by Fusarium tricinctum in Minnesota

Seed, seedling, and root rots of soybean caused by a complex of soilborne fungi are possibly the most important diseases of soybean in Minnesota, causing losses estimated at 380,000 tons in 2005. F. solani and F. oxysporum are the predominant Fusarium species isolated from soybean taproots in Minnesota. For soybeans grown in unamended field soil in a growth chamber at 10 and 16C, the predominant Fusarium species isolated from taproots were F. solani and F. tricinctum. Three isolates of F. trieinctum were obtained from these plants. One of the isolates produced lesions on soybean seedlings after two weeks, using an inoculum layer method in inoculated sterile sand. F. tricinctum has been previously reported as pathogenic on soybean in Ontario, Canada. Its preference for lower temperatures might account for the low frequency of isolation from Minnesota grown soybean. Its role in soybean root rot in the field is not known. F. tricinctum could contribute to seedling rot early in the season when the soil temperature is below 20C.