Cross Pathogenicity Studies Show South Dakota Isolates of Fusarium acuminatum, F. equiseti, F. graminearum, F. oxysporum, F. proliferatum, F. solani, and F. subglutinans from Either Soybean or Corn are Pathogenic to Both Crops

In South Dakota, despite that integrated pest management options are available, Fusarium root rot is an emerging disease on soybean (Glycine max L.) and corn (Zea mays L.). Surveys were conducted across South Dakota on soybean and corn fields in 2014 and 2015, respectively, to assess the prevalence of species of Fusarium causing root rot. Fusarium acuminatum, F. equiseti, F. graminearum, F. oxysporum, F. proliferatum, F. solani, and F. subglutinans were identified common to soybean and corn. A total of 21 isolates, representing these seven species, were evaluated for their pathogenicity on soybean ('Williams 82') and corn ('B73') using the inoculum layer inoculation method in the greenhouse. At 14 days postinoculation, the seedlings were evaluated for root rot severity (1-to-5 rating scale), and relative treatment effects (RTEs) were estimated. A significant effect of the treatments was observed on RTE for soybean (P = 1.1 x 10(-7)) and corn (P = 3.0 x 10(-14)). Two F. proliferatum isolates and one F. graminearum isolate from corn caused significantly greater RTE than the other treatments (including the noninoculated control) on soybean and corn. Results indicate that soybean and corn can serve as inoculum sources of the seven species of Fusarium that are pathogenic to both crops.