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Abstract
Southern soybean stem canker caused by Diaporthe aspalathi has caused major soybean losses for growers in the Southeast U.S. The most effective disease management tool for growers is the use of stem canker resistant soybean varieties. A fast, reliable greenhouse assay for stem canker would help ensure elite germplasm is resistant to this disease. An existing toothpick assay was modified to include culturing D. aspalathi on oxgall agar on toothpicks pre-soaked in oxgall liquid medium. Inoculation was performed at growth stage V2 between cotyledons and the first trifoliate, inoculation sites were sealed with petroleum jelly and seedlings were incubated in humidity chambers for 72 h. Stem canker disease was highly consistent on susceptible lines and was not observed on resistant germplasm. More than 99.0% disease incidence was observed across three isolates of D. aspalathi after 4 weeks. This improved greenhouse assay will assist in future breeding efforts for stem canker.