Evaluation of soybean cultivars for resistance to Phomopsis longicolla and Sclerotinia sclerotiorum using excised leaves

The resistance of short-season soybean cultivars in Canada to Phomopsis longicolla and Sclerotinia sclerotiorum was measured on excised leaves based on the disease severity. Lesions caused by both fungi were first observed at inoculation sites within 24 to 36 h after excised leaflets were inoculated, varying among cultivars, and whole leaflets rot within 5-6 d for susceptible cultivars. Of the 74 cultivars evaluated, 20 were significantly more resistant to P. longicolla (LSD = 1.1, P < 0.05) and 19 to S. sclerotiorum (LSD = 1.0, P < 0.05), with mean severity ratings ranging from 1.3 to 2.3 caused by both fungi. Seven cultivars including Medallion, M. Arrow Brown, Alta, Portage, AC Albatros, Comet, and Pagoda, showed partial resistance to both of pathogens. These resistant cultivars identified in this study may be used as sources of resistance in future field breeding programs in Canada.