The Causal Fungus of Stem Rot Disease of Faba Beans in Greece

Morphological and physiological characteristics of isolates from diseased faba bean plants affected by the causal fungus of stem rot disease of faba beans (Vicia faba L.) were compared with isolates of Sclerotinia sclerotiorum from diseased cucumber plants. Under controlled conditions, isolates from diseased faba bean plants exhibited slower growth rate at different temperatures and weaker pathogenicity on faba bean cultivars compared with isolates of S. sclerotiorum. For six consecutive years apothecia production in the field occurred from autumn to winter for sclerotia derived from diseased faba bean plants, whereas production of sclerotia of S. sclerotiorum occurred in late spring. Microscopic observations demonstrated dimorphism in ascospores (large and small ascospores) produced by isolates from diseased faba bean plants in a 4 : 4 ratio. Length to width ratio of the ascospores was 1.98. Based on all the above, it was concluded that the causal fungus of stem rot of faba beans in Greece belonged to S. trifoliorum