The Role of White Mold‐Infected White Bean (Phaseolus vulgaris L.) Seeds in the Dissemination of Sclerotinia sclerotiorum (Lib.) de Bary

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Abstract
Sclerotinia sclerotiorum survived in infected seeds of white beans as dormant mycelium in testa and cotyledons. The rate of survival averaged 85 to 89% and did not change appreciably over a 3‐year period. When the infected bean seeds were sown in soil or sand, 88 to 100% failed to germinate. The seeds that failed to germinate, depending on the severity of seed infection, were rotted by S. sclerotiorum. In place of each seed, 3 to 6 sclerotia were formed. A low percentage of these sclerotia germinated carpogenically with or without preconditioning, (2.5 and 11.5% respectively). Myceliogenic germination of sclerotia with and without preconditioning was 35.5% and 70.5% on water agar and 81.0% and 93.0% on glucose agar, respectively. Both, preconditioning and nonpreconditioned sclerotia which were scattered on soil surface could germinate myceliogenically and infect bean leaves by contact. It is therefore, concluded that dormant mycelia in the infected seeds play an important role notonly in dissemination of the fungus but also in epidemiology of the disease.