Limited-Term Inoculation: A Method to Screen Bean Plants for Partial Resistance to White Mold. J. E. Hunter, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. M. H. Dickson, Department of Seed and Vegetable Sciences, and J. A. Cigna, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. Plant Dis. 65:414-417. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-414.

Partial resistance to white mold (Sclerotinia sclerotiorum) was detected in Phaseolus vulgaris and P. coccineus with a screening technique referred to as limited-term inoculation. Pieces of autoclaved celery colonized by the fungus were attached to the stems of 2- to 5-wk-old bean plants for a limited length of time, depending on the age of the plants and the conditions under which they had been grown. When infection periods of 12, 18, and 24 hr were used, 2-wk-old plants of P. vulgaris ‘Bush Blue Lake 47’ and ‘Black Valentine’ were ranked as susceptible and partially resistant, respectively, and P. coccineus ‘Tenderpod’ was ranked as resistant. These rankings agree with other greenhouse and field observations. An ascosporic inoculation method gave variable results, and escapes occurred. Although high levels of resistance were not found in P. vulgaris, the limited-term inoculation method is sensitive and rapid enough to use to select for partial resistance. The method also has the advantage of not requiring plants to be in bloom or the production of ascospores for inoculum.