Tolerance of white bean (Phaseolus vulgaris) to white mold (Sclerotinia sclerotiorum) associated with tolerance to oxalic acid

The growth of Sclerotinia sclerotiorum in white beans (Phaseolus vulgaris) was much slower in the tolerant cv. Ex Rico-23 than in the susceptible cvs. Kentwood and Seafarer. The difference was paralleled by the rate of diffusion in leaf tissue of oxalic acid, a phytotoxin of the white mold fungus (Sclerotinia sclerotiorum). Uptake of oxalic acid into excised leaves through the petiole resulted in more severe brown-rot-like symptoms in the leaves of cv. Kentwood than in those of Ex Rico-23. When [¹⁴C] oxalic acid was fed through petioles, radioactivity in the interveinal tissue of Kentwood was about three times higher than that in Ex Rico-23. Autoradiographs of leaves showed that radioactivity in Ex Rico-23 was confined to major veins and that activity in the interveinal tissue was low, whereas in Seafarer and Kentwood radioactivity did not accumulate in the veins but was distributed uniformly throughout the leaf tissue, with a slight accumulation along leaf margins.