Epidemiological Aspects of Uromyces appendiculatus on Dry Bean (Phaseolus vulgaris) After Treatment with Bacillus subtilis

The number of pustules per leaf area, the average diameters of pustules and average spore production and spore viability were determined on fully expanded primary leaves of dry bean (Phaseolus vulgaris) which had been treated with a suspension of 106 cells of Bacillus subtilis. either as culture broth or as lyophilized broth, 24, 48, 72, 96 or 120 h before inoculation with urediniospores of Uromyces appendiculatus. Urediniospores were collected from treated plants, inoculated to new plants and the number of pustules per leaf area determined. The number of pustules per leaf, spore production per leaf area and the viability of spores were all significantly reduced by previous application of either liquid cultures or lyophilized broth, with greater reductions occurring at shorter intervals before inoculation with U. appendiculatus. There was no effect of treatment on the diameter of pustules. This reduction of disease severity could be of significance in the production of grown beans.