Bean anthracnose: Inoculation methods and influence of plant stage on resistance of Phaseolus vulgaris cultivars

Bean anthracnose, caused by Collelotrichum lindemuthianum, severely reduces bean production world-wide and rapid methods are required to investigate b ean-C. lindemuthianum interactions. In this study, bean cvs Boterkoning, Sa xa and Admires were inoculated with C. lindemuthianum race 69 using three d ifferent methods: germinated seed inoculation, seedling inoculation and det ached leaf inoculation. Although the methods gave similar results, inoculat ion of detached leaves was the best method. In order to compare the suscept ibility of bean at different developmental stages, cvs Prelude, Boterkoning , Saxa and Admires were used. Leaves harvested from 6-, 8-, 10-, 12- and 14 -day-old plants were inoculated with C. lindemuthianum races 9, 69, 385, an d 401. Race 9 was virulent to the four bean cultivars at all the tested sta ges; cvs Admires and Saxa were resistant to races 69, 385 and 401, whereas cv. Boterkoning was susceptible. Plants of cv. Prelude were sensitive at 8 days of age, but resistant when 12 and 14 days old. The present results sug gest that the resistance of certain bean cultivars is not equally expressed at all the developmental stages.