Effects of seed infection and hydration on the buildup of common bacterial blight and its impact on the yield of dry beans

Abstract

Common bacterial blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli (Xap), is a serious foliar disease in most of the dry bean (Phaseolus vulgaris L.) growing regions. A 4 yr study examined the effects of different sources of infection and seed hydration on CBB development, yield components, and yield in seven resistant or susceptible dry bean lines and cultivars. The five agronomic treatments examined included clean seed, diseased seed, hydrated diseased seed, clean seed with a Xap spray, and diseased seed with a Xap spray. Disease development, the yield components, and yield were strongly influenced by weather conditions. In comparison with the diseased-seed treatment, the use of clean (disease-free) seed reduced the incidence of CBB leaf infection in the susceptible dry bean cultivars, but no similar benefit was observed in the resistant lines and cultivars. During the three dry growing seasons, the seed-hydration treatment increased the incidence of CBB leaf infection compared with the diseased-seed treatment for the susceptible cultivars but not for the resistant lines and cultivars. In the wet growing season, no significant difference in the incidence of leaf infection was observed between the hydrated-seed and diseased-seed treatments in any of the cultivars, possibly because the wet soil conditions promoted pathogen development within the bean plants that year. Seed hydration did not improve seed yield in the dry years, but sometimes decreased it under wet conditions. Therefore, seed hydration cannot be recommended for use in the production of dry beans.