Characterization of halo blight races on dry beans in South Africa

Isolates of the halo blight pathogen Pseudomonas syringae pv. phaseolicola were collected in the bean-producing areas in South Africa from 1991 to 1996. Of the 1,128 isolates collected, 967 were identified as P. syringae pv. phaseolicola. The majority of these isolates were obtained from a wide range of Phaseolus vulgaris cultivars, and the rest from P. coccineus and P. lunatus. Two hundred fifty-five isolates, representative of all the localities and cultivars sampled, were categorized into different races according to their reaction on a set of differential cultivars. Seven races (1, 2, 4, 6, 7, 8, and 9) were identified, with race 8 the most prevalent. Races 1, 2, 6, and 8 were widely distributed through the whole production area, while races 4, 7, and 9 were restricted to one or two localities