RACES AND SURVIVAL OF PSEUDOMONAS-SYRINGAE PV PHASEOLICOLA IN NORTHERN TANZANIA

The pathogenic variation among 118 isolates of Pseudomonas syringae pv. phaseolicola associated with halo blight of bean (Phaseolus vulgaris) in the Arusha and Kilimanjaro regions of northern Tanzania from November 1988 to February 1990 was examined with four differential bean cultivars. The three races recovered were race 2 (52.5%), race 1 (45.0%), and race 3 (2.5%). Some strains of race 2, designated as 2P, produced a brown, diffusible pigment on agar media. Some race 2P strains grew at 34 C, whereas the non-pigment-producing strains of race 2 and of races 1 and 3 failed to grow at this temperature. Race 2 strains obtained from bean debris from Monduli in the Arusha region induced systemic chlorosis and stunting on the usually resistant differential bean cultivar Edmund. The ability of P. s. phaseolicola to survive in bean debris and in dead standing bean plants varied according to race, geographic location, depth in the soil, and bean genotype.