Resistance of Xanthomonas campestris pv. vesicatoria isolates from Tanzania to copper and implications for bacterial spot management

Abstract

Thirty isolates of Xanthomonas campestris pv. vesicatoria (Xcv) from Tanzania were evaluated for sensitivity to copper sulphate (CuSO 4 :5H 2 0) using dilution plate counts. Ninety-three percent (28/30) of the isolates produced countable colonies on nutrient glucose agar amended with 0.8 mM CuSO 4. All the Xcv isolates (7/7) from Arusha (northern Tanzania) grew on the copper medium. Isolates of the pathogen from Iringa (southern Tanzania) produced variable results (15/21). However, neither of the two Xcv isolates from Morogoro (Eastern Tanzania) grew on the copper medium. These results indicate long-term exposure of Xcv isolates from Tanzania to selection pressure for copper tolerance.