Sensitivity to copper in Xanthomonas campestris pv. Viticola

Abstract

Bacterial canker, caused by Xanthomonas campestris pv. viticola, affects grapevines in the irrigated areas of the São Francisco river valley, in the states of Pernambuco and Bahia. Several practices for disease management have been adopted including copper sprays. This is the only available chemical control method and most frequently used in the areas affected by the disease. The objective of this work was to determine the sensitivity to copper of strains of X. campestris pv. viticola collected in different locations and over a period of years, from 1998 to 2006. Variation in sensitivity to copper oxychloride and copper sulfate was observed among the 21 strains tested. The minimum inhibitory concentration (MIC) varied from 10 to 60 μg/mL Cu2+, for both compounds. A general increase in copper tolerance over the years was also observed, with the Brazilian strains being more tolerant than the type-strain, collected in 1972 in India. The differences observed in copper sensitivity may lead to the selection and dominance of the more tolerant strains in the bacterial population as copper compounds continue to be used in the region.