Assessment of copper resistance in Pseudomonas syringae pv. phaseolicola, the pathogen of halo blight on snap bean

摘要

Halo blight, caused by Pseudomonas syringae pv. phaseolicola (Psp), is one of major bacterial diseases on beans worldwide. The disease infects leaves and pods of beans and is most destructive in areas such as south Florida where temperatures are moderate, rainfalls are frequent, and abundant inoculum is present. Application of fixed copper is the primary method currently used by growers to reduce halo blight damage. However, the development of copper resistance in the pathogen populations has become a primary concern in managing this disease. A total of 35 strains of Psp were isolated from snap bean samples collected from commercial fields in 2009 and 2010 in Homestead, Florida. Results from this study indicate that 80% of the Psp strains (28 of 35) from commercial snap bean fields were resistant to copper, based on bacterial populations after 24-h exposure in liquid NB media. Growth of the Psp strains on CYE agar was similar to that in liquid NB, both amended with copper, suggesting that assays on CYE agar amended with copper can be used for rapid assessment of copper resistance in Psp populations. Data from greenhouse experiments indicated that addition of mancozeb improved the efficacy of copper hydroxide for management of halo blight on snap bean caused by copper-resistant Psp strains. (C) 2017 Elsevier Ltd. All rights reserved.