Pathogenicity and virulence of Ugandan isolates of common bacterial blight disease pathogen

Breeding for resistance is a major component in the integrated management of common bacterial disease of beans (Phaseolus vulgaris L.). Use of less virulent strains or strains with attenuated virulence may lead to selection of resistant genotypes with intermediate response, when exposed to more virulent strains of the pathogen. The objective of this study to identify and characterise Ugandan isolates of common bacterial blight disease-causing pathogens for virulence. Bacteria were isolated from leaf samples collected from districts of Kabale, Masaka, Bukomansimbi, Mubende, Mbale, Bulambuli and Apac, all in Uganda, during the first season of 2016. The bacteria were tested for pathogenicity, as well as virulence on both breeding and local varieties. The study identified three most virulent isolates, namely MBL020, KAB-3 and BUL-14, all belonging to Xathomonas citri pv fuscans. These isolates are very similar to those previously identified from Uganda (NCPB 670 and NCCPB 1402) more than 50 years ago. The study further revealed that NAROBEAN1, NAROBEAN 2, NAROBEAN 4, VAX 3, VAX5 and NE 2- 14- 8 had better resistance compared to other tested genotypes. Key words: Phaseolus vulgaris, Uganda, virulent strains