The alarming vulnerability of Coffea canephora varieties and germplasm to a virulent strain of Pseudomonas syringae pv. garcae , the cause of bacterial halo blight of coffee in Brazil

Bacterial halo blight caused by Pseudomonas syringae pv. garcae is a limiting disease to the coffee crop due to difficulty and low efficiency of the chemical control on field conditions. The simultaneous use of windbreaks and resistant cultivars seem to be the most appropriate measure of disease management. Although the bacterial halo blight resistance has been extensively studied in Coffea arabica, information about the reaction of C. canephora germplasm is not available. Thus, the objective of this study was to identify resistance sources to the bacterial halo blight in C. canephora germplasm, for use in breeding programs. Several commercial cultivars, botanical varieties, clones and hybrids of C. canephora were tested against a highly virulent P. syringae pv. garcae strain through artificial inoculations in greenhouse conditions. Only 1.4% of 2.421 evaluated plants were considered resistant to the disease. Our results showed the alarming vulnerability of Coffea canephora crop and germplasm to the bacterial halo blight from Brazil and the need to select resistant cultivars.