Identification of sources of resistance to Xanthomonas campestris in Brachiaria spp. In 1997 bacterial wilting was observed in some the Brachiaria accessions of the Improvement Program of the International Center of Tropical Agriculture (CIAT), in Palmira,Colombia,both in the greenhouse in Palmira (Valle) and in the field in Puerto Lopez (Meta). Samples of Brachiaria CIAT 1051 were collected with typical symptoms of the disease, from which a pathogenic bacterium identified as Xanthomonas campestris was isolated. In order to find sources of resistance to the disease, 35 Brachiaria materials, sexual and hybrid populations were evaluated in the greenhouse. Of these, 18 showed resistance. A study of resistant and susceptible material was performed, to confirm the relation between Brachiaria susceptibility and the population level of the bacteria on the plant, for which two materials were selected,BR97-405 (resistant) and CIAT 1015 (susceptible). A tool was successfully developed to evaluate sources of resistance to bacterial diseases in Brachiaria spp. relating the population level with susceptibility, which will make it possible to avoid losses caused by this pathogen in the field.