Abstract

Populations of Xanthomonas campestris pv. phaseoli and other Xanthomonas occur in natural form la non symptomatic weeds. Sevently seven samples of twenty one weed species from fields Infested with common blight "Tizón común" In San Juan, Higuey, Constanza of the Dominkan Republic were evaluated. The isolationswere obtained by adding 10 ml of the buffer (12.5 mM K2PO4 + 10 mM Mg SO4, ph < 7.1). The pathogenicity tests were performed on the Dark Red Kidney bean, by inoculating plants, trifoliates and seed pods. To confirm the starch hydrolisis reaction with methyl violet and methyl green, an evaluation of the production of brown dye and thin layer chromatography for the Xanthomonadin pigment was made. Of the observed results, fourteen samples and eight species of weeds of X. campestris pv. phaseoli and 23 species of weeds of atypical Xanthomonas were found. The pathogenic isolations from leaf innoculum at two weeks the yellow zone had expanded and covered a wide area around the necrotic brown center. The bean seed pods inoculated with pathogenic isolates showed typical symptoms around ten days. All the pathogenic isolates on the leaves became pathogenic on the seed pods. None of the isolates of collected weeds after harvest. In the "Constanza" area showed any symptoms on the bean leaves. The weed samples collected from the common blight Infested fields had more pathogenic of isolates X. campestris pv. phaseolithan the samples taken from the outside ends of the fields or after harvest. We found eight weed species all belonging to six botanic families which might act as sympto-matic hosts suggests that other species could contain epiphitic X. campestris pv. phaseoli.