A simple inoculation technique for evaluation of cotton genotypes for resistance to bacterial blight caused by Xanthomonas axonopodis pv. malvacearum

Different methods of artificial inoculation were tested for evaluation of cotton genotypes for resistance to bacterial blight caused by Xanthomonas axonopodis pv. malvacearum (Xam). Among them sandpaper inoculation method recorded the maximum disease incidence of 85 per cent followed by pressurized spraying (75 per cent) and hypodermic syringe (70 per cent) methods. Symptoms were expressed 15-21 days after inoculation in the form of typical water-soaked spots and vein blight on leaves; black arm on stem and boll rot on bolls. Seven varieties and three hybrids of cotton were screened against the incidence of bacterial blight using eight pathogenic isolates of Xam collected from different cotton-growing regions of Tamil Nadu, India. Among them cultivar K-11 showed 100 per cent resistance reaction against all isolates of Xam under greenhouse conditions.