Bacterial leaf blight of cowpea in Egypt: 1 Causal organism and factors affecting its growth

ABSTRACT

Naturally infected plants showed leaf blight and stem canker symptoms. Leaf inoculated plants exhibited irregular reddish brown blotches followed by leaf wilting, while stem or pod inoculated ones develop either cankers or brownish water-soaked spots, respectively, at the sites of inoculation. Diagnostic tests suggested the pathogen to be Xanthomonas campestris p.v. vignicola. Varietal response test showed that isolate varied as regards the severity of symptoms they initiated in a given variety of bean or cowpea. Host range studies revealed that the pathogen is able to initiate a hypersensitive reaction in tobacco, tomato, squash, braod bean and common apricot. Trials on antibacterial compounds revealed that Terramycin, Penicillin, Chloramphenicol, Streptomycin and Erythromycin as well as Marfazin and formaldehyde had the most pronounced inhibitory effect on growth of the bacterial isolates tested