Pathological and biochemical characterization of bacterial canker pathogen from capsicum

Abstract

Bacterial canker affected capsicum plants resulted in production of white milky ooze and vascular discoloration of the longitudinal cut section of the infected stem. The typical colony of the bacterium developed on the Nutrient agar medium exhibited circular, mucoid, shining characters and was creamish in colour. Purified bacterium when inoculated on capsicum seedlings produced typical disease symptoms i.e cupping and downward turning of the leaflets, chlorosis followed by partial wilting, proliferation of stem which then developed to form cracks and formation of cankers confirming the pathogenicity of test bacterium. The Bacterial cells were non-motile Gram-positive and non-spore forming. The yellow pigmentation of the bacterium revealed short rods with straight to slightly curve in shape. Colonies of the bacterium obtainedcreamish to yellow, convex, glistening with convex margins. The absence of high-domedshining colonies, tips of the strips were blackened indicating the production of hydrogen sulphide, Bacterium streaked onto plates with TTC (2-3-5 tri phenyl tetrazolium chloride) solution exhibited no bacterial growth and resultedin the formation of bubbles when mixed with a drop of freshly prepared H2O2 (3%) holds promise to distinguish Clavibacter michiganensis. Thus results on identification of bacterium based on pathological, biochemical and pathogenicity tests exhibited the existence of Clavibacter michiganensis to be responsible for causing bacterial canker of capsicum in Himachal Pradesh.