Abstract

Stalk rot of sorghum plants caused by Erwinia chrysanthemi is one of the most destructive diseases of sorghum crop. Twenty one of bacterial isolates were isolated from stalk of sorghum plants from different location of U.S. Nagar district of Uttarakhand, India. Biochemical, physiological and morphological characterization of E. chrysanthemi was done for confirmation of the bacterium specie. Bacterial suspension [0.7% Tween-40 (v/v) + 2 × 10⁸ cell/ml] of each isolate was inject-inoculated with a 21G hypodermic needle into the stalk of plants for pathogenicity testing of the test bacterium. Reactions of biochemical and physiological testing are clearly evident enough to support the confirmation of test bacterium to taxonomic assignation of E. chrysanthemi causing soft roton sorghum plants. Out of 31 diseased samples of different locations examined, in 21 samples, the pathogen was detected as E. chrysanthemiby usingset of biochemical and physiological testing. As all the bacterium produced typical stalk rot disease symptoms on sorghum plant and water-insoluble blue pigment (indigoidine) on nutrient glycerol MnCl₂.4H₂O (2 mM) agar medium  it was confirmed as chrysanthemi species.

Key words: Blue pigment, characterization, Erwinia chrysanthemi, Stalk rot, sorghum.