Kumar Lambani and Shamarao Jahagirdar
Department of Plant Pathology, College of Agriculture, University of Agricultural Sciences, Dharwad – 580 005, India.
The identification of the pathogen Xanthomonas axonopodis pv. glycines involved in causation of the disease was done by conducting studies on its morphological, biochemical, cultural and physiological features of the pathogen as per the standard microbiological procedures. The bacterium was gram negative, rod shaped with round ends. The cells appeared as single, some in pairs and in clusters having single polar flagellum. The cells measured 0.4 -0.25 x 1.25- 3.00 mm in size. The biochemical features of the pathogen revealed that the bacterium liquified the gelatin, produced the H2S, positive for starch hydrolysis and acid produced by carbon sources (sucrose,glucose and dextrose) but it was negative for acid production by nitrogen (peptone) sources. Among the eight different solid media tested, NGA medium was significantly supported for the luxurious growth of the pathogen as evidenced by the maximum recovery of bacterial colonies (96.00). Significantly least number of colonies (39.40) was recorded on Xan-D medium. The XPS agar medium supported absolutely no growth of the bacterium. Circular, flattened, slightly raised, convex with yellow to bright yellow colour on SX and NA medium. They occurred singly or rarely in aggregates. Where as, on both YDCA and GYCA, colonies were circular, slightly raised, glistering with yellow colour. Highly irregular to irregular, slightly raised, light yellow coloured colonies were observed in NGA media. Optimum temperature requirement for the growth of pathogen was studied and found that the temperature level of 30oC was optimum in which significantly maximum numbers of bacterial colonies were recorded. The pathogen colonies were reduced below and beyond of 30oC. Similarly, the effect of hydrogen ion concentration on the growth of pathogen was studied and found that pH of 7.0 as optimum where maximum numbers of colonies were recorded. The colonies were found reduced beyond and below pH level of 7.0.
Keywords: Xanthomonas axonopodis pv. glycines, Morphology, Gram negative, biochemical, starch hydrolysis, cultural, NGA, physiological, temperature and pH.