Morphological and Biochemical Characterization of Xanthomonas axenopodis pv. citri Isolates Causing Citrus Canker Disease in Pakistan

Abstract

Citrus canker inflicted by bacterial pathogen, Xanthomonas axonopodis pv. citri (Xac) is very destructive disease. It is distributed worldwide and declared as quarantine pathogen due to its ability of damage when established. In the current perusal, 25 Xac isolates representing Faisalabad and Sargodha were characterized for their biochemical and morphological features. The pathogen was isolated and identified on the basis of microscopy, morphological characters and biochemical characters. After isolation and purification of pathogen, 25 isolates were used for biochemical characterization of pathogen. Six biochemical tests were used for confirmation of pathogen. In Gram’s staining, Kovac’s oxidase and Arginin dihydrolase tests, all Xac isolates showed negative results while positive results were observed in case of starch hydrolysis, tween 80 hydrolysis and gelatin liquification tests. Pathogenicity test was also performed and on all citrus varieties, development of typical symptoms was observed which confirmed the pathogen. Although, isolates were diverse and vary in level of aggressiveness. Albeit, this study is baseline for formulating appropriate management strategy in controlling citrus canker disease.