Morphological and Biochemical Characterization of Four Isolates of Xanthomonas Associated with Different Tissues of Acid Lime (Citrus aurantifolia)

Abstract

Four isolates of Xanthomonas axonopodis pv. citri obtained from different parts of acid lime were evaluated for cultural variability and biochemical characteristics at the Department of Plant Pathology, VNMKV, Parbhani, during Kharif 2021–22. Isolates recovered from leaves, fruits, stem, and thorn were designated Xac1, Xac2, Xac3, and Xac4, respectively. Cultural characteristics were assessed through microscopic and visual observations, while biochemical characteristics were examined using Gram staining, potassium hydroxide solubility, catalase, starch hydrolysis, anaerobic growth, and tetrazolium salt tolerance tests. All four isolates were morphologically single rods and produced filiform colonies with convex elevation, an entire margin, and a mucoid, glistening surface. Pigmentation varied among isolates: Xac1 was yellow, Xac2 was brownish yellow, and Xac3 and Xac4 were light yellow. The isolates showed negative reactions in Gram staining, the anaerobic growth test, and the tetrazolium salt tolerance test, whereas positive reactions were recorded for potassium hydroxide solubility, catalase activity, and starch hydrolysis. No biochemical variation was detected among the isolates. Thus, the isolates displayed variation in pigmentation but were uniform in the other recorded cultural characteristics and in the biochemical reactions examined. These findings document the cultural and biochemical characteristics of isolates recovered from different acid lime plant parts under the conditions of the study.