Diagnosis of Xanthomonas axonopodis pv citri isolates, the causal agent of citrus canker by pathogenicity and PCR based methods

Abstract

Citrus canker caused by Xanthomonas axonopodis pv citri (Xac) is one of most destructive diseases of citrus in terms of damage to trees and fruit quality and remained as one of the important quarantine disease. Under field conditions, though Asiatic citrus canker disease is relatively easy to diagnose, the accurate detection of pathogen for various pathological studies is necessary. In present study, a total of 13 plant samples collected from various parts of Karnataka state were diagnosed by an integrated approach using pathogenecity, isolation and molecular techniques. Five isolates were able grow on nutrient glucose agar medium characteristic of Xanthomonas axonopodis pv. citri.. The pathogenicity of all the above five isolates (XAC 1, 2, 3, 4 and 5) was proved with typical canker lesions on leaves of citrus after five to eight days of incubation period. All five isolates of Xac were confirmed at molecular level by amplifying highly conserved nucleotide sequence est A region (777 bp) using Xc-lip primer pair that distinguishes Xanthomonads from bacteria. The study revealed that integrated approach as reliable technique for detection of Xac for laboratory analysis.