Journal of Plant Pathology & Microbiology

Abstract

Pathogenic and Genetic Characterization of Xanthomonas campestris Pv. campestris Races Based on Rep-PCR and Multilocus Sequence Analysis

Priyanka Singh Rathaur, Dinesh Singh, Richa Raghuwanshi and Yadava DK

Xanthomonas campestris pv. campestris (Pammel) Dowson (Xcc) is the causal agent of black rot disease of crucifers worldwide. Seventy five isolates of Xcc were collected from 12 agro-climatic regions of India to determine the distribution pattern of races and diversity of the population. Based on pathogenic reaction on seven standard differential crucifers, race 1, 4 & 6 were found to be prevalent. For assessing the pathogenic diversity, forty one cultivars of crucifers comprising seven Brassica and coeno species were inoculated artificially under field conditions. Brassica juncea cultivars (Pusa Bold, Varuna, Pusa Vijay, Pusa Mustard 21 and Pusa Mustard 25) showed resistance against all the strains of Xcc, whereas the Brassica olerecea cultivar Pusa Ageti was found to be resistant to races 1 and 4. Genetic characterization of these 75 strains of Xcc was carried out using rep-PCR (ERIC, REP and BOXPCRs) followed by phylogenetic analysis. The strains of Xcc clustered into 6 groups at 50% similarity coefficient and among these groups, 28 strains of Xcc belonging to races 1, 4 & 6 were clustered together under Group 5. Sequences of the 16S rRNA, hrpF and efP genes of five strains representing the races 1, 4 and 6 were used for multilocus sequence analysis. Based on sequence analysis of 16S rRNA and hrpF genes, the Indian strains were found to be very closely related to the strain Xcc ATCC 33913 (race 3, UK), whereas based on efP sequences, they were found to be closely related to strains race 1 Xcc B100 (Italy) and race 9 Xcc 8004 (UK).