Pathogenic Variability and Antibiotic Sensitivity in Xanthomonas campestris

pv campestris isolates Causing Black rot of Cauliflower

Sain S. K., Gour H. N.1 and Sharma Pratibha

Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi-110012; 1Department of Plant Pathology, Maharana Pratap University of Agricultural & Technology, Udaipur, Rajasthan-3130001, India. email: sain.skumar@gmail.com

Abstract

Management of Xanthomonas campestris pv. campestris that causes severe black rot in crucifers and cauliflower is difficult in fields. The isolates of black rot pathogen were collected from Pusa, Gaziabad and Yamunapar regions of New Delhi, and Sikar and Udaipur districts of Rajasthan and virulence was tested on 10 cultivars of cauliflower. They were grouped into three pathogenic sub-groups or races (R-1nd, R-2sk, and R-3ud) based on pathogenic variability and disease reactions on cauliflower. The isolates under the group R-1nd were more virulent than others. These isolates also varied in their response to starch, gelatin and casein hydrolysis and levan production. Variability was also observed in the antibiotic sensitivity tests. The isolates were insensitive to moderately sensitive to all the antibiotics except ampicillin to which most isolates were sensitive at 10 and 25 µg. Ten isolates (less virulent to virulent) were observed to contain single indigenous plasmid of 1 kb, except two isolates Xc-4 (less virulent) and Xc-8 (virulent) which had no plasmid. SDS PAGE profile of all the isolates was similar in protein bands of molecular weights ranging from 8 to 200 kDa. Although isolates showed variability in virulence and antibiotic sensitivity, there was no correlation with the presence or absence of indigenous plasmid or with protein profile.

Key words: Black rot, cauliflower, Xanthomonas campestris pv. campestris, pathogenic variability, antibiotic sensitivity, indigenous plasmid

Citation: Sain SK, Gour HN and Sharma P. 2008. Pathogenic variability and antibiotic sensitivity in Xanthomonas campestris pv campestris isolates causing black rot of cauliflower. J Mycol Pl Pathol 38(3):599-605.