Standardization of Indian cultivars of Brassica spp. for characterization of Xanthomonas campestris pv. campestris races causing black rot disease of crucifer crops

Abstract

Xanthomonas campestris pv. Campestris (Xcc) causing black rot disease of crucifer crops, is a serious worldwide problem resulting in >50% loss under environmental conditions favorable to the pathogen. For the characterization of Xanthomonas campestris pv. campestris races to standardize the Indian cultivars of Brassica spp. total of 184 representatives lines of the family crucifereae from of five economically important Brassica species, i.e. B. carinata, B. juncea, B. napus, B. oleracea, and B. rapa grown in India were inoculated by 75 strains of Xcc, belonging to three races 1, 4 and 6 in 2012-13 and 2013-14. Disease reaction of these cultivars was compared with the standard differential hosts of crucifer for disease incidence and diseases severity. Indian cultivars of B. juncea (Pusa Bold, Pusa Varuna, Pusa Vijay, Pusa Mustard-21, Pusa Mustard-25, Pusa Sag), B. olerecea var. botrytis (Pusa Sukti), B. olerecea var. capitata (KGMR) and B. rapa (Pusa Swarnima) were at par with the standard differentials of respective Brassica species and thus could be suitable to useas alternative differential hosts for characterization of Xcc races. 20 cultivars of Brassica spp. grown in India were further validated as differential crucifer host to characterize the races of Xcc on the molecular basis using four set of primers, viz. CAPS (ACS2) CAPS (BTPT) and CAPS (NDPK3) and among them, Br 019305 primer amplified at 906 bp in all cultivars, while primer CAPS (ACS2), CAPS (BTPT) and CAPS (NDPK3) primers were amplified multiple bands. Combined phylogenetic UPGMA study at 75% similarity coefficient, 19/20 accessions were divided into three groups and distinguished resistant and susceptible cultivars against black rot disease.