Race-specific genetics of resistance to black rot disease [Xanthomonas campestris pv. campestris (Xcc) (Pammel) Dowson] and the development of three random amplified polymorphic DNA markers in cauliflower

Abstract

SummaryIn order to understand the genetics of resistance to black rot disease caused by Xanthomonas campestris pv. campestris (Xcc) (Pammel) Dowson in cauliflower (Brassica oleracea var. botrytis L.) and to identify random amplified polymorphic DNA (RAPD) markers that segregate with the resistance genes, susceptible (‘Pusa Himjyoti’, female parent) and resistant (‘BR-161’, pollen parent) plants were crossed. Six generations of plants (30 P1, 30 P2,30 F1, 120 F2, 90 B1, and 90 B2) were evaluated for the presence or absence of black rot disease in a randomised block design with three replications. The pattern of segregation of resistance was tested by the χ2 test at the 5% level of significance. All F1 progeny plants were resistant, and the segregation of resistant and susceptible plants in the F2 and two backcross generations (B1 and B2) showed that a single dominant gene caused resistance to the black rot pathogen in ‘BR-161’. Three polymorphic RAPD markers (OPO-04833, OPAW-202538, and OPG-25625) were found by bulk segregant analysis, which produced unique amplicons 833 bp, 2,538 bp, and 625 bp in length, respectively. These markers were associated in coupling phase to the resistance allele. Best fit ratios of 3:1 (resistant:susceptible) in the F2 plants with the three RAPD markers, suggested that the markers were linked to the single gene controlling black rot resistance. These markers will be useful to identify more closely-linked markers and to develop black rot-resistant hybrid cauliflower varieties.