Response of Brassica oleracea var. capitata to wound and spray inoculations with Xanthomonas camplestris pv. campestris

Eighteen cabbage breeding lines and cultivars were evaluated for resistance to black rot caused by Xanthomonas campestris pv. campestris following wound and spray inoculations at the juvenile and mature stages. Plants were evaluated using four inoculation procedures (juvenile wound, juvenile spray, mature wound, and mature spray) in replicated greenhouse and field experiments. The breeding lines Badger # 16, Cornell 101, Cornell 102, NY 4002 and accession PI 426606 exhibited high levels of resistance following all inoculation procedures. 'Silver Dynasty' was the most resistant commercial cultivar based on the four tests, yet ranked 12th following the juvenile wound inoculation. The juvenile spray inoculation had a high correlation with both wound and spray inoculations in field experiments (0.89 and 0.86, respectively); however, the juvenile wound inoculation did not correlate well with mature wound and spray inoculations (0.58 and 0.51, respectively). The results indicate that the juvenile wound inoculation is not the most appropriate approach for determining field resistance in Brassica oleracea, and that resistant material could be selected against using this approach. A high correlation between juvenile spray inoculation disease severity ratings and mature plant resistance indicates that plants can be evaluated effectively at the juvenile stage for mature plant resistance to black rot.