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- Author or Editor: Laura Fredrick Marek x
Black rot, caused by Xanthomonas campestris pv. campestris (Pam.) Dawson (Xcc), is a serious disease of vegetable crucifers worldwide. The USDA NC-7 and NE-9 regional PI stations maintain vegetable, mustard, and oilseed crucifers, of which 4084 accessions were available for testing, representing 23 genera and 125 species. These accessions were evaluated for resistance to black rot after wound inoculation with race 1 of the pathogen. Accessions that were symptomless for race 1 of Xcc were replanted and inoculated with race 4 of the pathogen to identify accessions with resistance to both races. Symptomless responses were observed in 362 accessions of the mustard species (Brassica juncea, Brassica carinata, and Brassica nigra), in particular, B. juncea for which 353 of the 389 accessions tested were symptomless. Resistance was identified in five accessions of B. carinata out of 63 evaluated (PI 193460, PI 193959, PI 194254, PI 280230, PI 633077) determined by repeated symptomless responses after inoculation and four accessions of B. nigra from the 83 evaluated (PI 197401, A 25399, A 25401, PI 458981). Five accessions of Brassica rapa (PI 633154, A9285, PI 340208, PI 597831, PI 173847) were identified, which represent promising new sources of resistance to Xcc. Incomplete resistance was identified in an accession of Eruca sativa (PI 633207), an accession of Lepidium spp. (PI 633265), an accession of Sinapis arvensis (PI 296079), and two accessions of B. napus (PI 469733 and PI 469828). These identified accessions represent germplasm that can be used in breeding for resistance to Xcc in vegetable crucifers through interspecific crossing.