Chloroplast DNA (cpDNA) was used to identify polymorphisms between crucifer species using the polymerase chain reaction-random fragment-length polymorphism (PCR-RFLP) technique. Ten primer pairs based on cpDNA gene sequences were used to amplify cpDNA fragments in Brassica oleracea L., B. rapa L., B. nigra (L.) Koch, B. napus L., B. carinata Braun, B. juncea (L.) Czern, and Raphanus sativus L. accessions. Amplified DNA sequences were then digested using 11 restriction enzymes to identify polymorphisms between the 7 species. Of the 110 combinations, 38 generated polymorphisms that discriminated one or more of the species. Genotyping of these polymorphisms in 10 accessions of each of the diploid species (B. oleracea, B. nigra, B. rapa and R. sativus) did not reveal segregating polymorphisms among accessions within species, indicating that they can be used to help determine species identity. Ten accessions of each of the amphidiploids B. napus, B. carinata and B. juncea were genotyped to infer their maternal ancestry. The diploid source of cpDNA in B. carinata was B. nigra in all accessions tested and B. rapa for nine of ten B. juncea accessions tested. Two B. napus accessions amplified polymorphisms shared with B. rapa, and eight accessions produced unique polymorphisms from neither B. rapa, B. oleracea or B. nigra. The polymorphisms identified in this study can be used to help confirm identity of the diploid crucifer species for taxonomic and conservation studies.
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