Chloroplast DNA Variations in Wild Brassicas and Their Implication in Breeding and Population Genetics Studies

Abstract

Evaluation of chloroplast DNA (cpDNA) diversity in wild relatives of crop brassicas is important for characterization of cytoplasm and also for population genetics/phylogeographic analyses. The former is useful for breeding programs involving wide hybridization and synthesis of alloplasmic lines, while the latter is important for formulating conservation strategies. Therefore, PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism) technique was applied to study cpDNA diversity in 14 wild brassicas (including 31 accessions) which revealed a total of 219 polymorphic fragments. The combination of polymorphisms obtained by using only two primer pair-restriction enzyme combinations was sufficient to distinguish all 14 wild brassicas. Moreover, 11 primer pairs-restriction enzyme combinations revealed intraspecific polymorphisms in eight wild brassicas (including endemic and endangered species, B. cretica and B. insularis, resp.). Thus, even within a small number of accessions that were screened, intraspecific polymorphisms were observed, which is important for population genetics analyses in wild brassicas and consequently for conservation studies.

Figure 1

PCR-RFLP patterns in some wild relatives of brassicas obtained in the combination DT-TaqI. Lanes 1–18 are Dvi1, Das1, Dca1, Deru1, Bto1, Bcr2, Bcr1, Bel1, Bel2, Bel3, Bel4, Bgr1, Bma1, Bma2, Bma3, Bba1, Bba2, and Bso1, respectively. Intraspecific variations shown in B. cretica (lanes 6 and 7), B. elongata (lanes 8 to 11), and B. maurorum (lanes 13 to 15). See Table 1 for code of species and accessions. M: 100 bp ladder (left) and 50 bp ladder (right) molecular size markers; arrow indicates 500 bp band.

Figure 2

Dendrogram obtained by UPGMA clustering analysis of PCR-RFLP marker data, of 31 accessions corresponding to 14 wild relatives of brassicas and Cardamine flexuosa as outgroup. See Table 1 for code of species and accessions.