Chloroplast and nuclear DNA studies in a few members of the Brassica oleracea L. group using PCR-RFLP and ISSR-PCR markers: a population genetic analysis

A population genetic analysis of chloroplast and nuclear DNA was performed covering nine wild populations of Brassica oleracea. Three members of the n = 9 group, all close to B. oleracea, Brassica alboglabra Bailey, Brassica bourgeaui (Webb) O. Kuntze and Brassica montana Pourret, were also studied to better understand their relationship with B. oleracea. Chloroplast DNA was analysed using the PCR-RFLP (polymerase chain reaction - restriction fragment length polymorphism) method. The ISSR-PCR (inter-simple sequence repeat - polymerase chain reaction) technique was adopted to study nuclear DNA. Twelve primer pairs of chloroplast DNA showed very good amplification. The amplified product of each primer pair, digested by three restriction enzymes, revealed no variation of cpDNA among the taxa studied. This indicates they may have the same chloroplast genotype. Seven selected ISSR primers have detected genetic variation, both within and among the populations/taxa surveyed. The information obtained on the intra- and inter-populational genetic diversity of wild populations of B. oleracea neatly defined the individual plants. It could provide important guidelines for backing management and conservation strategies in this species. The study confirms a close relationship between B. alboglabra, B. bourgeaui and B. montana, which is parallel to their morphological similitude.

A population genetic analysis of chloroplast DNA in wild populations of Prunus avium L. in Europe

A population genetic study of chloroplast DNA was carried out in 23 wild populations of Prunus avium sampled from several European deciduous forests. An analysis of approx. 9% of the chloroplast genome detected mostly insertion-deletion mutations and one point mutation. In all, 16 haplotypes were detected. Six haplotypes were shared by two or more populations and 10 were unique. One haplotype was present in 21 of the 23 populations and 161 of 211 individuals, which probably indicates its ancient origin. The level of population subdivision, using unordered and ordered alleles, was low, GSTC=0.29 and NSTC=0.33, respectively. The difference between GSTC and NSTC is nonsignificant, indicating an absence of correlation between haplotype phylogeny and geographical distribution. The absence of phylogeographic structure in wild cherry may be attributed to long distance gene flow among populations by birds, animals and anthropogenic activities. The minimum-length spanning tree depicting the phylogenetic relationships between the haplotypes indicates the possible existence of two lineages represented by the haplotypes H3 and H4. The information about homogeneity or heterogeneity of populations in terms of haplotype constitution and detection of rare haplotypes in some populations will be useful for formulation of conservation and management strategies of wild cherry.

Molecular systematics of Brassica and allied genera (Subtribe Brassicinae, Brassiceae) - chloroplast DNA variation in the genus Diplotaxis

Chloroplast DNA restriction site variation for 17 endonucleases was surveyed for the large single-copy region of the genome in 26 taxa of the genus Diplotaxis and compared with previously mapped site mutations in other members of the Subtribe Brassicinae (Tribe Brassiceae, Cruciferae). A total of 259 restriction site and length mutations were observed, 206 (80%) of which showed variation at the interspecific level. Phylogenetic analysis indicated a clear division of the genus Diplotaxis into the same two lineages for the Subtribe Brassicinae, described previously by Warwick and Black as Rapa/ Oleracea and Nigra. Levels of genetic divergence and taxon groupings suggested by the restriction site variation were highly consistent with previously recognized cytodemes or crossing groups and the geographical distribution of Diplotaxis taxa. However, the data were inconsistent with the morphologically based taxonomic delimitation of the genus, certain subgeneric circumscriptions, and even species delimitation in the case of D. virgata. Diplotaxis species were separated into three major groups in each of the two lineages. In the Rapa/ Oleracea lineage, Group A included D. erucoides ssp. erucoides and D. cossoniana. Group B included two subgroups: B (i) D. tenuifolia, D. cretacea, and D. simplex and B (ii) D. harra. Group C included D. viminea and D. muralis. Within the Nigra lineage, group D included D. siettiana, D. ibicensis, D. brevisiliqua, and D. gomezcampoi. Group E included D. brachycarpa. Group F included three subgroups: F (i) D. assurgens, D. tenuisiliqua, an accession of D. virgata from southern Morocco (DVA), and D. siifolia; F (ii) D. berthautii and D. virgata f. sahariensis; and F (iii) D. catholica, D. catholica var. rivulorum, D. virgata ssp. virgata. These groups often showed greater genetic closeness to other species from other genera in the Subtribe than to other species of Diplotaxis.