Volatiles from twelve wild Tunisian populations of Lavandula multifida L. growing in different bioclimatic zones were assessed by GC (RI) and GC/MS. Thirty-six constituents, representing 83.48% of the total oil were identified. The major components at the species level were carvacrol (31.81%), beta-bisabolene (14.89%), and acrylic acid dodecyl ester (11.43%). These volatiles, together with alpha-pinene, were also the main compounds discriminating the populations. According to these dominant compounds, one chemotype was revealed, a carvacrol/beta-bisabolene/acrylic acid dodecyl ester chemotype. However, a significant variation among the populations was observed for the majority of the constituents. A high chemical-population structure, estimated both by principal component analysis (PCA) and unweighted pair group method with averaging (UPGMA) cluster analysis based on Euclidean distances, was observed. Both methods allowed separation of the populations in three groups defined rather by minor than by major compounds. The population groups were not strictly concordant with their bioclimatic or geographic location. Conservation strategies should concern all populations, because of their low size and their high level of destruction. Populations exhibiting particular compounds other than the major ones should be protected first.
Abstract• The genetic diversity of nine wild Tunisian Crataegus azarolus var. aronia L. populations from different bioclimates was assessed using RAPD markers.• Eight selected primers generated a total of 105 bands, 81 of which were polymorphic. Shannon's index (H ) ranged from 0.222 to 0.278 according to a population with an average of 0.245. The genetic variation within the species (H SP = 0.423) was relatively low. A high differentiation (G ST = 0.421) among populations coupled with a low level of gene flow (N m = 0.472) were observed. The analysis of molecular variance (AMOVA) revealed also significant differentiation among populations (Φ ST = 0.371), even at a low scale space. The majority of variation occurred within populations (63.31%). The Mantel test performed on genetic (Φ ST ) and geographic distance matrices among population pairs did not reveal an isolation by distance.• Interpretation of Neighbour-joining tree based on Nei's and Li's genetic distance among individuals showed distinct population groupings. The UPGMA dendrogram based on Φ ST values revealed two population sub-clusters, each including populations from different bioclimates and/or geographic regions.• The low level of genetic diversity and the high genetic structure of populations resulted from genetic drift caused both by habitat fragmentation and the low size of populations.• The high differentiation among populations and the similar low level of diversity within populations suggest that in situ conservation should interest all populations. The ex situ conservation should be based on the collection of seeds rather within than among populations because of the maximum of variation was revealed within populations. Mots-clés :RAPD / Crataegus azarolus / diversité génétique / populations naturelles / conservation Résumé -Analyse de la diversité génétique de populations tunisiennes de Crataegus azarolus L. var. aronia L. par des marqueurs RAPD.• La diversité génétique de neuf populations naturelles de Crataegus azarolus var. aronia L. en Tunisie, appartenant à différents étages bioclimatiques, a été analysée par des marqueurs RAPD.• Huit amorces retenues ont généré 105 bandes dont 81 sont polymorphes. L'indice de Shannon (H ) varie de 0,222 à 0,278 selon les populations avec une moyenne de 0,245. La variabilité génétique au sein de l'espèce est relativement faible (H SP = 0, 423). Une différenciation importante entre les populations (G ST = 0, 421) et un faible flux de gènes entre elles (N m = 0, 472) ont été observés. L'analyse de la variance moléculaire (AMOVA) a révélé, elle aussi, une différenciation significative entre les populations considérées ensemble (Φ ST = 0, 371) ou regroupées selon leur localisation bioclimatique. La majeure proportion de la variabilité réside à l'intérieur des populations (63,31 %). Le test de Mantel, effectué sur les matrices des distances génétiques (Φ ST ) et géographiques entre les paires des populations, n'a pas révélé une isolation par distance.• Le dendrogramme, établi à partir des distances génétiqu...
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