Genetic diversity and structure of wild Tunisian Thymus capitatus (L.) Hoffm. et Link. (Lamiaceae) assessed using isozyme markers

The genetic diversity and population structure of 25 natural populations of Thymus capitatus, from five ecological areas, were analysed using eight isozymes. For all populations, 11 polymorphic loci were detected, and several of them showed rare alleles. A high genetic diversity within populations (A p=1.82; P=62.88%; H o=0.116) and an excess of heterozygosity were observed. A high level of inbreeding within populations was observed (F IS=0.471). High differentiation and low gene flow (N m=0.821) were detected among populations (F ST=0.219). The genetic variation within and among ecological groups varied according to the bioclimate. Population structuration depends on geographic distance between sites rather than on bioclimate (Mantel's test; r=0.251; P=0.004). Nei's genetic distances (D) values calculated between pairs of populations were globally low with a mean of 0.047. The unweighted pairwise groups method using arithmetic average dendrogram showed fourth sub-clusters. Population groupings occur with evident relationship to geographic location. The substantial differentiation and the high genetic similarities between populations indicate that populations have been recently isolated as a result of anthropic pressure. In situ conservation must first focus on populations with a high level of genetic diversity and rare alleles. Ex situ preservation should be elaborated by collecting seeds within populations that showed a high level of genetic diversity in each ecological group. © 2011 Blackwell Publishing Ltd.This research was supported by a grant of the Ministry of Scientific Research and Technology and the National Institute of Applied Science and Technology (Research grant 99/UR/09-10).Peer Reviewe

Initiatives féminines en agriculture et dynamiques des territoires

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Genetic diversity of wild Thymus capitatus (Lamiaceae) in Tunisia using molecular markers

In Tunisia, Thymus capitatus L. populations are severely destroyed due to deforestation and over-collecting. The species occurs in small scattered populations decreasing progressively in size. Yet, no conservation or improvement programs are attempted to preserve and promote the potential value of this resource. In this work, we assessed the genetic diversity of nine Tunisian populations of Thymus capitatus L. from different bioclimates, using 103 polymorphic randomly amplified polymorphic DNA (RAPD) loci. The analysis of the genetic variation within and among populations is primordial to elaborate conservation and improvement programs. The species showed a low diversity within populations (0.276<H’<0.327) due to genetic drift caused by the habitat fragmentation. A high genetic differentiation (GST=0.359 and ΦST=0.284) and a low gene flow (0.435<Nm<0.970) among populations, indicating a short seed and/or pollen dispersal distance, were revealed. The absence of isolation by distance and the high level of differentiation among populations suggested the existence of important historical gene flow between them. The UPGMA dendrogram analysis basedon ΦST distance matrix showed that most populations clustered independently to bioclimate or geographical distance indicating that genetic differentiation mainly occurs at local space scale due to genetic drift. Given the high proportion of the within-population diversity and the high amount of among populations variation, the ex-situ conservation should be made by the collection of seeds/cuttings rather within than among populations. The in-situ conservation should be made appropriately according to populations in their bioclimate

Deverra triradiata Hochst. ex Boiss. from the Northern Region of Saudi Arabia: Essential Oil Profiling, Plant Extracts and Biological Activities

Devrra triradiata Hochst. ex Boiss is an occasional plant species in the Northern region of Saudi Arabia. The shrub is favored on sandy desert wadis, gypsaceous substrate, and sandy gravel desert. In folk medicine, the plant is used for many purposes; to relieve stomach pains, against intestinal parasites, and for the regulation of menstruation. The present study describes the chemical composition of the essential oils (EOs) of different plant parts of D. triradiata. In vivo and in vitro biological activities of plant extracts and essential oils were also studied. Phenylpropanoids, elemicin (flowers: 100%), dillapiole (Stems: 82.33%; and seeds: 82.61%), and apiol (roots: 72.16%) were identified as the major compounds. The highest antioxidant activity was recorded for the EOs of roots and stems (IC50 = 0.282 µg/mL and 0.706 µg/mL, respectively). For plant extracts, ethyl acetate showed the highest antioxidant activities (IC50 = 2.47 and 3.18 µg/mL). EOs showed high antifungal activity against yeasts with low azole susceptibilities (i.e., Malassezia spp. and Candida krusei). The MIC values of EOs ranged between 3.4 mg/mL and 56.4 mg/mL. The obtained results also showed phytotoxic potential of plant extracts both on the germination features of Triticum aestivum seeds and the vegetative growth of seedlings

The genus <i>Artemisia</i> L. in the northern region of Saudi Arabia: essential oil variability and antibacterial activities

<p>Four species of the genus <i>Artemisia</i> L. (<i>Artemisia monosperma</i>, <i>Artemisia scoparia</i>, <i>Artemisia judaica</i> and <i>Artemisia sieberi</i>) growing in the northern region of Saudi Arabia were investigated with respect to their volatile oil contents. The yield of oil varied between 0.30 and 0.41%, % (w/w). <i>A</i>. <i>monosperma</i> showed the highest number of compounds with 30 components representing 93.78% of oil composition. However, <i>A</i>. <i>judaica</i> showed the lowest number of compounds with only 16 components representing 87.47% of essential oil. <i>A</i>. <i>scoparia</i> and <i>A</i>. <i>sieberi</i> are both composed of 17 components, representing 97.14 and 94.2% of total oil composition. <i>A</i>. <i>sieberi</i> and <i>A</i>. <i>judaica</i> were dominated by spathulenol (30.42 and 28.41%, respectively). For <i>A</i>. <i>monosperma</i>, butanoic acid (17.87%) was a major component. However, <i>A</i>. <i>scoparia</i> was a chemotype of acenaphthene. (83.23%). Essential oil of studied species showed high antibacterial activities against common human pathogens.</p

Valorization of Lyophilized Olive Mill Wastewater: Chemical and Biochemical Approaches

Lipid composition and antioxidant activity have been carried out in order to valorize the composition of olive mill wastewater extracts with different solvents (supercritical carbon dioxide, n-hexane, dichloromethane and ethanol). The antioxidant activity was evaluated using ABTS (2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picrylhydrazyl) tests. The total phenolics and flavonoid contents were, also, determined. The chemical composition of the extracted oil was established, respectively, by gas chromatography–flame ionization detector and high-performance liquid chromatography methods. The results showed that the oleic acid and equivalent carbon number of forty-eight were the major compounds of the analyzed oils. Residual olive mill wastewater from the Sousse region displayed the highest DPPH radical-scavenging activity (31.10 ± 0.10 μg/mL). The chemical analysis of extracts of OMWs showed that the n-hexane fraction contained an abundance of oleic acid (61.62%) and an equivalent carbon number of forty-eight (53.14%). The best antioxidant activity was determined for the ethanol fraction (14.5 μg/mL). The final results showed a significant difference and variations in polar and apolar components. Moreover, n-hexane extracts showed high percentages of Monounsaturated fatty acids (MUFA) with 64% of OMWs oil composition and the dichloromethane extracts contained the largest amount of flavonoids (160.30 ± 1.70 mg EQ/g DM)