Better knowledge of medicinal plant species and their conservation is an urgent need worldwide. Decision making for conservation strategies can be based on the knowledge of the variability and population genetic structure of the species and on the events that may influence these genetic parameters. Achyrocline flaccida (Weinm.) DC. is a native plant from the grassy fields of South America with high value in folk medicine. In spite of its importance, no genetic and conservation studies are available for the species. In this work, microsatellite and ISSR (inter-simple sequence repeat) markers were used to estimate the genetic variability and structure of seven populations of A. flaccida from southern Brazil. The microsatellite markers were inefficient in A. flaccida owing to a high number of null alleles. After the evaluation of 42 ISSR primers on one population, 10 were selected for further analysis of seven A. flaccida populations. The results of ISSR showed that the high number of exclusive absence of loci might contribute to the inter-population differentiation. Genetic variability of the species was high (Nei’s diversity of 0.23 and Shannon diversity of 0.37). AMOVA indicated higher genetic variability within (64.7%) than among (33.96%) populations, and the variability was unevenly distributed (FST 0.33). Gene flow among populations ranged from 1.68 to 5.2 migrants per generation, with an average of 1.39. The results of PCoA and Bayesian analyses corroborated and indicated that the populations are structured. The observed genetic variability and population structure of A. flaccida are discussed in the context of the vegetation formation history in southern Brazil, as well as the possible anthropogenic effects. Additionally, we discuss the implications of the results in the conservation of the species.

The in vitro development of a plant is controlled by factors that promote a series of plant responses, which interfere with tissue organogenesis and morphology. For plants of the family Lamiaceae, these factors remain unknown or poorly understood, hindering in vitro cultivation of these plants. The basil cultivar ‘Grecco a palla’ has attractive chemical properties for medicinal, pharmaceutical, and cosmetic industries; however, its production is limited due to the lack of appropriate cultivation conditions. Two types of explants of this species (nodal segments and stem apexes) were grown in culture media with auxin and cytokinin, and their development was followed for 60 days. During in vitro cultivation, both explants were subjected to higher concentrations of plant growth regulators (PGRs) produced only calluses, without induction of shoots. Small amounts of regulators favored hyperhydricity as nodal segments or stem apexes in the absence of PGRs produced plants with disturbances, including brittle, light green, and thick leaves. In this case, there was an increase in the cell layers of palisade parenchyma, which had large cell spaces and larger cells. This tissue also advanced to spongy parenchyma and compressed it. The stomatal density was low; however, the stomata were larger with additions mainly in the guard cells and the stomatic opening. Therefore, stem apexes in the absence of PGRs produced more vigorous plants, whereas nodal segments with low amounts of cytokinins and auxins developed a well-branched and abundant root system.

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The species Ocimum basilicum has many cultivars with different chemotypes. The basil cultivar ‘Albahaca Dante’ has great economic potential. Nevertheless, there is little data about the production of volatiles and the growth using elicitors. This study aims to evaluate growth, physiological disorders, enzymatic activity, biochemistry, stomatal analysis, and the volatile compounds of Ocimum basilicum L.' Albahaca Dante' cultivated in vitro under different concentrations of zinc sulfate (ZnSO4) and methyl jasmonate (MeJa). The experiment was conducted in a completely randomized design (CRD). Five treatments were evaluated based on the combination of MeJa x Zinc Sulfate, using a Murashige and Skoog medium. The results demonstrate that MeJa reduced the formation of abnormal seedlings. Nevertheless, the growth and the number of leaves were not incremented compared in half without elicitors. The number of volatile compounds was lower in the treatment without elicitors and with 25µM ZnSO4 + 1µMMeja. Methyl chavicol was the main compound in both treatments. In this case, the seedlings had smaller stomata with higher density. The seedlings that were developed under unfavorable conditions (75µM ZnSO4 + 1µM MeJa and 75µM ZnSO4 + 5µM MeJa) produced compounds such as Eugenol, Linalool, Methyleugenol, α-Bergamotene, and showed a reduction in the stomatal density, but larger size. The elicitors influenced the activity of antioxidant enzymes, except for 75µM ZnSO4 + 1µM MeJa, which occasioned an acute decrease of all enzymes. The elicitors altered the volatile composition of this basil cultivar and its biochemical responses