Summary• Here peppermint growth and terpene production of in vitro generated plants ( Mentha piperita ) in response to inoculation with a leaf fungal endophyte were characterized.• Peppermint plants were studied by means of morphometric, biochemical and image analysis, employing both in vitro and in pot cultures. Leaf essential oils were analysed by gascromatography-mass spectrometry.• The endophyte induced profound effects on the growth of peppermint, which responded with taller plants bearing more expanded leaves. The observed increase of leaf dry matter over leaf area suggested a real improvement of peppermint metabolic and photosynthetic apparatus. Root architecture was of the herring-bone type, showing greater dry biomass percentage over the total. A sustained lowering of (+)-menthofuran and an increase of (+)-menthol percentage concentrations were found in plants from both in vitro and pot cultures.• The study represents the first report on specialized endophytic fungi in peppermint green tissues and highlights some of the principal morphological and biochemical aspects of this mutualism. Effects exerted on plant growth and essential oil production in peppermint suggest further biotechnological applications.

Vetiver is the only grass cultivated worldwide for the root essential oil, which is a mixture of sesquiterpene alcohols and hydrocarbons, used extensively in perfumery and cosmetics. Light and transmission electron microscopy demonstrated the presence of bacteria in the cortical parenchymatous essential oil-producing cells and in the lysigen lacunae in close association with the essential oil. This finding and the evidence that axenic Vetiver produces in vitro only trace amounts of oil with a strikingly different composition compared with the oils from in vivo Vetiver plants stimulated the hypothesis of an involvement of these bacteria in the oil metabolism. We used culture-based and culture-independent approaches to analyse the microbial community of the Vetiver root. Results demonstrate a broad phylogenetic spectrum of bacteria, including alpha-, beta- and gamma-Proteobacteria, high-G+C-content Gram-positive bacteria, and microbes belonging to the Fibrobacteres/Acidobacteria group. We isolated root-associated bacteria and showed that most of them are able to grow by using oil sesquiterpenes as a carbon source and to metabolize them releasing into the medium a large number of compounds typically found in commercial Vetiver oils. Several bacteria were also able to induce gene expression of a Vetiver sesquiterpene synthase. These results support the intriguing hypothesis that bacteria may have a role in essential oil biosynthesis opening the possibility to use them to manoeuvre the Vetiver oil molecular structure.

Puya raimondii Harms is an outstanding giant rosette bromeliad found solely around 4000 m above sea level in the Andes. It flowers at the end of an 80 - 100-year or even longer life cycle and yields an enormous (4 - 6 m tall) spike composed of from 15,000 to 20,000 flowers. It is endemic and currently endangered, with populations distributed from Peru to the north of Bolivia. A genomic DNA marker-based analysis of the genetic structure of eight populations representative of the whole distribution of P. raimondii in Peru is reported in this paper. As few as 14 genotypes out of 160 plants were detected. Only 5 and 18 of the 217 AFLP marker loci screened were polymorphic within and among these populations, respectively. Four populations were completely monomorphic, each of the others displayed only one to three polymorphic loci. Less than 4 % of the total genomic variation was within populations and genetic similarity among populations was as high as 98.3 %. Results for seven cpSSR marker loci were in agreement with the existence of a single progenitor. Flow cytometry of seed nuclear DNA content and RAPD marker segregation analysis of progeny plantlets demonstrated that the extremely uniform genome of P. raimondii populations is not compatible with agamospermy (apomixis), but consistent with an inbreeding reproductive strategy. There is an urgent need for a protection programme to save not only this precious, isolated species, but also the unique ecosystem depending on it.

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Essential oils were isolated from Artemisia abrotanum L., A. absinthium L., A. alba Turra, A. annua, L., A. campestris L. ssp. campestris, A. campestris L. ssp. borealis (Pallas) H. M. Hall et Clements, A. chamaemelifolia Vill., A. genipi Weber, A. glacialis L., A. petrosa Baumg. ssp. eriantha Ten., A. umbelliformis Lam., A. vallesiaca All., A. verlotiorum Lamotte, A. vulgaris L., growing spontaneously in the north‐west Italian Alps. GC‐MS analyses were carried out in order to determine the percentage composition of the oils. The data obtained were statistically processed in order to partition the species according to their oil composition. The results showed the presence of two main groups of plants. The first group composed of A. genipi, A. umbelliformis and A. petrosa was characterized by the presence of α‐thujone, while camphor and 1,8‐cineole characterized the oil of the remaining plants.

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Berardia subacaulis Vill. is a monospecific genus that is endemic to the South-western Alps, where it grows on alpine screes, which are extreme habitats characterized by soil disturbance and limiting growth conditions. Root colonization by arbuscular mycorrhizal fungi (AMF) is presumably of great importance in these environments, because of its positive effect on plant nutrition and stress tolerance, as well as on structuring the soil. However, there is currently a lack of information on this topic. In this paper, we tested which soil characteristics and biotic factors could contribute to determining the abundance and community composition of AMF in the roots of B. subacaulis, which had previously been found to be mycorrhizal. For such a reason, the influence of soil properties and environmental factors on AMF abundance and community composition in the roots of B. subacaulis, sampled on three different scree slopes, were analysed through microscopic and molecular analysis. The results have shown that the AMF community of Berardia roots was dominated by Glomeraceae, and included a core of AMF taxa, common to all three scree slopes. The vegetation coverage and dark septate endophytes were not related to the AMF colonization percentage and plant community did not influence the root AMF composition. The abundance of AMF in the roots was related to some chemical (available extractable calcium and potassium) and physical (cation exchange capacity, electrical conductivity and field capacity) properties of the soil, thus suggesting an effect of AMF on improving the soil quality. The non-metric multidimensional scaling (NMDS) ordination of the AMF community composition showed that the diversity of AMF in the various sites was influenced not only by the soil quality, but also by the slope. Therefore, the slope-induced physical disturbance of alpine screes may contribute to the selection of disturbance-tolerant AMF taxa, which in turn may lead to different plant-fungus assemblages.

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