Matevž Likar

Fungal community structure under goat willows (Salix caprea L.) growing at metal polluted site: the potential of screening in a model phytostabilisation study

Goat willow (Salix caprea L.) was selected in a previous vegetation screening study as a potential candidate for the later-stage phytostabilisation efforts at a heavily metal polluted site in Slovenia. The aims of this study were to identify the fungi colonising roots of S. caprea along the gradient of vegetation succession and to estimate their colonisation levels in relation to metal pollution in order to reveal its mycorrhizal status at the site. Additionally the metal accumulation capacity of S. caprea and photosynthetic pigments were analysed as indications of its fitness at four differentially polluted plots. Despite high concentrations of leaf accumulated Cd, no significant differences in photosynthetic pigment concentrations were observed. The roots were colonised by arbuscular mycorrhizal (AM) fungi, ectomycorrhizal (EM) fungi, and dark septate endophytes (DSE), with EM as the dominant type on all the plots. Molecular characterisation showed poor correlation of the root EM community with the above-ground sporocarp diversity. Members of Sordariaceae were the most frequent colonisers with an average colonisation of 21% of all root tips, followed by Thelephoraceae with 10%. DSE colonisation increased with increasing Pb concentrations and decreasing organic matter (OM).

Importance of soil and vineyard management in the determination of grapevine mineral composition

The spatial variability of the mineral composition of grapevines in production vineyards along the east Adriatic coast was determined and compared between conventional and sustainable vineyard management. Cluster analysis shows a high level of spatial variability even within the individual locations. Factor analysis reveals three factors with strong loading for the macronutrients K and P and the micronutrient Mn, which explain 67% of the total variance in the mineral composition. Here, 26% to 34% of the variance of these three elements can be explained by abiotic and biotic soil parameters, with soil concentrations of K, Fe and Cu, organic matter content, and vesicular colonisation showing the strongest effects on the mineral composition of the grapevines. In addition, analysis of the mineral composition data shows significant differences between differently managed vineyards, with increased bioaccumulation of P and K in sustainable vineyards, while Zn bioaccumulation was increased in conventional vineyards. Our data confirm the importance of soil and vineyard management in the concept of terroir, and demonstrate the effects of sustainable management practices on the mineral nutrition of grapevines that result from modified nutrient availability related to changes in the abiotic and biotic characteristics of the soil.

Mycorrhizal status and diversity of fungal endophytes in roots of common buckwheat (Fagopyrum esculentum) and tartary buckwheat (F. tataricum).

To determine the mycorrhizal status and to identify the fungi colonising the roots of the plants, common buckwheat (Fagopyrum esculentum) and tartary buckwheat (F. tataricum) were inoculated with an indigenous fungal mixture from a buckwheat field. Root colonisation was characterised by the hyphae and distinct microsclerotia of dark septate endophytes, with occasional arbuscules and vesicles of arbuscular mycorrhizal fungi. Sequences of arbuscular mycorrhizal fungi colonising tartary buckwheat clustered close to the Glomus species group A. Sequences with similarity to the Ceratobasidium/Rhizoctonia complex, a putative dark septate endophyte fungus, were amplified from the roots of both common and tartary buckwheat. To the best of our knowledge, this is the first report of arbuscular mycorrhizal colonisation in tartary buckwheat and the first molecular characterisation of these fungi that can colonise both of these economically important plant species.

Dark Septate Endophytes and Mycorrhizal Fungi of Trees Affected by Pollution

Plants have developed intimate associations with different groups of fungal endophytes. In return for carbohydrates, these fungal endophytes help to improve the nutrient status and water balance of their host plant. In addition, they can protect the host plant against biotic and abiotic stresses, such as increased metal concentrations in the soil. Many endophytic fungi can survive at high concentrations of toxic metals, and can adapt to metal stress, which results in tolerant genotypes. Such fungi have developed many mechanisms that help them to maintain their metal homeostasis. These include passive mechanisms, such as metal binding to the cell wall, as well as active extracellular and intracellular chelation and transmembrane transport of metals. By restricting the uptake of toxic metals and improving the supply of essential elements to the host, fungal endophytes can ameliorate potential metal toxicity for their host plant. In this chapter, I discuss the effects of metal-enriched environments on the interactions between fungal endophytes and their host plants, along with the processes involved in the maintenance of metal homeostasis in fungi, and their ability to improve the fitness of plants in metal-enriched environments.

Neighbouring weeds influence the formation of arbuscular mycorrhiza in grapevine

Grapevine (Vitis vinifera L.) and two selected weeds from Mediterranean Croatian vineyards (Plantago lanceolata L. and Tanacetum cinerariifolium (Trevir.) Sch.Bip.) were examined in pot culture experiments, individually or when combined, to see whether multiple hosts influenced the formation of the symbiosis with arbuscular mycorrhizal fungi (AMF). The results after six-month period showed that plant identity and density significantly influenced development of mycorrhizal intra- and extraradical mycelium and/or sporulation. Grapevine and T. cinerariifolium individually and in combination resulted in a greater development of arbuscular mycorrhizae in terms of spore production, extraradical mycelium length and root colonization compared with pots containing P. lanceolata. Herbaceous weed species seemed to promote a different set of dominant AMF, potentially providing a wider spectrum of AMF for colonising grapevine roots. This indicates the value of encouraging host plant diversity in vineyards. AMF sequences obtained in this study are the first data reported for soils in Croatia.

UV-B radiation affects flavonoids and fungal colonisation in Fagopyrum esculentum and F. tataricum

In the present study, we have evaluated the effects of increased UV-B radiation that simulates 17% ozone depletion, on fungal colonisation and concentrations of rutin, catechin and quercetin in common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tataricum). Induced root growth and reduced shoot:root ratios were seen in both of these buckwheat species after enhanced UV-B radiation. There was specific induction of shoot quercetin concentrations in UV-B-treated common buckwheat, whereas there were no specific responses for flavonoid metabolism in tartary buckwheat. Root colonisation with arbuscular mycorrhizal fungi significantly reduced catechin concentrations in common buckwheat roots, and induced rutin concentrations in tartary buckwheat, but did not affect shoot concentrations of the measured phenolics. Specific UV-B-related reductions in the density of microsclerotia were observed in tartary buckwheat, indicating a mechanism that potentially affects fungus-plant interactions. The data support the hypothesis that responses to enhanced UV-B radiation can be influenced by the plant pre-adaptation properties and related changes in flavonoid metabolism.

Hypoxia and inactivity related physiological changes precede or take place in absence of significant rearrangements in bacterial community structure: The PlanHab randomized trial pilot study

We explored the assembly of intestinal microbiota in healthy male participants during the randomized crossover design of run-in (5 day) and experimental phases (21-day normoxic bed rest (NBR), hypoxic bed rest (HBR) and hypoxic ambulation (HAmb) in a strictly controlled laboratory environment, with balanced fluid and dietary intakes, controlled circadian rhythm, microbial ambiental burden and 24/7 medical surveillance. The fraction of inspired O2 (FiO2) and partial pressure of inspired O2 (PiO2) were 0.209 and 133.1 ± 0.3 mmHg for NBR and 0.141 ± 0.004 and 90.0 ± 0.4 mmHg for both hypoxic variants (HBR and HAmb; ~4000 m simulated altitude), respectively. A number of parameters linked to intestinal environment such as defecation frequency, intestinal electrical conductivity (IEC), sterol and polyphenol content and diversity, indole, aromaticity and spectral characteristics of dissolved organic matter (DOM) were measured (64 variables). The structure and diversity of bacterial microbial community was assessed using 16S rRNA amplicon sequencing. Inactivity negatively affected frequency of defecation and in combination with hypoxia increased IEC (p < 0.05). In contrast, sterol and polyphenol diversity and content, various characteristics of DOM and aromatic compounds, the structure and diversity of bacterial microbial community were not significantly affected over time. A new in-house PlanHab database was established to integrate all measured variables on host physiology, diet, experiment, immune and metabolic markers (n = 231). The observed progressive decrease in defecation frequency and concomitant increase in IEC suggested that the transition from healthy physiological state towards the developed symptoms of low magnitude obesity-related syndromes was dose dependent on the extent of time spent in inactivity and preceded or took place in absence of significant rearrangements in bacterial microbial community. Species B. thetaiotamicron, B. fragilis, B. dorei and other Bacteroides with reported relevance for dysbiotic medical conditions were significantly enriched in HBR, characterized with most severe inflammation symptoms, indicating a shift towards host mucin degradation and proinflammatory immune crosstalk.

High incidence of arbuscular mycorrhizal fungi in rare and endangered wild grapevine

Abstract High levels of arbuscular mycorrhizal fungi colonisation of 90–100%, as well as high vesicular and arbuscular colonisation were found in the roots of the rare and endangered wild grapevine (Vitis vinifera subsp. sylvestris) along the Neretva River in southwestern Bosnia and Herzegovina, surpassing colonisation in region vineyads.

Arbuscular Mycorrhizal Fungi and Dark Septate Endophytes in Grapevine: The Potential for Sustainable Viticulture?

Viticulture is an important agronomic sector that has the potential to greatly benefit by improvements in our understanding of grapevine cultivation. Although conventional viticulture relies to a great extent on pesticide and fertilizer application, more sustainable approaches involve management practices that favor plant–fungus interactions that have positive effects on the nutritional quality of the grapes and reduce production costs (i.e., of pesticides and fertilizers) and thus reduce the negative effects on the environment. Fungal endophytes that colonize grapevines belong to different taxa, with the majority of reports focusing on fungi that form arbuscular mycorrhizal associations. These fungal endophytes have been demonstrated to confer beneficial growth and nutrition effects to their plant hosts via improved exploitation of the substrate and improved tolerance of the grapevine to abiotic and biotic stresses. Here, we review current knowledge on the importance and potential of these diverse fungal groups for grapevine production and expose the gaps in our understanding of possible functions of fungal groups that are currently little studied. In addition, we underline the effects of sustainable agricultural practices on fungal communities, to boost the progress in different viticultural techniques on the interactions between fungal endophytes and grapevines.