Biomass yield, mineral content, and nutritive value of Poa pratensis as affected by non-clavicipitaceous fungal endophytes

Plant-growth promoting activity of three fungal endophytes isolated from plants living in dehesas and their effect on Lolium multiflorum

Endophytic fungi have been demonstrated to produce bioactive secondary metabolites, some of which promote plant growth. Three endophytic fungi isolated from healthy plants living in dehesas of Extremadura (Spain) were identified and evaluated for their ability to produce phytohormone-like substances, antioxidant activity, total polyphenol content, phosphate solubilization ability and siderophore and ammonia production. The filtrates and extracts produced by the three endophytes were applied to Lolium multiflorum seeds and seedlings under both in vitro and greenhouse conditions, to analyse their influence on plant growth traits such as germination, vigour index, chlorophyll data, number and length of leaves and roots, and dry weight. All three endophytes, which were identified as Fusarium avenaceum, Sarocladium terricola and Xylariaceae sp., increased the germination of L. multiflorum seeds by more than 70%. Shoot and root length, plant dry weight and the number of roots were positively affected by the application of fungal filtrates and/or extracts, compared with controls. The tentative HPLC-MS identification of phytohormone-like substances, such as gibberellin A2 and zeatin, or the antioxidant acetyl eugenol, may partially explain the mechanisms of L. multiflorum plant growth promotion after the application of fungal filtrates and/or extracts.

Potential of Fungal Endophytes Isolated from Pasture Species in Spanish Dehesas to Produce Enzymes under Salt Conditions

Endophytic fungi have been found to produce a wide range of extracellular enzymes, which are increasingly in demand for their industrial applications. Different by-products from the agrifood industry could be used as fungal growth substrates for the massive production of these enzymes, specifically as a way to revalorize them. However, such by-products often present unfavorable conditions for the microorganism’s growth, such as high salt concentrations. Therefore, the objective of the present study was to evaluate the potential of eleven endophytic fungi—which were isolated from plants growing in a harsh environment, specifically, from the Spanish dehesas—for the purposes of the in vitro production of six enzymes (i.e., amylase, lipase, protease, cellulase, pectinase and laccase) under both standard and salt-amended conditions. Under standard conditions, the studied endophytes produced between two and four of the six enzymes evaluated. In most of the producer fungal species, this enzymatic activity was relatively maintained when NaCl was added to the medium. Among the isolates evaluated, Sarocladium terricola (E025), Acremonium implicatum (E178), Microdiplodia hawaiiensis (E198), and an unidentified species (E586) were the most suitable candidates for the massive production of enzymes by using growth substrates with saline properties (such as those found in the many by-products from the agrifood industry). This study should be considered an initial approach by which to further study the identification of these compounds as well as to develop the optimization of their production by directly using those residues.

Protective Effects of Filtrates and Extracts from Fungal Endophytes on Phytophthora cinnamomi in Lupinus luteus

Fungal endophytes have been found to protect their hosts against multiple fungal pathogens. Frequently, the secondary metabolites produced by the endophyte are responsible for antifungal activity. To develop new bio-products that are more environmentally friendly than synthetic pesticides against Phytophthora cinnamomi, a serious pathogen of many plant species, the antifungal activity of filtrates or extracts from four endophytes was evaluated in different in vitro tests and in plants of Lupinus luteus. In the dual culture assays, the filtrate of one of the endophytes (Drechslera biseptata) completely inhibited the mycelial growth of the pathogen. Moreover, it showed a very low minimal inhibitory concentration (MIC). Epicoccum nigrum, an endophyte that also showed high inhibitory activity and a low MIC against P. cinnamomi in those two experiments, provided a clear growth promotion effect when the extracts were applied to L. luteus seedlings. The extract of Fusarium avenaceum also manifested such a promotion effect and was the most effective in reducing the disease severity caused by the pathogen in lupine plants (73% reduction). Results demonstrated the inhibitory activity of the filtrates or extracts of these endophytes against P. cinnamomi. A better insight into the mechanisms involved may be gained by isolating and identifying the metabolites conferring this inhibitory effect against this oomycete pathogen.

Effect of fungal endophytes on plant growth and nutrient uptake in Trifolium subterraneum and Poa pratensis as affected by plant host specificity

The introduction of well-adapted species, such as Trifolium subterraneum (subclover) and Poa pratensis (Kentucky bluegrass), might enhance the forage yield and quality of dehesa pastures for feeding livestock. However, the climatic hardness and poor soils in these agrosystems may limit plant establishment and development. Since fungal endophytes have been found to alleviate the environmental stresses of their host, the aim of this study was to assess the effect of five isolates on forage yield, nutritive value, and plant mineral uptake after their inoculation in the two abovementioned plant species. Two experiments were established (under greenhouse and field conditions) using plants inoculated with two isolates in 2012/2013 (Epicoccum nigrum, Sporormiella intermedia) and three isolates in 2013/2014 (Mucor hiemalis, Fusarium equiseti, Byssochlamys spectabilis). Fusarium equiseti (E346) increased the herbage yield of T. subterraneum under greenhouse conditions, and B. spectabilis improved the forage quality of T. subterraneum by reducing fiber content and of P. pratensis by increasing crude protein. S. intermedia increased the mineral uptake of Ca, Cu, Mn, Pb, Tl, and Zn in subclover, and M. hiemalis increased the uptake of K and Sr in Kentucky bluegrass. These results evidence the potential of the studied fungal endophytes to enhance herbage yield and nutritional value of forage, although further studies should include all of the target forage species as certain host specificity in the effect was observed.

First Inventory of Fungi in Symptomless and Symptomatic Chinese Mesona Indicates Phytopathological Threat

Chinese mesona (Platostoma palustre) plays an important role as special crop in Southeast Asia and Taiwan for the production of herbal tea, grass jelly, and further processed food. In order to assess the potential threat of fungi to Chinese mesona, we surveyed isolates from symptomless plants in the area of mesona production, as well as from leaf spots of potted plants in a garden shop and a plantation in a botanical garden in Taiwan. From leaves, stems, and roots of 15 symptomless plants sampled at five collection events over two years, 154 isolates from 810 surface-sterilized plant fragments were obtained and identified based on DNA sequence data of the internal transcribed spacer region, and partially of the β-tubulin and histone H3 genes. The most common species belonged to the genera Cercospora, Colletotrichum, and Fusarium and were considered to be potential plant pathogens. Latent pathogenicity was confirmed by an infection experiment with an endophytic strain of Corynespora cassiicola. Observation of leaf spot disease associated with Cercospora kikuchii suggested pathogenicity of this fungus, which was also isolated as an endophyte from symptomless leaves. We hypothesize that the most common endophytic fungi are latent pathogens in the host and may cause plant disease when the host becomes weakened by senescence or changed cultivation condition. Leaf spots of plants in the botanical garden were associated with a species of Pseudocercospora, which was not found among the endophytic isolates and is newly described based on morphology and analysis of translation elongation factor 1 alpha gene sequences.

Effect of Fungal Endophytes on Biomass Yield, Nutritive Value and Accumulation of Minerals in Ornithopus compressus

Yellow serradella (Ornithopus compressus), a valuable pasture species in Mediterranean areas, presents a high diversity of endophytic mycoflora. In the present work, the hypothesis of a significant effect of fungal endophytic species on the parameters of forage production, nutritive value and mineral status of herbage was tested. O. compressus plants were inoculated with each of seven endophytes (four in 2012/2013 and three in 2013/2014). After inoculation, two experiments (under greenhouse and field conditions) were established. Results evidenced a certain influence of several endophytes on herbage yield, nutritive value and mineral status of O. compressus forage. Byssochlamys spectabilis increased herbage biomass yield by around 42% in the field experiment. Stemphylium sp. improved the nutritive value of forage either by increasing crude protein, digestibility and the concentration of essential minerals (such as B, Mo, P or S) or by reducing the concentration of toxic elements such as Al or Pb. In conclusion, the results presented here provide evidence that plant inoculation with endophytes could be a suitable strategy to increase forage yield and its nutritive value or to deal with potential nutrient deficiencies or potential mineral toxicity in forage.