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Impact of a natural soil salinity gradient on fungal endophytes in wild barley (Hordeum maritimum With.)

Publication . Hammami, Haifa; Baptista, Paula; Martins, Fátima; Gomes, Teresa; Abdelly, Chedly; Mahmoud, Ouissal Metoui Ben

Occurrence and distribution pattern of fungal endophytes in different tissues of halophytic plants across saline depressions are poorly studied. We investigated the endophytic fungal communities inhabiting roots, stems and leaves of Hordeum maritimum collected in a soil salinity gradient, i.e. non-saline, slightly saline and saline, using a culture-dependent approach. A total of 20 taxa belonging to Ascomycota phylum were identified by ITS rRNA gene sequence. Pyronema domesticum and Alternaria spp. were the most frequently isolated. Roots host higher diversity and were more frequently colonized by endophytes than aboveground organs. Endophytic composition of all organs surveyed differed according to salinity gradient. Contrary to expectations, the colonization rate of roots increased with soil salinity, indicating that under salt stress the endophyte-plant association is promoted. All the isolates exhibited in vitro saline tolerance, especially those belonging to genera Xylaria, Chalastospora, Alternaria and Pyronema. Fungal tolerance to NaCl under in vitro conditions appears to be more dependent on the isolates than on the sites of their isolation, suggesting that under natural conditions other factors, beyond soil salinity, should be taken into account. These findings highlight the importance of fungal endophytes in the protection and/or adaptation of both interacting species (plant-fungus) to salt stress under natural conditions. Graphical Abstract: [Figure not available: see fulltext.]

2016Journal article

Open access

Illuminating Olea europaea L. endophyte fungal community

Publication . Costa, Daniela; Fernandes, Telma; Martins, Fátima; Pereira, J.A.; Tavares, Rui Manuel; Santos, Pedro M.; Baptista, Paula; Lino-Neto, Teresa

A wide array of fungal endophytes is known to inhabit plant tissues and were recently recognized as essential for plant health. A better description of the scarcely known endophyte microbiota in olive tree phyllosphere is the first step for elucidating the microbial interactions that lead to olive disease establishment. In this work, the fungal endophytic community of the phyllosphere of different olive tree cultivars (Cobrançosa, Galega vulgar, Madural, Picual, Verdeal Transmontana) is revealed by using a metabarcoding strategy targeting ITS1 barcode. A total of 460 OTUs were obtained, increasing the broad view of fungal endophytes inhabiting the olive tree phyllosphere, in particular yeast endophytes. New endophytes were persistently found in all cultivar tissues. Different olive tree cultivars depicted distinct endophyte communities. Olive cultivars exhibited dissimilar amounts of fungi with distinct ecological functions, which could explain at least in part their differential susceptibility/tolerance to olive diseases.

2021Journal article

Open access

Microbial community of olives and its potential for biological control of olive anthracnose

Publication . Preto, Gilda Conceição Raposo; Baptista, Paula; Pereira, J.A.

Olive anthracnose is an important fruit disease in olive crop worldwide and no effective method is currently available for their control. Fruit-associated microorganisms may be explored for designing new strategies for the biological control of this disease. The main aim of this work was to assess the diversity of fungal endophytes and epiphytes inhabiting olive fruits of two cultivars with different susceptibilities to olive anthracnose, and select the strains with the greatest antagonistic effect against Colletotrichum acutatum, the main causal agent of this disease. Culture-dependent method was used to assess fungal diversity in olives from cvs. Madural (susceptible) and Verdeal Transmontana (moderately tolerant), and the isolates obtained were identified for molecular identificantion using internal transcribed spacer (ITS1, 5.8, ITS2) region of the rDNA. The in vitro effect of the isolates against C. acutatum was analysed by the dual-culture method. Results revealed that only endophytic fungal communities composition differ significantly between cultivars. Cultivar Madural was distinguished by the higher abundance of Gibberella spp. whereas cv. Verdeal Transmontana was characterized by the exclusive occurrence of Neofabraea vagabunda. Although epiphytic community of both cultivars overlapped, several fungal genera preferred either olives from cv. Madural (e.g. Chaetomium) or from cv. Verdeal Transmontana (e.g. Cytospora, Epicoccum and Quambalaria). All the seven fungal tested were able to inhibited C. acutatum growth (inhibition coefficients up to 30.9), and caused morphological changes in its hyphae. Some fungi also inhibited significantly C. acutatum sporulation (from 46-86%) and germination (from 21-74%). Altogether, the results offer new insights into plant-microbe-microbe interactions and highlighted the potential use of these antagonistic fungi in the biocontrol of olive anthracnose.

2016Master thesis

Restricted access

Antimicrobial activity of endophytic fungi from olive tree leaves

Publication . Malhadas, Cynthia; Malheiro, Ricardo; Pereira, J.A.; Pinho, P. Guedes de; Baptista, Paula

In this study, the antimicrobial potential of three fungal endophytes from leaves of Olea europaea L. was evaluated and the host plant extract effect in the antimicrobial activity was examined. The volatile compounds produced by endophytes were identified by GC/MS and further correlated with the antimicrobial activity. In potato dextrose agar, both Penicillium commune and Penicillium canescens were the most effective inhibiting Gram-positive and -negative bacteria (up to 2.7-fold compared to 30 µg/mL chloramphenicol), whereas Alternaria alternata was most effective inhibiting yeasts (up to 8.0-fold compared to 25 μg/mL fluconazole). The presence of aqueous leaf extract in culture medium showed to induce or repress the antimicrobial activity, depending on the endophytic species. In the next step, various organic extracts from both A. alternata mycelium and cultured broth we re prepared; being ethyl acetate extracts displayed the widest spectrum of anti-microorganisms at a minimum inhibitory concentration ≤0.095 mg/mL. The volatile composition of the fungi that displayed the highest (A. alternata) and the lowest (P. canescens) antimicrobial activity against yeasts revealed the presence of six volatiles, being the most abundant components (3-methyl-1-butanol and phenylethyl alcohol) ascribed with antimicrobial potentialities. Overall the results highlighted for the first time the antimicrobial potential of endophytic fungi from O. europaea and the possibility to be exploited for their antimicrobial agents. Graphical Abstract: [Figure not available: see fulltext.]

2017Journal article

Open access

Fungal endophyte communities in above- and belowground olive tree organs and the effect of season and geographic location on their structures

Publication . Martins, Fátima; Pereira, J.A.; Bota, Paulo; Bento, Albino; Baptista, Paula

Studies comparing fungal endophytes between above- and belowground woody crop organs and the factors that may structure their communities are lacking. Due to its great impact on the Mediterranean Basin, the olive tree was chosen for the isolation of endophytic fungi from roots, leaves and twigs in two seasons in north-eastern Portugal. Nine hundred seventy-six isolates belonging to 38 fungal species were obtained. Phomopsis columnaris, Fusarium oxysporum and Trichoderma gamsii were the most frequently isolated, collectively representing 69% of the isolates. Fungal diversity in the roots was higher than in the aboveground organs and higher in spring than autumn. Endophyte community similarity between the above- and belowground organs and between seasons was low. Species composition also varied spatially, with the fungal composition of the roots varying more among locations than that of the aboveground organs. Our results suggest olive tree endophyte community structure is affected by plant organ, location and season.

2016Journal article

Restricted access