Browsing by Author "Costa, Helgeneusa Neto da"
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- Exploring common but untapped fungal strains from olive trees to be used as biocontrol agents or plant-growth promotingPublication . Costa, Helgeneusa Neto da; Baptista, PaulaThe use of plant growth promoting microorganisms, which act directly promoting growth or indirectly as agents of biocontrol of diseases, has been gaining importance as a sustainable tool for increasing agricultural production. In this regard, microorganisms that live in association with plants, either on the surface (epiphytes) or inside (endophytes) their tissues, are seen as the most promising. These beneficial properties have been seen mainly at the level of fungi of the order Phaeomoniellales. Therefore, in this work a collection of fourteen isolates of this order previously obtained from olive leaves was characterized. In particular, we proceeded to their molecular identification using a multi-locus approach and to the evaluation of their biotechnological potential to act as biocontrol agent and plant growth promoting fungi in olive tree. The phylogenetic analysis of six loci, namely internal transcribed spacer region (ITS), actin (ACT), chitin synthase 1 (CHS-1), beta tubulin (β-tubulin), translation elongation factor 1-alpha (TEF-1α) and histone H3 (HIS), allowed to assigned isolates into Phaeomoniellales (eight isolates) and Eurotiales (five isolates) order. Curiously, three of the identified species (Celerioriella umnquma, Pseudophaeomoniella globosa and Pseudophaeomoniella oleae) were reported for the first time in Portugal. The same analysis indicated that five isolates, assigned to Penicillium, were previously misidentified. Penicillium species separation was better when ACT, β-tubulin and/or ITS are simultaneously used; while ITS, TEF-1α and β-tubulin was the best set of loci for resolving Pseudophaeomoniella species. The five Penicillium strains were screened for their ability to produce compounds frequently associated to biocontrol and plant growth promotion traits. Although none of the isolates were able to reduce significantly the in vitro growth of the causal agent of olive anthracnose, Colletotrichum fioriniae, it was found that some isolates increased significantly the production of cellulase, amylase and siderophores, when challenged by the pathogen. All five Penicillium isolates were able to solubilize phosphate and to produce indole acetic acid (IAA). Overall, N172, N162 (Penicillium sp. 2) and N299 (Penicillium sp. 3) isolates were the most promising as biocontrol agents and plant growth promotors. Their effect in in planta assays must be conducted in the future.
- Potential of the endophyte Penicillium commune in the control of olive anthracnose via induction of antifungal volatiles in host plantPublication . Silva, Sofia; Costa, Helgeneusa Neto da; Lopes, Teresa; Ramos, Vitor; Rodrigues, Nuno; Pereira, J.A.; Lino-Neto, Teresa; Baptista, PaulaOlive anthracnose, caused by several Colletotrichum species, is the most economically harmful fruit disease of the olive crop. This work aimed to evaluate the ability of the endophyte Penicillium commune CIMO 14FM009 to protect the olive tree against Colletotrichum nymphaeae via induction of plant volatile organic compounds (VOCs). Accordingly, olive tree branches were inoculated with the endophyte and one month later with the pathogen. After 0, 3, and 24 h of pathogen inoculation, the volatile composition of leaves and fruits was analyzed by HSSPME- GC/MS, and compared with controls (branches inoculated with buffer, endophyte, or pathogen). The effect of plant-derived volatiles on C. nymphaeae was also evaluated. Penicillium commune induced the release of VOCs on the olive trees, with the capacity to reduce significantly the growth (up to 1.4-fold) and sporulation (up to 1.2-fold) of C. nymphaeae. This effect was most notorious on olives than on leaves, and occurred 3 h after pathogen-challenge, suggesting the need for a stressful stimulus for the production of antifungal VOCs. The observed inhibition was associated to a specific set of VOCs released from olives (mostly belonging to the alcohols and esters chemical classes) and leaves (mostly belonging to the alkenes). Curiously, a set of VOCs belonging to alkene, alkane and ester classes, were emitted exclusively in olive branches inoculated with C. nymphaeae. These findings provide new possibilities for controlling olive anthracnose using P. commune and/or volatiles, which efficacy should be tested in future works.