Publications by authors named "Patricio Barr��a"

5 Publications

  • Page 1 of 1

Antifungal Effects of Drimane Sesquiterpenoids Isolated from against Gaeumannomyces graminis var. tritici.

Appl Environ Microbiol 2020 11 24;86(24). Epub 2020 Nov 24.

Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus, Temuco, Chile

var. tritici is a soilborne pathogen that causes "take-all" disease, affecting cereal roots. In wheat, var. tritici is the most important biotic factor, causing around 30 to 50% losses of yield. Chemical control of this fungal disease is difficult because var. tritici is able to reside for a long time in soils. Therefore, the development of environmentally friendly biotechnological strategies to diminish the incidence of soilborne diseases is highly desirable. Natural products are a promising strategy for biocontrol of plant pathogens. A special emphasis is on medicinal plants due to their reported fungitoxic effects. (canelo) is a medicinal plant that is widely used by the Mapuche ethnic group from Chile due to its anti-inflammatory activity. In addition, inhibitory effects of canelo against phytopathogenic fungi and pest insects have been reported. In this study, we isolated, purified, and identified six drimane sesquiterpenoid compounds from canelo (drimenin, drimenol, polygodial, isodrimeninol, valdiviolide, and drimendiol). Then, we evaluated their antimicrobial effects against var. tritici. Compounds were identified by comparing Fourier-transform infrared spectroscopy (FTIR) data and the retention time in thin-layer chromatography (TLC) with those of pure standards. The putative antagonistic effects were confirmed by assessing hyphal cell wall damage using confocal microscopy and lipid peroxidation. Here, we reported the high potential of drimane sesquiterpenoids as natural antifungals against var. tritici. Polygodial and isodrimeninol were the most effective, with 50% lethal concentrations (LCs) between 7 and 10 μg ml and higher levels of fungal lipid peroxidation seen. Accordingly, natural sesquiterpenoids purified from canelo are biologically active against var. tritici and could be used as natural biofungicides for sustainable agriculture. More than two billion tons of pesticides are used every year worldwide. An interesting sustainable alternative to control plant pathogens is the use of natural products obtained from plants, mainly medicinal plants that offer secondary metabolites important to human/animal health. In this study, we isolated and identified six pure drimane sesquiterpenoids obtained from the bark of Additionally, we evaluated their antifungal activities against (the main biotic factor affecting cereal production, especially wheat) by assessing fungal cell wall damage and lipid peroxidation. The compounds obtained showed important antifungal properties against var. tritici, mainly isodrimenol, which was the second-most-active compound after polygodial, with an LC against var. tritici of around 9.5 μg ml This information could be useful for the development of new natural or hemisynthetic antifungal agents against soilborne phytopathogens that could be used in green agriculture.
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http://dx.doi.org/10.1128/AEM.01834-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7688224PMC
November 2020

Occurrence of Soil Fungi in Antarctic Pristine Environments.

Front Bioeng Biotechnol 2019 7;7:28. Epub 2019 Mar 7.

Agrosphere (IBG-3), Institute of Bio- and Geosciences, Forschungszentrum Jülich, Jülich, Germany.

The presence of fungi in pristine Antarctic soils is of particular interest because of the diversity of this microbial group. However, the extreme conditions that coexist in Antarctica produce a strong selective pressure that could lead to the evolution of novel mechanisms for stress tolerance by indigenous microorganisms. For this reason, in recent years, research on cold-adapted microorganisms has increased, driven by their potential value for applications in biotechnology. Cold-adapted fungi, in particular, have become important sources for the discovery of novel bioactive secondary metabolites and enzymes. In this study, we studied the fungal community structure of 12 soil samples from Antarctic sites, including King George Island (including Collins Glacier), Deception Island and Robert Island. Culturable fungi were isolated and described according to their morphological and phenotypical characteristics, and the richness index was compared with soil chemical properties to describe the fungal community and associated environmental parameters. We isolated 54 fungal strains belonging to the following 19 genera: and an uncultured Zygomycete. The isolated fungi were comprised of 70% Ascomycota, 10% Zygomycota, 10% Basidiomycota, 5% Deuteromycota and 5% Mucoromycota, highlighting that most strains were associated with similar genera grown in cold environments. Among the culturable strains, 55% were psychrotrophic and 45% were psychrophilic, and most were Ascomycetes occurring in their teleomorph forms. Soils from the Collins Glacier showed less species richness and greater species dominance compared with the rest of the sites, whereas samples 4, 7, and 10 (from Fildes Bay, Coppermine Peninsula and Arctowski Station, respectively) showed greater species richness and less species dominance. Species richness was related to the C/N ratio, whereas species dominance was inversely related to C and N content. Thus, the structure of the fungal community was mainly related to soil chemical parameters more than sample location and altitude.
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http://dx.doi.org/10.3389/fbioe.2019.00028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6416174PMC
March 2019

Microbial Community Composition in Take-All Suppressive Soils.

Front Microbiol 2018 19;9:2198. Epub 2018 Sep 19.

Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín (CSIC), Granada, Spain.

var. (Ggt) is the main soilborne factor that affects wheat production around the world. Recently we reported the occurrence of six suppressive soils in monoculture areas from indigenous "Mapuche" communities, and evidenced that the suppression relied on the biotic component of those soils. Here, we compare the rhizosphere and endosphere microbial community structure (total bacteria, actinomycetes, total fungi, and ascomycetes) of wheat plants grown in suppressive and conducive soils. Our results suggested that Ggt suppression could be mediated mostly by bacterial endophytes, rather than rhizosphere microorganisms, since the community structure was similar in all suppressive soils as compared with conducive. Interestingly, we found that despite the lower incidence of take-all disease in suppressive soils, the Ggt concentration in roots was not significantly reduced in all suppressive soils compared to those growing in conducive soil. Therefore, the disease suppression is not always related to a reduction of the pathogen biomass. Furthermore, we isolated endophytic bacteria from wheat roots growing in suppressive soils. Among them we identified spp. and spp. able to inhibit Ggt growth . Since the disease, but not always pathogen amount, was reduced in the suppressive soils, we propose that take all disease suppressiveness is not only related to direct antagonism to the pathogen.
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http://dx.doi.org/10.3389/fmicb.2018.02198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6156431PMC
September 2018

Nutrient Use Efficiency of Southern South America Proteaceae Species. Are there General Patterns in the Proteaceae Family?

Front Plant Sci 2018 27;9:883. Epub 2018 Jun 27.

Laboratorio de Biología Vegetal, Facultad de Ciencias, Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile.

Plants from the Proteaceae family can thrive in old, impoverished soil with extremely low phosphorus (P) content, such as those typically found in South Western Australia (SWA) and South Africa. The South Western (SW) Australian Proteaceae species have developed strategies to deal with P scarcity, such as the high capacity to re-mobilize P from senescent to young leaves and the efficient use of P for carbon fixation. In Southern South America, six Proteaceae species grow in younger soils than those of SWA, with a wide variety of climatic and edaphic conditions. However, strategies in the nutrient use efficiency of Southern South (SS) American Proteaceae species growing in their natural ecosystems remain widely unknown. The aim of this study was to evaluate nutrient resorption efficiency and the photosynthetic nutrients use efficiency by SS American Proteaceae species, naturally growing in different sites along a very extensive latitudinal gradient. Mature and senescent leaves of the six SS American Proteaceae species (, and ), as well as, soil samples were collected in nine sites from southern Chile and were subjected to chemical analyses. Nutrient resorption (P and nitrogen) efficiency in leaves was estimated in all species inhabiting the nine sites evaluated, whereas, the photosynthetic P use efficiency (PPUE) and photosynthetic nitrogen (N) use efficiency (PNUE) per leaf unit were determined in two sites with contrasting nutrient availability. Our study exhibit for the first time a data set related to nutrient use efficiency in the leaves of the six SS American Proteaceae, revealing that for all species and sites, P and N resorption efficiencies were on average 47.7 and 50.6%, respectively. No correlation was found between leaf nutrient (P and N) resorption efficiency and soil attributes. Further, different responses in PPUE and PNUE were found among species and, contrary to our expectations, a higher nutrient use efficiency in the nutrient poorest soil was not found. We conclude that SS American Proteaceae species did not show a general pattern in the nutrient use efficiency among them neither with others Proteaceae species reported in the literature.
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http://dx.doi.org/10.3389/fpls.2018.00883DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6030812PMC
June 2018

Understanding the Strategies to Overcome Phosphorus-Deficiency and Aluminum-Toxicity by Ryegrass Endophytic and Rhizosphere Phosphobacteria.

Front Microbiol 2018 1;9:1155. Epub 2018 Jun 1.

Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Temuco, Chile.

Phosphobacteria, secreting organic acids and phosphatases, usually favor plant performance in acidic soils by increasing phosphorus (P) availability and aluminum (Al) complexing. However, it is not well-known how P-deficiency and Al-toxicity affect the phosphobacteria physiology. Since P and Al problems often co-occur in acidic soils, we have therefore proposed the evaluation of the single and combined effects of P-deficiency and Al-toxicity on growth, organic acids secretion, malate dehydrogenase () gene expression, and phosphatase activity of five Al-tolerant phosphobacteria previously isolated from ryegrass. These phosphobacteria were identified as sp. RC3, sp. RC5, sp. RCJ4, sp. RCJ6, and sp. RJAL6. The strains were cultivated in mineral media modified to obtain (i) high P in absence of Al-toxicity, (ii) high P in presence of Al-toxicity, (iii) low P in absence of Al-toxicity, and (iv) low P in presence of Al-toxicity. High and low P were obtained by adding KHPO at final concentration of 1.4 and 0.05 mM, respectively. To avoid Al precipitation, AlCl × 6HO was previously complexed to citric acid (sole carbon source) in concentrations of 10 mM. The secreted organic acids were identified and quantified by HPLC, relative gene expression was determined by qRT-PCR and phosphatase activity was colorimetrically determined using p-nitrophenyl phosphate as substrate. Our results revealed that although a higher secretion of all organic acids was achieved under P-deficiency, the patterns of organic acids secretion were variable and dependent on treatment and strain. The organic acid secretion is exacerbated when Al was added into media, particularly in the form of malic and citric acid. The gene expression was significantly up-regulated by the strains RC3, RC5, and RCJ6 under P-deficiency and Al-toxicity. In general, Al-tolerant phosphobacteria under P deficiency increased both acid and alkaline phosphatase activity with respect to the control, which was deepened when Al was present. The knowledge of this bacterial behavior is important to understand and predict the behavior of phosphobacteria . This knowledge is essential to generate smart and efficient biofertilizers, based in Al-tolerant phosphobacteria which could be expansively used in acidic soils.
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http://dx.doi.org/10.3389/fmicb.2018.01155DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5992465PMC
June 2018
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