Hector Herrera, Javiera Soto, Luz E. de Bashan, Inmaculada Sampedro and Cesar Arriagada. 2019. Root-Associated Fungal Communities in Two Populations of the Fully Mycoheterotrophic Plant Arachnitis uniflora Phil. (Corsiaceae) in Southern Chile. Microorganisms. 7(12), 586 (WOS. Impact Factor 4.152  Q2). microorganisms7120586

Ortiz, J. Soto, J. Fuentes, A. Herrera, H. Meneses, C. Arriagada, C. 2019. The Endophytic Fungus Chaetomium cupreum Regulates Expression of Genes Involved in the Tolerance to Metals and Plant Growth Promotion in Eucalyptus globulus Roots. Microorganisms. 7(11), 490 (WOS. Impact Factor 4.152  Q2). microorganisms7110490

Javiera Soto., Javier Ortiz., Hector Herrera., Alejandra Fuentes., L. Almonacid., Trevor C. Charles and César Arriagada. 2019. Enhanced Arsenic Tolerance in Triticum aestivum Inoculated with Arsenic-Resistant and Plant Growth Promoter Microorganisms from a Heavy Metal-Polluted Soil. Microorganisms. 7(9), 348 (WOS. Impact Factor 4.152  Q2). microorganisms7090348

Hector Herrera, Graciela Palma, L. Almonacid, Reinaldo Campos, Alejandra Fuentes, Inmaculada Garcia-Romera, César Arriagada. 2019. Improving Soil Simazine Dissipation Through an Organic Amendment Inoculated with Trametes versicolor. Journal of Soil Science and Plant Nutrition. Volume 19, pp 262–269 (WOS. Impac Factor 2.156 Q2)

Héctor Herrera, Inmaculada García-Romera, Claudio Meneses, Guillermo Pereira, César Arriagada. 2019. Orchid Mycorrhizal Interactions on the Pacific Side of the Andes from Chile. Journal of Soil Science and Plant Nutrition. Volume 19, pp 187–202. (WOS. Impact Factor 2.156 Q2).

J. Ortiz., J. Soto., L. Almonacid., A. Fuentes., R. Campos-Vargas & C. Arriagada. 2019. Alleviation of metal stress by Pseudomonas orientalis and Chaetomium cupreum strains and their effects on Eucalyptus globulus growth promotion. Plant and Soil. Volume 436pp 436-449. (WOS. Impact Factor 3.299  Q1).

Root-Associated Fungal Communities in Two Populations of the Fully Mycoheterotrophic Plant Arachnitis uniflora Phil. (Corsiaceae) in Southern Chile

Author Full Names: Herrera, Hector; Soto, Javiera; de Bashan, Luz E.; Sampedro, Inmaculada; Arriagada, Cesar


The microbiological interactions of the roots of non-photosynthetic plants in South America have been scarcely explored. This study analyzes culturable fungal diversity associated with the mycoheterotrophic plant Arachnitis uniflora Phil. (Corsiaceae) in southern Chile, growing in two different understoreys of native (Nothofagus-dominated) and mixed forest (native, Cupressussempervirens, and Pinusradiata). Rhizospheric and endophytic fungi were isolated, cultured, and purified to identify microorganisms associated with A. uniflora roots. We showed the different fungi associated with the plant, and that these distributions are influenced by the sampling site. We isolated 410 fungal strains (144 endophytic and 266 from the rhizosphere). We identified 13 operative taxonomical units from plants sampled in the mixed forest, while 15 were from the native forest. Rhizospheric microorganisms were mainly related to Penicillium spp., whereas some pathogenic and saprophytic strains were more frequent inside the roots. Our results have also shown that the fungal strains are weak for phosphate solubilization, but other pathways such as organic acid exudation and indole acetic acid production can be considered as major mechanisms to stimulate plant growth. Our results point to new fungal associates of A. uniflora plants reported in Andean ecosystems, identifying new beneficial endophytic fungi associated with roots of this fully mycoheterotrophic plant.

DOI: 10.3390/microorganisms7120586

UT (Unique WOS ID): WOS:000506646400004

The Endophytic Fungus Chaetomium cupreum Regulates Expression of Genes Involved in the Tolerance to Metals and Plant Growth Promotion in Eucalyptus globulus Roots

Author Full Names: Ortiz, Javier; Soto, Javiera; Fuentes, Alejandra; Herrera, Hector; Meneses, Claudio; Arriagada, Cesar


The endophytic strain Chaetomium cupreum isolated from metal-contaminated soil was inoculated in Eucalyptus globulus roots to identify genes involved in metal stress response and plant growth promotion. We analyzed the transcriptome of E. globulus roots inoculated with C. cupreum. De novo sequencing, assembly, and analysis were performed to identify molecular mechanisms involved in metal stress tolerance and plant growth promotion. A total of 393,371,743 paired-end reads were assembled into 135,155 putative transcripts. It was found that 663 genes significantly changed their expression in the presence of treatment, of which 369 were up-regulated and 294 were down-regulated. We found differentially expressed genes (DEGs) encoding metal transporters, transcription factors, stress and defense response proteins, as well as DEGs involved in auxin biosynthesis and metabolism. Our results showed that the inoculation of C. cupreum enhanced tolerance to metals and growth promotion on E. globulus. This study provides new information to understand molecular mechanisms involved in plant-microbe interactions under metals stress.

DOI: 10.3390/microorganisms7110490

UT (Unique WOS ID): WOS:000502273600013

Enhanced Arsenic Tolerance in Triticum aestivum Inoculated with Arsenic-Resistant and Plant Growth Promoter Microorganisms from a Heavy Metal-Polluted Soil

Author Full Names: Soto, Javiera; Ortiz, Javier; Herrera, Hector; Fuentes, Alejandra; Almonacid, Leonardo; Charles, Trevor C.; Arriagada, Cesar


In soils multi-contaminated with heavy metal and metalloids, the establishment of plant species is often hampered due to toxicity. This may be overcome through the inoculation of beneficial soil microorganisms. In this study, two arsenic-resistant bacterial isolates, classified as Pseudomonas gessardii and Brevundimonas intermedia, and two arsenic-resistant fungi, classified as Fimetariella rabenhortii and Hormonema viticola, were isolated from contaminated soil from the Puchuncavi valley (Chile). Their ability to produce indoleacetic acid and siderophores and mediate phosphate solubilization as plant growth-promoting properties were evaluated, as well as levels of arsenic resistance. A real time PCR applied to Triticum aestivum that grew in soil inoculated with the bacterial and fungal isolates was performed to observe differences in the relative expression of heavy metal stress defense genes. The minimum inhibitory concentration of the bacterial strains to arsenate was up to 7000 mg.L-1 and that of the fungal strains was up to 2500 mg.L-1. P. gessardi was able to produce siderophores and solubilize phosphate; meanwhile, B. intermedia and both fungi produced indoleacetic acid. Plant dry biomass was increased and the relative expression of plant metallothionein, superoxide dismutase, ascorbate peroxidase and phytochelatin synthase genes were overexpressed when P. gessardii plus B. intermedia were inoculated.

DOI: 10.3390/microorganisms7090348

UT (Unique WOS ID): WOS:000489131300075

Improving Soil Simazine Dissipation Through an Organic Amendment Inoculated with Trametes versicolor

Author Full Names: Herrera, Hector; Palma, Graciela; Almonacid, Leonardo; Campos, Reinaldo; Fuentes, Alejandra; Garcia-Romera, Inmaculada; Arriagada, Cesar


The aim of this research was to investigate the effect of applying sewage sludge combined with wheat crop residue as an organic amendment on the dissipation rate of simazine spiked at 2 and 20 mg kg(-1) in an Andisol soil from southern Chile. Changes in some soil enzymes related to soil quality were measured by spectrophotometry, simazine dissipation rates were measured by gas chromatography, and biomass production in the contaminated soil was evaluated. Results of this study indicated that application of the organic amendment inoculated with Trametes versicolor enabled a decrease in negative effects of the herbicide on soil enzymatic activities and a reduction in final concentrations of simazine (similar to 80% at both doses). The simazine half-life time was reduced from 14 to 10 days and from 36 to 15 days for doses of 2 and 20 mg kg(-1), respectively. These findings prove that the combined strategy of biostimulation and bioaugmentation using these residues can be effectively used to reduce residue pesticides in soils, mainly by increasing the microbiological activity, thus improving simazine dissipation in an Andisol soil.

DOI: 10.1007/s42729-019-0019-7

UT (Unique WOS ID): WOS:000473628300002

Orchid Mycorrhizal Interactions on the Pacific Side of the Andes from Chile.

Author Full Names: Herrera, Hector; Garcia-Romera, Inmaculada; Meneses, Claudio; Pereira, Guillermo; Arriagada, Cesar


In order to confront the constant decline in global biological diversity, amelioration strategies are needed for threatened species to design reintroduction policies, particularly in plants with critical reproduction steps, such as orchids. Orchids are part of a highly diverse plant family, with several species under imminent extinction risk. This is the case of Chilean Orchidaceae, which has shown a constant decay in their populations due to an increase in the alteration processes of their natural distribution habitats. Successful orchid reintroductions require a full understanding of orchid mycorrhizal fungi and their dynamic according to different developmental stages and environmental conditions because orchid seeds need mycorrhizal fungi to obtain nutritional compounds at early developmental stages. This article performed a critical literature review of the ecological studies conducted on Chilean orchids and their relationships with mycorrhizal fungi in order to focus on the best scientific approach to achieve successful restoration programs involving orchid seeds and compatible mycorrhizal fungi.

DOI: 10.1007/s42729-019-00026-x

UT (Unique WOS ID): WOS:000471078200019

Alleviation of metal stress by Pseudomonas orientalis and Chaetomium cupreum strains and their effects on Eucalyptus globulus growth promotion

Author Full Names: Ortiz, J.; Soto, J.; Almonacid, L.; Fuentes, A.; Campos-Vargas, R.; Arriagada, C.

Source Title: PLANT AND SOIL

AimPseudomonas orientalis and Chaetomium cupreum isolated from metal(oid)s-contaminated soil were characterized to evaluate their role in plant growth promotion and enhance the tolerance of Eucalyptus globulus to copper stress.MethodsWe evaluated minimum inhibitory concentration and explored plant-promoting traits under copper stress. Moreover, changes in morphology and the accumulation of metals on the cell surface were determined by scanning electron microscopy images coupled with energy dispersive x-ray spectroscopy (SEM-EDX). The effect of inoculation with P. orientalis and C. cupreum on E. globulus plants established in soils contaminated with copper was determined through root and shoot biomass and antioxidant response.ResultsBoth strains showed high tolerance to metal(oid)s, whereas phosphate solubilization was only detected in P. orientalis. Under copper stress, C. cupreum presented a higher production rate of siderophores and indole acetic acid (4.5mmday(-1), 15.042gmL(-1)). SEM images and EDX analysis reflected cellular changes in fungus and proved biosorption of copper. Inoculation of P. orientalis and C. cupreum on Eucalyptus globulus plants significantly increased plant growth and mitigated the toxic effects of copper.ConclusionsAccording to these results, both microorganisms contribute positively to stimulated plant growth and to decreasing stress caused by high concentrations of copper in soil, especially C. cupreum.

DOI: 10.1007/s11104-019-03946-w

UT (Unique WOS ID): WOS:000462031100029