Herrera, H.; Sanhueza, T.; Martiarena, R.; Valadares, R.; Fuentes, A.; Arriagada, C. Mycorrhizal Fungi Isolated from Native Terrestrial Orchids from Region of La Araucanía, Southern Chile. Microorganisms 2020, 8, 1120.(WOS. Impact Factor 4.152  Q2). microorganisms8081120

Inmaculada Sampedro, Daniel Pérez-Mendoza, Laura Toral, Esther Palacios, César Arriagada and Inmaculada Llamas.  Effects of Halophyte Root Exudates and Their Components on Chemotaxis, Biofilm Formation and Colonization of the Halophilic Bacterium Halomonas Anticariensis FP35(T). Microorganisms 2020, 8(4), 575 (WOS. Impact Factor 4.152  Q2).  https://doi:10.3390/ microorganisms8040575

Fuentes AHerrera HCharles TC, Arriagada C. Fungal and Bacterial Microbiome Associated with the Rhizosphere of Native Plants from the Atacama Desert. Microorganisms, 8(2), 209(WOS. Impact Factor 4.152  Q2). microorganisms8020209

Héctor Herrera, Tedy Sanhueza, Alžběta Novotná, Trevor C. Charles and Cesar Arriagada. Isolation and Identification of Endophytic Bacteria from Mycorrhizal Tissues of Terrestrial Orchids from Southern Chile. Diversity-Basel 12(2), 55; (WOS. Impact Factor 2.465 Q2).

Héctor Herrera, Alžběta Novotná, Javier Ortiz, Javiera Soto, CesarArriagada. Isolation and identification of plant growth-promoting bacteria from rhizomes of Arachnitis uniflora, a fully mycoheterotrophic plant in southern Chile. Applied Soil Ecology. 103512 (WOS. Impact Factor: 3.187 Q2). j.apsoil.2020.103512

Vidal, C.; Ruiz, A.; Ortiz, J.; Larama, G.; Perez, R.; Santander, C.; Ferreira, P.A.A.; Cornejo, P. Antioxidant Responses of Phenolic Compounds and Immobilization of Copper in Imperata cylindrica, a Plant with Potential Use for Bioremediation of Cu Contaminated Environments. Plants 2020, 9, 1397. plants9101397 (WOS. Impact Factor 3.935  Q1)

Mycorrhizal Fungi Isolated from Native Terrestrial Orchids from Region of La Araucania, Southern Chile

Author Full Names: Herrera, Hector; Sanhueza, Tedy; Martiarena, Rodolfo; Valadares, Rafael; Fuentes, Alejandra; Arriagada, Cesar


Mycorrhizal interactions of orchids are influenced by several environmental conditions. Hence, knowledge of mycorrhizal fungi associated with orchids inhabiting different ecosystems is essential to designing recovery strategies for threatened species. This study analyzes the mycorrhizal associations of terrestrial orchids colonizing grassland and understory in native ecosystems of the region of La Araucania in southern Chile. Mycorrhizal fungi were isolated from peloton-containing roots and identified based on the sequence of the ITS region. Their capacities for seed germination were also investigated. We detectedTulasnellaspp. andCeratobasidiumspp. in the pelotons of the analyzed orchids. Additionally, we showed that someCeratobasidiumisolates effectively induce seed germination to differing degrees, unlikeTulasnellaspp., which, in most cases, fail to achieve protocorm growth. This process may underline a critical step in the life cycle ofTulasnella-associated orchids, whereas theCeratobasidium-associated orchids were less specific for fungi and were effectively germinated with mycorrhizal fungi isolated from adult roots.

DOI: 10.3390/microorganisms8081120

UT (Unique WOS ID): WOS:000564675500001

Effects of Halophyte Root Exudates and Their Components on Chemotaxis, Biofilm Formation and Colonization of the Halophilic Bacterium Halomonas Anticariensis FP35(T)

Author Full Names: Sampedro, Inmaculada; Perez-Mendoza, Daniel; Total, Laura; Palacios, Esther; Arriagada, Cesar; Llamas, Inmaculada


Increase in soil salinity poses an enormous problem for agriculture and highlights the need for sustainable crop production solutions. Plant growth-promoting bacteria can be used to boost the growth of halophytes in saline soils. Salicornia is considered to be a promising salt-accumulating halophyte for capturing large amounts of carbon from the atmosphere. In addition, colonization and chemotaxis could play an important role in Salicornia-microbe interactions. In this study, the role of chemotaxis in the colonization of the halophilic siredophore-producing bacteria, Halomonas anticariensis FP35(T), on Salicornia hispanica plants was investigated. The chemotactic response of FP35(T) to Salicornia root exudates showed optimum dependence at a salt concentration of 5 % NaCl (w/v). Oleanolic acid, the predominant compound in the exudates detected by HPLC and identified by UPLC-HRMS Q-TOF, acts as a chemoattractant. In vitro experiments demonstrated the enhanced positive effects of wild-type H. anticariensis strain FP35(T) on root length, shoot length, germination and the vigour index of S. hispanica. Furthermore, these positive effects partially depend on an active chemotaxis system, as the chemotaxis mutant H. anticariensis FP35 Delta cheA showed reduced plant growth promotion for all the parameters tested. Overall, our results suggest that chemotaxis responses to root exudates play an important role in interactions between Salicornia and halophilic bacteria, enhance their colonization and boost plant growth promotion. Preliminary results also indicate that root exudates have a positive impact on H. anticariensis FP35(T) biofilm formation under saline conditions, an effect which totally depends on the presence of the cheA gene.

DOI: 10.3390/microorganisms8040575

UT (Unique WOS ID): WOS:000533510400016

Fungal and Bacterial Microbiome Associated with the Rhizosphere of Native Plants from the Atacama Desert

Author Full Names: Fuentes, Alejandra; Herrera, Hector; Charles, Trevor C.; Arriagada, Cesar


The rhizosphere microbiome is key in survival, development, and stress tolerance in plants. Salinity, drought, and extreme temperatures are frequent events in the Atacama Desert, considered the driest in the world. However, little information of the rhizosphere microbiome and its possible contribution to the adaptation and tolerance of plants that inhabit the desert is available. We used a high-throughput Illumina MiSeq sequencing approach to explore the composition, diversity, and functions of fungal and bacterial communities of the rhizosphere of Baccharis scandens and Solanum chilense native plants from the Atacama Desert. Our results showed that the fungal phyla Ascomycota and Basidiomycota and the bacterial phyla Actinobacteria and Proteobacteria were the dominant taxa in the rhizosphere of both plants. The linear discriminant analysis (LDA) effect size (LefSe) of the rhizosphere communities associated with B. scandens showed the genera Penicillium and Arthrobacter were the preferential taxa, whereas the genera Oidiodendron and Nitrospirae was the preferential taxa in S. chilense. Both plant showed similar diversity, richness, and abundance according to Shannon index, observed OTUs, and evenness. Our results indicate that there are no significant differences (p = 0.1) between the fungal and bacterial communities of both plants, however through LefSe, we find taxa associated with each plant species and the PCoA shows a separation between the samples of each species. This study provides knowledge to relate the assembly of the microbiome to the adaptability to drought stress in desert plants.

DOI: 10.3390/microorganisms8020209

UT (Unique WOS ID): WOS:000519618200065

Isolation and Identification of Endophytic Bacteria from Mycorrhizal Tissues of Terrestrial Orchids from Southern Chile

Author Full Names: Herrera, Hector; Sanhueza, Tedy; Novotna, Alzbeta; Charles, Trevor C.; Arriagada, Cesar


Endophytic bacteria are relevant symbionts that contribute to plant growth and development. However, the diversity of bacteria associated with the roots of terrestrial orchids colonizing Andean ecosystems is limited. This study identifies and examines the capabilities of endophytic bacteria associated with peloton-containing roots of six terrestrial orchid species from southern Chile. To achieve our goals, we placed superficially disinfected root fragments harboring pelotons on oatmeal agar (OMA) with no antibiotic addition and cultured them until the bacteria appeared. Subsequently, they were purified and identified using molecular tools and examined for plant growth metabolites production and antifungal activity. In total, 168 bacterial strains were isolated and assigned to 8 OTUs. The orders Pseudomonadales, Burkholderiales, and Xanthomonadales of phylum Proteobacteria were the most frequent. The orders Bacillales and Flavobacteriales of the phylla Firmicutes and Bacteroidetes were also obtained. Phosphate solubilization was detected in majority of isolates; however, it was significantly higher in Collimonas pratensis and Chryseobacterium sp. (PSI = 1.505 +/- 0.09 and 1.405 +/- 0.24, respectively). Siderophore production was recorded only for C. pratensis (0.657 +/- 0.14 mm day(-1)), Dyella marensis (0.131 +/- 0.02 mm day(-1)), and Luteibacter rhizovicinus (0.343 +/- 0.12 mm day(-1)). Indole acetic acid production was highly influenced by the isolate identity; however, the significantly higher activity was recorded for Pseudomonas spp. (ranging from 5.507 +/- 1.57 mu g mL(-1) to 7.437 +/- 0.99 mu g mL(-1)). Additionally, six bacterial isolates were able to inhibit the growth of some potential plant pathogenic fungi. Our findings demonstrate the potential for plant growth promoting capabilities and some antifungal activities of endophytic bacteria inhabiting the mycorrhizal tissue of terrestrial orchids, which may contribute especially at early developmental stages of orchid seedlings.

DOI: 10.3390/d13080344

UT (Unique WOS ID): WOS:000688989600001

Isolation and identification of plant growth-promoting bacteria from rhizomes of Arachnitis uniflora, a fully mycoheterotrophic plant in southern Chile

Author Full Names: Herrera, Hector; Novotna, Alzbeta; Ortiz, Javier; Soto, Javiera; Arriagada, Cesar


DOI: 10.1016/j.apsoil.2020.103512

UT (Unique WOS ID): WOS:000511288300007

Fully mycoheterotrophic plants have attracted attention due to their ability to obtain carbon and mineral nutrients directly from fungal hyphae. However, research on bacteria associated with full mycoheterotrophs is limited. This study identifies rhizosferic and endophytic bacteria associated with A. uniflora rhizomes and analyzes their ability to produce microbial metabolites of various functions. Eight bacterial OTUs were revealed, and their potential roles in plant-growth promotion and antimicrobial activities were demonstrated. These findings suggest that root-system associated bacteria can be considered as essential microorganisms for growth and development of fully mycoheterotrophic plants.

Controlled mycorrhization of the endemic Chilean orchidChloraea gavilu(Orchidaceae)

Author Full Names: Pereira, Guillermo; Herrera, Hector; Arriagada, Cesar; Cid, Hertes; Garcia, Jose Leonardo; Atala, Cristian


Orchids require mycorrhizal fungi (OMF) for their germination and growth. Propagation and re-introduction initiatives would likely require inoculation with such fungi. All Chilean Orchidaceae species are terrestrial and likely associate with OMF. We collected adult individuals of the endemic Chilean orchidChloraea gaviluand transported them to a glasshouse where we obtained mature capsules through manual auto-pollination. We asymbiotically germinated seeds in vitro using Malmgren Modified Terrestrial Orchid-Medium (MM). Embryos were put in glass flasks with MM where roots and leaves developed for 16 weeks. Plants were then transplanted to 165 mL pots and randomly separated into three groups; plants inoculated separately withCeratobasidiumOMFs isolated from two Chilean orchid species (Chloraea virescensandCodonorchis lessonii), and uninoculated (control) plants. Plants were then put in a growth chamber. Three months later, inoculated individuals showed pelotons inside parenchyma cells in the roots. Four months after inoculation, mycorrhizal plants had higher root and shoot biomass compared to control plants. At the end of the experiment, the highest mycorrhization was achieved with theCeratobasidiumstrain isolated fromC. lessonii. The artificial mycorrhization of endemic orchids could be a key strategy for future conservation and propagation initiatives, especially for endangered or commercially interesting species.

DOI: 10.1080/11263504.2020.1801875

UT (Unique WOS ID): WOS:000562194000001