Cultivable root endophytic fungi associated with Acrocomia aculeata and its antagonistic activity against phytopathogenic oomycetes.

Macaw palm (Acrocomia aculeata Jacq.) is a palm, native to Brazilian territory that stands out due to the amount of oil produced with applications in the biodiesel industry, cosmetics, and food. Its commercial exploitation in Brazil, including phytosanitary management is based on concepts and practices of regenerative agriculture, which has the responsibility of sustainable cultivation by avoiding, for example, the use of chemical pesticides. Recently, root and stem rot disease were reported in macaw palm seedlings caused by Phytophthora palmivora. Managing this plant pathogen is complex, and the chemical control of this soil-borne oomycete is not viable, in addition to the negative impact on the environment. Many microorganisms are studied and used as biological control agents (BCAs) against pathogens, among them the community of endophytic fungi associated with plants. This is a sustainable biotechnological alternative for plant disease control. The community of cultivable endophytic fungi associated with healthy roots of macaw palm was explored using the extinction cultivation technique and a screening was carried out to select potential antagonists against oomycetes through the dual culture test. Specific gene regions from the best isolates were amplified for identification. A total of 250 isolates were obtained, and 46 were selected for in vitro tests against representatives of phytopathogenic oomycetes. After tests against Phytophthora heterospora, Phytophthora palmivora, Pythium aphanidermatum, and Pythium deliense, two isolates were selected as potential antagonists. The phylogenetic analysis of selected isolates showed that they belong to two different species: Talaromyces sayulitensis COAD 3605 and Epicoccum italicum COAD 3608. The percentage of inhibition of phytopathogenic oomycetes testedwas until 82% in the antagonism tests conducted. From the 46 isolates selected, only 2 were selected which showed great antagonistic activity towards all oomycetes tested. These fungi will be used in upcoming studies that aim to determine the effectiveness of endophytes in controlling diseases caused by oomycetes in the field.

Mycorrhizal fungal communities associated with three metal accumulator plants growing in an abandoned Pb smelting factory.

Plants associated with mycorrhizal fungi has the ability to establish on metal-contaminated soils playing an important role in phytoremediation programs. The objective of this study was to examine the presence of arbuscular mycorrhizal fungi (AMF) (spores density, diversity, indicator species, and root colonization) and dark septate endophytic fungi (DSE fungal root colonization) in three metal accumulator plants (Sorghum halepense, Bidens pilosa, and Tagetes minuta) growing in soils with high Pb content. The Pb content in AMF spores and plant biomass were also assessed. Rhizosphere soil samples were taken from the three dominant plant species at six study sites surrounding the abandoned Pb smelter and one uncontaminated site. The three studied plants were colonized by AMF and DSE fungi. A total of 24 AMF morphospecies were present in the Pb-contaminated areas. The AMF indicator species in the control site (non-contaminated area) was Funneliformis mosseae and in the most contaminated site were Gigaspora decipiens and Denticustata biornata. There was an increase in mycorrhizal variables such as the number of AMF vesicles, spore number, Pb content in AMF spores and plant biomass and DSE colonization (in Sorghum) with increasing soil Pb contamination, but a decrease in AMF diversity and richness was found. For upcoming soil restoration projects, it is crucial to understand the mycorrhizal fungi as well as the plant community that has adapted to the highly contaminated environment.

Are dark septate endophytes an ancestral ecological state in the evolutionary history of the order Chaetothyriales?

Dark septate endophytes (DSE) are pigmented fungi that colonize plant roots. They represent a morpho-functional status composed of many species belonging to the phylum Ascomycota, distributed in different orders. The order Chaetothyriales has representatives with diverse lifestyles, among which the rock-inhabiting one has been proposed to be the ancestral ecological character state. However, all taxa have the phenotypic characteristic of being highly melanized. This trait has been considered relevant in most Chaetothyriales because it allows them to tolerate extreme or toxic environmental conditions. In the present study, aiming to reconstruct the evolutionary history of this order, we analyzed the contribution of the DSE habit to the diversification of the Chaetothyriales. We also report the distribution of the DSE habit among the main families and/or clades within the order. Our results suggest that DSE had a key position in the evolution of the order Chaetothyriales, both as an ancestral ecological character and as a character from which other specialized forms such as Domatium probably derived.

Endorhizal fungal symbiosis in lycophytes and metal(loid)-accumulating ferns growing naturally in mine wastes in Mexico.

Ferns and lycophytes are pioneer plants that can be useful for revegetation. Their natural distribution and interaction with soil fungal endophytes can increase plant fitness but have received little attention. This study aimed to identify these plant species in mine wastes, and determine colonization by arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE). The pseudo-total and diethylenetriamine pentaacetic acid (DTPA)-extractable rhizosphere concentrations of As, Cu, Cd, Pb, and Zn, bioavailability index (BI), and bioconcentration factor (BCF) were analyzed. Six ferns and one lycophyte were identified. Arsenic and metal concentrations were high, which were plant and site-dependent. All species showed hyperaccumulation of As in fronds, especially Argyrochosma formosa (2,883) and Notholaena affinis (2,160) had the highest concentrations (mg kg-1). All plants were colonized by AMF (3%-24%) and DSE (2%-33%). Astrolepis sinuata and Myriopteris notholaenoides had the maximum colonization by AMF and A. formosa by DSE. This study identifies for the first time five ferns and one lycophyte species on mine wastes, their As hyperaccumulation capacity and the simultaneous fungal colonization by AMF and DSE. These are relevant plant traits for phytoremediation. However, fungal identification and the role colonization by AMF and DSE requires full analysis.

Arsenic accumulator ferns and a lycophytes species naturally established on three polluted sites were found. Astrolepis integerrima, A. sinuata, Myriopteris notholaenoides, Notholaena affinis, N. sulphurea, and the lycophyte Selaginella lepidophylla are for the first time reported in these sites. This is the first evidence of DSE colonization in these plants growing on mine wastes in interaction with AMF-colonization. These plants may be useful in developing phytoremediation alternatives.

Azospirillum brasilense and Zinc Rates Effect on Fungal Root Colonization and Yield of Wheat-Maize in Tropical Savannah Conditions.

A successful microbial inoculant can increase root colonization and establish a positive interaction with native microorganisms to promote growth and productivity of cereal crops. Zinc (Zn) is an intensively reported deficient nutrient for maize and wheat production in Brazilian Cerrado. It can be sustainably managed by inoculation with plant growth-promoting bacteria and their symbiotic association with other microorganisms such as arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE). The objective of this study was to evaluate the effect of Azospirillum brasilense inoculation and residual Zn rates on root colonization and grain yield of maize and wheat in succession under the tropical conditions of Brazil. These experiments were conducted in a randomized block design with four replications and arranged in a 5 × 2 factorial scheme. The treatments consisted of five Zn rates (0, 2, 4, 6 and 8 kg ha-1) applied from zinc sulfate in maize and residual on wheat and without and with seed inoculation of A. brasilense. The results indicated that root colonization by AMF and DSE in maize-wheat cropping system were significantly increased with interaction of Zn rates and inoculation treatments. Inoculation with A. brasilense at residual Zn rates of 4 kg ha-1 increased root colonization by AMF under maize cultivation. Similarly, inoculation with A. brasilense at residual Zn rates of 2 and 4 kg ha-1 reduced root colonization by DSE under wheat in succession. The leaf chlorophyll index and leaf Zn concentration were increased with inoculation of the A. brasilense and residual Zn rates. The inoculation did not influence AMF spore production and CO2-C in both crops. The grain yield and yield components of maize-wheat were increased with the inoculation of A. brasilense under residual Zn rates of 3 to 4 kg ha-1 in tropical savannah conditions. Inoculation with A. brasilense under residual Zn rates up to 4 kg ha-1 promoted root colonization by AMF and DSE in the maize cropping season. While the inoculation with A. brasilense under 2 and 4 kg ha-1 residual Zn rates reduced root colonization by AMF and DSE in the wheat cropping season. Therefore, inoculation with A. brasilense in combination with Zn fertilization could consider a sustainable approach to increase the yield and performance of the maize-wheat cropping system in the tropical savannah conditions of Brazil.

Dark septate endophytes (DSE): potential bioremedial promoters of oil derivatives.

Oil spills are a global environmental problem. One of the management tools used to solve this problem is phytoremediation, a process that uses the capacity of plants and microorganisms to metabolize the components of the oil. The aims of the present study were to isolate, identify and characterize the fungi obtained from plants growing in an oil-contaminated area and evaluate their growth response and emulsifying and degrading capacity in two petroleum derivatives (kerosene and lube oil). Four dark septate endophytes (DSE) strains were isolated and identified: Exserohilum pedicellatum, Ophiosphaerella sp., and two Alternaria alternata strains. E. pedicellatum was found in an oil-contaminated environment for the first time. All strains were grown in kerosene, although some showed inhibition, whereas in lube oil, all showed growth induction. Ophiosphaerella sp. showed "drops" in kerosene, but the four strains showed surfactant capacity in lube oil. Ophiosphaerella sp. showed the highest emulsifying activity index but both A. alternata strains presented the highest lube oil degradation, which was directly related to the weight of the fungal biomass. There was not relationship between emulsifying capacity and oil degradation. However, these fungi show technological potential for application in phytoremediation processes.

Isolation, identification, and characterization of cadmium-tolerant endophytic fungi isolated from barley (Hordeum vulgare L.) roots and their role in enhancing phytoremediation.

Four hundred endophytic fungi isolates with different colony morphologies were isolated from roots of Hordeum vulgare L. collected from un-engineered landfills (the measured cadmium was 0.9 mg kg-1) of Kermanshah province in West Iran. Based on morphology and phylogeny of DNA sequence data for the internal transcribed spacer (ITS) rDNA and comparing the sequences with that available in NCBI database, 11 isolates are identified as dark septate endophytes (DSE) including Alternaria alternata, Microdochium bolleyi, Bipolaris zeicola, Alternaria sp., and Pleosporales sp., and the other nine are not dark septate endophytes (non-DSE) including Fusarium redolens, Fusarium tricinctum, Fusarium monliforme, Clonostachys rosea, and Epicoccum nigrum. Tolerance of DSE and non-DSE strains for Cd were investigated in potato dextrose agar medium. Minimum inhibitory concentrations (MIC) of Cd from nitrate salt source (Cd (NO3)2) and EC50 were determined. The means of MIC and EC50 values for DSE fungi species were 1254.5 and 209.74 mg/kg, compared to 800 and 150.3 mg/kg for non-DSEs. Among the endophytic fungi isolated, Alternaria sp. (TBR5) and Bipolaris zeicola (Tw26) showed the highest tolerance to Cd with a MIC value of 2000 mg/L and 1800 mg/L, respectively. Barley plants were inoculated with TBR5 and Tw26 in Cd-added sands (0, 10, 30, 60 mg Cd/kg sand). In terms of Cd accumulation, our results showed that TBR5 and Tw26 inoculation increased the amount of Cd in the barley roots. TBR5 and Tw26 significantly improved (p < 0.05) plant growth in the presence of Cd by enhancing plant growth attributes such as chlorophyll content, root weight, plant length, fresh weight, and dry weight of plants. This is the first study on the abundance and identification of endophytic root fungi of barley in a cadmium-contaminated soil in Iran. The results of this study showed that DSE and non-DSE have the potential to improve the efficiency of phytoremediation.

Subterranean Desert Rodents (Genus Ctenomys) Create Soil Patches Enriched in Root Endophytic Fungal Propagules.

Subterranean rodents are considered major soil engineers, as they can locally modify soil properties by their burrowing activities. In this study, the effect of a subterranean rodent of the genus Ctenomys on soil properties and root endophytic fungal propagules in a shrub desert of northwest Argentina was examined. Our main goal was to include among root endophytic fungi not only arbuscular mycorrhiza but also the dark septate endophytes. We compared the abundance of fungal propagules as well as several microbiological and physicochemical parameters between soils from burrows and those from the surrounding landscape. Our results show that food haulage, the deposition of excretions, and soil mixing by rodents' burrowing promote soil patchiness by (1) the enrichment in both types of root endophytic fungal propagules; (2) the increase in organic matter and nutrients; and (3) changes in soil edaphic properties including moisture, field capacity, and texture. These patches may play a critical role as a source of soil heterogeneity in desert ecosystems, where burrows constructed in interpatches of bare soil can act, once abandoned, as "islands of fertility," promoting the establishment of plants in an otherwise hostile environment.

Arbuscular mycorrhizal colonization in Asteraceae from white sand savannas, in Pinar del Rio, Cuba / Colonizacion micorrizica arbuscular en Asteraceae de las sabanas de arenas blancas, de Pinar del Rio, Cuba

Asteraceae family shows a great diversity in Cuba and presents threatened taxons in high number. Pinar del Río has 19 threatened species belonging to this family and three of them are characteristic of a sandy (quartzitic) soil at the Reserva Florística Manejada San Ubaldo-Sabanalamar (Floristic Reserve San Ubaldo-Sabanalamar). The arbuscular mycorrhizal status and colonization rate in Aster grisebachii, Erigeron bellidiastroides, Erigeron cuneifolius, Pectis juniperina and Sachsia polycephala (Asteraceae) from this Reserve was determined in October 2009 and April 2010, during hydrologic rainy and dry period, respectively. All species were mycotrophic in both periods with a high percentage of colonization rates, between 66 and 100% in rainy period and between 84 and 100% in dry period. Vesicles, arbuscules, spores, hyphal and arbuscular coils of arbuscular mycorrhizae were observed. Paris -type and Arum -type morphologies (both) were observed indistinctly in all the species, and Intermediate type was observed only in Aster grisebachii and Erigeron bellidiastroides, which could be a hint that these species are colonized by more than one fungal species, and therefore enhancing the relevance of fungal identity as a considerable character in the morphology association. Also, septate hyphae and microsclerotium of dark septate endophytes were identifyed inside the roots of all the species.

La familia Asteraceae muestra una gran diversidad en Cuba y presenta un elevado número de taxones amenazados. Pinar del Río cuenta con 19 especies amenazadas pertenecientes a esta familia, de las cuales tres son características de los suelos arenosos cuarcíticos de la Reserva Florística Manejada San Ubaldo-Sabanalamar. Se determinó el estatus micorrízico arbuscular y la tasa de colonización de Aster grisebachii, Erigeron bellidiastroides, Erigeron cuneifolius, Pectis juniperina y Sachsia polycephala (Asteraceae) presentes en esta Reserva, en octubre del 2009 y abril del 2010, durante los períodos hidrológicos húmedo y seco, respectivamente. Todas las especies estaban micorrizadas en ambos períodos con elevados porcentaje de colonización micorrízica, entre 66 y 100% en el período lluvioso y entre 84 y 100% en el período seco. Se identificaron vesículas, arbúsculos, esporas, enrollados hifales y arbusculares característicos de las micorrizas arbusculares. Los tipos morfológicos Paris y Arum (ambos) fueron observados indistintamente en todas las especies, y el tipo Intermedio solo se observó en Aster grisebachii y Erigeron bellidiastroides, lo cual sugiere la colonización de estas especies por más de una especie fúngica y con ello la importancia de la identidad fúngica en la determinación de la morfología de la asociación. Se identificaron además, hifas septadas y microesclerosios de endófitos oscuros septados en el interior de las raíces de todas las especies estudiadas.