Acaulospora Mellea Research Articles

Arbuscular Mycorrhizal Fungi (AMF) diversity and population in UPV Nature Trail, Miagao, Iloilo, Philippines

Abstract. De Asis EPT, Demetillo FMM, Paguntalan DP. 2023. Arbuscular Mycorrhizal Fungi (AMF) diversity and population in UPV Nature Trail, Miagao, Iloilo, Philippines. Biodiversitas 24: 6692-6703. Arbuscular Mycorrhizal Fungi (AMF) are soil microorganisms that form the most prevalent mutualistic associations with plant species. Studies revealed its global distribution in various terrestrial habitats, but available local literature remains few. This study investigated AMF diversity in the University of the Philippines Visayas (UPV) Nature Trail, Miagao, Iloilo, Philippines. AMF spores were isolated using wet sieving, decanting, and centrifugation. A total of 2815 individual spores were documented, with 114 distinct morphospecies representing 16 genera, nine families, and four orders classified. Glomus clarum, Acaulospora sp.7, and Scutellospora pellucida tallied the highest abundance across all points. Scutellospora pellucida (FOC=83.3%) recorded the highest species richness, followed by Ambispora sp. (FOC=77.78%), then Acaulospora mellea and Glomus australe (FOC=72.22%). Overall, Shannon-Weiner diversity index (H=3.6019) and Simpson diversity index (D=0.0420) revealed a very high AMF diversity in the trail, while the Pielou evenness index (J=0.7605) suggested a semi-balanced number of individuals among each morphospecies. A more abundant, even, and diverse, albeit not statistically significant, AMF community was recorded in forested areas compared to non-forested areas of the trail. Results generally suggest that the AMF community is diverse and abundant regardless of the location, ecosystem type, and faunal association.

Native arbuscular mycorrhizal fungi and Nauclea orientalis for potential reclamation of tropical coal mining areas

Reclaiming tropical coal mines is a formidable task. The symbiosis between AMF and plants like Nauclea orientalis is crucial for thriving in tough environments. This study aimed to assess the potential of native AMF and N. orientalis in overburden pit soil for post-mining reclamation. Fifteen AMFs isolated from post-coal mining were screened for nutrient uptake, plant growth, and colonization using Sorghum bicolor as hostplant. The top three AMFs were rDNA amplicon sequenced and further analyzed for their spore ontogeny at varying pH and aluminum concentrations. The most promising AMF strains were then tested by inoculating them into N. orientalis growing in four soil substrates: soil (S), overburden (O), soil mixed overburden (v/v 1:1, M1), and soil mixed overburden (v/v 1:3, M2). Non-inoculated plants served as control. Plant biomass, AMF colonization, root and shoot P, Al, Fe concentrations, and soil chemical properties were analyzed. Phylogenetic analysis revealed the three best-screened AMFs were Acaulospora mellea, Uncultured Glomus gene clone: N8-89, and Glomus clarum isolate AU402B. Overburden resulting from coal mining led to decreased soil pH and P levels while increasing concentrations of Al3+, H+, S, Fe, and Mn. A. mellea, Uncultured Glomus, and G. clarum demonstrated high P, K, Mg uptake and yield. G. clarum exhibited the best spore ontogeny at pH 4.5 and Al concentrations of 2 µM and 5 µM. Additionally, G. clarum, alongside N. orientalis, mitigated the toxicity of soil Al, Fe, and Mn. G. clarum improved plant growth in M1 and M2 and produced high plant biomass in OM and M2M. These findings suggest that the application of selected native AMF can significantly enhance plant adaptation in challenging conditions, potentially reducing the necessity for topsoil in reclamation efforts by 50–75 %.

An alternative risk assessment framework for tropical soil multi-metal contamination using arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) are a key group of soil organisms involved in several ecosystem services, but they had not been explored in retrospective ecological risk assessment (ERA) schemes, partially due to a lack of experimental protocols. We aimed to perform a site-specific test to assess the effects of multiple metal contaminated soil (Zn, Cu, Cd, and Pb) on several ecotypes of AMF and evaluate the conceptual fitness of the performed AMF test to include in the TRIAD approach of ERA schemes. The results demonstrated that increasing metal contaminated soil proportions that inhibited 50 % (IC50) of spore germination varied from 28 to >80. Ecotypes such as Claroideoglomus etunicatum (IC50 > 80) and Racocetra gregaria (IC50 > 80) experienced 50 % reduction in spore germination at metals concentrations of 10,776.3 for Zn, 1015.2 Cu, 65.5 Cd, 140.2 mg dm−3 Pb, that are 3 times higher than those for Acaulospora mellea CMM101 (IC50 28 [16.2–39.8]) (3441.7 Zn, 333.9 Cu, 17.8 Cd, 56.5 mg dm−3 Pb). In the evaluation of the suitability of the AMF ecotoxicological test to ERA, both spore germination and germinative tube growth were best evaluated and thus suitable in the following descending order: Tier III, Tier II, and Tier I. Variable effects of multiple-metal contamination on the ecotypes indicates how AMF community is affected in its pre-symbiotic structures. The ecotoxicological test allowed the selection of two species with the greatest sensitivity (Ambispora appendicula and Rhizophagus clarus CMM103) to the metal matrix, with the potential to best fit ERA objectives. The site-specific ecotoxicological test with AMF ex-situ proved adequate as an alternative test for Tiers II and III of TRIAD ERA schemes for metal contaminated areas. Data generated through test results, such as the inhibition concentrations (ICs), could be incorporated into ERAs risk indexes, increasing its ecological relevance, and reducing overall uncertainties.

Influence of arbuscular mycorrhizal fungi on biological control of coffee leaf rust (Hemileia vastatrix BERK. & BROOME)

Inoculating plants with arbuscular mycorrhizal fungi (AMF) protects host plants against biotic stressors such as diseases. Therefore, the objective of this study was to evaluate the influence of arbuscular mycorrhizal fungi in the biological control of coffee leaf rust (CLR) infections. The research involved two varieties of coffee (Caturra and Pache) and three inocula of AMF: Moyobamba (Acaulospora mellea, Acaulospora sp.1, Glomus geosporum, Glomus sp.1, and Glomus sp.2), El Dorado (Acaulospora rugosa, Acaulospora spinosissima, Acaulospora lacunosa, Glomus sinuosum and Ambispora appendicula) and Huallaga (Acaulospora mellea, Acaulospora sp.1, Acaulospora sp.2, Glomus macrocarpum and Glomus sp.2), in addition to a control treatment without application of AMF (non-AMF). Inoculation of vegetatively propagated coffee plants with AMF was observed to induce tolerance to CLR. The incidence of CLR in non-AMF coffee plants was 43.7 %, while in the coffee plants subjected to the inocula Moyobamba, El Dorado and Huallaga, the incidences were 22.1, 22.7 and 13.2 %, respectively. Likewise, the severity in non-AMF coffee plants was 34.8 %, while in the coffee plants subjected to the three kinds of inocula, the severities were 21.1, 20.4 and 12.0 %, respectively. Thus, mycorrhizal inoculation of coffee plants at the nursery stage reduces the negative effect of CLR infection after the plants are taken to field conditions, representing a sustainable option for their biological control.

Rehabilitation promotes rapid recovery of arbuscular mycorrhizal fungi in iron mining areas

Arbuscular mycorrhizal fungi (AMF) perform important ecological functions in the rehabilitation of degraded areas, acting through several mechanisms, such as the production of glomalin-related soil proteins (glomalin), which act as cementing agents and nutritional reserves and sequester carbon in soil. The aim of the present study was to determine whether a short rehabilitation time influenced the soil AMF community diversity and glomalin production in areas undergoing rehabilitation after iron mining. We analyzed the number of spores, mycorrhizal colonization, AMF species richness, and concentrations of easily extractable and total glomalin-related soil proteins. Species richness was reduced by approximately 50 % after mining activity. However, after the initial rehabilitation of degraded areas, we observed an increase in the number of spores, colonization, and AMF species. Families Glomeraceae and Acaulosporaceae were considered dominant in the studied areas. Glomus sp.1 and Acaulospora mellea were the most frequent morphotypes. The relationship between glomalin and the levels of dissolved organic carbon, total carbon, and total nitrogen in the soil was found to be an interesting and easily interpretable parameter of the influence of AMF on the storage of organic matter in the soil, indicating the degree of equilibrium and/or recovery of revegetated environments. Rehabilitation, even in early stages, favored improvements in AMF status and provided increases in total glomalin-related soil protein production, which may have contributed to the enrichment of carbon and nitrogen in the soil. These characteristics are indicative of the success of the rehabilitation actions carried out in these areas after mining activity.

Arbuscular mycorrhizal fungi and humic substances increased the salinity tolerance of rice plants

Salinity induces salt uptake by plant cells, which hinders plant growth and results in decreased agronomic crop yields. Humic substances (HSs) have been shown to be ecological agricultural alternatives to stimulate plant development under both normal and abiotic stress conditions. At the same time, arbuscular mycorrhizal fungi (AMF) provide nutrients and provide salinity tolerance through the osmotic balance between Na+ and K+. This study aimed to evaluate the effects of the combination of AMF and HSs on the growth of rice plants under salinity stress. The experiment was carried out in a greenhouse: Pots filled with sand were treated with a nutrient solution (as a control), 40 mg HS L−1 or 200 mM NaCl and inoculated with Acaulospora mellea, Glomus formosanum, Rhizoglomus clarum, or Glomus spp. The HSs and AMF stimulated biomass production and root growth compared to those of uninoculated plants. The leaf P content increased in the presence of HSs and AMF under stress conditions. The sodium concentration was higher in the shoots of plants not treated with HSs than in those of the control plants. The potassium concentration decreased in the shoots under saline conditions. HSs and AMF alone or in combination promoted mycorrhizal colonization, especially that of A. mellea. AMF and HSs stimulated plant growth, improved root morphological characteristics, and increased P accumulation in rice plants under salt-stress conditions. These results support the production of biofertilizers with protective effects for sustainable agriculture.

Contribution of arbuscular mycorrhizal fungi and soil amendments to remediation of a heavy metal-contaminated soil using sweet sorghum

Owing to their potential advantages such as waste reduction, recycling, and economic attributes, fast-growing bioenergy crops have the capacity to effectively phytoremediate heavy metal-contaminated soils. However, little is known about the role of microbial and chemical amendments in phytoremediation using bioenergy crops. Here, we studied the contributions of inoculation with the arbuscular mycorrhizal fungus (AMF) Acaulospora mellea and three soil amendments, i.e., hydroxyapatite (HAP), manure, and biochar, at doses of 0.1% and 1% (weight:weight) to heavy metal phytoremediation using sweet sorghum grown on an abandoned agricultural soil, with environmentally realistic contamination (2.6 mg kg−1 Cd, 1796 mg kg−1 Pb, and 1603 mg kg−1 Zn), in a plant growth chamber. Mycorrhizal colonization, plant biomass and metal accumulation, metal availability, and soil pH were determined in harvested seedlings 12 weeks after sowing. The results showed that root colonization by indigenous AMF decreased by 28%-46% with HAP, but increased after manure and biochar applications as compared to the no amendment control (CK). The AMF inoculation increased root colonization rates by 16%-128% and in particular, alleviated the inhibition of HAP. The remediation effects were highly dependent on the amendment type and dose. Among the three soil amendments, HAP was the most effective in promoting plant growth and phytostabilization of Cd, Pb, and Zn and phytoextraction of Cd, particularly at a dose of 1%. Compared to CK, 1% HAP decreased DTPA-extractable Cd, Pb, and Zn concentrations in soil by 31%-43%, 30%-38%, and 22%-23%, respectively. Manure and biochar also exerted positive effects on heavy metal immobilization, as indicated by lower DTPA extractability, but only the 1% manure treatment showed plant growth-promoting effect. The AMF inoculation did not affect plant growth, but increased soil pH and induced synergistic interactions with amendments on the immobilization of Cd and Pb. In conclusion, soil amendments, particularly HAP, produced positive impacts and synergistic interactions with AMF on the phytostabilization of heavy metals using sweet sorghum. Accordingly, sweet sorghum combined with soil amendments and AMF may be an effective strategy for heavy metal phytoremediation.

Micropropagation and Arbuscular Mycorrhizae Assisted Growth in Phlomis cashmeriana Royle ex Benth., an endemic medicinal herb of Kashmir Himalaya

ABSTRACT Phlomis cashmeriana (Lamiaceae) is an ornamental cum medicinal perennial herb endemic to Kashmir Himalaya. Two arbuscular mycorrhizal (AM) fungal inocula on post-transplanting performance of ‘in vitro’-raised P. cashmeriana plantlets were tested. The two AM fungal inocula consisted of two mono-specific cultures of Funneliformis geosporus and Acaulospora mellea applied in combination and one crude consortium of AM fungal spores isolated from rhizosphere soil of P. cashmeriana growing in natural habitat. Complete plantlets of P. cashmeriana were raised by direct and indirect organogenesis from leaf and node explants on Murashige and Skoog medium supplemented with various cytokinins and auxins. In vitro-raised plantlets responded to both the mycorrhizal treatments in a significantly different way. The inoculated plantlets fared significantly better than the un-inoculated ones in terms of the plant height, number of shoots etc. Among the two inocula tested, plantlets inoculated with the mixed consortium of AM fungi consistently performed better in terms of survival rate of plantlets (100%) and other parameters viz., plant height, number of shoots and roots per plant, number of leaves per plant, leaf area and biomass production. The study suggests the use of mixed consortium of AM fungi over mono-specific cultures for the sustainable cultivation and conservation of in vitro-raised P. cashmeriana – a medicinally important endemic plant species of Kashmir Himalaya. Therefore, this is easy to use AMF and also the present research can be extended to other such medicinally important plant species which require conservation and sustainable development.

ARBUSCULAR MYCORRHIZAL FUNGAL COMMUNITIES IN PASTURE AND TROPICAL RIPARIAN FOREST ECOSYSTEMS IN GUAJARÁ-MIRIM, RONDÔNIA, BRAZIL

Understanding the dynamics of soil organisms in natural environments can be very useful for determining the quality of forest and agricultural ecosystems. This study aimed to assess arbuscular mycorrhizal fungal (AMF) communities in pasture and regenerating riparian forest sites in Guajara-Mirim, Rondonia, Brazil. Ten soil samples were randomly collected from each ecosystem in three seasons (2018 dry and rainy seasons and 2019 dry season). AMF species richness, frequency, spore density, Shannon–Wiener diversity index, Simpson’s dominance index, and ideal sample size were determined. Species richness varied among sites and seasons, with a tendency toward higher richness in pasture soil in the 2018 dry season. The dominant AMF species in both ecosystems were Glomus macrocarpum and Acaulospora mellea . The pasture site in the 2018 dry season had higher AMF diversity than the riparian forest in the 2018 rainy season and the 2019 dry season. The complete linkage distance between the pasture site in the 2019 dry season and all other sites/seasons was 100%. More than 10 soil samples are needed to accurately determine the richness of AMF species in pasture and riparian forest sites in Guajara-Mirim, Brazil.

Contribution of Nano-Zero-Valent Iron and Arbuscular Mycorrhizal Fungi to Phytoremediation of Heavy Metal-Contaminated Soil.

Soil pollution with heavy metals has attracted increasing concern, which calls for the development of new remediation strategies. The combination of physical, chemical, and biological techniques can achieve more efficient remediation. However, few studies have focused on whether nanomaterials and beneficial microbes can be jointly used to facilitate phytoremediation. Therefore, we studied the role of nano-zero-valent iron (nZVI) and arbuscular mycorrhizal (AM) fungi in the phytoremediation of an acidic soil polluted with Cd, Pb and Zn, using sweet sorghum. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and mapping analyses were conducted to explore the mechanisms of metal immobilization by nZVI. The results showed that although both bare nZVI (B-nZVI) and starch-stabilized nZVI (S-nZVI) inhibited root mycorrhizal colonization, Acaulospora mellea ZZ successfully colonized the plant roots. AM inoculation significantly reduced the concentrations of DTPA-Cd, -Pb, and -Zn in soil, and the concentrations of Cd, Pb, and Zn in plants, indicating that AM fungi substantially facilitated heavy metal immobilization. Both B-nZVI and S-nZVI, ranging from 50 mg/kg to 1000 mg/kg, did not impede plant growth, and generally enhanced the phytoextraction of heavy metals. XRD, EDS and mapping analyses showed that S-nZVI was more susceptible to oxidation than B-nZVI, and thus had more effective immobilization effects on heavy metals. Low concentrations of nZVI (e.g., 100 mg/kg) and AM inoculation had synergistic effects on heavy metal immobilization, reducing the concentrations of Pb and Cd in roots and enhancing root Zn accumulation. In conclusion, our results showed that AM inoculation was effective in immobilizing heavy metals, whereas nZVI had a low phytotoxicity, and they could jointly contribute to the phytoremediation of heavy metal-contaminated soils with sweet sorghum.

Diversity of arbuscular mycorrhizal fungi (Glomeromycota) in adjacent areas of different land use in Nepal

Disturbances can affect the incidence of Arbuscular Mycorrhizal Fungi (AMF) in both agricultural and natural ecosystems. The present study is a first attempt for the qualitative assessment of AMF diversity in adjacent areas of a forest ecosystem with different land uses and assess levels of mycorrhizal colonization by these fungi. A total of five soil samples were taken randomly from each of the following areas situated within the same landscape: undisturbed coniferous forest (UF), degraded forest (DF) and cultivated land (CL). A total of 22 taxa of arbuscular mycorrhizal fungi belonging to eight genera were identified morphologically, Glomus and Acaulospora being the most common. Species richness ranged from 11-14 among land use areas, with 14 species in UF and 11 species in CL. Acaulospora mellea, Gigaspora sp. and two non-identified Glomus species were detected in all areas. While species richness did not differ significantly amongst areas, diversity at the family level was 43% less in CL than in UF. Mean mycorrhizal colonization was higher in DF (28%) than CL (20%). We concluded that land use mainly affected fungal diversity only at the family level and had no impact on mycorrhizal development in sampled roots. This work provides the first step to identify native AMF species in Nepal that might be cultured for further use by small farmers in a sustainable agriculture approach.

Growth enhancement of the highly prized tropical trees siamese rosewood and burma padauk

This study aims to evaluate the efficiency of the co-inoculation of arbuscular mycorrhizal fungi (AMF) and mycorrhizal helper bacteria (MHB) to promote the growth of siamese rosewood and burma padauk seedlings. The experiment was carried out in the pot experiment for 120 days. Three different species of AMF, Glomus clarum KKU−CLD−1, Clomus proliferum PC2−2 and Acaulospora mellea KKU−NBP−NB−2, were individually inoculated with and without the Stenotrophomonas maltophilia KKU−CLD−4.3−3−1. The results showed that the mycorrhizal helper bacteria strain S. maltophilia KKU−CLD−4.3−3−1 isolated from C. proliferum PC2−2 possessed high plant-growth promoting properties. The co-inoculation of our AMF species and MHB, especially in the treatment of C. proliferum PC2−2 and S. maltophilia KKU−CLD−4.3−3−1 could provide higher plant biomass, more nitrogen and phosphorus uptake and higher chlorophyll A, B contents compared to the non-inoculated control. The maximum growth of both types of seedlings was promoted by the treatment consisting of A. mellea KKU−NBP−SB−2, S. maltophilia KKU−CLD−4.3−3−1, and rock phosphate fertilizer. Co-inoculation of AMF and MHB could better promote plant growth parameters and improved phosphorus and nitrogen uptake in both types of seedlings than in the treatment with single inoculation. These suggested that our AMF and MHB were capable of being used as biofertilizer for the growth of Siamese rosewood and Burma padauk seedlings.

Roles of arbuscular mycorrhizal fungi on acclimatization of clones of Coffea arabica L. produced by somatic embryogenesis

ABSTRACT The production of Coffea arabica L. clone seedlings through the somatic embryogenesis technique is one of the alternatives of greatest demand for coffee producers. However, clones can face difficulties related to acclimatization carried out under greenhouse conditions, which can increase the production costs. A tested alternative with promising results is inoculation with arbuscular mycorrhizal fungi (AMF) during the seedling acclimatization process. Thus, this study aimed to promote the improvement of the seedling production process through somatic embryogenesis associated with inoculation with AMF. For the production of the clones, seedlings were used in the phase when they presented four pairs of leaves (Clone 1 “Fruiting red Catucaí” and Clone 2 “Acauã”), using “somatic embryogenesis” bioreactors, followed by inoculation with Rhizophagus clarus, Gigaspora margarita and Acaulospora mellea, a mixture of R. clarus and G. margarita and a mixture of R. clarus, G. margarita and A. mellea. After six months, agronomic parameters, leaf nutrient contents and root mycorrhizal colonization were evaluated. The studied clones behaved differently when inoculated with AMFs. Clone 1 showed the best development in the greenhouse, which was determined by the agronomic parameters. Thus, Clone 1 is indicated for the production of vigorous seedlings when associated with inoculation with AMFs.

Arbuscular Mycorrhiza Enhances Biomass Production and Salt Tolerance of Sweet Sorghum.

Arbuscular mycorrhizal (AM) fungi (AMF) are widely known to form a symbiosis with most higher plants and enhance plant adaptation to a series of environmental stresses. Sweet sorghum (Sorghum bicolor (L.) Moench) is considered a promising alternative feedstock for bioalcohol production because of its sugar-rich stalk and high biomass. However, little is known of AMF benefit for biomass production and salt tolerance of sweet sorghum. Here, we investigated the effects of Acaulospora mellea ZZ on growth and salt tolerance in two sweet sorghum cultivars (Liaotian5 and Yajin2) under different NaCl addition levels (0, 0.5, 1, 2, and 3 g NaCl/kg soil). Results showed AMF colonized the two cultivars well under all NaCl addition levels. NaCl addition increased mycorrhizal colonization rates in Yajin2, but the effects on Liaotian5 ranged from stimulatory at 0.5 and 1 g/kg to insignificant at 2 g/kg, and even inhibitory at 3 g/kg. High NaCl addition levels produced negative effects on both AM and non-AM plants, leading to lower biomass production, poorer mineral nutrition (N, P, K), higher Na+ uptake, and lower soluble sugar content in leaves. Compared with non-AM plants, AM plants of both cultivars had improved plant biomass and mineral uptake, as well as higher K+/Na+ ratio, but only Yajin2 plants had a low shoot/root Na ratio. AM inoculation increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and soluble sugar content in leaves. Overall, both cultivars benefited from mycorrhization, and Yajin2 with less salt tolerance showed higher mycorrhizal response. In conclusion, AMF could help to alleviate the negative effects caused by salinity, and thus showed potential in biomass production of sweet sorghum in saline soil.

Acaulosproa koreana, a New Species of Arbuscular Mycorrhizal Fungi (Glomeromycota) Associated with Roots of Woody Plants in Korea

A new species of arbuscular mycorrhizal fungi (Glomeromycota), Acaulospora koreana, was isolated from forest soils in South Korea. This novel fungus was collected from the rhizosphere of Lindera obtusiloba and Styrax obassia in forest and propagated with Sorghum bicolor in pot. Morphological characteristics of spores of A. koreana are rarely distinguished from Acaulospora mellea, which is reported as one of the most abundant mycorrhizal species in Korea. However, molecular evidence of rDNA sequence using improved primers for glomeromycotan fungal identification strongly supported that A. koreana is different from A. mellea but also any other species belonging to the genus Acaulospora. This is the first novel glomeromycatan fungus introduced in South Korea, but it suggests that there is a high possibility for discovering new arbuscular mycorrhizal fungi considering the abundance of plant species and advanced phylogenetic analysis technique.

Morphological and molecular diversity of arbuscular mycorrhizal fungi in revegetated iron-mining site has the same magnitude of adjacent pristine ecosystems

Arbuscular mycorrhizal fungi (AMF) are important during revegetation of mining sites, but few studies compared AMF community in revegetated sites with pristine adjacent ecosystems. The aim of this study was to assess AMF species richness in a revegetated iron-mining site and adjacent ecosystems and to relate AMF occurrence to soil chemical parameters. Soil samples were collected in dry and rainy seasons in a revegetated iron-mining site (RA) and compared with pristine ecosystems of forest (FL), canga (NG), and Cerrado (CE). AMF species were identified by spore morphology from field and trap cultures and by LSU rDNA sequencing using Illumina. A total of 62 AMF species were recovered, pertaining to 18 genera and nine families of Glomeromycota. The largest number of species and families were detected in RA, and Acaulospora mellea and Glomus sp1 were the most frequent species. Species belonging to Glomeraceae and Acaulosporaceae accounted for 42%–48% of total species richness. Total number of spores and mycorrhizal inoculum potential tended to be higher in the dry than in the rainy season, except in RA. Sequences of uncultured Glomerales were dominant in all sites and seasons and five species were detected exclusively by DNA-based identification. Redundancy analysis evidenced soil pH, organic matter, aluminum, and iron as main factors influencing AMF presence. In conclusion, revegetation of the iron-mining site seems to be effective in maintaining a diverse AMF community and different approaches are complementary to reveal AMF species, despite the larger number of species being identified by traditional identification of field spores.

Occurrence of arbuscular mycorrhizal fungi on King George Island, South Shetland Islands, Antarctica

Arbuscular mycorrhizal fungi make up an important ecological niche in ecosystems, and knowledge of their diversity in extreme environments is still incipient. The objective of this work was to evaluate the density and diversity of arbuscular mycorrhizal fungi in the soil of King George Island in the South Shetland Islands archipelago, Antarctica. For that, soil and roots of Deschampsia antarctica were collected at the brazilian research station in Antarctica. The spore density, species diversity and mycorrhizal colonization in the roots were evaluated. There was a low density of spores (27.4 ± 17.7) and root mycorrhizal colonization (6 ± 5.1%), which did not present statistical difference. Four species of arbuscular mycorrhizal fungi were identified, distributed in two genera: three species of the genus Glomus (Glomus sp1, Glomus sp2 and Glomus sp3) and one of the genus Acaulospora, which was identified at species level (Acaulospora mellea). Greater soil diversity was verified with pH 5.9 and phosphorus concentration of 111 mg dm-3, occurring two species of genus Glomus and A. mellea. Based on literature data, this may be the first record of this species of Acaulospora mellea in Antarctic soils, colonizing D. antarctica plants.

Efecto de micorrizas nativas y fósforo en los rendimientos del maíz en Guárico, Venezuela

En suelos de sabana del estado Guárico – Venezuela, se evaluó la eficiencia de cuatro especies de hongos formadores de micorrizas nativa y su mezcla: Scutellospora pellucida, Scutellospora calospora, Glomus leptotichum y Acaulospora mellea en la toma de N y P, y su efecto en los rendimientos del cultivo de maíz hibrido HIMECA 3005 con 4 dosis de P (0, 27, 54 y 80 kg ha-1 de P2O5). Se sembró a 0,9 m entre hileras y 0,4 m entre plantas, la cuantificación del P y N foliar se hizo muestreando la hoja opuesta a la mazorca, por los métodos de Murphy – Riley y destilación con Kjeldalh; los redimientos se evaluaron en los tres surcos centrales de cada parcela. Se utilizó un diseño de bloques al azar con arregló factorial. Encontrándose que las dosis de P y los morfotipos evaluados influyeron en la toma de N y P, siendo 54 kg ha-1 de P2O5 y la mezcla de inóculos los de mejor eficiencia para la toma de N; mientras que la dosis de 54 kg ha-1 de P2O5 más Scutellospora pellucida para la toma de P. Se concluyó que estos inóculos pueden disminuir la aplicacion de P en un 25% e incrementar los rendimientos del maíz hasta en un 100% (de 2 a 4 t ha-1 ) con base en la producción de la zona.
 Palabras clave: Micorrizas, suelos de sabana, absorción de nutrientes.

Effects of soil physical and chemical parameters, and farm management practices on arbuscular mycorrhizal fungi communities and diversities in coffee plantations in Colombia and Mexico

Arbuscular mycorrhizal fungi (AMF) are essential for growth of coffee plants in acidic and phosphate deficient soils in Central and South America. We investigated the species richness of Glomeromycotean fungi in 9–13 years old coffee plantations in Colombia and Mexico. Fungal species richness was related to physical and chemical soil factors, soil aggregate stability, and farm management practices. Using morphological spore characteristics 85 AMF species were found. AMF species similarity within the plantations was 62–73 %, and the most regularly AMF species found in both countries were: Acaulospora mellea, Acaulospora spinosa, Ambispora fennica, Diversispora aurantia, Dominikia aurea, Glomus brohultii, Rhizoglomus clarum and Rhizoglomus intraradices. In both countries species richness was differently influenced by agronomic management intensity and soil parameter. In Colombia, where soils were more fertile with higher organic matter and soil pH than in Mexico, soil parameter explained the variations in species diversity, while in Mexico, agronomic management intensities explained the variations in species richness among sites. Soil aggregate stability slightly explains the AMF species richness in Colombia and Mexico. It can be concluded that the Glomeromycotean species richness is very high in older coffee plantations in Colombia and Mexico, and that agronomic inputs have positive effects on species richness in very acidic soils with lower organic matter contents, while in more fertile soils like in Colombia, soil parameter define more the AMF richness.

Species richness and root colonization of arbuscular mycorrhizal fungi in Syngonanthus elegans, an endemic and threatened species from the Cerrado domain in Brazil

ABSTRACT Syngonanthus elegans is an endangered plant species occurring in the Brazilian Cerrado whose interaction with arbuscular mycorrhizal fungi (AMF) is poorly understood. The aim of this work was to evaluate the occurrence of AMF species and mycorrhizal colonization of S. elegans in two sampling areas named "Soberbo" stream (Soberbo) and "Parque Nacional das Sempre-Vivas" (Park), both found in Diamantina-MG, Brazil. In each area, one plot (100 x 100 m) was established, and roots and soil samples near the roots were collected from 10 plants in each plot. Further sampling included three specimens each of Loudetiopsis chrysothrix and Xyris sp.. Typical mycorrhizal colonization structures were observed in S. elegans roots, and colonization was measured at 75%. Considering both sites and all three hosts, 26 AMF species were recovered, 8 of which were identified only at the genus level. Glomus sp. 1, Scutellospora pernambucana, Acaulospora cavernata and Acaulospora mellea were classified as dominant in both areas. Other species were also considered dominant, including Glomus sp. 4 in Soberbo and Dentiscutata biornata and Gigaspora albida in Park. Trap cultures revealed the presence of seven additional species. For S. elegans, AMF species richness was slightly higher in Park than in Soberbo. Simpson diversity and evenness were slightly higher in Soberbo for S. elegans-associated AMF communities. Overall, S. elegans is highly colonized by arbuscular mycorrhizal fungi and is associated with a wide range of AMF species in the field, suggesting that this association is important for the establishment and survival of this threatened species. Some of the observed species may be new to science.