Arbuscular mycorrhizal fungi enhanced cadmium uptake in Photinia frase through altering root transcriptomes and root-associated microbial communities / 生物工程学报

As a non-essential metal, cadmium (Cd) pollution poses severe threats to plant growth, environment, and human health. Phytoextraction using nursery stocks prior to their transplantation is a potential useful approach for bioremediation of Cd contaminated soil. A greenhouse pot experiment was performed to investigate the growth, Cd accumulation, profiles of transcriptome as well as root-associated microbiomes of Photinia frase in Cd-added soil, upon inoculation of two types of arbuscular mycorrhizal fungi (AMF) Sieverdingia tortuosa and Funneliformis mosseae. Compared with the control, inoculation of F. mosseae increased Cd concentrations in root, stem and leaf by 57.2%, 44.1% and 71.1%, respectively, contributing to a total Cd content of 182 μg/plant. KEGG pathway analysis revealed that hundreds of genes involved in 'Mitogen-activated protein kinase (MAPK) signaling pathway', 'plant hormone signal transduction', 'biosynthesis of secondary metabolites' and 'glycolysis/gluconeogenesis' were enriched upon inoculation of F. mosseae. The relative abundance of Acidobacteria was increased upon inoculation of S. tortuosa, while Chloroflexi and Patescibacteria were increased upon inoculation of F. mosseae, and the abundance of Glomerales increased from 23.0% to above 70%. Correlation analysis indicated that ethylene-responsive transcription factor, alpha-aminoadipic semialdehyde synthase, isoamylase and agmatine deiminase related genes were negatively associated with the relative abundance of Glomerales operational taxonomic units (OTUs) upon inoculation of F. mosseae. In addition, plant cysteine oxidase, heat shock protein, cinnamoyl-CoA reductase and abscisic acid receptor related genes were positively associated with the relative abundance of Patescibacteria OTUs upon inoculation of F. mosseae. These finding suggested that AMF can enhance P. frase Cd uptake by modulating plant gene expression and altering the structure of the soil microbial community. This study provides a theoretical basis for better understanding the relationship between root-associated microbiomes and root transcriptomes of P. frase, from which a cost-effective and environment-friendly strategy for phytoextraction of Cd in Cd-polluted soil might be developed.

Inoculation of arbuscular mycorrhizal fungi as a strategy to improve annatto (Bixa orellana L. ) growth

This study aimed to assess the occurrence of arbuscular mycorrhizal fungi (AMF) in annatto (Bixa orellana L.) cultivars and their response to AMF inoculation using biometric parameters. The occurrence surveys were conducted in annatto fields in three municipalities from Pernambuco Forest Zone: Lagoa de Itaenga, Gloria de Goitá, and Vitoria de Santo Antão, and in four cultivars (Red Piave, Green Piave, Red Peruvian Paulista, and Green Peruvian Paulista). In a greenhouse, biometric parameters of annatto seedlings of Red Piave, Red Peruvian Paulista, Embrapa-36, and Embrapa-37 cultivars inoculated with AMF isolated from annatto fields. The Red Piave cultivar exhibited greater root colonization than the Green Peruvian Paulista in the Lagoa de Itaenga and Vitoria de Santo Antão municipalities. The cultivar Red Piave showed a more beneficial association with AMF in plants and soil than cultivar Green Peruvian Paulista did, in both Lagoa de Itaenga and Vitoria de Santo Antão. AMF inoculation was effective in promoting the growth of annatto plants, particularly those inoculants with S. heterogama and C. etunicatum.

Effect and Mechanism of Arbuscular Mycorrhizal Fungi in Herbs / 中国实验方剂学杂志

Arbuscular mycorrhizal fungi （AMF） can establish mycorrhizal symbiosis system with most terrestrial plants，and play important roles in their growth and development. However，there is no systematic analysis and summarization of their roles in the growth, biosynthesis and accumulation of active substances of herbs，as well as stress-resistance mechanism. First，the main research methods of AMF were summarized in the paper，including the separation of AMF spores，morphological identification，chemical staining and molecular identification. The main morphological structures of some AMF were detailed in the table. In terms of growth promotion，AMF promoted the growth by prolonging mycelium，enhancing phosphatase secretion，organic acid，activation of soil and increasing absorption efficiency. In the aspect of biosynthesis and accumulation of flavonoids，terpenoids and other active substances in herbs，AMF improved the contents by regulating activities of signal substances and key enzymes involved in the metabolism of secondary products. In addition，AMF could alleviate a series of stresses caused by drought，heavy metal，high salt，high or low temperature by improving the activity of antioxidant enzymes，enhancing the ability of plants to scavenge free radicals，complexing toxic heavy metals，diluting high salt concentration，or inducing the expressions of key genes. Finally，the application prospects and in-depth study of AMF in the ecological planting of herbs were discussed, in order to provide reference for promoting relevant research.

Preliminary investigation on arbuscular mycorrhiza fungi of cultivated Panax quinquefolium roots / 中国中药杂志

In this study, the infection of root arbuscular mycorrhizal fungi(arbuscular mycorrhizal fungi, AMF of Panax quinquefolium in Shandong province was investigated, and the distribution characteristics and infection regularity of AMF were found out. The AMF of P. quinquefolium roots in different habitats was examined by alkali dissociation-trypickin blue staining method to study the infection rate and infection intensity. The contents of ginsenoside(Rb_1, Re, Rg_1, Rb_2, Rd and Rh_1) in the roots of P. quinquefolium was determined by HPLC. The experimental data were SPSS 17.0 statistical software for One-way analysis of variance, cluster analysis and correlation analysis. The results showed that the AMF infection in roots of P. quinquefolium, and there were obvious structures such as hyphae, arbuscular branches and vesicles, and the AMF infection rate and infection intensity showed obvious spatial and temporal heterogeneity with the growth age and origin of P. quinquefolium. The infection rate of AMF in roots of P. quinquefolium from 1 to 3 years increased significantly with the increase of growth years(P<0.05). The infection intensity and infection rate of P. quinquefolium showed a similar change trend, the AMF infection rate and infection intensity reached the highest level in the third year. Cluster analysis showed that the infection rates of roots of P. quinquefolium in similar geographical locations could be clustered together. Correlation analysis showed that the AMF infection rate of P. quinquefolium root was significantly positively correlated with the infection intensity, and the AMF infection rate and infection intensity were significantly positively correlated with the contents of ginsenoside Rg_1, Re and Rb_1. This study explored the distribution characteristics and regularity of AMF in roots of P. quinquefolium under the protected cultivation conditions, and provided basic data for ecological cultivation of P. quinquefolium and research and development of biological bacterial fertilizer.

Arbuscular mycorrhizae fungi a potential eco-friendly tool for sustainable agriculture under changing climatic conditions/ in biotic and abiotic stress conditions

Los hongos micorrízicos arbusculares (HMA) son biotrofos obligados que viven en asociación simbiótica con las raíces de las plantas. Se encuentran entre los microorganismos del suelo más extendidos que proporcionan a la planta huésped nutrientes y protección contra patógenos. Las prácticas agrícolas modernas, como la labranza frecuente, el alto empleo de fertilización inorgánica pesticidas junto con condiciones climáticas cambiantes debido al calentamiento global, tienen enormes impactos en la colonización de los HMA, la interacción con las plantas y la productividad de los cultivos. Los HMA afectan positivamente la tolerancia de las plantas al estrés biótico y abiótico, a los ecosistemas severos y sus patógenos al alterar la estructura de las raíces, la exudación, la microflora de la rizosfera, la producción de antifúngicos y antibacterianos, y al competir con los patógenos por la absorción de nutrientes. Por lo tanto, juegan un papel importante en el crecimiento, la productividad y la calidad de las plantas. Además, el efecto de un fungicida varía según su modo de acción y las especies de HMA asociadas, lo que sugiere que estos hongos tienen un gran potencial como herramienta para la agricultura sostenible ecológica en el actual escenario de calentamiento global.

Arbuscular Mycorrhizal Fungi (AMF) are obligate biotrophs living in symbiotic association with roots of plants. They are among the most widespread soil microorganisms that provide the host plant with nutrients and pathogen protection. Modern farming practices like frequent tillage, high input inorganic fertilization and pesticide along changing climatic conditions due to global warming, have huge impacts on AMF colonization, interaction with plants and on crop productivity. AMF positively affect the plant tolerance to biotic and abiotic stresses, harsh ecosystems and plant pathogens by altering root structure, exudation, rhizosphere microflora, production of antifungals, antibacterials, and competing with pathogens for nutrient uptake. Thus, it plays a significant role in plant growth, productivity and quality. Further, the effect of a fungicide is varied depending on its mode of action and the associated AMF species, suggesting that these fungi have a strong potential as a tool for eco-friendly sustainable farming in the present scenario of global warming.

The Effect of an Arbuscular Mycorrhizal Inoculum on the Growth and Fruiting of Fragaria ananassa (Weston) Duchesne Ex Rozier (Rosaceae) in Morocco

The effect of composite endomycorrhizal inoculums was studied on the strawberry plant growth under greenhouse conditions. After six months, a significative effect was observed. Leaves number, fruits number, fresh roots weight and fresh fruits weight under greenhouse conditions compared to controls were 28.9/11.2, 58/1, 12.59g/9.62g and 367g/230g. Mycorrhizal intensity, arbuscular content and spores number in mycorrhized and non mycorrhized strawberry seedlings were respectively 54.1, 28.3 and 220. The spores detected belong to eight species and four genera: Glomus, Rhizophagus, Gigaspora and Scutellospora.

Dinámica de la diversidad temporal de los hongos micorrícicos arbusculares de Larrea tridentata (Sesse & Mocino ex DC) Coville en un ecosistema semiárido / Temporal diversity dynamics of the arbuscular mycorrhizal fungi of Larrea tridentata (Sesse & Mocino ex DC) Coville in a semi-arid ecosystem

Los hongos micorrícicos arbusculares (HMA) de los ambientes áridos y semiáridos son importantes para el desarrollo de las plantas que crecen bajo estrés biótico y abiótico en áreas naturales o en agroecosistemas. Existe poca información sobre la diversidad temporal de los HMA en plantas perennes de ecosistemas áridos en el norte de México. En este estudiose evaluaron la colonización micorrícica y la diversidad temporal de los HMA en la rizosfera de Larrea tridentata, planta perenne de amplia distribución en el Desierto Chihuahuense. Se obtuvieron muestras de la rizosfera y de raíces de 15 plantas, en 3 fechas de muestreo del año 2015. Se encontró un total de 17 especies de HMA, distribuidas en 12 géneros y 7 familias dentro del phylum Glomeromycota. La especie más abundante fue Funneliformis geosporum. Esta especie pertenece a la familia Glomeraceae, la única que estuvo representada con varios géneros en L. tridentata. El mayor porcentaje de micorrización se presentó en febrero, con un 83,22%, en septiembre fue del 75,27% y en mayo del 65,27%. El muestreo realizado en febrero presentó el mayor número de especies (16), seguido por el de mayo (15) y el de septiembre (12). El análisis estadístico mostró diferencias significativas en el número de esporas entre los muestreos de febrero y los de mayo y septiembre.

Arbuscular mycorrhizal fungi (AMF) of arid and semiarid ecosystems are important for the development of plants that grow under biotic stress in wild or in agro-ecosystems. There is little information on the temporal diversity of these organisms in perennial plants from arid ecosystems in northern Mexico. On this study, the mycorrhizal colonization and the temporal diversity of AMF in the rhizosphere of Larrea tridentata, perennial plant abundant in the Chihuahuan Desert region were explored. Samples of the rhizosphere and roots of fifteen plants in each of the three sampling dates during the 2015 year were obtained. A total of 17 species of HMA belonging to 12 genera and 7 families within the phylum Glomeromycota in all three sampling dates were found. Funneliformis geosporum was the dominant species belonging to the family Glomeraceae which possess the highest genera number on L. tridentata.The highest mycorrhization percentage was in February with 83.22, followed by September and May with 75.27 and 65.27%, respectively. A maximum of 16 AM fungal species were isolated and identified from L. tridentata rhizosphere in February, 15 species in May and 12 species in September. Statistical analysis showed significant differences between sampling dates in the spores number.

Study of Arbuscular Mycorrhizal Fungi Diversity and Its Effect on Growth and Development of Leek Plants (Allium porrum L.)

The effect of a composite endomycorrhizal inoculum, native to the rhizosphere of the olive tree, was studied on the growth of leek plants (Allium porrum L.). Inoculation of leek plants was carried out by contacting the root system of leeks with the inoculum endomycorrhizal derived from the olive tree rhizosphere. After five months of inoculation, a significant effect is observed on the growth of the inoculated plants according to witnesses. Indeed, the average values of the aerial weight (11.62 g) and root weight (18.52 g), the diameter (0.5 cm) and the number of leaves (7) of the inoculated plants are higher than those noted in the control plants, respectively 4.42 g, 7.95 g, 0.3 cm, 5.57. Moreover, the frequency and intensity of mycorrhization, respectively 96.66% and 50.33%, the arbuscules contents (44.33%) and vesicles (32.44%) are very important. The roots of control plants are not mycorrhizal. The average number of spores formed in the rhizosphere of the inoculated plants is 160 spores per 100 g of soil. These spores are those of 85 endomycorrhizal species belonging to 16 different genera: Glomus (34 species), Acaulospora (18 species), Gigaspora (5 species), Entrophospora (3 species), Scutellospora (5 species), Pacispora (2 species), Claroideoglomus (2 species), Dentiscutata (1 species), Septoglomus (1 species), Paraglomus (2 species), Rhizoglomus (2 species), Ambispora (3 species), Cetraspora (1 species), Funneliformis (1 species), Diversispora (4 species) and Viscospora (1 species). Statistical analyzes were performed by analysis of variance by the ANOVA test at the 5% level using the STATISTICA software. Leek, is a mycotrophic plant that can be used to multiply an endomycorrhizal inoculum suitable for use in nurseries, and to produce seedlings of different plant species that are vigorous and resistant to pathogens and water stress after transplantation.

Effect of Arbuscular mycorrhizal fungi (AMF) and Azospirillum on growth and nutrition of banana plantlets during acclimatization phase.

The effect of the co-inoculation of arbuscular mycorrhizal fungi (AMF) and Azospirillum on micro-propagated banana seedlings development during their adaptation phase was determined. At the time of transplanting, banana seedlings were inoculated with an indigenous mycorrhizal inoculum containing 10 spores/g at four doses: 0, 50, 100 and 200 g. Seventy days after fungal inoculation, 20 ml of Azospirillum in four concentrations (0, 106, 107 and 108 CFU/ml) were applied. Finally, after 98 days from the start of the experiment a second dose (40 ml) of Azospirillum in the concentrations mentioned above was inoculated. Plants were harvested 5 months after transplanting and the growth and nutritional parameters were evaluated. The analysis of the data showed that banana plants co-inoculated with 200 g of AMF and 1.5E8 CFU/ml of Azospirillum presented greater development, an increase of 7 times in height, 4 times in perimeter, 16 times in leaf area, 12 times in aerial biomass, and 8 times in root biomass relative to control plants. The results achieved were due to synergism between fungus-bacteria when inoculated at higher doses, with lower doses stimulating growth is minimal. The co-inoculation in high doses demonstrates adequate support and cooperative effect between HMA and Azospirillum crops. In addition, co-inoculation promotes optimal nutritional status because microorganisms allowed plants achieve greater absorption of phosphorus and nitrogen relative to those treated with single inoculation and the control.

Arbuscular mycorrhizal fungi in Mimosa tenuiflora (Willd. ) Poir from Brazilian semi-arid

Abstract Many plant species from Brazilian semi-arid present arbuscular mycorrhizal fungi (AMF) in their rhizosphere. These microorganisms play a key role in the establishment, growth, survival of plants and protection against drought, pathogenic fungi and nematodes. This study presents a quantitative analysis of the AMF species associated with Mimosa tenuiflora, an important native plant of the Caatinga flora. AMF diversity, spore abundance and root colonization were estimated in seven sampling locations in the Ceará and Paraíba States, during September of 2012. There were significant differences in soil properties, spore abundance, percentage of root colonization, and AMF diversity among sites. Altogether, 18 AMF species were identified, and spores of the genera Acaulospora, Claroideoglomus, Dentiscutata, Entrophospora, Funneliformis, Gigaspora, Glomus, Racocetra, Rhizoglomus and Scutellospora were observed. AMF species diversity and their spore abundance found in M. tenuiflora rhizosphere shown that this native plant species is an important host plant to AMF communities from Brazilian semi-arid region. We concluded that: (a) during the dry period and in semi-arid conditions, there is a high spore production in M. tenuiflora root zone; and (b) soil properties, as soil pH and available phosphorous, affect AMF species diversity, thus constituting key factors for the similarity/dissimilarity of AMF communities in the M. tenuiflora root zone among sites.

Optimization of the production of mycorrhizal inoculum on substrate with organic fertilizer

The system for production of inoculum of arbuscular mycorrhizal fungi (AMF) using sand and vermiculite irrigated with nutrient solution is promising. However, organic amendments added to the substrate can stimulate sporulation of AMF and replace the nutrient solution. The aim of this study was to maximize the production of AMF (Acaulospora longula, Claroideoglomus etunicatum, Dentiscutata heterogama and Gigaspora albida) using selected organic substrates (vermicompost, coir dust and Tropstrato) together with sand and vermiculite. The production of spores varied among the tested AMF and according to the organic source added to the substrate. The vermicompost promoted higher sporulation of A. longula in relation to the other AMF and substrates. The Tropstrato® inhibited the sporulation of D. heterogama while the reproduction of C. etunicatum was not affected by the organic compounds. The inoculum of A. longula also showed a high number of infective propagules and promoted biomass accumulation in maize plants. The system of inoculum production using sand and vermiculite + 10% vermicompost favors the production of infective inoculum of A. longula with the fungus benefiting growth of corn plants.

Root Age-Dependent Changes in Arbuscular Mycorrhizal Fungal Communities Colonizing Roots of Panax ginseng

In this study, we examined arbuscular mycorrhizal fungal (AMF) community structure colonizing field-cultivated ginseng roots according of different ages, such as 1- to 5-year-old plant, collected from Geumsan-gun, Korea. A total of seven AMF species namely, Funnelliformis caledonium, F. moseae, Gigaspora margarita, Paraglomus laccatum, P. occultum, Rhizophagus irregularis, and Scutellospora heterogama were identified from the roots using cloning, PCR-restriction fragment length polymorphism and sequence analysis of the large subunit region in rDNA. AMF species diversity in the ginseng roots decreased with the increase in root age because of the decreased species evenness. In addition, the community structures of AMF in the roots became more uniform. These results suggest that the age of ginseng affects mycorrhizal colonization and its community structure.

Diversity of arbuscular mycorrhizal fungi in irrigated and non-irrigated fields of southern Karnataka, India.

The two different agro-ecosystems were selected to study the spore density, species abundance, and diversity of arbuscular mycorrhizal fungi (AMF) in irrigated (Mandya district) and non-irrigated (Hassan district) agricultural fields in southern Karnataka region, India. A total of 22 AMF species were recorded during the study. Out of which 13 sp. were of Glomus, 4 sp. of Acaulospora, 1 sp. of Cetraspora, 1 sp. of Dentiscutata and 3 sp. of Gigaspora. The difference in species richness of AMF species in irrigated fields ranged from 5-12 sp. as compared to non-irrigated fields (5-11 sp.) and the difference may be attributed to the nutritional status of the soil. We also assumed that lower AMF colonization and abundance would be affected by water stress. Highest spore number and percent colonization of AM fungi were recorded in irrigated sites, showing 356-748 spore density and 70-92 % colonization. Whereas, in non-irrigated sites, 174-341 spore density and 40-72 % colonization was recorded. Different agro-climatic conditions like irrigation, soil pH, soil organic carbon, phosphorous correlated with the abundance and colonization of AM fungi.

Evaluación de un sistema para la micorrización in vitro en plantas demora de castilla (Rubus glaucus, Benth) / Evaluation of an in vitro mycorrhization system of blackberry plants (Rubus glaucus, Benth) / Avaliação de um sistema para micorrização in vitro em plantas de amora-preta (Rubus glaucus, Benth)

Objetivo. Obtener un sistema de micorrización in vitro en sistemas de cultivo autotrófico para plantas de mora de castilla (Rubusglaucus, Benth). Materiales y métodos. Se utilizaron esporas y fragmentos de raíces con vesículas del Hongo Formador de MicorrizaArbuscular (HFMA) Glomus sp. (GEV02). Se estableció un sistema de cultivo autotrófico para plántulas de mora, comparando dosmétodos de inoculación directa con el HFMA. Se cuantificó el número de esporas producidas, la longitud del micelio extraradical; asícomo el porcentaje de colonización del HFMA. Adicionalmente se midió la longitud aérea y radical, el peso fresco y seco de la partefoliar y radical para determinar el desarrollo de las plantas. Resultados. El sistema de cultivo autotrófico fue exitoso para plantas demora de castilla (Rubus glaucus, Benth); observándose un óptimo crecimiento de la parte aérea y radical de la planta. Adicionalmenteen este estudio se pudo obtener un sistema que permitió el desarrollo de Glomus sp (GEV02) bajo condiciones in vitro, con formaciónde estructuras típicas de la simbiosis como una buena colonización intraradical, con producción de arbúsculos y vesículas, así comoel desarrollo de micelio extraradical con hifas ramificadas y la formación de nuevas esporas. Conclusión. Las plantas de moramicropropagadas se asociaron con éxito, por primera vez, con un hongo formador de micorriza arbuscular bajo condiciones in vitro,permitiendo el desarrollo del sistema simbiótico HFMA Glomus sp., asociado a las raíces de plántulas de mora castilla micropropagadas...

Objective. Obtain an in vitromycorrhization system in autotrophic culture systems of blackberry plants (Rubus glaucus, Benth). Materials and methods. We usedspores and root fragments with vesicles of Arbuscular Mycorrhizal Fungus (AMF) Glomus sp (GEV02). We established an autotrophicculture system of blackberry plantlets comparing two methods of direct inoculation of the AMF. We measured the number of sporesproduced, the length of the extraradical mycelium as well as the percentage of colonization of the AMF. Additionally, we measuredthe shoot and root length, and the fresh and dry weight of the leaf and root parts to determine the plant development. Results. Theautotrophic culture system was successful for blackberry plants (Rubus glaucus, Benth; an optimal shoot and root growth was observed.Additionally, we obtained a system that allowed the development of Glomus sp. in in vitro conditions, with the formation of structurestypical of the symbiosis as well as a good intraradical colonization, with the production of arbuscules and vesicles, development ofextraradical mycelium with branched hyphae, and formation of new spores. Conclusion. For the first time, micropropagated blackberryplants associated successfully with an AMF under in vitro conditions, enabling the development of the symbiotic system AMF Glomussp. associated to roots of micropropagated blackberry plantlets...

Objetivo. Obter umsistema de micorrização in vitro em sistemas de cultura autotróficos para plantas de amora-preta (Rubus glaucus, Benth). Materiais emétodos. Foram usados esporos e fragmentos de raízes com vesículas do Fungo Formador Micorrízico Arbuscular (FFMA) Glomus sp.(GEV02). Foi estabelecido um sistema de cultivo autotrófico para mudas de amora-preta, comparando dois métodos de inoculação diretacom o FFMA. Foi quantificado o número de esporos produzidos, o comprimento do micélio extra radicular; bem como a porcentagemde colonização do FFMA. Além disso, foi medido o comprimento e o peso fresco e seco da parte folhar e radicular para determinar odesenvolvimento das plantas. Resultados. O sistema de cultivo autotrófico foi bem-sucedido para as plantas de amora-preta (Rubusglaucus, Benth), onde foi observado um crescimento ótimo da parte aérea e da raidicular da planta. Além disso, neste estudo foi obtido umsistema que permitiu o desenvolvimento de Glomus sp (GEV02) sob condições in vitro, com formação de estruturas típicas da simbiosecomo uma boa colonização intra radicular, com produção de arbúsculos e vesículas, assim como o desenvolvimento de micélio extraradicular com hifas ramificada e a formação de novos esporos. Conclusão. As plantas de amora-preta micropropagadas associaram-secom sucesso, pela primeira vez, com um fungo formador micorrízico arbuscular em condições in vitro, permitindo o desenvolvimentodo sistema simbiótico FFMA Glomus sp., associado às raízes das plântulas de amora-preta micropropagadas...

Mecanismos de defensa y respuestas de las plantas en la interacción micorrícica: una revisión / Plant defense mechanisms and responses in the arbuscular mycorrhizal symbiosis: a review

El establecimiento de la simbiosis planta-hongos formadores de micorrizas Arbusculares (HFMA) requiere procesos armónicos a nivel espacio-temporal, que dependen de señales para el reconocimiento, colonización e intercambio bidireccional de nutrientes. Las plantas presentan respuestas de defensa frente a posibles organismos invasores; sin embargo, frente a HFMA estas son débiles, localizadas y no impiden la colonización del hongo. Los beneficios de la simbiosis generalmente se asocian a nutrición vegetal, aunque, también está relacionada con el incremento de la tolerancia-resistencia de plantas a los estreses bióticos. La resistencia inducida HFMA (MIR) es importante en el control de patógenos foliares, comedores de hojas y necrótrofos, encontrándose protección de plantas micorrizadas tanto a nivel local como sistémico, relacionada con los niveles de ácido jasmónico en tejidos. Un mecanismo en la MIR está asociado con el “priming”, que permite una rápida y eficiente respuesta de defensa de plantas micorrizadas. Se han planteado posibles mecanismos de atenuación de las respuestas de defensa, considerando: activación de supresores de defensa; plantas que producen respuestas de defensa frente a HFMA y otras que no las producen, y plantas que suprimen las respuestas de defensa en la simbiosis. Aunque el control de la simbiosisestá regulado básicamente por la planta, aún se desconoce el papel de los HFMA en el debilitamiento de las respuestas de defensa. Recientemente, se ha dado un avance importante en entender los mecanismos mediante los cuales se establece y mantiene la biotrofía del hongo, al describirse la proteína SP7 que interactúa con el factor de transcripción PR, ERF19 en el núcleo de la célula vegetal. Se ha sugerido que SP7 es un efector que actúa oponiéndose al programa de inmunidad de la planta.

Harmonic processes between plant and arbuscular mycorrhyzal fungi (AMF) are required for the symbiosis formation between the two organisms. These processes depend on specific signalling for the plant-fungus recognition, colonisation and bidirectional nutrient exchange. Plants show defence responses against invasive organisms, however they react weakly and localised when challenged by AMF. The benefits derived from the mycorrization are described for the nutritional aspect; however, it is known that mycorrhized plants are more tolerant to biotic stresses. Mycorrhizal induced resistance (MIR) is especially important for the control of foliar pathogens, leaf cutters and necrotrophs. There has also been found that mycorrhizal plants are protected both locally and systemically and their protection is related with jasmonic acid levels at their tissues. One of the most important mechanisms for MIR is the so called “priming” that allows plants to exert a fast and efficient defence response. Possible mechanisms to unravel mycorrhizal plants lower defence systems include: defence suppressor activation, differential plants response towards AMF from inexistent to low, and plant defence response suppression during the AMF symbiosis. The symbiosis control is known to be regulated by the plant, however, no role has been assigned to the AMF for the weakening of the plant defence system. Recently, a big step towards understanding of the fungal role has been made. A protein SP7 that interacts with a PR transcription factor ERF19, in the plant nucleus, has been described. This discovery indicates a possible mechanism to establish and maintain the biotrophic status of the AMF counteracting the immune plant system.

Diversity of Arbuscular Mycorrhizal Fungi in Oak-Pine Forests and Agricultural Land Prevalent in the Kumaon Himalayan Hills, Uttarakhand, India.

The diversity and abundance of arbuscular mycorrhizal fungi (AMF) was assessed in the Kumaon Himalayan foothills. Four typical ecosystems were selected in the Sat-Tal area located in the Nainital, district in Uttarakhand, India, representing vegetation change due to human settlement and selective logging of native oak. Besides a natural oak forest, a mixed pine-oak forest, a pure pine stand and an arable field were sampled. The latter was cropped with black gram (Vigna mungo L. Hepper) and maize (Zea mays L.) during the rainy season from June to September and rotated with wheat (Triticum aestivum L.) during winter for the last 10 years. Only cow dung compost used for fertilization. The highest AMF spore abundance throughout the year was recorded in soil samples from the pine-oak mixed forest, followed by the pine and oak forests and the agricultural field. At all sites, the lowest spore abundance was recorded at the end of the winter season in March, and the highest in October after the rainy season. Whereas in October, Glomus claroideum, Acaulospora scrobiculata and A. spinosa were found at all sites, in March it was only G. intraradices which occurred everywhere. The highest AMF spore morphotype richness was recorded in samples from the oak forest. In AMF-trap cultures set up with field soil inocula, the dominant species recovered were G. intraradices, G. etunicatum and A. scrobiculata. As compared to the field samples, trap culturing of one year enhanced spore abundance but entailed a loss of AMF richness. The study revealed differences in AMF community composition and structure among sites characterized by different land use systems.

Microbial activity, arbuscular mycorrhizal fungi and inoculation of woody plants in lead contaminated soil

The goals of this study were to evaluate the microbial activity, arbuscular mycorrhizal fungi and inoculation of woody plants (Caesalpinia ferrea, Mimosa tenuiflora and Erythrina velutina) in lead contaminated soil from the semi-arid region of northeastern of Brazil (Belo Jardim, Pernambuco). Dilutions were prepared by adding lead contaminated soil (270 mg Kg-1) to uncontaminated soil (37 mg Pb Kg soil-1) in the proportions of 7.5 percent, 15 percent, and 30 percent (v:v). The increase of lead contamination in the soil negatively influenced the amount of carbon in the microbial biomass of the samples from both the dry and rainy seasons and the metabolic quotient only differed between the collection seasons in the 30 percent contaminated soil. The average value of the acid phosphatase activity in the dry season was 2.3 times higher than observed during the rainy season. There was no significant difference in the number of glomerospores observed between soils and periods studied. The most probable number of infective propagules was reduced for both seasons due to the excess lead in soil. The mycorrhizal colonization rate was reduced for the three plant species assayed. The inoculation with arbuscular mycorrhizal fungi benefited the growth of Erythrina velutina in lead contaminated soil.

Inoculation of tomato seedlings with Trichoderma Harzianum and Arbuscular Mycorrhizal Fungi and their effect on growth and control of wilt in tomato seedlings

A green house study was conducted to investigate the ability of an isolate of Trichoderma harzianum (P52) and arbuscular mycorrhizal fungi (AMF) in enhancing growth and control of a wilt pathogen caused by Fusarium oxysporum f. sp. lycopersici in tomato seedlings. The plants were grown in plastic pots filled with sterilized soils. There were four treatments applied as follows; P52, AMF, AMF + P52 and a control. A completely randomized design was used and growth measurements and disease assessment taken after 3, 6 and 9 weeks. Treatments that significantly (P < 0.05) enhanced heights and root dry weights were P52, AMF and a treatment with a combination of both P52 and AMF when compared the control. The treatment with both P52 and AMF significantly (P < 0.05) enhanced all growth parameters (heights; shoot and root dry weight) investigated compared to the control. Disease severity was generally lower in tomato plants grown with isolate P52 and AMF fungi either individually or when combined together, though the effect was not statistically significant (P0.05). A treatment combination of P52 + AMF had less trend of severity as compared to each individual fungus. T. harzianum and AMF can be used to enhance growth in tomato seedlings.

Interactions between an arbuscular mycorrhizal fungus (Scutellospora heterogama) and the root-knot nematode (Meloidogyne incognita) on sweet passion fruit (Passiflora alata)

The effects of inoculation of sweet passion fruit plants with the arbuscular mycorrhizal (AM) fungus Scutellospora heterogama on the symptoms produced by Meloidogyne incognita race 1 and its reproduction were evaluated in two greenhouse experiments. In the 1st, the M. incognita (5000 eggs/plant) and S. heterogama (200 spores/plant) inoculations were simultaneous; in the 2nd, the nematodes were inoculated 120 days after the fungal inoculation. In both the experiments, 220 days after AM fungal inoculation, plant growth was stimulated by the fungus. In disinfested soil, control seedlings (without S. heterogama) were intolerant to parasitism of M. incognita, while the growth of mycorrhized seedlings was not affected. Sporulation of S. heterogama was negatively affected by the nematodes that did not impair the colonization. M. incognita did not affect mycorrhizal seedling growth. The establishment of mycorrhiza prior to the nematode infection contributed for the reduction of symptoms severity and reproduction of M. incognita in disinfested soil.

O efeito da inoculação com Scutellospora heterogama (200 esporos/planta) em relação aos sintomas e reprodução de Meloidogyne incognita raça 1 (5000 ovos/planta) foi avaliado em plantas de maracujazeiro doce em dois experimentos em casa de vegetação. No primeiro experimento, inoculações com nematóide e FMA foram simultâneas; no segundo, nematóides foram inoculados 120 dias após o estabelecimento da simbiose micorrízica. Após o 220º dia da inoculação do FMA o fungo estimulou o crescimento da planta nos dois experimentos. No solo desinfestado as mudas não inoculadas com S. heterogama mostraram intolerância ao parasitismo de M. incognita. A esporulação de S. heterogama foi negativamente afetada pela presença do nematóide. M. incognita não afetou o crescimento das mudas micorrizadas ou o desenvolvimento do FMA. O estabelecimento da micorriza antes do nematóide contribui para a redução da severidade dos sintomas e reprodução de M. incognita em solo desinfestado.

ANATOMICAL ASSESSMENT OF ACCESSORY MENTAL FORAMEN USING 3D CONE BEAM COMPUTED TOMOGRAPHY IN KOREAN