Publications by authors named "Luciano Avio"

18 Publications

  • Page 1 of 1

Possible role of arbuscular mycorrhizal fungi and associated bacteria in the recruitment of endophytic bacterial communities by plant roots.

Mycorrhiza 2021 Jul 20. Epub 2021 Jul 20.

Department of Agriculture, Food and Environment, University of Pisa, 56124, Pisa, Italy.

Arbuscular mycorrhizal fungi (AMF) represent an important group of root symbionts, given the key role they play in the enhancement of plant nutrition, health, and product quality. The services provided by AMF often are facilitated by large and diverse beneficial bacterial communities, closely associated with spores, sporocarps, and extraradical mycelium, showing different functional activities, such as N fixation, nutrient mobilization, and plant hormone, antibiotic, and siderophore production and also mycorrhizal establishment promotion, leading to the enhancement of host plant performance. The potential functional complementarity of AMF and associated microbiota poses a key question as to whether members of AMF-associated bacterial communities can colonize the root system after establishment of mycorrhizas, thereby becoming endophytic. Root endophytic bacterial communities are currently studied for the benefits provided to host plants in the form of growth promotion, stress reduction, inhibition of plant pathogens, and plant hormone release. Their quantitative and qualitative composition is influenced by many factors, such as geographical location, soil type, host genotype, and cultivation practices. Recent data suggest that an additional factor affecting bacterial endophyte recruitment could be AMF and their associated bacteria, even though the mechanisms allowing members of AMF-associated bacterial communities to actually establish in the root system, becoming endophytic, remain to be determined. Given the diverse plant growth-promoting properties shown by AMF-associated bacteria, further studies are needed to understand whether AMF may represent suitable tools to introduce beneficial root endophytes in sustainable and organic agriculture where the functioning of such multipartite association may be crucial for crop production.
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http://dx.doi.org/10.1007/s00572-021-01040-7DOI Listing
July 2021

Genetic variability assessment of 127 Triticum turgidum L. accessions for mycorrhizal susceptibility-related traits detection.

Sci Rep 2021 Jun 28;11(1):13426. Epub 2021 Jun 28.

Department of Agriculture, Food and Environment (DAFE), University of Pisa, Via del Borghetto 80, 56124, Pisa, Italy.

Positive effects of arbuscular mycorrhizal fungi (AMF)-wheat plant symbiosis have been well discussed by research, while the actual role of the single wheat genotype in establishing this type of association is still poorly investigated. In this work, the genetic diversity of Triticum turgidum wheats was exploited to detect roots susceptibility to AMF and to identify genetic markers in linkage with chromosome regions involved in this symbiosis. A tetraploid wheat collection of 127 accessions was genotyped using 35K single-nucleotide polymorphism (SNP) array and inoculated with the AMF species Funneliformis mosseae (F. mosseae) and Rhizoglomus irregulare (R. irregulare), and a genome-wide association study (GWAS) was conducted. Six clusters of genetically related accessions were identified, showing a different mycorrhizal colonization among them. GWAS revealed four significant quantitative trait nucleotides (QTNs) involved in mycorrhizal symbiosis, located on chromosomes 1A, 2A, 2B and 6A. The results of this work enrich future breeding activities aimed at developing new grains on the basis of genetic diversity on low or high susceptibility to mycorrhization, and, possibly, maximizing the symbiotic effects.
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http://dx.doi.org/10.1038/s41598-021-92837-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8239029PMC
June 2021

The arbuscular mycorrhizal fungus Funneliformis mosseae induces changes and increases the concentration of volatile organic compounds in Vitis vinifera cv. Sangiovese leaf tissue.

Plant Physiol Biochem 2020 Oct 28;155:437-443. Epub 2020 Jul 28.

Chemistry Department, Universidad Técnica Federico Santa María, Avenida España, 1680, Valparaíso, Chile; Center of Biotechnology "Dr. Daniel Alkalay Lowitt", Universidad Técnica Federico Santa María, General Bari 699, Valparaíso, Chile. Electronic address:

Arbuscular mycorrhizal fungi (AMF) are beneficial obligate symbionts of plant roots. Volatile organic compounds (VOCs) participate in plant communication and defence. The aim of this study was to analyse the effects of the arbuscular mycorrhizal fungus Funneliformis mosseae IMA1 on VOCs in Vitis vinifera cv. Sangiovese leaf tissue. Grapevine plants inoculated with F. mosseae IMA1 were incubated for 23 weeks. VOCs were extracted from leaves and identified using headspace solid-phase microextraction (HS-SPME) coupled to GC-MS. VOCs in leaf tissue were strongly enhanced (85%) by F. mosseae IMA1. The mycorrhizal fungus IMA1 modified the levels of specific VOCs synthesised in different anabolic pathways. An increase in volatiles that have been related to plant defences under pathogen/herbivore attack or linked to water stress, such as (E)-2-hexenal, 3-hexenal, geraniol, benzaldehyde and methyl salicylate, was observed in mycorrhizal plants. In contrast, some C-norisoprenoids decreased strongly in mycorrhizal plants. The study of the effects of AMF on VOCs in grapevine plants may provide useful information to establish sustainable viticultural practices.
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http://dx.doi.org/10.1016/j.plaphy.2020.06.048DOI Listing
October 2020

Gene expression in Rhizoglomus irregulare at two different time points of mycorrhiza establishment in Helianthus annuus roots, as revealed by RNA-seq analysis.

Mycorrhiza 2020 May 29;30(2-3):373-387. Epub 2020 Mar 29.

Department of Agriculture, Food, and Environment, University of Pisa, Pisa, Italy.

Arbuscular mycorrhizal fungi (AMF) play a fundamental role in plant growth and nutrition in natural and agricultural ecosystems. Despite the importance of such symbionts, the different developmental changes occurring during the AMF life cycle have not been fully elucidated at the molecular level. Here, the RNA-seq approach was used to investigate Rhizoglomus irregulare specific and common transcripts at two different time points of mycorrhizal establishment in Helianthus annuus in vivo. Four days after inoculation, transcripts related to cellular remodeling (actin and tubulin), cellular signaling (calmodulin, serine/threonine protein kinase, 14-3-3 protein, and calcium transporting ATPase), lipid metabolism (fatty acid desaturation, steroid hormone, and glycerophospholipid biosynthesis), and biosynthetic processes were detected. In addition to such transcripts, 16 days after inoculation, expressed genes linked to binding and catalytic activities; ion (K, Ca, Fe, Zn, Mn, Pi, ammonia), sugar, and lipid transport; and those involved in vacuolar polyphosphate accumulation were found. Knowledge of transcriptomic changes required for symbiosis establishment and performance is of great importance to understand the functional role of AMF symbionts in food crop nutrition and health, and in plant diversity in natural ecosystems.
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http://dx.doi.org/10.1007/s00572-020-00950-2DOI Listing
May 2020

Mycorrhizal networks facilitate the colonization of legume roots by a symbiotic nitrogen-fixing bacterium.

Mycorrhiza 2020 May 25;30(2-3):389-396. Epub 2020 Mar 25.

Embrapa Agrobiologia, Rodovia BR 465, km 7, Seropédica, RJ, 23891-000, Brazil.

Arbuscular mycorrhizal fungi (AMF) absorb and translocate nutrients from soil to their host plants by means of a wide network of extraradical mycelium (ERM). Here, we assessed whether nitrogen-fixing rhizobia can be transferred to the host legume Glycine max by ERM produced by Glomus formosanum isolate CNPAB020 colonizing the grass Urochloa decumbens. An H-bridge experimental system was developed to evaluate the migration of ERM and of the GFP-tagged Bradyrhizobium diazoefficiens USDA 110 strain across an air gap compartment. Mycorrhizal colonization, nodule formation in legumes, and occurrence of the GFP-tagged strain in root nodules were assessed by optical and confocal laser scanning microscopy. In the presence of non-mycorrhizal U. decumbens, legume roots were neither AMF-colonized nor nodulated. In contrast, G. formosanum ERM crossing the discontinuous compartment connected mycorrhizal U. decumbens and G. max roots, which showed 30-42% mycorrhizal colonization and 7-11 nodules per plant. Fluorescent B. diazoefficiens cells were detected in 94% of G. max root nodules. Our findings reveal that, besides its main activity in nutrient transfer, ERM produced by AMF may facilitate bacterial translocation and the simultaneous associations of plants with beneficial fungi and bacteria, representing an important structure, functional to the establishment of symbiotic relationships.
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http://dx.doi.org/10.1007/s00572-020-00948-wDOI Listing
May 2020

Diversity of a phosphate transporter gene among species and isolates of arbuscular mycorrhizal fungi.

FEMS Microbiol Lett 2020 01;367(2)

Dipartimento di Scienze Agrarie, Alimentari e Agro-ambientali, Università di Pisa, 56124 Pisa, Italy.

Arbuscular mycorrhizal fungi (AMF) are a key group of beneficial obligate biotrophs, establishing a mutualistic symbiosis with the roots of most land plants. The molecular markers generally used for their characterization are mainly based on informative regions of nuclear rDNA (SSU-ITS-LSU), although protein-encoding genes have also been proposed. Within functional genes, those encoding for phosphate transporters (PT) are particularly important in AMF, given their primary ability to take up Pi from soil, and to differentially affect plant phosphate nutrition. In this work, we investigated the genetic diversity of PT1 gene sequences and sequences of the taxonomically relevant SSU-ITS-LSU region in two isolates of the species Funneliformis coronatus, three isolates of the species Funneliformis mosseae and two species of the genus Rhizoglomus, originated from geographically distant areas and cultured in vivo. Our results showed that partial PT1 sequences not only successfully differentiated AMF genera and species like ribosomal gene sequences but also highlighted intraspecific diversity among F. mosseae and F. coronatus isolates. The study of functional genes related to the uptake of key mineral nutrients for the assessment of AMF diversity represents a key step in the selection of efficient isolates to be used as inocula in sustainable agriculture.
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http://dx.doi.org/10.1093/femsle/fnaa024DOI Listing
January 2020

Responses of Vitis vinifera cv. Cabernet Sauvignon roots to the arbuscular mycorrhizal fungus Funneliformis mosseae and the plant growth-promoting rhizobacterium Ensifer meliloti include changes in volatile organic compounds.

Mycorrhiza 2020 Jan 23;30(1):161-170. Epub 2020 Jan 23.

Chemistry Department, Universidad Técnica Federico Santa María, Avenida España, 1680, Valparaíso, Chile.

Arbuscular mycorrhizal (AM) fungi and plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms that may associate with grapevine roots, improving stress tolerance, growth, and nutrition. AM fungi and PGPR enhance the production of plant secondary metabolites, including volatile organic compounds (VOCs) that play a key role in the interaction of plants with the environment and are involved in defence mechanisms. The aim of this study was to analyse the effects of an AM fungus and a rhizobacterium on plant growth and VOCs in Vitis vinifera cv. Cabernet Sauvignon roots to gain insight into the potential role of plant-rhizosphere microorganisms in vine growth and defence. Grapevines were inoculated or not with the AM fungus Funneliformis mosseae IN101 and/or the plant growth-promoting rhizobacterium Ensifer meliloti TSA41. Both microbial strains enhanced plant growth. Fifty-eight VOCs extracted from ground roots were identified using headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry. VOCs were induced by F. mosseae IN101, increasing up to 87% compared with control plants. Monoterpenes were strongly enhanced by F. mosseae IN101, increasing up to 113% compared with control plants. Interestingly, monoterpene alcohols related to plant defence, such as myrtenol, p-cymen-7-ol, and p-mentha-1.8-dien-7-ol were increased. By contrast, E. meliloti TSA41 did not significantly affect VOCs. The knowledge of the effects of AM fungi and PGPR on grapevine VOCs may contribute to an integrated and sustainable management of vineyards.
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http://dx.doi.org/10.1007/s00572-020-00933-3DOI Listing
January 2020

Bacteria Associated With a Commercial Mycorrhizal Inoculum: Community Composition and Multifunctional Activity as Assessed by Illumina Sequencing and Culture-Dependent Tools.

Front Plant Sci 2018 14;9:1956. Epub 2019 Jan 14.

Department of Agriculture, Food and Environment, University of Pisa, Pisa, Italy.

The implementation of sustainable agriculture encompasses practices enhancing the activity of beneficial soil microorganisms, able to modulate biogeochemical soil cycles and to affect soil fertility. Among them, arbuscular mycorrhizal fungi (AMF) establish symbioses with the roots of most food crops and play a key role in nutrient uptake and plant protection from biotic and abiotic stresses. Such beneficial services, encompassing improved crop performances, and soil resources availability, are the outcome of the synergistic action of AMF and the vast communities of mycorrhizospheric bacteria living strictly associated with their mycelium and spores, most of which showing plant growth promoting (PGP) activities, such as the ability to solubilize phosphate and produce siderophores and indole acetic acid (IAA). One of the strategies devised to exploit AMF benefits is represented by the inoculation of selected isolates, either as single species or in a mixture. Here, for the first time, the microbiota associated with a commercial AMF inoculum was identified and characterized, using a polyphasic approach, i.e., a combination of culture-dependent analyses and metagenomic sequencing. Overall, 276 bacterial genera were identified by Illumina high-throughput sequencing, belonging to 165 families, 107 orders, and 23 phyla, mostly represented by Proteobacteria and Bacteroidetes. The commercial inoculum harbored a rich culturable heterotrophic bacterial community, whose populations ranged from 2.5 to 6.1 × 10 CFU/mL. The isolation of functional groups allowed the selection of 36 bacterial strains showing PGP activities. Among them, 14 strains showed strong IAA and/or siderophores production and were affiliated with Actinomycetales (), Bacillales (), Enterobacteriales (), Rhizobiales (). This work demonstrates for the first time that an AMF inoculum, obtained following industrial production processes, is home of a large and diverse community of bacteria with important functional PGP traits, possibly acting in synergy with AMF and providing additional services and benefits. Such bacteria, available in pure culture, could be utilized, individually and/or in multispecies consortia with AMF, as biofertilizers and bioenhancers in sustainable agroecosystems, aimed at minimizing the use of chemical fertilizers and pesticides, promoting primary production, and maintaining soil health and fertility.
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http://dx.doi.org/10.3389/fpls.2018.01956DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339933PMC
January 2019

Designing the Ideotype Mycorrhizal Symbionts for the Production of Healthy Food.

Front Plant Sci 2018 14;9:1089. Epub 2018 Aug 14.

Institute of Agricultural Biology and Biotechnology, C.N.R., UOS Pisa, Pisa, Italy.

The new paradigm in agriculture, sustainable intensification, is focusing back onto beneficial soil microorganisms, for the role played in reducing the input of chemical fertilizers and pesticides and improving plant nutrition and health. Worldwide, more and more attention is deserved to arbuscular mycorrhizal fungi (AMF), which establish symbioses with the roots of most land plants and facilitate plant nutrient uptake, by means of a large network of extraradical hyphae spreading from colonized roots to the surrounding soil and functioning as a supplementary absorbing system. AMF protect plants from biotic and abiotic stresses and are able to modulate the activity of antioxidant enzymes and the biosynthesis of secondary metabolites (phytochemicals), such as polyphenols, anthocyanins, phytoestrogens and carotenoids, that play a fundamental role in promoting human health. An increasing number of studies focused on the use of AMF symbionts for the production of functional food, with enhanced nutritional and nutraceutical value. Yet, while several plant species were investigated, only few AMF were utilized, thus limiting the full exploitation of their wide physiological and genetic diversity. Here, we will focus on AMF effects on the biosynthesis of plant secondary metabolites with health-promoting activity, and on the criteria for a finely tuned, targeted selection of the best performing symbionts, to be utilized as sustainable biotechnological tools for the production of safe and healthy plant foods.
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http://dx.doi.org/10.3389/fpls.2018.01089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6102486PMC
August 2018

Genetic markers associated to arbuscular mycorrhizal colonization in durum wheat.

Sci Rep 2018 Jul 13;8(1):10612. Epub 2018 Jul 13.

Dipartimento di Scienze Agrarie, Alimentari e Agro-Ambientali, Università di Pisa, Via del Borghetto 80, 56124, Pisa, Italy.

In this work we investigated the variability and the genetic basis of susceptibility to arbuscular mycorrhizal (AM) colonization of wheat roots. The mycorrhizal status of wild, domesticated and cultivated tetraploid wheat accessions, inoculated with the AM species Funneliformis mosseae, was evaluated. In addition, to detect genetic markers in linkage with chromosome regions involved in AM root colonization, a genome wide association analysis was carried out on 108 durum wheat varieties and two AM fungal species (F. mosseae and Rhizoglomus irregulare). Our findings showed that a century of breeding on durum wheat and the introgression of Reduced height (Rht) genes associated with increased grain yields did not select against AM symbiosis in durum wheat. Seven putative Quantitative Trait Loci (QTLs) linked with durum wheat mycorrhizal susceptibility in both experiments, located on chromosomes 1A, 2B, 5A, 6A, 7A and 7B, were detected. The individual QTL effects (r) ranged from 7 to 16%, suggesting a genetic basis for this trait. Marker functional analysis identified predicted proteins with potential roles in host-parasite interactions, degradation of cellular proteins, homeostasis regulation, plant growth and disease/defence. The results of this work emphasize the potential for further enhancement of root colonization exploiting the genetic variability present in wheat.
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http://dx.doi.org/10.1038/s41598-018-29020-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045686PMC
July 2018

Beneficial mycorrhizal symbionts affecting the production of health-promoting phytochemicals.

Electrophoresis 2014 Jun;35(11):1535-46

Fresh fruits and vegetables are largely investigated for their content in vitamins, mineral nutrients, dietary fibers, and plant secondary metabolites, collectively called phytochemicals, which play a beneficial role in human health. Quantity and quality of phytochemicals may be detected by using different analytical techniques, providing accurate quantification and identification of single molecules, along with their molecular structures, and allowing metabolome analyses of plant-based foods. Phytochemicals concentration and profiles are affected by biotic and abiotic factors linked to plant genotype, crop management, harvest season, soil quality, available nutrients, light, and water. Soil health and biological fertility play a key role in the production of safe plant foods, as a result of the action of beneficial soil microorganisms, in particular of the root symbionts arbuscular mycorrhizal fungi. They improve plant nutrition and health and induce changes in secondary metabolism leading to enhanced biosynthesis of health-promoting phytochemicals, such as polyphenols, carotenoids, flavonoids, phytoestrogens, and to a higher activity of antioxidant enzymes. In this review we discuss reports on health-promoting phytochemicals and analytical methods used for their identification and quantification in plants, and on arbuscular mycorrhizal fungi impact on fruits and vegetables nutritional and nutraceutical value.
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http://dx.doi.org/10.1002/elps.201300568DOI Listing
June 2014

Risk management tools and the case study Brassica napus: evaluating possible effects of genetically modified plants on soil microbial diversity.

Sci Total Environ 2014 Sep 9;493:983-94. Epub 2014 Jul 9.

Consiglio per la Ricerca e la Sperimentazione in Agricoltura, Centro di Ricerca per lo studio delle relazioni tra Pianta e Suolo, Via della Navicella 2, 4, Roma 00184, Italy.

The cultivation of GMPs in Europe raises many questions about the environmental risks, in particular about their ecological impact on non-target organisms and on soil properties. The aim of a multidisciplinary group engaged in a LIFE+project (MAN-GMP-ITA) was to validate and improve an existing environmental risk assessment (ERA) methodology on GMPs within the European legislative framework on GMOs. Given the impossibility of evaluating GMO impact directly, as GMPs are banned in Italy, GMPs have not been used at any stage of the project. The project thus specifically focused on the conditions for the implementation of ERA in different areas of Italy, with an emphasis on some sensitive and protected areas located in the North, Centre, and South of the country, in order to lay the necessary baseline for evaluating the possible effects of a GMP on soil communities. Our sub-group carried out soil analyses in order to obtain soil health and fertility indicators to be used as baselines in the ERA model. Using various methods of chemical, biochemical, functional and genetic analysis, our study assessed the changes in diversity and functionality of bacterial populations, and arbuscular mycorrhizal fungi. The results show that plant identity and growth, soil characteristics, and field site climatic parameters are key factors in contributing to variation in microbial community structure and diversity, thus validating our methodological approach. Our project has come to the conclusion that the uneven composition and biological-agronomical quality of soils need to be taken into consideration in a risk analysis within the framework of ERA for the release of genetically modified plants.
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http://dx.doi.org/10.1016/j.scitotenv.2014.06.086DOI Listing
September 2014

Genetic and phenotypic diversity of geographically different isolates of Glomus mosseae.

Can J Microbiol 2009 Mar;55(3):242-53

Institute of Agricultural Biology and Biotechnology, C. N. R, Pisa, Italy.

In this work, we combined morphological taxonomy and molecular methods to investigate the intraspecific diversity of Glomus mosseae, whose global distribution has been reviewed by a survey of scientific literature and Web-available records from international germplasm collections (International Culture Collection of Vesicular Arbuscular Mycorrhizal Fungi and International Bank of Glomeromycota). We surveyed 186 publications reporting the occurrence of G. mosseae from at least 474 different sites from 55 countries throughout all continents, producing a geographical map of their distribution. The relationships among G. mosseae isolates originating from Europe (United Kingdom), the United States (Arizona, Florida, and Indiana), Africa (Namibia), and West Asia (Syria) were analyzed. The level of resolution of internal transcribed spacer (ITS) sequences strongly supports the morphological species definition of G. mosseae. An ITS - restriction fragment length polymorphism assay with the enzyme HinfI yielded a unique profile for all G. mosseae isolates, allowing a straightforward identification of this morphospecies. Genetic variability among G. mosseae isolates was revealed by the inter-simple-sequence repeat (ISSR) - polymerase chain reaction: the magnitude of genetic divergence shown by the investigated geographical isolates was higher than 50%, consistent with previous data on vegetative compatibility and functional diversity. The variability of ISSR patterns suggests that intraspecific diversity is much higher than that foreseen by morphology and rDNA regions, and should be further investigated by using other genes, such as those related to functional diversity.
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http://dx.doi.org/10.1139/w08-129DOI Listing
March 2009

Functional diversity of arbuscular mycorrhizal fungal isolates in relation to extraradical mycelial networks.

New Phytol 2006 ;172(2):347-57

Institute of Biology and Agricultural Biotechnology, UO Pisa, CNR, Via del Borghetto 80, 56124 Pisa, Italy.

We investigated the functional significance of extraradical mycorrhizal networks produced by geographically different isolates of the arbuscular mycorrhizal fungal (AMF) species Glomus mosseae and Glomus intraradices. A two-dimensional experimental system was used to visualize and quantify intact extraradical mycelium (ERM) spreading from Medicago sativa roots. Growth, phosphorus (P) and nitrogen (N) nutrition were assessed in M. sativa plants grown in microcosms. The AMF isolates were characterized by differences in extent and interconnectedness of ERM. Phenotypic fungal variables, such as total hyphal length, hyphal density, hyphal length per mm of total or colonized root length, were positively correlated with M. sativa growth response variables, such as total shoot biomass and plant P content. The utilization of an experimental system in which size, growth rate, viability and interconnectedness of ERM extending from mycorrhizal roots are easily quantified under realistic conditions allows the simultaneous evaluation of different isolates and provides data with a predictive value for selection of efficient AMF.
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http://dx.doi.org/10.1111/j.1469-8137.2006.01839.xDOI Listing
December 2006

At the root of the wood wide web: self recognition and non-self incompatibility in mycorrhizal networks.

Plant Signal Behav 2006 Jan;1(1):1-5

Department of Crop Plant Biology; CNR; UO Pisa; Pisa, Italy.

Arbuscular mycorrhizal (AM) fungi are mutualistic symbionts living in the roots of 80% of land plant species, and developing extensive, below-ground extraradical hyphae fundamental for the uptake of soil nutrients and their transfer to host plants. Since AM fungi have a wide host range, they are able to colonize and interconnect contiguous plants by means of hyphae extending from one root system to another. Such hyphae may fuse due to the widespread occurrence of anastomoses, whose formation depends on a highly regulated mechanism of self recognition. Here, we examine evidences of self recognition and non-self incompatibility in hyphal networks formed by AM fungi and discuss recent results showing that the root systems of plants belonging to different species, genera and families may be connected by means of anastomosis formation between extraradical mycorrhizal networks, which can create indefinitely large numbers of belowground fungal linkages within plant communities.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2633692PMC
http://dx.doi.org/10.4161/psb.1.1.2277DOI Listing
January 2006

Patterns of below-ground plant interconnections established by means of arbuscular mycorrhizal networks.

New Phytol 2004 Oct;164(1):175-181

Dipartimento di Chimica e Biotecnologie Agrarie, Università di Pisa, Italy.

•  The ability of arbuscular mycorrhizal (AM) networks originating from plants of different species, genera and families to become interconnected by means of hyphal anastomoses was assessed. •  An in vivo two-dimensional experimental model system was used to reveal the occurrence of linkages between contiguous mycorrhizal networks spreading from Allium porrum root systems and those originating from Daucus carota, Gossypium hirsutum, Lactuca sativa, Solanum melongena, colonized by Glomus mosseae. •  Percentages of hyphal contacts leading to anastomosis between extraradical networks originating from different plant species ranged from 44% in the pairing A. porrum-S. melongena to 49% in A. porrum-G. hirsutum. DAPI and Sytox stainings detected nuclei in the middle of fusion bridges connecting different mycorrhizal networks. •  Present data suggest that, by means of anastomoses, AM fungal mycelium would potentially create an indefinitely large network interconnecting different plants in a community, and that, in the absence of sexual recombination, the intermingling of nuclei in extraradical mycelium may provide endless opportunities for the exchange of genetic material.
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http://dx.doi.org/10.1111/j.1469-8137.2004.01145.xDOI Listing
October 2004

Genetic diversity of isolates of Glomus mosseae from different geographic areas detected by vegetative compatibility testing and biochemical and molecular analysis.

Appl Environ Microbiol 2003 Jan;69(1):616-24

Dipartimento di Chimica e Biotecnologie Agrarie, Università di Pisa. Istituto di Biologia e Biotecnologia Agraria, C.N.R., Pisa, Italy.

We detected, for the first time, the occurrence of vegetative incompatibility between different isolates of the arbuscular mycorrhizal fungal species Glomus mosseae. Vegetative compatibility tests performed on germlings belonging to the same isolate showed that six geographically different isolates were capable of self-anastomosing, and that the percentage of hyphal contacts leading to fusions ranged from 60 to 85%. Successful anastomoses were characterized by complete fusion of hyphal walls, protoplasm continuity and occurrence of nuclei in the middle of hyphal bridges. No anastomoses could be detected between hyphae belonging to different isolates, which intersected without any reaction in 49 to 68% of contacts. Microscopic examinations detected hyphal incompatibility responses in diverse pairings, consisting of protoplasm retraction from the tips and septum formation in the approaching hyphae, even before physical contact with neighboring hyphae. Interestingly, many hyphal tips showed precontact tropism, suggesting that specific recognition signals may be involved during this stage. The intraspecific genetic diversity of G. mosseae revealed by vegetative compatibility tests was confirmed by total protein profiles and internal transcribed spacer-restriction fragment length polymorphism profiles, which evidenced a higher level of molecular diversity between the two European isolates IMA1 and BEG25 than between IMA1 and the two American isolates. Since arbuscular mycorrhizal fungi lack a tractable genetic system, vegetative compatibility tests may represent an easy assay for the detection of genetically different mycelia and an additional powerful tool for investigating the population structure and genetics of these obligate symbionts.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC152401PMC
http://dx.doi.org/10.1128/AEM.69.1.616-624.2003DOI Listing
January 2003
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