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Possible role of arbuscular mycorrhizal fungi and associated bacteria in the recruitment of endophytic bacterial communities by plant roots
Get PDFArbuscular 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 N2 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
Diversity of phosphate transporter genes among species and isolates of arbuscular mycorrhizal fungi
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Field functional diversity of arbuscular mycorrhizal fungi in a crop rotation of Trifolium alexandrinum and Zea mays.
No full textSoil microbes play a major role in the functioning of agroecosystems. Arbuscular mycorrhizal fungi (AMF) are beneficial microbes fundamental in soil fertility and plant nutrition, enhancing plant P and N uptake by means of their extraradical mycelium (ERM) spreading from mycorrhizal roots into the surrounding soil (Smith and Read, 2008). Many studies have been carried out with plants grown in sterile soil with or without AMF inoculation (Avio et al., 2006), while little is known about mycorrhizal symbiosis in nonsterile soils, which can contain diverse microorganisms differently influencing plant growth. Furthermore, the impact of agricultural practices on mycorrhizal colonization and host plant response in the field is not yet clearly understood. Greenhouse and field studies were performed in order to assess inter- and intraspecific functional diversity of geographically different isolates of the AMF species Glomus intraradices and Glomus mosseae, and of indigenous isolates inoculated on Trifolium alexandrinum and Zea mays, in a 2-year crop rotation
Effects of long-term land use on arbuscular mycorrhizal fungi and glomalin-related soil protein
No full textThe maintenance of soil health and productivity is a central aim of sustainable agriculture. Arbuscular mycorrhizal fungi (AMF) are soil biota fundamental for soil fertility and plant nutrition, which may be used in the evaluation of the impact of agronomic practices on soil quality. In the present study we evaluated the influence of three different land uses on AMF populations and correlated glomalin-related soil protein (GRSP) content with AMF biomass parameters, such as spore density and biovolume. Among the differently managed sites - maize monoculture, grassland and poplar grove - maize soil showed the lowest AMF spore number and GRSP content. The same morphological taxa were found in the three sites, except for one additional morphotype in poplar grove. A good correlation between GRSP and spore biovolume was found, suggesting that GRSP may represent a useful biochemical parameter for the assessment of biological soil fertility in sustainable agriculture
Cambiamenti nelle comunità native di funghi micorrizici arbuscolari nelle radici di mais in successione a cover crops
No full textI funghi micorrizici arbuscolari (AMF) formano simbiosi mutualistiche con circa l’80% delle specie vegetali e la
grande maggioranza delle piante coltivate. Gli AMF sono considerati dei veri e propri biofertilizzanti e biostimolanti
naturali, capaci di influenzare la fertilità dei suoli, la nutrizione delle piante e la loro produttività, e quindi fondamentali
negli agroecosistemi sostenibili e biologici. Nelle gestioni colturali a basso impatto ambientale sono spesso utilizzate le
rotazioni e le cover crops per aumentare la fertilità dei suoli. Tali colture, rappresentate da diverse specie vegetali ospiti,
possono influenzare la diversità e la struttura delle comunità AMF in pieno campo. In questo studio, utilizzando i
primers AML1 e AML2, che amplificano la regione V3-V4 dei Glomeromycota, è stata verificata l’ipotesi che le
comunità vegetali presenti in due diversi trattamenti, con cover crops a bassa ed alta diversità di specie, fossero in grado
di influenzare le comunità AMF native presenti nelle radici della successiva coltura di mais. Nel trattamento a bassa
diversità di specie era presente solamente Vicia villosa Roth, mentre nel trattamento ad alta diversità di specie erano
presenti Vicia villosa Roth, Trifolium alexandrinum L., Trifolium incarnatum L., Avena sp. e Phacelia tanacetifolia
Benth. Sono stati analizzati, mediante clonaggio, analisi RFLP e sequenziamento, gli apparati radicali di tre piante per
ogni specie vegetale provenienti da tre parcelle di terreno per ogni trattamento. In totale sono stati identificati 16 diversi
tipi di sequenze di AMF, dopo aver esaminato 505 cloni provenienti da 24 librerie genomiche. Le sequenze trovate in
maggior quantità erano quelle omologhe ad Acaulospora cavernata (34,7% delle sequenze), seguite da quelle
assimilabili a Funneliformis mosseae (10,7%), Claroideoglomus lamellosum (9,9%) e Rhizophagus intraradices (6,7%).
Sequenze simili a Funneliformis caledonium, Diversispora aurantia, Diversispora epigaea e Archaeospora schenckii
erano presenti in percentuale molto bassa, meno del 2% del totale. Le sequenze di A. cavernata erano le più abbondanti
nelle cover crops, mentre quelle di F. mosseae, R. intraradices e Glomus sp. erano rinvenute soprattutto in mais. Questi
dati mostrano che la composizione delle comunità AMF presenti nelle radici di mais non dipende dall’identità e dalla
diversità delle colture precedenti. I risultati ottenuti suggeriscono che la forza trainante delle dinamiche delle comunità
AMF negli agroecosistemi sia rappresentata principalmente dalla identità della pianta ospite, che può selettivamente
favorire o inibire lo sviluppo delle diverse specie di AMF, in relazione al loro significato funzionale
Inter- and Intraspecific functional diversity of arbuscular mycorrhizal fungi living in symbiosis with Trifolium alexandrinum and Medicago sativa.
No full textGenetic and phenotypic diversity of geographically different isolates of Glomus mosseae
No full textIn 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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