Characterisation of arbuscular mycorrhizal fungi in roots by means of epifluorescence microscopy and molecular methods

In this work we characterised different species of the arbuscular mycorrhizal (AM) fungal genusGlomus by using Restriction Fragment Length Polymorphisms (RFLPs), combining epifluorescence microscopy and nested PCR, for the easy retrieval of AM fungal DNAin planta. Epifluorescence microscopy allowed us to select highly colonised root segments for DNA extraction, enhancing the chance of fungal DNA amplification by PCR. The primer pair used in nested PCR after a first reaction performed by using NS31/AM1 primers, showed a high specificity forGlomus DNA amplification and yielded enough fungal DNA for RFLP analyses. RFLP patterns of PCR products from colonised roots matched with reference profiles obtained from spores and discriminated the fourGlomus species tested. The method described may be useful for checking the establishment of mycorrhizal colonisation by the inoculated fungal species in controlled experimental conditions

Exploiting Plant Functional Diversity in Durum Wheat???Lentil Relay Intercropping to Stabilize Crop Yields under Contrasting Climatic Conditions

Relay intercropping is considered a valuable agroecological practice to increase and stabilize crop yields while ensuring the provision of several ecosystem services as well as sustainability and resilience to changing climatic conditions. However, farmers are still reluctant in the use of intercropping practices since there is a huge knowledge gap regarding the time of sowing, sowing ratio, crop stand density, and cultivar choice. In this study, we carried out a 3-year field experiment in Central Italy to assess the effect of relay intercropping on the agronomic performance and competitiveness of winter durum wheat (Triticum durum Desf. cv. Minosse) and spring lentil (Lens culinaris Medik. cv. Elsa) under a low-input management system, comparing different crop stand types (monocrop vs. intercrop) and target plant densities (350 plants m2—full dose vs. 116 plants m2—1/3 dose). The results revealed that intercropping increased grain yield compared to monocropping: significantly (p < 0.0001) against both monocrops in 2021 and non-significantly against durum wheat in 2019 and 2020. Yield advantage in both intercropping systems ranged between 164 and 648%. Durum wheat competitiveness was stronger in 2019 and 2021, while lentil was the most competitive component in 2020. Intercropping favored P accumulation in durum wheat shoots. There was no difference in grain yield of both crops between the highly- and lowly-dense system in 2020 and 2021. Both intercropping strategies were as effective as mechanical hoeing in controlling weeds and proved beneficial in stabilizing lentil productivity. Further economic analysis capturing the additional costs incurred in intercropping and mechanical weeding would highlight the magnitude of profitability of these systems

At the root of the wood wide web: self recognition an nonself incompatibility in mycorrhizal networks.

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

Health-Promoting Properties of Plant Products: The Role of Mycorrhizal Fungi and Associated Bacteria

The concept of food quality, traditionally based on nutritional and sensory properties, has recently acquired an additional meaning, referring to the health-promoting properties of plant products, that are ascribed to plant secondary metabolites called phytochemicals, primarily represented by polyphenolic compounds and glucosinolates. The diversity and content of phytochemicals in plant products are affected by different variables, such as plant genotype, agronomic factors, and arbuscular mycorrhizal fungi (AMF), which establish mycorrhizal symbioses with most crops, including cereals, legumes, vegetables, fruit trees, sunflower, cotton, and sugarcane. AMF and associated bacteria enhance plant growth and health, and affect the production of polyphenols and carotenoids, and the activity of antioxidant enzymes. The production of health-promoting phytochemicals was shown to be differentially modulated by different AMF isolates and bacterial strains, in several food plants, i.e., tomato, lettuce, strawberry, artichoke, maize, grapevine, sunflower. Here, we provide an overview of recent studies concerning the multiple roles played by AMF and associated bacteria in the modulation of the biosynthesis of plant secondary metabolites with health-promoting activity, and discuss the development of designed multifunctional consortia to be used in sustainable agriculture

Changes in soil aggregation and glomalin-related soil protein content as affected by the arbuscular mycorrhizal fungal species Glomus mosseae and Glomus intraradices.

Arbuscular mycorrhizal (AM) fungi are key organisms of the soil/plant system, influencing soil fertility and plant nutrition, and contributing to soil aggregation and soil structure stability by the combined action of extraradical hyphae and of an insoluble, hydrophobic proteinaceous substance named glomalin-related soil protein (GRSP). Since the GRSP extraction procedures have recently revealed problems related to co-extracting substances, the relationship between GRSP and AM fungi still remains to be verified. In this work the hypothesis that GRSP concentration is positively correlated with the occurrence of AM fungi was tested by using Medicago sativa plants inoculated with different isolates of Glomus mosseae and Glomus intraradices in a microcosm experiment. Our results show that (i) mycorrhizal establishment produced an increase in GRSP concentration – compared to initial values – in contrast with non-mycorrhizal plants, which did not produce any change; (ii) aggregate stability, evaluated as mean weight diameter (MWD) of macroaggregates of 1–2 mm diameter, was significantly higher in mycorrhizal soils compared to non-mycorrhizal soil; (iii) GRSP concentration and soil aggregate stability were positively correlated with mycorrhizal root volume and weakly correlated with total root volume; (iv) MWD values of soil aggregates were positively correlated with values of total hyphal length and hyphal density of the AM fungi utilized. The different ability of AM fungal isolates to affect GRSP concentration and to form extensive and dense mycelial networks, which may directly affect soil aggregates stability by hyphal enmeshment of soil particles, suggests the possibility of selecting the most efficient isolates to be utilized for soil quality improvement and land restoration programs

Host compatibility and fertilization level modulate mycorrhizal establishment and growth of two ornamental shrubs

We evaluated mycorrhizal responses of two container-grown ornamental shrubs, Photinia × fraseri and Lantana camara cultivated in soilless substrate with two fertilization regimes and inoculated with two mycorrhizal inocula, a commercial one (Symb) and an experimental one (MicroLab). Fertilization rate, inoculum type and plant genotype differentially affected mycorrhizal colonization, plant growth and mineral nutrition. At high fertility levels a significant reduction of mycorrhizal colonization occurred in both shrubs inoculated with Symb, while MicroLab successfully colonized L. camara roots. In P. fraseri MicroLab increased shoot dry weight at low fertility by 44.3% and 78.6% compared with control and Symb, respectively. In L. camara Symb increased plant height and shoot fresh weight at both fertility levels, compared with MicroLab and Control. Our work shows that host plant/mycorrhizal symbionts compatibility and fertilization may modulate the establishment and performance of mycorrhizal symbioses in container-grown woody ornamental

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

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

Functional Complementarity of Arbuscular Mycorrhizal Fungi and Associated Microbiota: The Challenge of Translational Research

One of the main challenge for humanity in the years to come is represented by the production of enough food for a growing global population, while reducing the use of pesticides and chemical fertilizers and maintaining environmental quality and natural resources for future generations. The new paradigm in agriculture—sustainable intensification—may be implemented by the efficient use of practices enhancing the activity of beneficial soil microorganisms, essential elements of soil nutrient flows, at the basis of long-term soil productivity and health. There is a growing awareness of the essential roles played by soil microorganisms in human nutrition and welfare and of the economic importance of ecosystem services they provide in agriculture, forestry, and society (Philippot et al., 2013; Avio et al., 2018)

Arbuscular Mycorrhizal Fungi and Associated Microbiota as Plant Biostimulants: Research Strategies for the Selection of the Best Performing Inocula

Arbuscular mycorrhizal fungi (AMF) are beneficial soil microorganisms establishing mutualistic symbioses with the roots of the most important food crops and playing key roles in the maintenance of long-term soil fertility and health. The great inter- and intra-specific AMF diversity can be fully exploited by selecting AMF inocula on the basis of their colonization ability and efficiency, which are aaffected by fungal and plant genotypes and diverse environmental variables. The multiple services provided by AMF are the result of the synergistic activities of the bacterial communities living in the mycorrhizosphere, encompassing nitrogen fixation, P solubilization, and the production of phytohormones, siderophores, and antibiotics. The tripartite association among host plants, mycorrhizal symbionts, and associated bacteria show beneficial emerging properties which could be efficiently exploited in sustainable agriculture. Further in-depth studies, both in microcosms and in the field, performed on different AMF species and isolates, should evaluate their colonization ability, efficiency, and resilience. Transcriptomic studies can reveal the expression levels of nutrient transporter genes in fungal absorbing hyphae in the presence of selected bacterial strains. Eventually, newly designed multifunctional microbial consortia can be utilized as biofertilizers and biostimulants in sustainable and innovative production systems

Smart use of microbial-rich vermicomposting to enhance tripartite plant-microbe-soil interactions

Vermicomposting is a natural process that utilizes earthworms and associated microbiome to transform organic wastes into vermicompost by-products that are rich in beneficial microorganisms and nutrients such as carbon, phosphorus, nitrogen, magnesium, and calcium. Liquid vermicompost extract (LVE), a derivative of the vermicomposting process, has recently gained interest among scientists and organic farmers due to their potential ability to enhance tripartite plant-microbe-soil interactions that would lead to improved plant and root growth, soil health and overall crop yield productivity. To investigate the short-term effect of LVE on soil mycorrhizal inoculum potential (MIP) and plant-mycobiome interactions, a field trial was carried out at CiRAA E. Avanzi, San Piero a Grado, Pisa, Italy. The effect of LVE and its associated microbial and chemical components on soil MIP and AMF root colonization was evaluated on five summer crops, i.e. chickpea (Cicer arietinum L.), berseem clover (Trifolium alexandrinum L.), lentil (Lens culinaris L.), soybean (Glycine max L. Merrill), and sunflower (Helianthus annuus L.). The test plants were grown with or without the application of LVE in a split-plot trial with five replicates. Freshly made LVE from vermicomposting of wheat straws mixed with horse manure was screened for microbial properties using the Illumina Miseq sequencing platform. Seed inoculation with LVE was done before planting while field inoculation was done at the stem-elongation stage. Un-inoculated seeds and plots were used as controls. Soil MIP was assessed before planting and after harvesting, while AMF root colonization was evaluated at the mid-flowering stage of each crop. The bacterial 16S and fungal ITS sequence analyses showed a high bacteria and fungal abundance and taxonomic alpha diversity present in the LVE. The most dominant taxa included Mucor, Citrobacter, Pseudomonas, Arcobacter, Azomonas and Clostridium. These microbes are commonly found in agricultural soil and are linked to the hydrolysis of complex organic matter, nutrient recycling, production of growth-promoting factors and siderophores, while others are known to produce peptide antimycotics and antibiotics that protect plants against pathogenic soil microorganisms. The soil MIP significantly (p < 0.0001) differed between the two soil sampling times (before planting and after harvesting). It was evident that both seed and field inoculation with LVE significantly enhanced the soil MIP and this could benefit the next crop under rotation. AMF root colonization varied significantly across the crop species (p < 0.0001) and LVE treatment (p = 0.006). Highly nodulated lentils and berseem clover roots recorded significantly higher AMF root colonization than all the other crops. LVE inoculation had an overall positive effect on AMF root colonization with an average increase of 6.2% compared to the un-inoculated crops. These short-term results indicate that there could be a positive effect of the LVE inoculation on the soil MIP and AMF root colonization of our test crops, which could be attributed to the beneficial additive effects of the LVE that enhanced the tripartite plant-microbe-soil interactions