Mesofauna assemblages on the extraradical mycelium of Pinus greggii roots with three ectomycorrhizal fungi

Background: The extraradical mycelium (ERM) of ectomycorrhizal fungi is a network inhabited by soil mesofauna, mainly collembolans and mites, forming interactions during the fungal life-cycle, from grazing on hyphae to spore dispersal. However, it is still unknown if ERM of ectomycorrhizal fungi could influence the structure of mesofauna assemblages. Objective: To evaluate the abundance and community composition of the mesofauna inhabiting the ERM of Hebeloma mesophaeum, Laccaria laccata and Wilcoxina sp. in Pinus greggii roots. Methods: Mesofauna was collected from the root balls of P. greggii with 80 % of colonization using a washing method. Results and conclusions: An effect was observed due to ERM differences on species richness and species dominance, but not an effect on the abundance and community composition of the mesofauna. However, Wilcoxina sp. presented the lowest species richness and diversity. Fungus-feeding collembolans shaped species-rich assemblages, being isotomid-tullbergid forms the soil-dwelling taxa. Entomobryidae and Hypogastruridae were the most common families on the soil surface, not being found in Wilcoxina sp., and only a few predatory mites of the Mesostigmata and Endeostigmata were found. The ectomycorrhizal mycelium constitutes a trophic niche of the mesofauna and it might be an evolutionary force in structuring species composition and diversity.

The Protective Biochemical Properties of Arbuscular Mycorrhiza Extraradical Mycelium in Acidic Soils Are Maintained throughout the Mediterranean Summer Conditions

In acidic soils with manganese (Mn) toxicity, arbuscular mycorrhizal fungi (AMF) can improve plant host growth by enhancing nutrition and protecting against environmental stress. The intact extraradical mycelium (ERM) of AMF is able to survive Mediterranean summer conditions and provide an earlier colonization of winter crops. This study evaluated if summer season conditions hindered the beneficial effects of wheat colonization by the intact ERM associated with a native plant, in acidic soil. Wheat was grown in soil with intact or disrupted ERM associated with Ornithopus compressus (ORN), developed for 7 or 24 weeks, to simulate ERM summer survival. The activity of antioxidant enzymes was determined, and the quantitative analysis of Mn and macronutrients was performed by inductively coupled plasma mass spectrometry (ICP-MS), in wheat shoots and respective subcellular fractions. Wheat colonization by intact ERM decreased shoot Mn concentration but increased the proportion of Mn in the apoplast. Overall, antioxidant enzymatic activity decreased but the proportion of Mn-superoxide dismutase activity over the remaining isoforms increased, suggesting its important role in the AMF-mediated mitigation of Mn toxicity. Summer conditions did not substantially reduce the benefits provided by ORN ERM. A no-till strategy allied to the development of native microbiota can contribute to the sustainable optimization of acidic soil use.

Effect of Tillage System and Cover Crop on Maize Mycorrhization and Presence of Magnaporthiopsis maydis

The sustainability of agriculture requires the adoption of agricultural soil conservation practices with positive impacts on soil quality, which can promote beneficial soil microbiota like arbuscular mycorrhizal fungi (AMF) and its diversity. This study aims to assess the influence of the presence of intact extraradical mycelium as a preferential source of inoculum of the native AMF in order to guarantee a better colonization as well as its possible bioprotective effect against Magnaporthiopsis maydis. In order to vary the available extraradical mycelium, two experiments, with and without cover crop, were carried out, in which two tillage systems and two maize varieties were studied. The capitalization of the benefits, in terms of grain production and M. maydis presence, associated to the cover crop were only achieved with minimum tillage. Therefore, both cultural practices are necessary to reduce the fungus presence, coupling the effect of mycorrhization together with other benefits associated with the cover crop. Although in the absence of a cover crop and using conventional tillage, yields and lower levels of M. maydis are possibly achieved, this system is more dependent on the variety used, does not benefit from the advantages associated with the cover crop, is more expensive, and environmentally unsustainable.

Effect of Vermicompost and Selected Plant Preparations on the Development of Arbuscular Mycorrhizal Symbiosis in Lettuce (Lactuca sativa)

The aim of the pot experiment was to evaluate effect of vermicompost and promoting plant preparations application (Symbivit and Plantaktiv) on the development of arbuscular mycorrhizal symbiosis in lettuce, amount of extraradical mycelium of mycorrhizal fungi in soil and plant biomass production. Symbivit contains six species of mycorrhizal fungi and Plantaktiv contains magnesium sulfate activated by oxygen promoting activity of aerobic microorganisms in the soil. The application of vermicompost and promoting plant preparations did not have a statistically significant effect on lettuce root colonization by mycorrhizal fungi. The greatest length of extraradical mycelium was observed in variant with vermicompost application, in variant with addition of vermicompost and Symbivit, and in variant with vermicompost applied with both plant preparations. There was detected statistically significant difference when compared to control variant. Dry matter weight of aboveground biomass and root of the lettuce were statistically significantly increased in all variants, where vermicompost was applied, either alone or in combination with plant preparations. Separate application of Symbivit or Plantaktiv did not have a statistically significant effect either on the length of extraradical mycelium or dry matter weight of the lettuce.