Micorrize e qualità dei suoli

Abstract

Mycorrhizae, generally obligate mutualistic symbioses, established about 450 million years ago between mycelium of soil fungi and absorbent roots of plants, involve a large number of Mycota taxa and approximately 90% of the plant kingdom. The symbiosis is mutualistic since the mycorrhizal fungi stimulate the growth and other physiological processes of the host plants, while the plants provide them with trophic organic substances, useful for their development and fundamental for fruiting and sporification. In nature, three groups of mycorrhizal associations are distinguished, the ecto‐, the ectoendo‐ and the endomycorrhizae, depending both on the species of plants and fungi associated and on the ways in which mycelial hyphae and cells of the root organ interconnect. The advantages of such associations are expressed in all ecosystems, natural or marginal, while the rarefaction or absence of mutualistic fungi, mainly due to anthropic causes, can induce deleterious effects on the ecosystem. In fact, in addition to improving the vegetative performance of the hosts, their mycelia promote the aggregation of particles and the structure of the soil, also immobilizing any heavy metals and toxic substances present therein. In particular, in the case of arbuscular endomycorrhizal associations (AM), present in approximately 80% of plant species, the fungi that characterize them produce a protein, glomalin, with adhesive and aggregating activity on soil particles, also capable of storing carbon and adsorb any heavy metals present. In this regard, a study conducted in the Sicilian basin of the Southern Imera river highlighted that the soils with a greater population density of VA fungi, expressed as number of spores per gram of soil, had better qualities, while reduced populations were found in poorer soils. On the basis of these considerations, it is opportune to develop crop and soil management strategies aimed at maintaining the natural populations of mycorrhizal fungi and, in cases of greater anthropic pressure, at the reintroduction of these microorganisms through the distribution of commercial formulations based on suitable microbial propagules.