Studies on arbuscular mycorrhizal fungi in New Caledonian ultramafic soils: A synthesis
Résumé
If the knowledge about New Caledonian serpentine ecosystems has increased greatly during the past halfcentury, research on soil microflora and plant symbionts started only in the nineties and was mainly published during the last two decades. Here we synthesize the studies on arbuscular mycorrhizal fungi (AMF), focusing particularly on ecological and restoration aspects. Research on AMF consisted firstly of a global and inventory approach aiming to produce basic but essential lacking knowledge. These studies showed that AMF are abundant in ultramafic soils and concerned nearly all plant species of these ecosystems. Even Nihyperaccumulator plants and sedges, generally considered non-mycorrhizal, were found to be functionally colonized by AMF in New Caledonian ultramafic soils. The adaptation of AMF communities to the extreme conditions of these soils led to high levels of metal tolerance (particularly to Ni) and noticeable originality of the taxa. Several new species were described. A relatively high AMF diversity was found in the studied serpentine ecosystems. The influence of these symbionts on plant growth and adaptation was assessed in greenhouse and field conditions. An accurate selection of AMF isolates that improve plant growth, and plant metal tolerance was performed. It was demonstrated that combinations of AMF isolates with complementary functional traits showed high synergistic effects on plant development. Finally, a partnership with a biotechnological company led to the production of an efficient commercial inoculant now used in the ecological restoration of mine-degraded areas. Today studies are focused mainly on the additive effects of AMF and mycorrhiza-helper bacteria.
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