Cultivation of olive trees covers large coastal areas of land in Mediterranean regions, many of them characterized by low soil fertility and exposed to salinity and seasonal drought. In this frame, we developed mixed community inocula of arbuscular mycorrhizal fungi (AMF) derived from the extreme, seasonally arid environments of six Mediterranean sand dunes and evaluated their effects, in the form of community inocula, on rooted semi-woody olive tree cuttings (Olea europaea cv. Koroneiki). The plantlets were grown in the greenhouse for 10 months under 50 mM and 100 mM concentrations of NaCl, successively applied to induce osmotic stress. Inoculation had a positive effect on plant growth and nutrient uptake. However, the three best-performing inocula in early colonization and in plant growth enhancement also resulted in high plant sensitivity to high salinity, which was not observed for the other three inocula. This was expressed by decreased nutrient uptake and drastically lower plant growth, plant photosynthesis, and stomatal conductance (generally an over 50% reduction compared to no salinity application). Amplicon sequencing analysis of the olive plants under salinity stress showed that the AMF communities in the roots were clearly differentiated by inoculation treatment. We could not, however, consistently associate the plant responses observed under high salinity with specific shared AMF community membership or assembly attributes. The observed physiological overreaction to osmotic stress may be an adaptation trait, potentially brought about by host selection coupled to abiotic environmental filtering, in the harsh conditions from which the AMF inocula were derived. The overreaction may, however, be undesirable if conveyed to allochthonous plants at an agronomic level.

中文翻译：

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沿海沙丘上的丛枝菌根真菌接种物在盐分胁迫下阻止了橄榄插条的生长。

橄榄树的种植覆盖了地中海地区的大部分沿海土地，其中许多土地的特点是土壤肥力低，盐碱化和季节性干旱。在此框架中，我们开发了来自六个地中海沙丘的极端，季节性干旱环境的丛枝菌根真菌（AMF）混合群落接种物，并以群落接种物的形式评估了它们对生根的半木橄榄树插枝的影响（油橄榄简历。Koroneiki）。将小植株在温室中于50 mM和100 mM浓度的NaCl下生长10个月，依次施加以诱导渗透胁迫。接种对植物生长和养分吸收有积极影响。但是，在早期定殖和促进植物生长方面表现最好的三个接种物也导致了植物对高盐分的高度敏感性，而其他三个接种物则未观察到。营养减少，植物生长，植物光合作用和气孔导度大大降低（与不施用盐分相比通常降低了50％以上）来表示。盐胁迫下橄榄植物的扩增子测序分析表明，接种处理后根部的AMF群落明显不同。但是，我们不能 始终将在高盐度下观察到的植物反应与特定的共享AMF社区成员或装配属性相关联。在衍生AMF接种物的恶劣条件下，观察到的对渗透压的生理过度反应可能是适应性状，可能是通过与非生物环境过滤相结合的宿主选择而引起的。但是，如果以农艺水平转移到异源植物中，过度反应可能是不希望的。