Effect of native and allochthonous arbuscular mycorrhizal fungi on Casuarina equisetifolia growth and its root bacterial community

Exotic trees are often planted to recover degraded lands. Inoculation with mycorrhizal fungi can improve their survival. Plant growth is partly dependent on the strain used, but little attention has been paid to the selection of mycorrhizal fungi. The aim of this study was to determine whether the growth of Casuarina equisetifolia L. (Johnson) is affected by two different mycorrhizal inocula generated using fungal spores retrieved from an Australian site (allochthonous soil) and a Senegalese site (native soil) under C. equisetifolia trees. Comparative experiments were conducted with plants in a Senegalese soil, previously sterilized or not, and grown in a greenhouse. At harvest, parameters related to plant growth and mycorrhization were evaluated and soil bacterial communities were compared. Tree growth was significantly influenced by both types of inoculants. In unsterilized soil, plants inoculated with the native inoculant were taller than plants inoculated with the allochthonous inoculant and control plants. The frequency of mycorrhization with both inoculants was higher in unsterilized soil. The strongest effects of the mycorhizosphere on the soil microbiome were obtained with the allochthonous inoculum, and analysis of the taxonomic composition revealed mycorrhizal communities specific to each inoculum. These results suggest that the development of C. equisetifolia and its root bacterial community are dependent on the composition of the mycorrhizal inoculum. The functional consequences of this rhizosphere effect in terms of soil fertility should be further studied to better guide reforestation operations.

外来树种常被用于修复退化土地。接种菌根真菌（mycorrhizal fungi）可提升其存活率。植物生长在一定程度上依赖于所选用的菌株，但目前针对菌根真菌筛选的研究仍较为匮乏。本研究旨在明确：从澳大利亚样地（异地土壤，allochthonous soil）以及塞内加尔样地（本土土壤，native soil）的木麻黄（Casuarina equisetifolia L. (Johnson)）树下采集真菌孢子制备的两种不同菌根接种剂，是否会对木麻黄的生长产生影响。本研究以经灭菌与未灭菌处理的塞内加尔土壤为基质，在温室环境中开展植物对比试验。试验收获阶段，研究人员对植物生长及菌根定植相关参数进行了测定，并对土壤细菌群落开展了对比分析。结果显示，两种接种剂均对树木生长产生了显著影响：在未灭菌土壤中，接种本土接种剂的植株高度显著高于接种异地接种剂的植株与对照组植株；两种接种剂在未灭菌土壤中的菌根定植频率均更高。异地接种剂对土壤微生物组的菌根根际调控效应最为显著，分类学组成分析结果显示，两种接种剂各自对应特异性的菌根群落。上述结果表明，木麻黄的生长及其根系细菌群落结构均依赖于菌根接种剂的组成。未来需进一步探究该根际效应对土壤肥力的功能性影响，以更好地指导造林实践。