Abstract

Arbuscular Mycorrhizal Fungi (AMF) play a fundamental role in the development and survival of plant species in arid regions. The objectives of the present research were (1) to characterize the native AMF communities in olive orchard soils collected from arid regions of southern Tunisia and (2) to study the AMF-host specificity hypothesis. AMF spores were extracted from soil-root samples collected from orchards planted with two indigenous olive cultivars (Chemlali and Zarrazi) and located at three sites (Matmata, Zarzis and Tataouine) along an aridity gradient. First, the abundance of AMF spores was determined; then the AMF spores were grouped into several morpho-types and molecularly characterized by 18S rDNA nested-PCR approach. AMF abundance and diversity varied among cultivars and sites. Olive orchard soil of Zarzis site had the highest spore density (140 spores/100g soil), while the Tataouine site had the lowest density (100 spore/100 g soil). Pooled data of morpho-typing and sequence-driven analyses allowed the identification of 10 AMF taxa with the dominance of Glomeraceae family, represented by Glomus, Rhizophagus and Funneliformis genera, followed by Diversisporaceae family. The less arid site (Matmata) exhibited the highest AMF diversity, while the most arid-site (Tataouine) showed the lowest one. The cultivar Zarrazi displayed a higher ability to associate with AMF than Chemlali. For all analyzed sequences, five AMF taxa were associated with Chemlali and eight were associated with Zarrazi.

摘要

丛枝菌根真菌（AMF）在干旱地区植物物种的发育和生存中发挥着重要作用。本研究的目的是（1）表征从突尼斯南部干旱地区收集的橄榄园土壤中的原生 AMF 群落和（2）研究 AMF 宿主特异性假设。AMF 孢子是从种植两种本土橄榄品种（Chemlali 和 Zarrazi）的果园收集的土壤根样本中提取的，这些样本位于沿干旱梯度的三个地点（Matmata、Zarzis 和 Tataouine）。首先，确定 AMF 孢子的丰度；然后将 AMF 孢子分为几种形态类型，并通过 18S rDNA 巢式 PCR 方法进行分子表征。AMF 丰度和多样性因品种和地点而异。Zarzis 场地橄榄园土壤的孢子密度最高（140 个孢子/100g 土壤），而Tataouine 场地的密度最低（100 个孢子/100g 土壤）。形态分型和序列驱动分析的汇总数据允许鉴定 10 个 AMF 分类群，其中占主导地位Glomeraceae科，以Glomus属、Rhizophagus属和Funneliformis属为代表，其次是Diversisporaceae科。较不干旱的地点 (Matmata) 的 AMF 多样性最高，而最干旱的地点 (Tataouine) 的 AMF 多样性最低。品种 Zarrazi 与 AMF 的关联能力比 Chemlali 更高。对于所有分析的序列，五个 AMF 分类群与 Chemlali 相关，八个与 Zarrazi 相关。