Microbiology and Molecular Biology Team, Center of Plant and Microbial Biotechnology, Biodiversity and Environment, Faculty of Sciences, Mohammed V University in Rabat, Avenue Ibn Battouta, BP 1014, 10000 Rabat, Morocco.
Microbiology and Molecular Biology Team, Center of Plant and Microbial Biotechnology, Biodiversity and Environment, Faculty of Sciences, Mohammed V University in Rabat, Avenue Ibn Battouta, BP 1014, 10000 Rabat, Morocco.
Syst Appl Microbiol. 2023 Jul;46(4):126434. doi: 10.1016/j.syapm.2023.126434. Epub 2023 May 15.
In the present study, we analyzed the genetic diversity, phylogenetic relationships, stress tolerance, phytobeneficial traits, and symbiotic characteristics of rhizobial strains isolated from root nodules of Vachellia tortilis subsp. raddiana grown in soils collected in the extreme Southwest of the Anti-Atlas Mountains in Morocco. Subsequent to Rep-PCR fingerprinting, 16S rDNA gene sequencing of 15 representative strains showed that all of them belong to the genus Ensifer. Phylogenetic analysis and concatenation of the housekeeping genes gyrB, rpoB, recA, and dnaK revealed that the entire collection (except strain LMR678) shared 99.08 % to 99.92% similarity with Ensifer sp. USDA 257 and 96.92% to 98.79% with Sinorhizobium BJ1. Phylogenetic analysis of nodC and nodA sequences showed that all strains but one (LMR678) formed a phylogenetic group with the type strain "E. aridi" LMR001 (similarity over 98%). Moreover, it was relevant that most strains belong to the symbiovar vachelliae. In vitro tests revealed that five strains produced IAA, four solubilized inorganic phosphate, and one produced siderophores. All strains showed tolerance to NaCl concentrations ranging from 2 to 12% and grew at up to 10% of PEG6000. A greenhouse plant inoculation test conducted during five months demonstrated that most rhizobial strains were infective and efficient. Strains LMR688, LMR692, and LMR687 exhibited high relative symbiotic efficiency values (respectively 231.6 %, 171.96 %, and 140.84 %). These strains could be considered as the most suitable candidates for inoculation of V. t. subsp. raddiana, to be used as a pioneer plant for restoring arid soils threatened with desertification.
在本研究中，我们分析了从摩洛哥阿特拉斯山脉西南极端地区采集的土壤中生长的 Vachellia tortilis subsp. raddiana 根瘤中分离出的根瘤菌菌株的遗传多样性、系统发育关系、耐应激能力、植物有益特性和共生特征。15 株代表性菌株的 Rep-PCR 指纹图谱和 16S rDNA 基因测序结果表明，它们均属于根瘤菌属 Ensifer。系统发育分析和看家基因 gyrB、rpoB、recA 和 dnaK 的串联分析表明，整个菌株集合（除了 LMR678 菌株）与 Ensifer sp. USDA 257 的相似度为 99.08%至 99.92%，与 Sinorhizobium BJ1 的相似度为 96.92%至 98.79%。nodC 和 nodA 序列的系统发育分析表明，除 LMR678 菌株外，所有菌株均与“E. aridi”LMR001 （相似度超过 98%）形成一个系统发育群。此外，大多数菌株属于 vachelliae 共生型。体外试验表明，有 5 株菌产生 IAA，4 株菌溶解无机磷，1 株菌产生铁载体。所有菌株均能耐受 2%至 12%的 NaCl 浓度，并能在高达 10%的 PEG6000 下生长。在五个月的温室植物接种试验中，大多数根瘤菌菌株具有侵染性和高效性。菌株 LMR688、LMR692 和 LMR687 表现出较高的相对共生效率值（分别为 231.6%、171.96%和 140.84%）。这些菌株可被视为接种 V. t. subsp. raddiana 的最适宜候选菌株，可作为在受荒漠化威胁的干旱土壤上恢复植被的先锋植物。
