Arbuscular Mycorrhizal Fungus Improves Rhizobium<i>–Glycyrrhiza</i> Seedling Symbiosis under Drought Stress

• Main Authors: Zhipeng Hao, Wei Xie, Xuelian Jiang, Zhaoxiang Wu, Xin Zhang, Baodong Chen
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Agronomy
• Subjects: <i>Rhizophagus irregularis</i>; rhizobium; licorice; drought tolerance; nitrogen; phosphorus
• Online Access: https://www.mdpi.com/2073-4395/9/10/572

Rhizobia and arbuscular mycorrhizal (AM) fungi can potentially alleviate the abiotic stress on the legume <i>Glycyrrhiza</i> (licorice), while the potential benefits these symbiotic microbes offer to their host plant are strongly influenced by environmental factors. A greenhouse pot experiment was conducted to investigate the effects of single and combined inoculation with a rhizobium <i>Mesorhizobium tianshanense</i> Chen and an AM fungus <i>Rhizophagus irregularis</i> Walker &amp; Schuessler on <i>Glycyrrhiza uralensis</i> Fisch. seedling performance under different water regimes. Drought stress inhibited rhizobium nodulation but increased mycorrhizal colonization. Furthermore, co-inoculation of rhizobium and AM fungus favored nodulation under both well-watered and drought stress conditions. <i>Glycyrrhiza</i> seedling growth showed a high mycorrhizal dependency. The seedlings showed a negative growth dependency to rhizobium under well-watered conditions but showed a positive response under drought stress. <i>R. irregularis</i>-inoculated plants showed a much higher stress tolerance index (STI) value than <i>M. tianshanense</i>-inoculated plants. STI value was more pronounced when plants were co-inoculated with <i>R. irregularis</i> and <i>M. tianshanense</i> compared with single-inoculated plants. Plant nitrogen concentration and contents were significantly influenced by inoculation treatments and water regimes. <i>R. irregularis</i> inoculation significantly increased plant shoot and root phosphorus contents. AM fungus inoculation could improve <i>Glycyrrhiza</i> plant&#8722;rhizobium symbiosis under drought stress, thereby suggesting that tripartite symbiotic relationships were more effective for promoting plant growth and enhancing drought tolerance.