Abstract: Tomato inoculated with 3 AMF species, Rhizophagus irregularis, Gigaspora margarita and Acaulospora delicata, at different pH values (4.5 or 6.5), the influences of low pH on the arbuscule formation and function of AMF in tomato roots were investigated. The results indicated that low pH significantly inhibited the AMF colonization and the arbuscule formation in roots. Three AMF species varied greatly with G. margarita showing the highest colonization and R. irregularis showing the most sensitive arbuscule abundance to low pH. AMF significantly elevated the plant biomass and decreased the root to shoot ratio. The effects of low pH on alkaline phosphatase (ALP) activity shared the similar pattern with those on root colonization. AMF significantly increased the shoot phosphorus content and the LePT4 expression in roots; however, pH did not affect them. These results suggested that low pH was inhibitory to the establishment and maintenance of AMF-host symbiosis, and the beneficial effects of AMF was greater at low pH. Moreover, different AMF species/isolates could vary greatly in the ability to increase the resistance of hosts to low pH.

Key words: low pH, arbuscular mycorrhizal fungi, arbuscule formation, tomato

摘要： 以番茄Solanum lycopersicum为宿主，在pH 4.5和pH 6.5条件下分别接种3种丛枝菌根真菌(AMF)，即根内球囊霉Rhizophagus irregularis、珠状巨孢囊霉Gigaspora margarita和脆无梗囊霉Acaulospora delicata，探讨低pH对AMF在根系中的丛枝形成和功能的影响。结果表明，低pH能够显著抑制AMF对根系的侵染以及丛枝的形成；3个菌种之间存在差异，表现为珠状巨孢囊霉的侵染强度最高，根内球囊霉的丛枝丰度对低pH最敏感；AMF显著增加番茄的生物量，降低其根冠比；番茄在pH 6.5的菌根依赖性低于在pH 4.5的对应值，对根内球囊霉的菌根依赖性最低；低pH对碱性磷酸酶(ALP)活性的影响与根系侵染有相似的模式；AMF显著提高地上部磷含量，增强根系LePT4的表达，但pH的影响并不显著。以上结果表明，低pH对AMF与植物共生关系的建立和维持有一定的抑制作用，低pH胁迫条件下AMF的促生作用更大，不同AMF菌种/菌株提高植株低pH抗性的能力存在差异。

关键词: 低pH, 丛枝菌根真菌, 丛枝形成, 番茄