Arbuscular mycorrhizal fungi assisted by mycorrhizal helper bacteria improved the resistance of cucumber seedlings to cadmium stress by reshaping the soil microbial community

Arbuscular mycorrhizal fungi (AMF) have a certain effect on alleviating heavy metal stress. However, it is not clear that the effect of dual inoculation of AMF and mycorrhizal helper bacteria (MHB) on alleviating cadmium stress in cucumber seedlings and its regulatory mechanism. Therefore, we used Funneliformis mosseae was used as the test AMF, and Alcaligenes faecalis was used as the test MHB. We studied the effects of no inoculation (CK), single inoculation of AMF (F), single inoculation of MHB (S), and double inoculation of AMF and MHB (FS) on alleviating cadmium stress in cucumber seedlings. Compared with the other three treatments, FS treatment significantly increased plant fresh weight, plant N content, plant P content, plant K content, nitrate N content, available P content, available K content. F, S and FS treatments significantly increased overground part Cd concentration and translocation factor, and significantly decreased underground part Cd concentration, Cd content in rhizosphere soil and retention rate compared with CK treatment. Different inoculation treatments changed the relative abundance, composition and diversity of bacteria in the rhizosphere soil of cucumber seedlings. F, S and FS treatments significantly increased Chao 1 index, simpson index and number of OTUs, and significantly reduced goods_coverage compared with CK treatment. In general, our results showed that double inoculation with Funneliformis mosseae and Alcaligenes faecalis enhanced the resistance of cucumber seedlings to Cd stress by shaping the rhizosphere beneficial microbial flora, activating soil nutrients, and promoting plant uptake.