Cowpea can effectively form tripartite symbiotic associations with nitrogen-fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) although the selection of compatible AMF species and rhizobial strains which are promoting cowpea growth remains a challenge. The aims of the current study were 1) to evaluate the response of cowpea plants to a symbiotic NFB and a multi-AMF inoculum and 2) to explore any interaction between the symbiotic NFB and the different AMF isolates. In a pot gnotobiotic trial, cowpea plants grown under limited N supply, were inoculated with or without a symbiotic nitrogen-fixing bacterium, Sinorhizobium meliloti, and combinations of three different AMF species namely Dominikia disticha, Claroideoglomus etunicatum and Rhizophagus irregularis. Experimental evaluation was determined through the measurement of above ground biomass, nutrient content and AMF root colonization. The presence of AMF species on cowpea roots was also determined with cloning and sequencing. Inoculation with both AMF and S. meliloti led to increased cowpea biomass production compared to inoculation with AMF only, but the presence of a positive effect depended on the specific AMF partners used. Inoculation with AMF alone had a highly positive impact on the growth and P uptake of cowpea, but the NFB inoculation was needed to address N deficiency in planta. The presence of both symbionts generally led to increased AMF colonization of the cowpea roots, however, plant colonization depended on the AMF species, and became even negative, when all three AMF inocula were used together. The AMF composition in plant roots was also altered in the presence of the S. meliloti. Plant nitrogen content of cowpea plants significantly increased under the presence of both symbionts compared to AMF alone, while phosphorus content was hardly affected by dual inoculations. The results show positive synergistic effects of the different AMF species and S.meliloti. Inoculation with all AMF isolates and S. meliloti led to high above ground biomass production and accumulation of N. The presence of S. meliloti increased P content in plants not inoculated with AMF. Finally, the efficiency of synergism depends on the specific AMF partners used and it is not related to their colonization levels.

the豆可以有效地与固氮细菌（NFB）和丛枝菌根真菌（AMF）形成三方共生关系，尽管选择合适的AMF种类和促进cow豆生长的根瘤菌菌株仍然是一个挑战。当前研究的目的是：1）评估of豆植物对共生NFB和多AMF接种物的反应，以及2）探索共生NFB与不同AMF分离株之间的任何相互作用。在盆栽的gnotobiotic试验中，将在有限氮供应条件下生长的cow豆植物接种或不接种共生固氮细菌melinotizomelium meliloti以及三种不同的AMF菌种：Dominikia disticha，Claroideoglomus etunicatum和不规则的根瘤菌。通过评估地上生物量，养分含量和AMF根定殖来确定实验评估。还通过克隆和测序确定了pea豆根上的AMF种类。与仅接种AMF相比，接种AMF和苜蓿链球菌导致cow豆生物量增加，但是阳性效果的存在取决于所使用的特定AMF配偶。单独接种AMF对cow豆的生长和P吸收有非常积极的影响，但是需要NFB接种来解决植物中的氮缺乏。两种共生菌的存在通常会导致the豆根的AMF定植增加，但是，当同时使用所有三个AMF接种物时，植物定植取决于AMF种类，甚至变为阴性。在苜蓿链霉菌（S. meliloti）存在下，植物根中的AMF组成也发生了变化。在两种共混物的存在下，to豆植物的氮含量均比单独使用AMF显着提高，而磷含量几乎不受双重接种的影响。结果表明，不同的AMF种类和S.meliloti具有积极的协同作用。接种所有AMF分离物和S. meliloti会导致地上生物量的高产和N的积累。S. meliloti的存在未接种AMF的植物中的P含量增加。最后，协同效应的效率取决于所使用的特定AMF合作伙伴，并且与他们的定居水平无关。