Nitrogen fixation is an important biological process in terrestrial ecosystems and for global crop production. Legume nodulation and N 2 fixation have been improved using nodule-enhancing rhizobacteria (NER) under both regular and stressed conditions. The positive effect of NER on legume-rhizobia symbiosis can be facilitated by plant growth-promoting (PGP) mechanisms, some of which remain to be identified. NER that produce aminocyclopropane-1carboxylic acid deaminase and indole acetic acid enhance the legume-rhizobia symbiosis through (i) enhancing the nodule induction, (ii) improving the competitiveness of rhizobia for nodulation, (iii) prolonging functional nodules by suppressing nodule senescence and (iv) upregulating genes associated with legume-rhizobia symbiosis. The means by which these processes enhance the legume-rhizobia symbiosis is the focus of this review. A better understanding of the mechanisms by which PGP rhizobacteria operate, and how they can be altered, will provide opportunities to enhance legume-rhizobial interactions, to provide new advances in plant growth promotion and N 2 fixation. Highlights • ACC deaminase and IAA synthesis enhance nodule formation. • ACC deaminase and IAA synthesis improve the competitiveness of rhizobia for nodule induction. • IAA synthesis enhances N 2 fixation by upregulating the expression of genes associated with legume-rhizobia symbioses. • ACC deaminase prolongs nodule function by delaying nodule senescence. • ACC deaminase can reduce the negative influence of very high IAA on nodule induction.

No abstract

No abstract

No abstract

No abstract