GH1 and infection: This might be due to the IAA produced by the two yeast isolates, and also the solubilized P. On the one hand, IAA is a plant growth hormone that has been reported to improve and promote nodule formation and enhance N2-fixation in legumes [44,45], induce physiological changes in bacteria such as increased biomass and exopolysaccharide production, as well as infection effectiveness and symbiotic behavior in soybean plants [46].