Endophytic Bacillus strains enhance pearl millet growth and nutrient uptake under low-P.

tBacterial endophytes are considered to have a beneficial effect on host plants, improv-ing their growth by different mechanisms. The objective of this study was to investigatethe capacity of four endophytic Bacillus strains to solubilize iron phosphate (Fe-P), pro-duce siderophores and indole-acetic acid (IAA) in vitro, and to evaluate their plant growthpromotion ability in greenhouse conditions by inoculation into pearl millet cultivated ina P-deficient soils without P fertilization, with Araxá rock phosphate or soluble triplesuperphosphate. All strains solubilized Fe-P and three of them produced carboxylate-typesiderophores and high levels of IAA in the presence of tryptophan. Positive effect of inocu-lation of some of these strains on shoot and root dry weight and the N P K content of plantscultivated in soil with no P fertilization might result from the synergistic combination ofmultiple plant growth promoting (PGP) traits. Specifically, while B1923 enhanced shoot androot dry weight and root N P content of plants cultivated with no P added, B2084 and B2088strains showed positive performance on biomass production and accumulation of N P K inthe shoot, indicating that they have higher potential to be microbial biofertilizer candidatesfor commercial applications in the absence of fertilization