Credibility assessment of endophytic PGPB on iron and zinc biofortification, soil health, and yield in three different varieties of soybean

Endophytic microorganisms within plant tissues offer immense potential to enhance plant growth. Present study investigates the efficacy of endophytic microorganisms in promoting soybean growth and biofortification, with a focus on zinc and iron assimilation. The two most promising zinc-solubilizing and siderophore-producing endophytes, PLSD1 and PLSD6, were selected for detailed analysis. These strains were assessed for a range of plant growth-promoting traits, including phosphorus and potassium solubilization, nitrogen fixation, HCN, ammonia, EPS production, biofilm formation, indole acetic acid, gibberellic acid synthesis, and biocontrol against fungal pathogens. Strain PLSD1 excelled in solubilizing zinc oxide (14.14 ± 0.25µg/ml) as measured by AAS, while PLSD6 showed strong siderophore production (67.52 ± 2.45%). GC-MS analysis identified gluconic acid as predominant organic acid during zinc solubilization. Morphological, biochemical tests, and 16SrDNA sequencing identified PLSD6 as Pantoea ananatis and PLSD1 as Pseudomonas protegens . Pot trials with soybean varieties Pant soybean 26, Pant soybean 25, and Pant soybean 1347 revealed significant enhancements in plant height, dry matter, nodules, pods, seed yield, and harvest index due to bacterial and it consortium treatments. Additionally, these treatments improved soybean biochemical attributes, such as chlorophyll, carotenoids, nitrate reductase activity, and leghemoglobin content. Soil quality parameters, including pH, EC, organic carbon, NPK levels, and enzymatic activity, also improved under bacterial treatments. Soybeans treated with bacterial consortia exhibited the highest zinc (27.2 ± 0.566 mg/gm) and iron (33.05 ± 0.295 mg/gm) content in grains. These results underscore the potential of bacterial endophytes to significantly enhance soybean growth and zinc and iron biofortification, contributing to sustainable agricultural productivity and food security.