Efficacy of molecularly diversified phosphorus-solubilizing rhizobacterial isolates in phytostimulation, antimicrobial attributes and phosphorus-transporter genes mediated plant growth performance in maize ( Zea mays L.)

This study evaluated a dual management approach to enhance plant-growth by improving soil fertility, reducing pathogenic stress using PGPR that affect phosphorus-transporter (pht) genes. Among 213 maize rhizobacterial isolates, 40 demonstrated the ability to solubilize tri-calcium phosphate, potassium, zinc, and silicon, showing various PGP traits. Nine of these isolates exhibited significant antagonistic activity against the plant pathogens Colletotrichum chlorophyti and Xanthomonas axonopodis. These pathogens cause root infection, reduces plant- immunity and growth. In pot experiments, these nine strains significantly improved root length, shoot length, chlorophyll content, fresh weight, proline, APX, CAT, GR, NPK, and Zn content in maize plants after 60 days under pathogenic stress. Notably, PSB-25 increased root length by up to 66% under C. chlorophyti stress and 64% under X. axonopodis stress. PSB21 enhanced proline content by 49%, APX by 70%, and GR by 41%, while PSB-16 raised CAT activity by 55% under X. axonopodis stress. Molecular diversity analysis of the 40 PS-RB strains using ERIC, BOX, REP, and ARDRA showed two major clusters with Jaccard coefficients from 0.72 to 1.00. 16S rRNA gene sequencing identified PSB10, PSB16, and PSB25 as Serratia sp., Enterobacter cloacae, and Enterobacter sp., respectively. The effects of PSB10, PSB16, and PSB25 on growth parameters under pathogen stress were also studied. Field trials indicated that treatment T6 (100% RDF + PSB16) was most effective in promoting plant growth. Additionally, significant differences in the expression of six Pht1 transporter genes were noted between PS-RB treated and untreated maize seedlings, and these genes improving phosphorus acquisition.