Laboratory scale evaluation of coco peat-plant growth promoting rhizobacteria formulations for plant growth under water stress condition

This research studied the efficacy of a biofertilizer formulation (plant growth promoting rhizobacteria (PGPR) encapsulated in coco peat) on growth enhancement of Zea mays (maize) under water stress condition. Rhizobacteria were isolated and screened for plant growth promoting (PGP) traits; Indole-3-acetic acid (IAA) production, phosphate solubilization, and 1-aminocyclopropane-1-carboxylate deaminase (acds) gene. Rhizobacteria were further tested for PGP activity via seed germination bioassay, and species with superior growth performance were further used for formulation. Formulations were prepared by homogenizing 20 mL of each PGPR standardized inoculum with 2 g of oven-dried coco peat. PGP potential of the formulations were evaluated in a pot experiment by measuring vegetative growth parameters (plant height, shoot length and root length) of the treated maize seeds weekly, for 14 days. Water stress was simulated by no watering of maize plants during the period of pot experiment. Ten rhizobacteria were isolated; two tested positive for IAA production and phosphate solubilization. Four rhizobacteria expressed superior growth performance during the seed germination bioassay and were identified by biochemical tests and 16 s rRNA sequencing as Priestia flexa, Klebsiella variicola, Actinomyces griseus and Staphylococcus sp. Coco peat-Priestia flexa and Coco peat-Staphylococcus sp. treatments sustained maize growth beyond Day 14. However, Paired t-test statistical analysis showed the differences between vegetative growth of treated maize seeds and the control were not significant (P > 0.05). Polymerase chain reaction revealed Priestia flexa and Klebsiella variicola possessed the (acds) gene. This study projects the potential of coco peat-PGPR formulations in mitigating water stress and enhancing growth in maize plants.