Effect of silver nanoparticles and *Bacillus cereus* LPR2 on the growth of *Zea mays*

The effect of Plant Growth Promoting Rhizobacteria (Bacillus sp.) and silver nanoparticles on Zea mays was evaluated. The silver nanoparticles were synthesized from Tagetes erecta (Marigold) leaf and flower extracts, whereas PGPR isolated from spinach rhizosphere. The silver nanoparticles (AgNPs) were purified using ultracentrifugation and characterized by UV-Vis spectroscopy and High Resolution Transmission Electron microscopy (HRTEM). The average particle size of AgNPs was approximately 60 nm. Almost all potential isolates produced indole acetic acid (IAA), ammonia and hydrogen cyanide (HCN), solubilized tricalcium phosphate and inhibited Macrophomina phaseolina in vitro, but isolate LPR2 was best. Based on 16S rRNA gene sequence, LPR2 was characterized as Bacillus cereus LPR2. Maize seeds bacterized with LPR2 and AgNPs individually showed a significant increase in germination (87.5%) followed by LPR2 + AgNPs (75%). Maximum root and shoot growth was observed in seeds coated with LPR2, followed by AgNPs and then the combination. Bacillus cereus LPR2 and silver nanoparticles enhanced plant growth and LPR2 strongly inhibited the deleterious fungal pathogen. Therefore, LPR2 and AgNPs could be utilized as bioinoculant and growth stimulator, respectively, for maize.