Indigenous plant growth-promoting rhizospheric and endophytic bacteria as liquid bioinoculants for growth of sweet pepper (Capsicum annuum L.)

Agrochemicals provide vital nutrients for plant growth to enhance crops yield, but they can pose major agro-environmental issues. Bioinoculants have attracted more and more attention due to their cost effective-eco-friendly and pollution-free characteristics. The aim of this study was to determine whether using a variety of bioinoculants that include both individual and group members could reduce the need for chemical fertilizer. In the modern era, individual and multiple strain formulation as bioinoculants and bacterial consortium is need of agricultural sustainability. A total 132 bacteria were sorted out from soil and internal tissues of the plant and screened for PGP characteristics including nitrogen fixer, phosphorus, and potassium solubilization. Among 132 bacteria, 13 were found to fix nitrogen, 17 and 14 bacteria were able to solubilize phosphorus, and potassium respectively. Efficient bacterial isolates were identified using 16S rRNA gene sequencing as Bacillus thuringiensis EU-CRP-15 (P-solubilizer), Bacillus horikoshii EU-CRK-18 (K-solubilizer), and Pseudomonas trivialis EU-CEN-2 (N-fixer). Inoculation of individual and consortium bioinoculants had a favorable effect on seed sprouting with the increase concentrations of inoculum. These three compatible and individual bacterial strains inoculated on sweet pepper enriched the growth and physiological characteristic of plant (plant length, root length, fresh weight, and biomass of the plant), and (chlorophyll, carotenoids, flavonoids, phenolics, and total soluble sugar content) over chemical fertilizers and untreated control plant. The plant growth promoting bacteria viz; N2-fixer as well as P and K solubilizers can be utilized as bioinoculants for the growth promotion of plants and increasing soil fertility.