Abstract
The region around the plant root referred to as the rhizosphere, is the zone where various microbial activity occurs. It performs crucial functions such as increasing the uptake of nutrients for plant development and preventing plant against plant pathogens. Keeping in mind the beneficial role performed by rhizospheric microorganisms, rhizobacterial species were isolated from the maize and soybean plant's rhizosphere. The isolated microorganisms were evaluated for their biochemical characteristics, plant growth-promoting potentials, tolerance to different environmental conditions, and their antifungal activity against Fusarium graminearum, a fungal pathogen that infects maize. The rhizobacterial isolates with multiple plant growth-promoting potentials were identified as Bacillus spp (80.77%), Rhodocyclaceae bacterium (3.85%), Enterococcus spp (3.85%). Massilia spp (3.85%. and Pseudomonas (7.69%) species based on their 16S rRNA molecular characterization. The bacterial isolates possessed antifungal activities against Fusarium graminearum, promote maize and soybeans seed under laboratory conditions, and exhibited different levels of tolerance to pH, temperature, salt, and heavy metal. Based on this, the whole genome sequencing of Bacillus sp. OA1, Pseudomonas rhizosphaerea OA2, and Pseudomonas sp. OA3 was performed using Miseq Illumina system to determine the functional genes and secondary metabolites responsible for their plant growth-promoting potential Thus, the result of this research revealed that the selected bacterial isolates possess plant growth-promoting potentials that can make them a potential candidate to be employed as microbial inoculants for protecting plants against phytopathogens, environmental stress and increasing plant growth and productivity.
Highlights
The rhizosphere is a region in the soil near the plant root, it is an interface between the soil and plant roots (Fasusi et al 2021)
It can be described as a home for plant roots where it is colonized by an enormous number of microbial species such as bacteria which are influenced by the organic compound that are present in the plant root, which is of great economic importance in promoting plant growth (Odelade and Babalola 2019)
This results in the release of organic matter via the soil, which promotes the activities of microorganisms like bacteria in the plant root region, which could be beneficial to enhance plant growth (Gouda et al 2018)
Summary
The rhizosphere is a region in the soil near the plant root, it is an interface between the soil and plant roots (Fasusi et al 2021). The plant rhizosphere consists of numerous PGPR species such as Bacillus Azospirillum, Klebsiella, and Paenibacillus azotofixans., Pseudomonas, Rhizobium, Azotobacter Acinetobacter, and Bacillus, which are recognized for their potential to stimulate plant growth (Goswami et al 2016) These PGPR species possess plant growth-promoting potentials that stimulate native plant growth, yield, and defense through different mechanisms such as phytohormones production indole-3-acetic acid (IAA) production (Asari et al 2017), Phosphate solubilization (Majeed et al 2015), production of hydrogen cyanide to suppress the deleterious effect of plant pathogens, production of metabolites, production of siderophore which promotes the uptake of iron and nutrient from the environment and making it available for plant growth through the root system, production of lytic enzyme and antimicrobial compounds (Kejela et al 2016) or production of the fungicidal compound, competitive with plant pathogens and enhancing plant tolerance to biotic and abiotic stress like metal, temperature, water, and salinity (Tewari and Arora 2013; Zolla et al 2013). The mechanisms of promoting plant growth and defense by these rhizobacteria could be direct or indirect
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