Molecular identification and functional characterization of rhizosphere bacteria for growth and yield optimization of maize (Zea mays)
Author(s):
Mohd Salman Khan and Mohammad Saghir Khan
Abstract:
The excessive and indiscriminate use of agrochemicals to enhance crop production has been shown to negatively impact microbial diversity and functionality, the soil-plant ecosystems, and human health. Microbiological strategies decrease reliance on chemical agents and alleviate risks to both environmental integrity and human health. This study was performed to isolate and characterize plant-beneficial bacteria found in the rhizospheres of maize, as well as to assess their impact on the growth performance of maize. Cultures were characterized through morphological and biochemical assays. From these, two optimal cultures designated AZ1 and PS1, were selected for further investigation into their plant-beneficial traits. In comparison, AZ1 demonstrated superior production levels of IAA (207 μg ml-1), siderophores +(21.51 μg ml-1), and phosphate solubilization (16 mm). Furthermore, both cultures exhibited positive qualitative traits for hydrogen cyanide and ammonia production. Later identified by 16S rRNA gene sequencing as A. chrocooccum (AZ1) and Pseudomonas fluorescens (PS1). Respectively. Subsequently, in a two-year study, maize plants co-inoculated with A. chrocooccum and P. fluorescens (T8) exhibited the highest total chlorophyll content (7.5 mg/g), whole plant length (230 cm/plant), total dry biomass 92.2 g/plant, grain yield (139.7 g/plant), and protein content (112.8 mg/g) during the second cropping season (2023). Ultimately, scanning electron microscopy (SEM) reveals significant bacterial colonization in the root rhizosphere of maize, thereby supporting the beneficial effects of bioinoculants. The findings indicate that A. chrocooccum and P. fluorescens, which display a range of plant growth-promoting activities, have the potential to be formulated into composite bioinoculants to enhance maize production while concurrently minimizing fertilizer usage.