Physiological response of maize plants and its rhizospheric microbiome under the influence of potential bioinoculants and nanochitosan

Background and aims Agriculture production is necessary to ensure food security for overgrowing human population. Chemical manures are extensively used in agriculture practices to increase the crop production, but they have adverse effect on soil fertility by decreasing the beneficial microorganisms which play an important role in maintenance of plant growth and soil health. Scientists have been focusing on other substitute to overcome these problems. Positive impact of agricultural friendly nanocompounds and rhizospheric bacteria are well known for assisting plant growth and maintaining microbial population residing in the soil system. Targeted and controlled release of nutrients and biocontrol efficacy provided by nanocompound is of great interest. However, ameliorative assessment of nanocompound and bioinoculants on crop plants and their effect on microbial population were checked by few. In this perspective, impact of nanochitosan (40 mg L-1) and bioinoculants (Pseudomonas taiwanensis and Pantoea agglomerans) on the Zea mays plant health parameters and soil quality were analyzed. Methods Effect of nanochitosan along with bioinoculants were evaluated on the plant health parameters and bacterial population of maize rhizosphere in a pot experiment. Agronomical and biochemical parameters such as plant height, chlorophyll, total carotenoid, protein and flavonoid content were evaluated after 30 days of the experiment. Antioxidant enzyme activities such as catalase and peroxidase of maize plant leaves were also assessed. Soil health was evaluated using physicochemical analysis, total bacterial count, phosphorus and potassium solubilizing bacteria and soil indicator enzymes such as dehydrogenase, fluorescein diacetate and alkaline phosphatase activities. Bacterial diversity of soil samples were targeted through hypervariable (V3-V4) region of 16S rRNA using metagenomic approach. Results Maize seeds bacterized with bioinoculants along with nanochitosan showed enhanced in plant height (54%), leaves number (67.18%), photosynthetic pigments (65.62%), sugar (79.13%), protein (71.93%), phenol (136.57%) and flavonoid content (167.61%) over control. Higher antioxidant enzyme activity such as catalase (80.15%) and peroxidase (25.52%) depict induction of stress tolerating mechanism in plants under the influence of nanochitosan. Our study revealed that physiochemical soil parameters, total bacterial count (101%), phosphate (111%) and potassium solubilizers (94.44%) were significantly enhanced in treated soil over control. Soil enzyme activities such as dehydrogenase (94.88%), fluorescein diacetate (112%) and alkaline phosphatase (32.09%) were significantly (P < 0.05) higher in combined treatment of bioinoculants and nanochitosan. Metagenomics study equally supported the overall positive influence of nanochitosan on the bacterial population. Most abundant bacterial genera were: Proteobacteria, Actinobacteria, Chloroflexi and Firmicutes in treated sample indicating abundance of beneficial plant growth promoting rhizobacteria. Few microbial communities were invariably observed in both samples. The study reported that application of nanochitosan along with bioinoculants consortium supported plant growth promoting bacteria which involved in nutrient assimilation and various growth stimulating activities. Conclusion Obtained results convincingly establish a positive consequence of nanochitosan and bioinoculants on maize agronomical parameters and soil health by improving the nutrient status, bacterial population and soil enzyme activities. This approach can be used in agriculture field to boost the beneficial microbial population which improved the crop yield and sustain the soil fertility.

Automated summary

This study analyzed the impact of nanochitosan and bioinoculants on maize plants and soil health. The results showed that the use of nanochitosan and bioinoculants improved plant health parameters and soil quality, including increased plant height, photosynthetic pigments, and bacterial population in the soil.