Co-application of Biogenic Selenium Nanoparticles and Rhizobacteria Improves Growth, Physiology, and Biochemical Characteristics of Lettuce

Abstract

Sustainable agriculture requires the inventive strategies that should be adopted to intensify crop production and stress resistance while minimizing the environmental impact. Plant growth-promoting bacteria (PGPB) and biogenic selenium nanoparticles (SeNPs) have each demonstrated the potential to enhance plant performance individually. Their combined effects on crop physiology and biochemistry, however, are yet unexplored. Twenty selenium (Se)-resistant Gram-positive bacterial strains were obtained from soil of agricultural fields and screened for the major PGP characteristics including nitrogen fixation, phosphate solubilization, and the production of phytohormones. Selective strains were employed to inoculate Lactuca sativa (lettuce) seeds. Treatment involved bacterial inoculation only, foliar SeNPs application, and combination of both. Growth factors (root length, leaf length, fresh weight), pigment content (chlorophyll a, b, carotenoids), protein content, and peroxidase activity were taken after 6 weeks under semi-field conditions. Combined application of chosen bacterial strains and SeNPs considerably promoted lettuce growth and stress-related biochemical reactions. NB11 + SeNP combination treatment displayed enhanced soluble protein levels by 75% and peroxidase activity by 65% against control (p ≤ 0.05). Heat map visualization validated strong positive correlations among enhanced growth and biochemical characters under combined treatments. PCA showed that the initial three principal components accounted for 77.1% of total variance with evident clustering of combined treatments showing significant multivariate improvement in plant performance. Synergistic application of SeNPs and Se-resistant PGPB is a promising method for enhancing plant growth, stress resistance, and nutritional content. This bio-based system facilitates sustainable crop management and provides a substitute for chemical fertilizers, particularly in stress-susceptible agricultural ecosystems.