Weed-Derived Endophytic Bacteria As Bioinoculants: Functional Characterization And Growth Enhancement In Vigna Unguiculata

Abstract

Endophytic bacteria from invasive weeds and non-crop plants are an untapped source of stress-tolerant, plant growth-promoting microbes. These typically non-pathogenic microbes inhabit healthy plant tissues and enhance plant development. The present study explores the plant growth-promoting potential of endophytic bacteria isolated from common weed plants—Eichhornia crassipes and Wedelia urticifolia—with a focus on their application as bioinoculants in cowpea (Vigna unguiculata) specifically the Pant Grain Cowpea-14 (PGCP-14) variety. A total of eleven bacterial isolates were screened under glasshouse conditions for their ability to enhance seedling vigor. Among them, three strains—ECR3, ECR4, and WUR5—exhibited significantly higher Seedling Vigor Index I and Seedling Vigor Index II compared to the untreated control and standard inputs like chemical fertilizers and farmyard manure. These strains were further subjected to molecular identification via 16S rRNA gene sequencing, revealing their identities as Paracoccusaestuarii (ECR3), Stenotrophomonas maltophilia (ECR4), and Bacillus paramycoides (WUR5). The selected isolates demonstrated various plant growth-promoting (PGP) traits including nitrogen fixation, solubilization of phosphate, potassium, and zinc, siderophore and phytohormone production, antifungal activity, and ACC deaminase activity. Notably, ParacoccusaestuariiECR3 was identified as the most effective strain based on its multifaceted PGP capabilities. This study highlights the untapped potential of weed-associated endophytes for sustainable agriculture, and suggests future exploration through advanced genomic tools such as Whole Genome Sequencing (WGS) for strain improvement and broader application.