Biopolymer-Based Biopriming Strategy with Trichoderma virens to Enhance Cowpea (Vigna unguiculata) Establishment

Biopriming cowpea (Vigna unguiculata) seeds with beneficial fungi and biopolymer matrices offer a sustainable strategy to enhance crop establishment in smallholder agriculture. This study evaluated four biopolymers—sodium alginate (SA), guar gum (GG), arabic gum (AG), and maltodextrin (MAL)—as film-coating delivery systems for Trichoderma virens. We assessed biopolymer-bioagent compatibility, optimal imbibition kinetics, conidium loading efficiency via scanning electron microscopy (SEM), early seedling growth promotion, and inoculant survival over 30 days of cold storage. Results indicated that while all matrices preserved seed viability, their efficacy varied significantly. SA demonstrated the highest initial conidia entrapment capacity and provided superior protection of the conidia throughout storage, maintaining peak fungal viability and 100% seed germination. Conversely, AG exhibited a stimulatory effect on seedling development, resulting in the highest total plant and radicle elongation compared to unformulated T. virens and the untreated control. Microstructural analysis confirmed that matrix architecture directly dictates conidia binding and distribution. In conclusion, biopolymer-based seed coatings significantly modulate the biopriming efficacy of T. virens. Selecting an optimal carrier requires balancing physical loading efficiency and shelf-life viability with plant growth-promoting activity (AG) for sustainable crop management.