Native Bacillus and Trichoderma Strains from Vietnamese Soils: A Dual-Function Bioinoculant for Lignocellulosic Waste Valorization and Sustainable Biocontrol in Brassica juncea

Abstract

Agricultural residues rich in cellulose remain underutilized, while soil-borne pathogens continue to threaten crop productivity. This study isolated and characterized native Bacillus and Trichoderma strains from Vietnamese soils to evaluate their cellulolytic capacity, antifungal potential and effects on mustard greens (Brassica juncea). Bacillus isolates were identified by 16S rRNA sequencing whereas Trichoderma strains were distinguished based on morphological and microscopic traits. Cellulase activity was assessed on carboxymethyl cellulose agar and antagonism against Neoscytalidium dimidiatum. Pythium sp. was tested through dual-culture assays. Among the isolates, Bacillus amyloliquefaciens and Trichoderma harzianum exhibited the strongest cellulolytic activity and fungal inhibition. Greenhouse trials further demonstrated that inoculation with these strains, individually or in combination, enhanced plant biomass and reduced disease symptoms under pathogen challenge. The results highlight the dual role of indigenous microbial inoculants in valorizing lignocellulosic waste and providing eco-friendly biocontrol. Such dual-function inoculants offer a sustainable alternative to chemical fungicides while promoting circular resource use in Vietnamese vegetable production systems.