In-Vitro Screening of Antagonistic Bioagents Trichoderma and Bacillus against Fusarium oxysporum f. sp. lycopersici

Abstract

Fusarium wilt of tomato, caused by Fusarium oxysporum f.sp. lycopersici (Fol), poses a serious threat to tomato cultivation worldwide. The present study focused on the isolation, characterization, and evaluation of native antagonistic microbes—Trichoderma spp. and Bacillus spp.—for their biocontrol potential against Fol under in vitro conditions. Ten Trichoderma isolates and ten Bacillus isolates were obtained from rhizosphere soils of healthy tomato plants across Tamil Nadu and characterized morphologically, biochemically, and molecularly. Dual culture assays and poisoned food technique revealed significant variation in antagonistic efficiency among isolates. Among fungi, Trichoderma asperellum Ta-02 exhibited the highest inhibition of Fol growth (73.43% in dual culture; 100% in poisoned food assay). Among bacteria, Bacillus subtilis Bs-06 recorded the highest suppression (70.56% in dual culture; 98% in poisoned food assay). ITS and 16S rRNA sequencing confirmed the identity of selected potent isolates, and sequences were submitted to GenBank (e.g., PV242065.1 for Ta-02 and OR985767.1 for Bs-06). The study highlights the promise of indigenous Trichoderma and Bacillus strains as eco-friendly alternatives to chemical fungicides for the sustainable management of tomato wilt.