Identification of Mancozeb-Tolerant and Phosphate-Solubilizing Fungal Bioagents for the Management of Fusarium Wilt of Chilli

Fusarium wilt, caused by Fusarium solani , is a destructive soil-borne disease of chilli ( Capsicum annuum L.) that causes yield losses ranging from 10 to 80% under favorable conditions. The present study, conducted during 2020–2022, aimed to isolate mancozeb-tolerant fungal bioagents and evaluate their efficacy for the integrated management of Fusarium wilt of chilli. Agricultural soil patches were pre-treated with mancozeb to facilitate the isolation of fungicide-tolerant antagonists using Trichoderma -selective medium. A total of 104 fungal isolates were recovered and screened for mancozeb tolerance, antagonistic activity, and phosphate-solubilizing ability. Among them, isolate SHO-13 exhibited the highest radial growth (35 mm) on mancozeb-amended medium, followed by WG-4 (33 mm), indicating high fungicide tolerance. In dual culture assays, SHO-13 showed the greatest inhibition of F. solani mycelial growth (84.97%), closely followed by WG-4 (84.34%). Both isolates also demonstrated efficient phosphate-solubilizing activity. Under in vivo conditions, seedling treatment with SHO-13 in combination with mancozeb significantly reduced Fusarium wilt incidence (5.50%) and markedly improved plant growth parameters, including plant height, biomass, and fruit yield, compared with untreated and fungicide-alone treatments. Based on morphological characteristics and ITS rDNA sequence analysis, isolate SHO-13 was identified as Trichoderma virens , and its ITS sequence was deposited in the NCBI GenBank database under accession number ON740648. The results demonstrate that the integration of mancozeb with the fungicide-tolerant, phosphate-solubilizing bioagent T. virens (SHO-13) provides an effective and environmentally sustainable strategy for the management of Fusarium wilt while promoting plant growth and soil health in chilli cultivation.