Journal of Applied Biology and Biotechnology

Fungal endophytes are beneficial plant counterparts and potent producers of bioactive plant growth-promoting metabolites. This study focuses on the isolation and screening of fungal endophytes with strong plant growth-promoting activities from the ethnomedicinal plant Coleus forskohlii (Willd.), Briq., collected from West Bengal, India, and characterization of the cell-free culture extracts. Out of the 13 major isolates, Diaporthe osmanthi COFS1 is the most effective producer of Indole acetic acid (31.72 ± 0.04 μg ml^-1), and also synthesized ammonia, siderophore, and solubilized phosphate (31.40 ± 0.28 μg ml^-1). The Indole-3-acetic acid production was confirmed by UV-VIS, TLC, FTIR, gas chromatography-mass spectrometry, HRMS, and H¹-nuclear magnetic resonance analyses. Gas chromatography-mass spectrometry analysis revealed putative PGP metabolites, including phenylethyl alcohol, 1-methylene-1H-indene, Indole-3-acetic acid, tryptophol, Indole-6-carboxaldehyde, and 2H-1-Benzopyran-2-one. The maximum IAA production was observed in Czapek Dox Broth (CDB) amended with 0.5 mg ml^-1 of L-tryptophan, pH 6.5, 30 g l^-1 sucrose, on the seventh day of the incubation period. The plant growth-promoting effects of fungal metabolites on the in vivo growth of Triticum aestivum L was evaluated. The application of 50% fungal extract resulted in a significant increase in the overall growth attributes compared with the uninoculated control plants, indicating its potential as a strong plant growth promoter.