Exploring the Plant Growth Promoting and Antifungal Potential of Endophytic and Rhizospheric fungi isolated from Litchi chinensis Sonn.: Metabolite profiling and Molecular characterization

The unique characteristics of Tezpur litchi varieties in terms of their size, quality, taste and relatively small seed size helped to recognize the Geographical Indication (GI) in 2014. The present study aimed to investigate the endophytic and rhizospheric fungal communities associated with Tezpur litchi (var. Bilati) for their plant growth-promoting (PGP) and biocontrol potential. Fungal isolates were evaluated for indole-3-acetic acid (IAA) production, phosphate solubilization activity (PSA), and antagonistic activity against the phytopathogen Alternaria alternata (MTCC 3880). The isolated fungi were found belonging to the genera Aspergillus , Colletotrichum , Fusarium , Penicillium , and Mycelia sterilia . Promising results were obtained for IAA production, with the highest values recorded at 179.25 ± 3 µg ml⁻¹ and 143.13 ± 3 µg ml⁻¹ by soil isolate SF32 and endophytic isolate BE23, respectively. All isolates exhibited varying degrees of PSA, with the highest value (3.44 ± 0.04 SI) observed in endophytic isolate LE07. Antifungal activity screening revealed significant inhibition of A. alternata by endophytic isolate BE14 (41.9 ± 1.4 mm zone of inhibition) and soil isolate SF32 (29.4 ± 0.8 mm). Subsequent molecular identification 18S ITS rDNA sequencing confirmed BE14 and SF32 as Penicillium citrinum and Aspergillus aculeatus , respectively. This study reports the association of P. citrinum in litchi and identifies the potential antifungal properties. Fourier transform infrared (FTIR) analysis of the crude metabolite from P. citrinum revealed the presence of various functional groups, including alcohols, alkanes, and aromatic compounds. Gas chromatography-mass spectrometry (GC-MS) analysis tentatively identified four major compounds: Succinic-acid-2,4,6-trichlorophenyl-3-methylbut-3-en-1-yl-ester, 1,5-but(3-cyclopentylpropoy)-1,1,3,3,5,5-hexamethyltrisiloxane, Hexamethyl-cyclotrisiloxane and Tris(tert-butyldimethylsilyloy)arsane. These findings suggest the presence of potentially bioactive metabolites with antifungal properties in P. citrinum . In conclusion, this study highlights the diverse fungal communities associated with Tezpur litchi and identifies potential candidates for promoting plant growth and managing fungal diseases through eco-friendly approaches. Further investigations are warranted to elucidate the specific mechanisms underlying the observed PGP and biocontrol activities of these promising fungal isolates.