Isolation and characterization of Plant growth-promoting hormones by an endophytic bacterium, Curtobacterium. citreum AVN2 isolated from the rhizome of Curcuma longa L

Endophytic bacteria have become essential in promoting plant growth and development, and provide resistance against phytopathogens through diverse biochemical mechanisms. This study isolated an endophytic bacterium, AVN2, from Curcuma longa's rhizome and identified it as () using 16S rRNA partial gene sequencing. C. citreum AVN2 was deposited in NCBI with accession number PQ215941. The strain exhibited significant antagonistic activity against . Sp. , a major causative agent of tomato wilt, in a dual culture assay, and is confirmed as a biocontrol agent by GC-MS analysis of its secondary metabolites, Lupeol, 2-Piperidinone, Stigmastan-3,5-diene, Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl)-, 5-Pyrrolidino-2-pyrrolidone, Diethyl Phthalate, Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro-. Plant growth-promoting characterization revealed the production of important growth-promoting phytohormones, including indole compounds (6.40 µg/mL), gibberellic acids (29.49 µg/mL), and cytokinins (Kinetin 15.49 µg/mL, and 6-Benzyladenosine 27.78 µg/mL), which were quantified by HPLC analysis. Seed bacterization with . bioformulation enhanced the seed vigour index of tomato seeds compared to the control. Bio-formulated AVN2 significantly enhanced root and shoot growth, and overall biomass under greenhouse conditions, demonstrating biocontrol efficacy and plant growth-promotion (PGP) potential. This study presents the first evidence of as an endophyte in , exhibiting dual biofertilizer and bioprotectant properties. These findings underscore its promise as a sustainable, eco-friendly alternative to chemical fertilizers and fungicides in horticultural crop production.