Eco-friendly enhancement of potato micropropagation using bacterial-derived IAA from Kocuria rosea

Indole-3-acetic acid (IAA), a key phytohormone widely synthesized by soil bacteria, plays a vital role in root development and stress resilience. This study aimed to optimize the culture conditions for IAA production by Kocuria rosea SS1 and to evaluate the efficacy of bacterial derived IAA on the micropropagation of potato (Solanum tuberosum L. cv. Spunta). Maximum IAA production (10.83 mg 100 mL^- 1, as quantified by HPLC) was achieved in nutrient broth at pH 7 and 30 °C, supplemented with 1 mM tryptophan and incubated under shaking conditions for three days. Filter-sterilized bacterial supernatant containing IAA (0.0-1.0 mgL^- 1) was incorporated into Murashige and Skoog (MS) medium and compared to commercial IAA in potato tissue culture. After 28 days, plantlets treated with bacterial IAA, particularly at 0.25 mgL^- 1; showed significant enhancements in fresh weight (1.5-fold), roots number (69.9%), leaves number (100%) and shoot length (50%) compared to the control, outperforming equivalent doses of synthetic IAA. Biochemical analyses revealed increased levels of total sugars, chlorophylls, carotenoids, and endogenous IAA and gibberellins. These findings demonstrate that the bacterial supernatant serves as a potent, eco-friendly biostimulant that enhances the growth and biochemical quality of in vitro-propagated potato plantlets, offering a sustainable alternative to synthetic growth regulators.