iA review on effect of plant growth regulators on in vitro multiplication of banana, bio-hardening and genetic assessment of micropropagated banana plantlets

Banana is a globally significant fruit crop and its large-scale cultivation increasingly relies on efficient micropropagation systems to produce disease-free, uniform and high-quality planting material. This review highlights major advancements in banana micropropagation, focusing on standardized protocols and recent improvements. The most reliable regeneration systems are based on shoot-tip and sucker-derived meristems due to their high morphogenic potential and reduced risk of somaclonal variation. Cytokinins such as BAP, kinetin and TDZ remain central to shoot induction and multiplication, while auxins like IBA and NAA are commonly used for rooting. Optimized PGR combinations have enhanced multiplication rates, minimized physiological disorders and improved plantlet vigor. Bio-hardening is a critical phase linking in vitro conditions to field environments. Gradual acclimatization through controlled humidity reduction, regulated light exposure and pathogen-free substrates is essential for successful survival. The incorporation of plant growth promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi and beneficial endophytes further enhances nutrient uptake, stress tolerance and field establishment of hardened plantlets. Substrate type, shading and irrigation management are key determinants of hardening success. Genetic stability assessment is vital for ensuring clonal fidelity in micropropagated banana. This review discusses the use of RAPD, ISSR, SSR, and AFLP markers to detect somaclonal variation. Among these, ISSR and SSR markers offer superior reproducibility and sensitivity. Studies consistently report high genetic uniformity in direct organogenesis systems, whereas callus-mediated regeneration and extended subculturing pose a greater risk of variation. Overall, integrating optimized micropropagation protocols, robust bio-hardening practices, and reliable molecular marker-based genetic stability analysis ensures the production of true-to-type, commercially viable banana planting material.