The Synergistic Interaction Between BAP and GA3 Eradicates Hyperhydricity and Enhances Biomass in Solanum tuberosum L. cv. ‘Superchola’ In Vitro Plantlets

The mass propagation of pre-basic seed potatoes (Solanum tuberosum L.) is frequently bottlenecked by the physiological degradation of in vitro plantlets, largely driven by cytokinin oversaturation. This study evaluated the morphogenic and physiological effects of the synergistic interaction between 6-Benzylaminopurine (BAP) and Gibberellic Acid (GA3) on the Andean cultivar ‘Superchola’. Using a completely randomized 3 × 3 factorial design, nodal segments were cultured on Murashige and Skoog (MS) medium supplemented with BAP (0.5, 1.0, 2.0 mg/L) and GA3 (0.0, 0.1, 0.25 mg/L) for 28 days. The results demonstrated that while moderate BAP concentrations (1.0 mg/L) maximized the absolute shoot multiplication rate, they simultaneously induced severe hyperhydricity (71.2%) and basal callogenesis (80.0%) when GA3 was deficient. Conversely, a strict synergistic interaction comprising 2.0 mg/L BAP and 0.1 mg/L GA3 completely eradicated hyperhydricity (0.0%), restricted callogenesis (5.0%), and yielded plantlets with the highest Morphological Vigor Index (81.2% elite classification). Furthermore, this specific hormonal balance maximized structural dry biomass accumulation (95 mg/explant) and normalized the fresh-to-dry weight ratio, proving the elimination of deceptive water retention. These findings confirm that an optimum BAP/GA3 combination is critical to suppressing physiological disorders during the in vitro multiplication phase.