This study investigates the effects on the in vitro microtuber formations of Solanum tuberosum L. cv. Marfona species, effected by the direction of planting the explants (horizontal or vertical), the type of medium (solid or two-phase), adding Jasmonic acid (JA) (0.0, 10 ng/L, 1 µg/L and 0.2 mg/L) and Gibberellic acid (GA3) (0.0 and 0.2 mg/L). The cultures were incubated in a climate chamber at 22-25 oC, and were subjected to a light intensity of 145 µmol m-2 s-1 for 8 hours in light and 16 hours in dark photoperiods (short day) for 4-6 weeks. Microtuber production was inhibited when GA3 was added. The maximum number of microtubers was observed when the explants were planted vertically and were grown in two-phase medium which did not contain GA3 and had 10 ng/L JA present. It was determined that two-phase medium with 0.2 mg/L JA but without GA3 was the most favourable medium for tuber growth (for both height and width). The best microtuber formation on single node explants were observed to occur in the short day photoperiod (8 hours light/16 hours dark) in a two-phase medium that contained 0.2 mg/L JA without the addition of GA3. The results shows that the effect caused by JA works antagonistically with that of GA3 thus causing the resulting microtuber formation observed.