Improving in vitro culture responses in passiflora ‘Possum Purple’ (Passiflora edulis Sims f. edulis)

Abstract

Micropropagation of Passiflora species remains challenging due to inherent morpho-physiological constraints, including limited regeneration capacity and poor adventitious root formation. Although the role of plant growth regulators has been extensively investigated, increasing attention has been directed toward the use of supplementary additives. In this study, the effects of 6-benzylaminopurine (BAP) combined with either silver nitrate (AgNO₃) or peptone were evaluated for shoot regeneration, growth, and proliferation in the cultivar ‘Possum Purple’. Rooting responses were subsequently assessed using different concentrations of indole-3-butyric acid (IBA) and naphthaleneacetic acid (NAA) under different pre-incubation conditions. In addition, the influence of substrate type on plantlet survival during the acclimatization phase was investigated. Nodal explants were cultured on full-strength MS medium during the initiation and multiplication phases, whereas half-strength MS medium was used for rooting. Shoot development and rooting performance were evaluated at defined culture intervals. Although AgNO₃ had no significant effect on shoot regeneration, it significantly reduced tissue browning, with the lowest browning observed at 17.7 µM AgNO₃. In contrast, the greatest shoot growth and proliferation during the multiplication phase were achieved on culture media supplemented with 8.88 µM BAP and 11.8 µM AgNO₃. Peptone provided only limited benefits for shoot regeneration and development, particularly in BAP-free media, and had no statistically significant effect on shoot multiplication. Rooting was maximized in microshoots cultured on medium containing 4.92 µM IBA following a 10-day dark pre-incubation. During acclimatization, the highest survival percentage (72%) was obtained in plantlets transferred to the Jiffy-7 substrate.