Silver nanoparticles enhance the in vitro plant regeneration via thin cell layer culture system in purple passion fruit

Key messageEfficient shoot regeneration was observed for thin cell layer explants of ex vitro leaves and internodes.Differences in endogenous hormones at different internode locations significantly influenced shoot induction.Somatic embryogenesis was first recorded from internode explants of Passiflora edulis Sims f. edulis and this process was significantly enhanced by silver nanoparticles. The current in vitro plant regeneration of purple passion fruit is mainly based on shoot organogenesis. In particular, thin cell layer (TCL) technology has emerged as a powerful technique for shoot organogenesis from many in vitro explant sources of purple passion fruit. This study further optimized the in vitro plant regeneration from ex vitro explant sources (leaves and internodes) via TCL technology combined with the addition of AgNPs on the culture medium. For leaf TCL explants, the results showed that the optimal shoot induction rate (96.30%) and the highest number of shoots (4.33 shoots/explant) were recorded on MS medium supplemented with 1.0 mg L- 1 BA and 1.5 mg L- 1 AgNPs. For internode TCL explants, different internode positions had a significant effect on shoot induction from tTCL explants. After 60 days of culture, the optimal shoot induction rate (70.37%) was observed in the tTCL explants at the 3rd internode from the shoot tip. This study also revealed that the difference in endogenous hormones at different internode positions was one of the significant factors affecting shoot induction from TCL explants. On the other hand, the results indicated that the shoot regeneration coefficient in lTCL was significantly higher than in tTCL. In addition, somatic embryogenesis was recorded for the first time in internode tTCL explants (22.45%). The addition of 3.0 mg L- 1 AgNPs significantly enhanced the proliferation and maturation of somatic embryos derived from internode tTCL explants. The present study contributes to a significant improvement in the micropropagation efficiency of purple passion fruit.