Purple-fleshed potatoes (PFP) are varieties of Solanum tuberosum L., which recently have been recorded to be more and more cultivated and consumed in all European countries, including Romania, as they are promoted for their content in bioactive compounds and benefits to human health. This paper presents a micropropagation protocol study for PFP varieties already traded into the Romanian market, namely Blue Danube (BD), Salad Blue (SB), Violet Negretin (VN), and Violet Queen (VQ). These varieties were tested for in vitro micropropagation also considering asepsis, initiation, callus formation, and microtuberization. To establish the optimum asepsis treatment, a preliminary experiment was performed and, the best results were obtained by using 70% EtOH (1 min) followed by 20% (v/v) Domestos^® (20 min). The MS formula (Murashige and Skoog 1962) was tested as the basic culture medium without growth regulators for all tested stages except for callus initiation and its further multiplication stages. The effect of glycine on direct organogenesis and shoot multiplication was evaluated for propagated micro-cuttings. We emphasize that the addition of glycine at a concentration of 15 mg/L to the culture medium induced a better plantlet vigor for all four varieties. Regarding the indirect organogenesis, culture medium supplemented with NAA (5.00 mg/L), GA₃ (1.00 mg/L), TDZ (1.00 mg/L) and glycine (15.00 mg/L) induced the best results for shoot cluster regeneration as well as turning of white callus from control to purple callus. Further, the microtuberization was successfully produced when sucrose was supplemented at 8% (w/v) into the culture medium. Among all four tested PFP varieties, SB has proven to give the best results regarding the adaptability for in vitro cultivation.

This research was designed to provide the first protocol to establish an efficient solution for direct organogenesis regeneration in Passiflora quadrangularis using nodal explants from young shoots. Passifloraceae tissue culture has been associated with problems such as recalcitrance, sensitivity to ethylene accumulation and browning of explants due to the presence of phenols in the tissues. Due to the high rate of endogenous contamination of the explants, a preliminary experiment was performed. The best results of surface sterilization were obtained using the pretreatment with 70% EtOH, 1 min and 50% NaOCl, 10 min along with the treatment of Rifampicin 15 µg/mL and Benomyl 2 g/L. The effects of plant growth regulators on the induction of direct organogenesis, multiplication of shoots in subcultures and in vitro rooting were evaluated. Additional compounds such as AgNO₃ and Pluronic F-68 were added to the culture media in order to reduce the effects of phenols and the sudden browning of the explants. Shoot proliferation increased to the sixth subculture after which it decreased. A maximum of 7.17 shoots were obtained from one shoot on Murashige and Skoog (MS) medium supplemented with 2 mg/L 6-benzylaminopurine and 1 mg/L thidiazuron. Supplementation of ½ MS medium with 1 mg/L 1-naphthaleneacetic acid was conducing to root formation in 61.11% of shoots. After acclimatization, the plants showed vigorous growth, green leaves, and well-developed roots. Although this species has previously shown difficulty in in vitro propagation, this protocol established based on the results proved to be efficient and reproducible.