Efficient plant regeneration through direct shoot organogenesis of Oxalis vulcanicola 'Sunset Velvet'

Oxalis vulcanicola 'Sunset Velvet', a cultivar of Oxalidaceae, is a perennial dicot known for its compact growth, vibrant foliage, and attractive flowers, making it a popular choice for ornamental potted plants. Despite its ornamental value and physiological significance, significant challenges remain in gene function validation and genetic transformation due to the lack of a well-established regeneration system. This study aimed to establish an effective tissue culture system for O. vulcanicola 'Sunset Velvet' to facilitate genetic transformation and large-scale propagation. Sterile stem segments with buds were used as explants, and a direct shoot organogenesis pathway was employed to initiate the culture system. Optimization of hormone combinations led to the selection of suitable induction, proliferation, and rooting media. The most effective disinfection protocol was a 2-min treatment with 75% ethanol, followed by a 15-min treatment with 3% sodium hypochlorite. The optimal medium for inducing multiple shoot formation consisted of MS + 0.50 mg·L⁻¹ NAA + 1.00 mg·L⁻¹ 6-BA + 30 g·L⁻¹ sucrose + 5 g·L⁻¹ agar, achieving an induction rate of 74.45 ± 6.94% and the longest shoot length of 0.99 ± 0.34 cm after 30 d of culture. For shoot proliferation, MS + 0.50 mg·L⁻¹ NAA + 1.00 mg·L⁻¹ 6-BA + 30 g·L⁻¹ sucrose + 5 g·L⁻¹ agar achieved a multiplication rate of 20.32 ± 0.54-fold, with a browning rate of 18.65 ± 0.32%. When 0.01 mg·L⁻¹ IBA was added to the medium, the multiplication rate decreased slightly to 17.39 ± 0.70-fold with the browning rate reduced to 10.21 ± 0.33%. For rooting, the best medium was 1/2 MS + 0.10 mg·L⁻¹ NAA + 30 g·L⁻¹ sucrose + 5 g·L⁻¹ agar, resulting in an average of 14.10 roots per plant, with an average root length of 2.73 ± 0.15 cm and plant height of 4.26 ± 0.05 cm, starting from stem segments with an initial height of 3 cm. These findings provide important technical support for the large-scale propagation and genetic transformation of O. vulcanicola 'Sunset Velvet'.