Establishment of in vitro regeneration system for leaves and petioles of Oxalis triangularis 'Purpurea'

To provide good acceptor materials for genetic transformation, the leaves and petioles of Oxalis triangularis 'Purpurea' were used as explants to establish a tissue culture system including callus induction, subculture, bulb induction, rooting, and transplanting of seedlings. The results showed that the best callus induction explants were petioles. When they were inoculated to MS + 1.00 mg<middle dot>L-1 6-BA + 0.50 mg<middle dot>L-1 NAA + 1.00 mg<middle dot>L-1 TDZ, granular callus induction rate was 53.33%. The optimal differentiation medium for the two different explants was MS + 1.00 mg<middle dot>L-1 6BA + 0.50 mg<middle dot>L-1 NAA. In this condition, petiole differentiation was 98.67% with an average differentiation coefficient of 11.19 in 45-d, and leaf differentiation was 97.38% with an average differentiation coefficient of 9.23 in 60-d. Four main types of healing tissues were produced during the induction of the two explants. The green granular callus and the green and purple loose callus were identified as embryonic callus. Villiform callus and green tight callus were identified as non-embryonic callus. The optimal subculture medium of embryonic callus was MS + 1.50 mg<middle dot>L-1 6-BA + 0.20 mg<middle dot>L-1 NAA. When moving the adventitious buds to rooting medium, the optimal medium was 1/2 MS + 0.30 mg<middle dot>L-1 NAA + 0.30 mg<middle dot>L-1 IBA. In this condition, for 60 d, the number of adventitious buds, average root length, and plant height were 28.16 per plant, 1.96 cm and 6.62 cm respectively. The germination rate of sterile bulbs was as high as 100% after transplanting for 30 d. Flower buds could be formed and flowered on the 45th day of transplanting. This result provides technical support for the artificial large-scale propagation of O. triangularis 'Purpurea'.