Adventitious shoot regeneration from in vitro cultured leaf explants of peach rootstock Guardian® is significantly enhanced by silver thiosulfate

Establishment of a stable and efficient in vitro regeneration system from leaf explants is a basic requirement for success in genetic transformation of peach. In this study, approximately 900 leaf explants of ‘Guardian®’ peach genotype were separated from in vitro shoots and cultured for shoot regeneration on ½ MS medium with different doses and combinations of thidiazuron (TDZ) and silver thiosulphate (STS). The results showed that callus bud formation and shoot regeneration occurred 4 and 6 weeks after culture initiation, respectively. All the regenerated shoots were from petioles of the leaf explants. Regeneration rates were significantly affected by different combinations of TDZ and STS (P < 0.05). Separation of means by Tukey test method revealed that on half strength MS media, high regeneration rates were obtained from the combinations of 6.81 µM TDZ + 10 µM STS, and of 9.08 µM TDZ + 10 µM STS (16 and 14 %, respectively). The number of shoots per regenerating explants was also significantly affected by growth regulator concentrations. The highest shoot number was obtained with the combination of 6.81 µM TDZ + 10 µM STS. Rooting percentage varied from 85 to 100 % depending on plant growth regulator used. On half strength MS medium containing 1.0 mg/l of IBA, an average of 7 roots per regenerating shoot was produced. The rooted plantlets were successfully acclimatized with 92 % survival rate under greenhouse conditions. This established regeneration system from leaf explants would facilitate the development of reliable peach genetic transformation procedures, helping accelerate peach genetic improvement using biotechnology approaches.