Use of Thidiazuron for High-Frequency Callus Induction and Organogenesis of Wild Strawberry (Fragaria vesca)

Abstract

Strawberry, belonging to the Fragaria genus, is an important crop that produces popular fruits globally. F. vesca, known as wild strawberry, has great characteristics, such as a robust and powerful aroma, making it an important germplasm resource. The present study aims to establish an efficient regeneration method for the in vitro propagation of F. vesca. Firstly, leaf explants were used to induce callus formation on a Murashige and Skoog medium with combinations of cytokinins (thidiazuron (TDZ) and 6-benzylaminopurine (BA)) and auxin (2,4-dichlorophenoxyacetic acid (2,4-D)). Among them, 0.45–4.54 µM TDZ combined with 0.45–4.53 µM 2.4-D exhibited a high induction rate after 4 weeks of culturing. Different explants were examined for their ability to form a callus, and whole leaves on the medium containing 2.27 µM TDZ and 2.27 µM 2,4-D showed the highest callus induction rate at 100% after 2 weeks of culturing in darkness. The highest shoot regeneration ability through organogenesis from the callus was obtained at 0.44 µM BA. After 2 weeks of culturing, the shoot regeneration rate and shoot number per explant were 96% and 19.4 shoots on an average, respectively. Rooting of shoots was achieved using indole-3-butyric acid (IBA) or an α-naphthaleneacetic acid (NAA)-containing medium, and the resulting plantlets were acclimatized successfully and formed flowers eventually. In this report, we demonstrated that shoot organogenesis was derived from the meristematic cells of calli and by transferring the induced calli to a 0.44 µM BA medium, the regeneration period can be shortened greatly. A protocol for the efficient regeneration of wild strawberry was established, which might be useful for their large-scale propagation or obtaining transgenic plants in the future.