Factors Influencing in Vitro Organogenesis of Chrysanthemum morifolium cv.  Resomee Splendid'

Chrysanthemum; also commonly known as mums or chrysanths, is one of the most important ornamental crops worldwide. Introducing desirable traits into this valuable plant by the conventional breeding has so far been faced with some restrictions due to the limited gene pool and cross-incompatibility. Therefore, breeders have decided to exploit Agrobacterium-mediated transformation methods in order to satisfy the growing market demands. However, more efficient in vitro regeneration protocols are required for this approach.
The objective of this research was to develop an efficient protocol for an in vitro plant regeneration by the examining the effects of various combinations and concentrations of the plant growth regulators (PGRs) and different explants types.
The leaf and petiole explants of the Chrysanthemum morifolium cv. ‘Resomee Splendid’ were collected from the in vitro grown plantlets. Murashige and Skooge (MS) medium was supplemented with different concentrations and combinations of benzylaminopurine (BAP), 1-naphthaleneacetic acid (NAA) and thidiazuron (TDZ). Thereafter, the effects of these hormonal treatments were investigated on shoot initiation percentage, the average number of shoots per explants, callogenesis, and the type of organogenesis in regard to both types of the explants.
Shoots were directly formed from leaf explants on the media that only contained BAP without callus formation. Amongst the other hormonal treatments, a combination of 4.5 mg.L-1 BAP plus 1 mg.L-1 NAA resulted in the direct organogenesis from the leaf explants, which was superior to the other combinations and concentrations. In regard to the petiole explants, direct shoot formation occurred in all the media except for the ones which were fortified with TDZ. In this case, considering the shoot initiation percentage and the mean shoot number per explants, the best results were achieved in the medium supplemented with 1.5 mg.L-1 BAP and 1 mg.L-1 NAA. Results showed that interaction of either BAP or TDZ with NAA was necessary for the callus induction.
Significant differences in shoot initiation percentage and the average number of shoots per explants were observed both in leaves and petioles grown on different media. Moreover, the callogenesis rates, as well as organogenesis types, showed some differences among the studied explants when compared on the same media.