Efficient Micropropagation by Ex Vitro Rooting of Myrtus communis L.

This survey aims to develop a successful protocol through in vitro multiplication and ex vitro rooting of a native shrub, i.e., Myrtus communis L., in order to obtain the rapid production of large number of healthy plants. The in vitro proliferation showed how the two different genotypes (MR and MB) produced higher values in terms of shoot lengths, mean multiplication index (MMI) and number of nodes when treated with 6-benzylaminopurine (BAP) compared to the thidiazuron (TDZ) + 1-naphthalene acetic acid (NAA) combination. Concerning in vitro rooting, the experiment resulted in a high rooting rate (75%) and an average number of roots (5.13) by quickly dipping the basal portions in an indole-3-butyric acid (IBA) concentration of 3300 mg L−1, followed by transfer to a hormone-free growth medium (BM). In comparison, the other two concentrations tested (0.3 and 0.6 mg L−1) resulted in higher root length values. During the acclimatization phase, the study showed how the different treatments affected the development of the test shoots differently. In particular, shoots of both genotypes pre-treated by quickly dipping them in Clonex® to induce ex vitro rooting showed abundant root production only 10 days after the treatment compared to the in vitro rooting, in which roots were formed after 30 days. This suggests that ex vitro pre-treatment with Clonex® not only accelerates the rooting process compared to in vitro treatment, resulting in lower costs and easier processing, but also significantly increases root density, contributing to improved transplant success and plantlets quality. These results support the thesis that ex vitro rooting optimises plant propagation protocols, offering economic and practical advantages for nurseries and other propagation systems.