Enhancement of sprouting and rooting of Quercus pubescens by benzylaminopurine and Indole-butyric acid in micropropagation

Abstract

Micropropagation has the advantage of genetic homogeneity and reduces difficulties related to obtaining pathogen-free plant material. However, some plant species present challenging problems when used for in vitro culture. This research work dealt with the micropropagation of Quercus pubescens Willd. with the aim of enhancing the percentage proliferation and rooting from micro-cuttings. Microcuttings, containing apical or axillary buds, were taken from two year-old branches using a clone of Q. pubescens grown at the Forest Nursery of Sant’Angelo in Vado, Pesaro-Urbino, Marche, Italy. A preliminary screening of the proliferation was performed using increasing concentration of benzylaminopurine (BA) in the culture medium (0.25; 0.5; 0.75; 1 mg/l) in order to select the best hormones to use in the experiment. From the results it was possible to deduce that BA plays a key role in influencing shoot proliferation, leading to the formation of a callus and to the production of new shoots. Moreover, we observed that, especially higher BA concentrations promoted the production of a larger number of shorter shoots compared to low concentrations, that produced the small number of longer shoots. Furthermore, these trials have shown that, in order to have a large number of seedlings with an optimal shoot length, it is necessary to divide the process of propagation in two phases. The first phase involves a high concentration of BA, with the aim of increasing the number of new micro-cuttings; the second phase, with lower levels of BA, to increase the length of the shoots. With regards to root induction, the hormone selected was indole-butyric acid (IBA). Results showed that micro-cutting exposed for 24h to higher hormone concentration gave the best results for root induction and root length. The study developed an efficient method for the micropropagation of Q. pubescens for the selection of genotypes in vitro and sterile (e.g., free microorganisms and insects) conditions. It is envisaged that the development of this protocol paves the way for further utilisation of micro-propagated Q. pubescens in new areas of research, such as in vitro mycorrhization.