Micropropagação e formação de microjardim clonal de Bambusa vulgaris Schrad. ex J. C. Wendl.

Abstract

Bamboos are cosmopolitan species of great importance based on its rapid growth, adaptability and wide variety of uses. However, they are challenging species for seed propagation, which makes vegetative propagation an alternative for the supply of plants. Micropropagation is applied to bamboos by allowing the production of large-scale clonal seedlings, small genetic variations and also promoting tissue rejuvenation. However, the technique application to certain species presents limitations, such as the contamination by endophytic microorganisms that may reduce in vitro establishment, which may compromise the process sanity. Asepsis techniques, time of tissues collection and matrices origins are factors that can reduce this contamination. However, some procedures may affect the propagules development and provide somaclonal variations. In this sense, this study sought a micropropagation protocol of Bambusa vulgaris in order to form a clonal microgarden. In the introduction phase, the influence of the monthly climatic conditions of propagules collection (April, May, July, September, October, November, January, February and March) and sites of material origin (A1- field, A2- vessels stored in a greenhouse and A3- shade house) was evaluated on contamination and establishment. In the next stage the explants that were submitted to a period of elongation were rooted ex vitro in mini-incubators, evaluating the influence of three culture media (M1- WPM, M2- MS and M3-water + agar) supplemented with growth regulators and antibiotic. Subsequently the individuals were submitted to acclimatization in the shade house and then transferred to a semi-hydroponic system where they formed a clonal microgarden. To verify the protocol efficacy, genetic fidelity analyzes were carried out using ISSR molecular markers and histological analyzes were made to observe the formation of adventitious roots. About 21.86% of the explants were established and there was no interaction between the origin and collection factors. The rooting percentage observed was 36.6% and no interaction was observed between the use of culture medium and the antibiotic use. However, treatment using MS culture medium in the absence of antibiotic resulted higher rooting than the others (80%). The micropropagated individuals presented adequate growth and adaptation to ex vitro conditions. Molecular analyzes were performed using 13 primers, however only 10 presented adequate amplification. These primers allowed the visualization of 39 discernible bands, all monomorphic bands, indicating the absence of genetic variations. To verify the adventitious roots formation were made cross sections that allowed to observe the direct rhizogenic formation occurring from meristematic cells and in the absence of callogenic cells, which allows inferring in a normal root formation. At the end of the experiment it was possible to form a clonal microgarden of Bambusa vulgaris, that show the viability of the technique tested.