Clonagem in vitro de híbridos de pimenteira-do-reino (Piper nigrum L.)

Abstract

The black pepper plant (Piper nigrum L.) produces a fruit of great worldwide value in the field of spices. The commercial propagation method is by cuttings, with low seedling production of plant/year. However, it is possible to have a great number of quality seedlings in a short period through micropropagation. In this process, among the factors that affect the in vitro morphogenesis, the cytokinins must be highlighted because of their influence on bud differentiation and on bud growth. Therefore, the aim of this work was to study the effect of different cytokinins combinations ( 6 - benzylaminopurine and thiadizuron) in the culture medium over the in vitro multiplication of intra- and interspecific black pepper hybrids, and the interaction cytokinin x hybrids, in five subculturings. The basal MS medium (MURASHIGE E SKOOG, 1962) was applied, with 30 g.L' sucrose, solidified with 2 g.L' Phytagel and supplemented with combinations of 0.5 mg.L' BAP and 0.0 or 0.25 uM TDZ. The culturing was conducted under controlled conditions of the growth room, for six weeks per subculture, and each of them was evaluated by the number of buds and shoots per explant, and by the shoots length. Data were statistically analyzed. The results showed that in the absence of TDZ, BAP induced a greater number of buds and shoots per explant in the majority of subcultures, having promoted the shoot formation of greater length and generally with normal morpho-physiological characteristics. The hybrids presented different responses in in vitro shoot differentiation, suggesting a genotypic influence. The successive subcultures reduced the multiplication capacity of the genotypes. The 12 MS medium containing only 0.5 mg.L' BAP is favorable to the differentiation and multiplication of black pepper shoots and there is varied response between genotypes.

The process of adventitious rooting of in vitro cultivated plants is a technique that has been applied in the vegetative propagation of several species. Many factors are related to rooting phase, having a positive and/or negative influence on the micropropagation establishing protocols, and are directly related to the steps of acclimatization and formation of seedlings. The aim of this work was to evaluate the response of intra and interspecific black pepper hybrids as for the induction of in vitro rooting by added auxins (IAA, IBA and NAA) to the 14 MS culture medium, and to evaluate the survival rate of rooted shoots in the steps of acclimatization and seedling formation. At the rooting phase, indoleacetic acid (IAA), naphthaleneacetic acid (NAA) and indolebutyric acid (IBA) were added to the culture medium at concentrations of 1.0; 1.5; 2.5 uM and zero auxin (control). Acclimatization was conducted in a plant nursery, with plastic trays containing vermiculite and being added 10 ml of nutritive solution per plant at every l15-day period. After 28 days, the plants were transferred to plastic bags containing a seedling formation substrate. After 28 days in the rooting substrate, the higher rooting percentages were obtained at 1.5uM IAA, being 100% for all hybrids. The acclimatization for 28 days with the vermiculite substrate yielded higher survival rates for plants that came from the 5 MS medium with IAA. At the formation phase of seedlings with soil as substrate, the plants presented 100% survival. Therefore, for the higher survival rate and formation of seedlings, it is recommended the rooting of shoots in basal medium of 1º MS and the adding of 1.54J,MIAA.