Micropropagação e diversidade genética em genótipos de palma forrageira

Abstract

Conventional forage palm planting has limitations that hinder its propagation and breeding programs. The application of tissue culture techniques through multiplication systems, semi-solid (SS) and temporary immersion bioreactors (BIT's) is an efficient alternative to ensure rapid plant multiplication. These may also contribute to genetic divergence studies. The objective of this study was to apply tissue culture techniques to the in vitro propagation of eleven forage palm genotypes, evaluating the efficiency of multiplication, semi-solid and BIT´s systems. And also evaluate the best system in genetic divergence studies. To evaluate the efficiency of the multiplication systems, the treatments were arranged in an 11 x 2 factorial scheme through a completely randomized design, combining eleven palm genotypes with two micropropagation methods (Semisolid and BIT), totaling 22 treatments with five replications each. After 30 days the following variables were evaluated: cladode length (CM), cladode diameter (DM), fresh mass (MF) and dry mass (MS). Joint variance analysis (p <0,05) was performed and, when significant, means were compared by the Scott-Knott grouping of means (p <0,05) There was a significant interaction between the multiplication systems and genotypes for all traits evaluated, with the bioreactor culture being the most responsive. Genotypes respond differently depending on genus, species and growing environment. To perform the divergence studies, the BIT multiplication system was selected, due to the best responses found in genotype propagation. Phenotypic data expressed at this stage were used as morphological markers. To evaluate the potential for estimating dissimilarity between genotypes, its effect was compared with RAPDtype molecular markers. Dissimilarity based on molecular markers was estimated using the Jaccard Index. The morphological characteristics were analyzed individually by the Scott-Knott grouping test (p <0,05). and together for dissimilarity by Euclidean distance. Individual dendrograms were obtained for each analysis using the UPGMA method. A tanglegram was generated to illustrate the similarities between the associations of the two dendrograms. Based on the morphological characterization, it was possible to obtain two distinct groups. Morphological similarity was observed between pairs of genotypes of different genera. Molecular investigation allowed differentiating genotypes at genus and species level, discriminating those considered morphologically similar. The comparison between morphological and molecular data revealed divergences and similarities. However it was possible through the morphological data obtained via BIT´s, to quantify the level of divergence and similarity between genotypes. In general, the BIT´s multiplication system was more responsive in the propagation of forage palm genotypes and the phenotypic data expressed in this phase of multiplication were applicable in genetic divergence studies.