Aplicação da galactomanana de sementes de Adenanthera pavonina L. como substituta parcial do Ágar em meios para o cultivo in vitro de tecidos e órgãos vegetais

Abstract

Plant tissue culture, which has several commercial applications, is the set of methodologies that permit the cultivation of cells, tissues, organs or parts of plant organs (explant) in a nutritious medium. The semi-solid culture medium, beyond various nutrients to the plant, needs a gelling agent, being agar the most used of them, however it’s expensive. Systems formulated by mixtures of polysaccharides (blends) may result in gels of great interest. This study aimed to evaluate the technical and economic feasibility of the use of galactomannan (Gm) of Adenanthera pavonina L. seeds as agar partial substituent in in vitro culture media of plants, using soy-perennial (Glycine wightii) as model. The endosperm (crude gum) were isolated, freeze-dried and crushed for subsequent extraction of Gm's. To evaluate the gelling potential of Gm's, different treatments (T) using blends of Agar+Gm were tested (Control: 1% + 0%; T1: 0% + 1%, T2: 0.9% + 0.1% Q3: 0.7% + 0.3%; Q4: 0.5% + 0.5%; T5: 0.3% + 0.7%). The blends were analyzed according to some qualitative, rheological and diffusion parameter. The effect of the blends in the development of callus coming from micropopagation of hypocotyl and cotyledon explants of G. wightii on MS medium, as well as in vitro germination and seedling development of this species. The yield of crude gum from the seeds of A. pavonina was

approximately 87%, and the yield of Gm extracted from the crude gum was 92%. In the qualitative analysis of the medium’s characteristics, T2, T3 and T4 have the best results, with good solidification, and good homogeneity and transparency similar to the control. The study of rheological parameters revealed that the best interactions, in terms of gel strength, occurred in the means T2, T3 and T4, which were similar to the control, demonstrating a synergistic effect due to the strong and efficient interaction between the agar and GM's. T3 and T4 mediums used in the diffusion assay showed that T4 had the highest diffusion, compared to T3 and control. Both cotlyledon and hypocotyl callus of G. wightii grown in the medium T3 showed a growth pattern similar to that of control. T4 medium was superior to T3 and Control, possibly influenced by the greater amount of Gm, which may have been used as a carbon source for the culture. The percentages of seed germination, growth rate and size of G. wightii seedlings in T3 and T4 media were significantly higher than control, indicating that the presence of Gm's in media can influence positively the germination. From an economic point of view, to be easily extracted from a plant widely distributed in the country and provide an excellent yield (~ 90%), the Gm of A. pavonina seeds may be a promising component in the partial replacement of the agar used in the tissue culture mediuns, providing a economy of 50% per kg of used agar.