Calogênese e indução de gemas axilares em mogno (Swietenia Macrophylla King)

Abstract

Resumo: brotacoes adventicias e axilares in vitro de mogno. Segmentos de epicotilos foram inoculados em meio MS com 0,25; 0,5 e 1,0 ƒÊM de BAP e 0,1; 0,25; 0,5; 1,0 e 1,25 ƒÊM de TDZ, ambos com 0,5 ƒÊM de ANA, e controle sem regulador. Segmentos foliares foram cultivados em meio MS contendo 0,5; 0,75 ou 1,0 ƒÊM de TDZ, sob irradiancia de 0,73 ƒÊmol.m-2.s-1 (penumbra); 0,75 ƒÊM de TDZ, sob irradiancia de 0,73 e 37 ƒÊmol.m-2.s-1 e 1,11; 2,22; 4,44 e 8,88 ƒÊM de BAP com 0,1 ƒÊM de ANA na penumbra, e em meio controle sem regulador. Para regeneracao de brotacoes adventicias, calos de epicotilos cultivados em meio MS com 1,0 ƒÊM de TDZ foram transferidos para o mesmo meio com 1,11; 2,22; 4,44 ou 8,88 ƒÊM de BAP na penumbra e controle sem regulador. Foram avaliadas porcentagem de formacao, oxidacao, consistencia e coloracao dos calos e formacao de brotacoes adventicias. Calos de diferentes consistencias e coloracoes foram obtidos. Os calos de epicotilos cultivados na presenca de 1,0 ƒÊM de BAP eram compactos (76,4%) e, com 1,0 ƒÊM de TDZ, friaveis (91,5%). Em explantes foliares, os melhores resultados de calogenese foram obtidos com 0,75 ƒÊM de TDZ na penumbra, onde 90% dos explantes formaram calos e 77,8% eram friaveis. Com 4,44 ƒÊM de BAP e 0,1 ƒÊM de ANA, a porcentagem de explantes formando calos foi de 93,3%, todos friaveis. Houve formacao de 3,33% de gemas adventicias no meio contendo 2,22 ƒÊM de BAP. Para multiplicacao de gemas axilares, foram utilizados segmentos nodais de plantulas germinadas in vitro, inoculados em meio MS contendo 2,5 ƒÊM de BAP combinada com varias concentracoes de CIN (0,25; 0,50; 1,0; 1,5 e 2,0 ƒÊM) e controle sem regulador. Em outro experimento, foram utilizados meios MS e SH com 2,5 ƒÊM de BAP e 2,2 ƒÊM de 2-iP com diferentes concentracoes de CaCl2 (MS: 220, 440 e 880 mg.L-1, SH: 100, 200 e 400 mg.L-1) e um tratamento sem CaCl2. Foram avaliados numero, massa fresca e porcentagem de oxidacao dos brotos. No primeiro experimento, nos meios contendo varias concentracoes de CIN combinada a BAP, houve intensa oxidacao em 90% dos explantes e 10% formaram brotacoes pouco vigorosas, impossibilitando o subcultivo. No experimento com os meios MS e SH, houve diferencas significativas para o numero de brotos, massa fresca das brotacoes e numero de folhas. Sintomas de clorose foliar foram observados nas maiores concentracoes de CaCl2. Em conclusao, intensa calogenese foi obtida em ambos os tipos de explantes, na presenca de difeentes concentracoes de TDZ ou BAP, combinadas ou nao com ANA; a regeneracao de gemas adventicias foi muito baixa. Houve a formacao de calos somente na penumbra. Apesar do elevado numero de brotos axilares obtidos nos tratamentos com CaCl2, estes, quando subcultivados em mesmo meio de origem, sofreram intensa oxidacao, impossibilitando o subcultivo. Portanto, nao foi possivel estabelecer um metodo eficiente de multiplicacao de brotacoes axilares.

Abstract: The aim of this work was to establish methods of adventitious and axillary shoot regeneration for mahogany. Epicotyl fragments were inoculated in MS medium supplemented with 0, 0.25, 0.5 and 1.0 ìM BAP and 0.1, 0.25, 0.5, 1.0 and 1.25 ìM TDZ, both along with 0.5 ìM NAA and a control without growth regulators. Leaves were cultivated in MS medium with 0, 0.5, 0.75 and 1.0 ìM TDZ under an irradiance of 0.73 ìmol m-2.s-1, 0.75 ìM TDZ under an irradiance of 0.73 and 37 ìmol m-2.s-1 and 0, 1.11, 2.22, 4.44 and 8.88 ìM BAP with 0.1 ìM NAA under an irradiance of 0,73 ìmol m-2.s-1. In order to regenerate adventitious shoots, callus originated from epicotyl explants, initially cultivated in 1.0 ìM TDZ, were transferred to medium supplemented with 0, 1.11, 2.22, 4.44 and 8.88 ìM BAP. Incidence of callus, its consistency and color, and also the number of adventitious shoots formed were recorded after 30 days of culture. In the experiments of axillary shoot formation, the number of shoots, their weight, levels of oxidation and contamination were evaluated. In all experiments, except in shoot regeneration, statistically significant differences were reached. Different consistencies and colors of callus were reached. Most of the calluses from epicotyl segments cultivated with 1.0 ìM BAP were compact (76.4%) and with 1.0 ìM TDZ most of them were friable (91.5%). The best results were obtained with 0.75 ìM TDZ under low light irradiance, 90% of production of callus, of which 77.8% were friable. With 4.44 ìM BAP and 0.1 ìM NAA the percentage of friable callus was 93.3%. Two adventitious buds were obtained (3.33%) with 2.22 ìM BAP. For induction of axillary shoots, nodal segments from in vitro cultivated plants were inoculated in MS medium with 2.5 ìM BAP combined with the following concentrations of KIN: 0.25, 0.50, 1.0, 1.5 and 2.0 ìM. In another experiment, MS and SH media were used with 2.5 ìM BAP and 2.2 ìM 2-iP with modification of CaCl2 concentrations: 0, 0.5x, 1x and 2x that of normal medium concentrations. In the first experiment with several concentrations of KIN in combination with BAP there was an intense oxidation in 90% of the explants. Only 10% of them produced weak shoots which did not permit any subculture. In the experiment with MS and SH media, when CaCl2 was twice the normal concentration, there was a higher number of shoots (6.8 in SH and 7.8 in MS) and higher weight of shoots (1.27g in SH and 1.63g in MS) than in the other concentrations. When shoots were subcultured in the same media they suffered intense oxidation that did not allow their subculture. In conclusion, callogenesis was reached in both kinds of explants in some TDZ or BAP concentrations, combined or not with ANA. Calluses were formed only in the shadow. Leaf chlorosis symptoms were observed in high concentrations of CaCl2. Despite the great number of axillary shoots obtained in CaCl2 treatments, when they were subcultured in the same medium they suffered intense oxidation that did not allow their subculture. Thus it was impossible to establish an efficient method of axillary shoot multiplication.