Tolerância aos estresses salino e térmico em cultivares de taro e mandioca tuberizadas in vitro

• Autor(a) principal: Fogaça, Cláudia Martellet
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1366
• topic: Minituberização in vitro; Estresse salino e térmico; Atividade de enzima; Micro tuberization in vitro; Salt and thermal stresses; Enzyme activity; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA::MELHORAMENTO VEGETAL

Tuberization is a complex process of the plant development, influenced by genetic, environmental and physiological factors, characterized by changes in the plant anatomy, hormones and biochemistry. Thus the tuberization in vitro, in addition to promote fast vegetative propagation, clean plants from diseases, conservation and exchange of germoplasms, is an excellent experimental tool for the study and control of tuber formation. With the goal to induce the micro tuberization in vitro, cultivars of cassava and taro were grown with different conditions, containing BAP and ANA, and rates of sucrose (3%, 6% and 8% w/v) with differentiated light regime. It was analyzed the length of aerial portion (CPA), number of roots (NR), diameter of the rhizomes (DR), pattern of the micro tubers development and anatomical changes. Based on results, it was verified that both taro and cassava respond to tuberization in vitro. The cultivar of taro Japonês showed the best response to the induction of micro rhizomes, in particular for the treatment containing 22.2 µM BAP and 8% sucrose. For the cassava, the cultivar Parasinha had better formation of tuber roots with 0.4 µM BAP, 1.6 µM ANA and 8% sucrose, in both semi solid and liquid growth media. The length of aerial portion, length of the longest root and number of roots were better in the cultivar of cassava Mantiqueira, but the induction of tuber roots was recalcitrant. Anatomically, the micro tubers were characterized by the presence of starch grains in both micro rhizomes and tuber roots of taro and cassava respectively. In order to study the effect of salt and low temperature in vitro grown cultivars of taro and cassava in MS medium containing different concentrations of salt (0, 50, 75 and 100 mmol L-1 NaCl) or grown at different temperatures (5, 10 and 25oC), for seven days. It was measured the level of ethylene at 5, 20 and 40 days under the salt stress and at 3 and 7 for the thermal stress. Also, it was determined the activity of oxidative enzymes (POD, PPO and CAT), presence of isozymes and morphological changes during the stresses. The addition of NaCl in the growth media induced oxidative stress, characterized by the increase in the activity of POD and CAT, and elevated concentration of ethylene in cassava. In the liquid media, the NaCl increased the production of ethylene and higher activity of CATin the cultivar Parasinha; it was evident, the differences in tolerance to the stresses among the cultivars of cassava and taro. The low temperature, in cassava, also increased the activity of POD and CAT, with differences in the different tissues, accompanied by elevated ethylene production. In taro it was detected two isozymes for POD and PPO in the rhizomes, with one POD and two PPO in the aerial portion. For the roots system, in cassava, it was identified two isozymes for POD and one for PPO.