Conservação in vitro de cultivares de mandioca (Manihot esculenta Crantz)

Abstract

The establishment of in vitro genebanks is one of the strategies to be considered in the germplasm conservation of cassava (Manihot esculenta crantz). The objective of this work was to evaluate slow growing conditions considering the use of osmotic regulators. The work was carried out at Embrapa Cassava and Fruit Crops and two studies were performed using lateral and apical meristems from different cultivars of the cassava genebank. In the first study four cultivars, Olho Roxo (BGM 0036), Riqueza (BGM 0043), Cigana Preta (BGM 0116) and Isabel de Souza (BGM 0555) were used in order to evaluate the effect of different concentrations of sucrose (0, 10, 20, 40 and 80 g.L-1) on plants growth. The 8S was used as basal medium (MS salts + 1 mg.L-1 of Thiamine + 100 mg.L-1 of inositol + 0,01of NAA + 0,02 mg.L-1 of BAP + 0,1 mg.L-1 of GA3). The best results were obtained with 10 g.L-1 and 20 g.L-1 of sucrose considering all evaluated parameters. The use of 40 g.L-1 of sucrose induced the highest growth in most cultivars with the exception of Cigana Preta (BGM 0116). On the other hand, the cultivar Riqueza (BGM 0043) was more efficient to retain green leaves and could be conserved for 12 months. The second study was constituted by two experiments considering the use of two concentrations of sucrose (0 e 20 g.L-1) and three concentrations (0; 5 and 10 g.L-1) of manithol or sorbitol alone or in combination with sucrose. In both experiments the absence of sucrose hindered plant development. On the other hand, manithol caused a stronger reduction effect in comparison with sorbitol. The concentration of 10 g.L-1 from both sugars inhibited growing making evident that the hydric stress promoted was not tolerated by plants, therefore affecting their development. The best result was obtained with 20 g.L-1 of sucrose without manithol and sorbithol allowing the plants conservation for 12 months.