Criopreservação de germoplasma de cana-de-açúcar

• Autor(a) principal: Melo, Cristiane Gamarano de
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4691
• topic: Criopreservação; Germoplasma; Gema apical; Cryopreservation; Germplasm; Shoot tip gems; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA::MELHORAMENTO VEGETAL

This study was carried out to develop some protocols for cryopreservation of sugarcane germplasm in liquid nitrogen at -196°C. The exposure time of the shoot tips encapsulated in the laminar flow chamber for obtaining the moisture contents of 30, 20 and 10% was determined in an assay. The results were analyzed and interpreted, by using the free R software. The medium points of each time under evaluation were united by straight line segments, as drawing a tendency line for the moisture loss. Then, with the aid of horizontal lines referring to moisture contents of 30, 20 and 10%, the drying times were directly identified in the graph at 5.7; 7.45 and 10.1 hours, respectively. To induce the tolerance of the shoot tips to drying process, the preculture was accomplished in liquid culture medium enriched with 0.3; 0.5 and 0.75M sucrose for one and two days. The entirely randomized experimental design was used under a factorial scheme 3X2X4 (sucrose concentrations, preculture time and drying time) with three replicates. The survival index data were analyzed and interpreted, by using the free R software. The variance analysis was performed and the averages were compared by the Tukey test at 5% significance, when necessary. According to the results, the following conclusions were drawn: independently of the preculture time to be one or two days, the preculture in the culture medium enriched with 0.3M sucrose was ideal to induce the tolerance of the tissues to drying; the shoot tips were sensitive to the concentration of 0.75M sucrose in the preculture solution. The 12h culture of the shoot tips in the basic culture medium resulted into reactivation of their metabolism through accumulation of the starch grain, besides the recovery of the stress generated by its extraction. The intensity of the starch synthesis was increased, when the shoot tips were precultured in the liquid culture medium containing sucrose at concentrations 0.30; 0.50 and 0.75M. In the cryopreservation of the encapsulated shoot tips, the effect of the sucrose concentration, drying time and defrosting method were studied under a factorial 3X4X3 (three sucrose concentrations, four drying times and three defrosting methods). Independently of the combination adopted when the shoot tips were cryopreserved, a null survival index was obtained. The histological analyses revealed that both cells and cellular walls of the cryopreserved explants were severely damaged.