Cryopreservation of zygotic embryos of syringe (<i>Hevea brasiliensis</i>) containing reserve fabric

Abstract

The conservation of recalcitrant rubber seeds is not very durable when compared to species that have orthodox seeds. Thus, the preservation of the species occurs especially in the field in the form of the entire plant, which requires a lot of physical space. Biotechnology, through the technique of cryopreservation, can be an auxiliary tool in maintaining the viability of seeds during their storage. Thus, the objective of this work was to evaluate the viability of rubber tree zygotic embryos, containing the reserve tissue, submitted to different forms of vitrification, followed by conservation through cryopreservation. To carry out the research, rubber seeds, produced in the state of São Paulo, were used. First, different forms of vitrification of the zygotic embryos containing the reserve tissue were studied. The embryos were evaluated immediately after vitrification and after seven days of storage in liquid nitrogen at a temperature of -196 ºC. The evaluations carried out were: determination of the water content, viability of the embryos by the tetrazolium test, in vitro germination and electrical conductivity. The results were analyzed in a completely randomized design, in a 2x5 factorial scheme, the first factor being the time of assessment (before and after cryopreservation) and the second factor, the forms of vitrification. It is concluded that it is necessary to test a longer period of exposure of embryos in the vitrification solutions, especially in the solutions that presented better results of viability and germination (solutions: • 50% glycerol; • 30% (w/v) glycerol, 15% (w/v) ethylene glycol, 15% (w/v) dimethyl sulfoxide (DMSO) and 0.4 M sucrose; and • 2 M glycerol followed by PVS). In addition, a higher level of dehydration of the embryos, which the species can support, must be analyzed, so that they can be exposed to cryopreservation.