Embriões zigóticos de Coffea arabica L. criopreservados por encapsulation-dehydration e aclimatizados por hidroponia

Abstract

Coffee is one of the most popular beverages in the world, comprising the basis of economy for several tropical countries, including Brazil. Coffee production is mainly based on Coffea arabica species, preferred by consumers due to the quality of the drink. Given the importance of coffee to the world economy, it is essential that genetic resources are conserved in the long term. Considering that arabica coffee is propagated mainly by seeds and reproduction occurs predominantly by self-pollination, seeds or embryonic axes are ideal for conserving the genetic resources. In this context, the objective of this study was to establish a protocol for the cryopreservation of zygotic embryos of cultivars of Coffea arabica (IAC 62 and IAC 144) through the techniques of encapsulation-dehydration and encapsulation-vitrification. To start this process, the zygotic embryos were extracted from the seeds and encapsulated in a sodium alginate matrix and culture medium. In the encapsulation-dehydration technique, after pre-culture, the encapsulated zygotic embryos were dehydrated and immediately immersed in liquid nitrogen (-196 °C) or inoculated in a culture medium. For the encapsulation-vitrification technique, after pre-culture, the encapsulated zygotic embryos were immersed in Loading Solution and subsequently immersed in Plant vitrification solution 2 (PVS2) and immersed in liquid nitrogen or inoculated in culture medium. Evaluations were carried out regarding seedling length, weight, and number of leaves, anatomical and biochemical analyzes regarding the activities of antioxidant metabolism enzymes (SOD, POD, CAT and APX), quantification of hydrogen peroxide, lipid peroxidation and proline content. After the regeneration of the seedlings formed by the development of cryopreserved zygotic embryos, acclimatization was performed in a hydroponic system with substrate. The results indicated that the zygotic embryos were able to survive and regenerate after the cryopreservation process when dehydrated after 8 hours. Seedlings regenerated from cryopreserved zygotic embryos showed statistically similar growth to seedlings whose zygotic embryos were not cryopreserved. The anatomical evaluations showed a retraction in the volume of the fundamental meristem cells because of the dehydration process and the biochemical analyzes indicated a higher content of proline and activity of SOD and POD enzymes. Acclimatized plants originated from zygotic embryos that were cryopreserved reached the same phenotypics characteristics of plants whose embryos were not cryopreserved. Regarding the encapsulation-vitrification technique, the zygotic embryos were not able to survive the freezing process. Thus, it is concluded that it is possible to cryopreserve zygotic embryos of arabica coffee cultivars through the encapsulation-dehydration technique, considering that the moisture content is a key factor for the survival of the explants and that the acclimatization can be carried out through of the hydroponic system with substrate.