Studies on the feasibility of cryopreservation of Coffea sp. species

Abstract

To guarantee the long-term sustainability of coffee growing, genetic diversity must be preserved. However, seeds of the Coffea sp genus have low longevity when preserved ex-situ, putting the existing genetic variability at risk. Cryopreservation is an alternative that has been widely researched for species that produce intermediate and recalcitrant seeds, and for Coffea arabica, a safe cryopreservation protocol for seed storage is already known. The main objective of this work was to explore new techniques used during cryopreservation and to understand the behavior of the Coffea arabica species during the process, to obtain a safe protocol for cryopreserving Coffea canephora seeds. The work was divided into three studies, the first of which investigated the use of the PVS2 cryoprotectant solution in seeds of the Coffea sp genus, to enable the cryopreservation of Coffea canephora seeds. The PVS2 solution was not toxic, but it did not protect the seeds from freezing damage in the protocols tested. During the study, the importance of parchment in protecting seeds during direct contact with liquid nitrogen was discovered. When analyzed, the parchments of Coffea arabica and Coffea canephora showed different chemical compositions and morphology. In the second study was investigated the use of hydroxyapatite and iron oxide nanoparticles in different concentrations in the seeds of the Coffea arabica and Coffea canephora species, to use them during the cryopreservation process. The results showed that the nanoparticles studied were non-toxic when used in the concentrations tested and could positively influence seed quality and be used during the cryopreservation process. In the third study, the gene expression of cryopreserved Coffea arabica seeds was analyzed to better understand the mechanisms involved in tolerance to ultra- low temperatures during the cryopreservation process. According to the results, seeds dried in silica gel at up to 17% moisture content have a more efficient stress signaling system, resulting in greater survival after cryopreservation.