Cryopreservation of Malus and Pyrus Wild Species in the ‘Fruit Genebank’ in Dresden-Pillnitz, Germany

SIMPLE SUMMARY: In Dresden-Pillnitz, Germany, the genebank preserves samples of wild apple and pear species in addition to fruit varieties in field collections. To protect this unique and valuable diversity from pests, diseases, and weather extremes, collections of duplicates in a different location are necessary. Cryopreservation, storage at ultralow temperature (usually in liquid nitrogen at –196 °C), is used for this purpose. Two different methods were applied; direct dormant bud cryopreservation and cryopreservation of shoot tips from in vitro culture. In apple, a total of 180 samples belonging to 32 species with an average survival rate after cryopreservation of 39% within ten years were processed using dormant buds. Samples numbering 116 reached the 40% survival criterion, which corresponds to successful treatment. Therefore, the dormant bud technique will become the method of choice for wild apple species in the future. In the case of pear wild species, a total of 35 samples belonging to 21 species using both techniques for cryopreservation were tested. In these experiments, the method using shoot tips showed better results compared to the dormant buds. Further trials with both techniques are planned for the future in order to make a final decision for the preservation of pear wild species. ABSTRACT: A unique and valuable diversity of the Malus and Pyrus wild species germplasm is maintained ex situ in field collections in the ‘Fruit Genebank’ in Dresden-Pillnitz, Germany. (1) Background: The establishment of a duplicate collection is necessary to preserve this material safely from abiotic and biotic stress factors. (2) Methods: Two different techniques, cryopreservation using dormant buds and PVS2 vitrification using in vitro shoot tips, were applied and compared. (3) Results: In Malus altogether 180 accessions belonging to 32 species were processed with an average recovery rate of 39% within ten years using the dormant bud method. Accessions, 116 in number, achieved the criterion of 40% recovery which was 64.44% of all accessions tested. In the case of Pyrus germplasm a total of 35 accessions of 21 species and both techniques for cryopreservation were tested. In the results of these experiments the PVS2 method led to better results compared to the dormant bud method. (4) Conclusions: In Malus the dormant bud technique will be the method of choice for the future to build up the duplicate collection. Further experiments using both techniques are planned in the future to make a final decision for Pyrus.