2019 ASHS Annual Conference

Specialized cider apples (Malus xdomestica Borkh.) contain quality attributes that provide important and noteworthy characteristics to finished cider, including bitterness and astringency (naturally provided through a sub-group of polyphenolic compounds called “tannins”), sharpness (naturally provided through organic acids, predominantly malic acid), sweetness (naturally provided through sugars and sugar-alcohols, such as sorbitol), and flavors (naturally provided through volatile aromatic compounds). In regions with long-standing traditions of cider production, numerous apple cultivars have been cultivated over the centuries. For example, the Herefordshire Pomona, which was published late 1800’s, lists more than 80 cider apple cultivars. More recent pomonas list 160 cider apple cultivars being grown in the cider producing counties in Western England and 300 in France. Even greater levels of diversity can be found in the cider producing regions of Spain, where more than 400 cider cultivars have been identified. To gain a greater understanding of the diversity of cider apples available in the United States, we have identified and analyzed 269 genotypes in the United States Department of Agriculture-Plant Genetic Resources Unit (USDA-PGRU) Malus germplasm collection in Geneva, NY. Our goal is to categorize genotypes that have desirable and perhaps unique juice quality, but that are also productive in modern orchard systems. France, the United States, and the United Kingdom each represent about 25% of our sample set with the remaining accessions originating from 21 other countries. As measured by the Folin-Ciocalteu assay, total polyphenols in the apple juice samples from these accessions had a nearly 50-fold difference in concentration (0.1-4.86 g·L^-1). Other important juice characteristics ranged greatly among genotypes and between years: soluble solid concentration (12.4; 2.8- 21.5 °Brix), titratable acidity (4.79; 0.26-22.9 g·L^-1), sucrose (54.4; 0-163 g·L^-1), glucose (31.1; 3.8-120.1 g·L^-1), fructose (100.7; 11.5-202.4 g·L^-1), and sorbitol (10; 0.3-49.3 g·L^-1). While greater diversity is beneficial from the standpoint of maintaining genetic resources and creating unique cider styles, it can be a challenge to new cider producers and apple tree nurseries to identify cultivars with the greatest chance for success in a given region. For this reason, our results should aid in determining genotypes to include in future cultivar evaluations.