Domestication, Genetics, and Genomics of the American Cranberry

The American cranberry (Vaccinium macrocarpon Aiton) is an iconic fruit species native to eastern North America. The United States is a leader in cranberry production. However, from a genetic perspective, the species has been understudied until very recently. Domesticated less than 200 years ago, breeding efforts did not start until 1929. The American cranberry is a long-lived woody perennial adapted to a temperate climate and well-drained moist acidic soils. Cranberry reproduces both sexually and asexually, through stolons, which are used for clonal asexual propagation of cultivars. The flower is hermaphroditic, relying largely on pollination by hymenoptera pollinators for fruit set. The species is diploid (2n = 2 x = 24), self-fertile, with a genome size of approximately 470 Mbp. Traits of economic importance include productivity, propagation vigor, disease resistance, fruit anthocyanins, brix, and increasingly fruit quality traits for sweetened-dried cranberry products, e.g., fruit firmness and size. Quantitative trait loci (QTL) have been identified for productivity, berry size, TAcy, fruit rot resistance, and other traits. The fruit of American cranberry fruit is recognized for potential benefits to human health due to very high levels of the flavonoid classes, anthocyanins, proanthocyanidins, and flavonols, which result in a very high anti-oxidant status. Recent restrictions on traditional pesticides to control insect and disease pests have altered the ecology with former challenges, e.g., false blossom, having a re-emergence. Genetic improvement of cranberry has been hampered by a long generation interval, including three years from pollination to flower, and assessment of yield requiring 6–8 years after field planting, with typically limited field acreage for breeding. Due to the high cost and effort and long time required for breeding, and due to the recent surge of molecular data and marker-trait association studies, marker-assisted selection will be extremely helpful for cranberry for breeding in the future.