Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/30/2017
Publication Date: 4/30/2017
Citation: Volk, G.M. 2017. Ensuring the genetic diversity of apples. In: Evans, K.Achieving sustainable cultivation of apples. Burleigh Dodds Science Publishing,Cambridge, UK. p.3-21.

Interpretive Summary: Apples are an important part of the American diet, but many of the cultivars that are currently produced are susceptible to pests, diseases and environmental threats. This chapter describes the threats to apple production and provides information about the relationships between domesticated apples and their progenitor species. It focuses on the value of wild apple species in breeding programs and describes three challenges to ensuring the genetic diversity of apples for future generations. These challenges are 1) understanding the diversity within and among apple species and domesticated cultivars, 2) capturing and maintaining the diversity of apple species and cultivars within genebanks, and 3) accessing the diversity in the form of plant genetic resources and data. New genomic and genetic technologies will facilitate the use of wild apple genetic resources in breeding programs focused on sustainably producing high quality fruit.

Technical Abstract: Apples (Malus × domestica Borkh.) are a nutritious source of antioxidants, polyphenolics, vitamins, and fiber. Many of the apple cultivars that are currently produced were identified over a century ago and do not offer resistance to pathogens and tolerance to climatic threats. Apple breeding programs seek to develop cultivars with a decreased susceptibility to key threats as well as produce high quality fruit that has an extended storage life and is amenable to high density production and mechanical harvesting. Previously, it has been difficult to use wild apple species for breeding because wild species usually have undesirable fruit, non-uniform ripening times, and other traits that are not amenable to commercial apple production. Apple progenitor species, M. sieversii, M. orientalis, M. sylvestris, M. prunifolia, and M. baccata also offer desirable variation, and may be more amenable to use in breeding programs. Genebanks provide breeders access to Malus wild species and local cultivars (which may also have desirable traits). The USDA-ARS National Plant Germplasm System maintains an apple collection with 3070 unique grafted trees representing M. × domestica cultivars and 33 Malus species, and 15 hybrid species that are available to breeding programs. New genomic and genetic technologies will facilitate the use of wild apple genetic resources in breeding programs focused on sustainably producing high quality fruit.