CROP WILD RELATIVES

The Research Institute of Pomology (IP), Chinese Academy of Agricultural Sciences (CAAS) in Xingcheng, China, maintains hundreds of apple accessions that originated from around the world. We have used 16 microsatellites to assess the diversity and differentiation of 391 accessions within the IP that represent Malus × domestica (from China, Japan, former Soviet Republics, and Western countries) as well as the crop’s wild relative species Malus baccata, Malus prunifolia, Malus × robusta, and Malus sieversii. We identified genetic relationships among these eight source categories that suggest that the M. × domestica cultivars from the former Soviet Republics are most closely related to M. sieversii and may represent an independent lineage of domesticated apples distinct from those found in Western Europe and North America. We show that the M. × domestica cultivars from China and Western sources are genetically similar, whereas the cultivars from Japan are distinct. We also describe two accessions of M. × domestica ssp. chinensis landraces that are believed to be over 2000 years old and are more similar to wild species than are most of the M. × domestica cultivars. We show that the wild, landrace, and cultivar accessions within the IP offer novel diversity to apple breeding programs.