A comprehensive approach toward conserving Malus germplasm

Authors: Volk, Gayle; Richards, Christopher; Forsline, Philip

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2009
Publication Date: 6/1/2010
Citation: Volk, G.M., Richards, C.M., Forsline, P.L. 2010. A comprehensive approach toward conserving Malus germplasm. Acta Horticulturae. 859:177-182.

Interpretive Summary: The USDA-National Plant Germplasm System apple (Malus) collection resides at the USDA-ARS Plant Genetic Resources Unit in Geneva, NY. Traditionally, the collection has been backed up at the USDA-ARS National Center for Genetic Resources Preservation in Ft Collins, CO. Dormant buds collected from the field trees can be cryopreserved and stored in a living state for many years. The orchard apple collection includes hundreds of M. sieversii and M. orientalis individuals. These wild relative species are valued primarily as materials that can be incorporated into apple breeding programs due to specific desirable traits such as disease resistance or fruit quality characteristics. We have developed subsets of individuals that represent the larger field collections of the wild M. sieversii and M. orientalis species. In addition to maintaining selected individuals in orchard core collections, we propose that wild species should be conserved as seeds from strategically selected crosses. Storage of seeds from wild apple species can efficiently complement the field and dormant bud collections.

Technical Abstract: The USDA-National Plant Germplasm System apple (Malus) collection has traditionally been conserved by maintaining orchards at the USDA-ARS Plant Genetic Resources Unit in Geneva, NY and cryopreserving dormant buds of clones. The orchard Malus collection includes hundreds of M. sieversii and M. orientalis individuals. These wild relative species are valued primarily for their diverse alleles, rather than for their specific genotypes. We have developed core collections based on both phenotypic and genotypic (microsatellite) characters to identify a limited number of individuals that represent the diversity of the wild collections. In addition to maintaining selected individuals in orchard core collections, we propose that wild species should be conserved as seeds from strategically selected crosses. This would ensure that many diverse individuals are available for future selection and physiology programs, rather than a limited number of specific genotypes. Crosses have been performed among core collection individuals for two of the three complementary core collections proposed for the M. sieversii collection to produce seeds that can be stored for long-term storage. This conservation approach that promotes preservation of selected clones as well as diverse sets of seeds for vegetatively propagated collections has several advantages. It ensures that valuable alleles in wild collections are conserved, reduces the labor involved in cryopreserving vegetative propagules, and also maintains diverse individuals in field settings that are available for pollen and dormant budwood distribution.