SorbusSensu Lato: A Complex Genus with Unfulfilled Crop Potential

Abstract

Sorbusa diverse genus in the Malinaesubtribe of the Rosaceae, has multiple common names including mountain ash, rowan, whitebeam, and service tree. More than 600 species have been ascribed to Sorbus, yet recent phylogenetic studies indicate this polyphyletic group consists of multiple genera. Sorbuss.l. has a circumpolar boreal distribution with non-indigenous introductions of species in New Zealand and the US. Several genebanks of the US National Plant Germplasm System (NPGS) conserve representatives of 33 taxa within this diverse group. The Woody Landscape Plant Germplasm Repository (WLPGR) of the US National Arboretum maintains 85 active accessions as seeds and living plants in Washington DC, with a focus on wild species and intergeneric hybrids of ornamental and landscape value. The USDA ARS National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon, maintains 38 Sorbusaccessions with a focus on species with potential as fruit crops or rootstocks and 26 intergeneric accessions of Sorbuscrossed with others of the Malinaesubtribe. While Sorbuss.l. have been recognized for their ornamental qualities in the nursery and landscaping industries, this group also has potential for its edible fruit and use in processed products for the nutraceutical, juice, and brewing industries. Wild Sorbuss.l. species offer a great opportunity for breeding and selection of improved edible and ornamental cultivars. During the last century, the classical giants of fruit breeding, Luther Burbank (Santa Rosa and Sebastopol, California) and Ivan Vladimirovich Michurin (Tambov, Russia), bred and selected Sorbuss.l. The NCGR-Corvallis conserves eight Burbank selections and seedlings and seven Michurin releases, and is working to add additional accessions of their crosses. Building on Burbank and Michurin’s breeding efforts, continued enhancement of wild plant material through controlled crosses could greatly improve flavor, reduce astringency, and enlarge fruit size for this crop. The possibilities of unique fruit development from intergeneric Sorbuss.l. crosses and backcrosses with other closely related genera is discussed. Expansion of the NPGS collections is planned to conserve additional species diversity. Germplasm in the NPGS system is available for research and can be requested from GRIN-Global.