From the Andes to the Rockies: Native strawberry collection and utilization

The commercial strawberry, Fragaria xananassa Duchesne in Lamarck (Staudt, 1999), has a narrow germplasm base, even though its progenitor species have an extensive geographical range (Hancock, 1999; Luby et al., 1991). It originated about 250 years ago when a few New World clones of F. chiloensis (L.) Miller and F. virginiana Miller accidentally hybridized in European gardens (Wilhelm and Sagen, 1972). Thomas A. Knight began the systematic breeding of strawberries in England in 1817, but had at his disposal only a small number of native and cultivated clones. Likewise, North American genetic improvement began in the mid-1800s with a restricted group of European F. xananassa cultivars, South American F. chiloensis, and North American F. virginiana (Darrow, 1966). The cultivars originating from this background played the predominant role in most public and private breeding programs for the next 100 years. The majority of the genes in modern North American cultivars still comes from only seven nuclear (Hancock and Luby, 1995; Sjulin and Dale, 1987) and 10 cytoplasmic sources (Dale and Sjulin, 1990), even though at least eight native clones have been incorporated into cultivars in the last half century. These include: 1) two unnamed clones of F. chiloensis from the Pacific Northwest, 2) two unnamed clones of F. virginiana from Oregon and Alaska, 3) two selections of F. viginiana from the Pocky Mountains (Sjulin and Dale, 1987), 4) the Huachi Grande done of F. chiloensis from Ecuador (Finn et al., 1998), and 5) the Del Norte clone of F. chiloensis from northern California (Moore. et al., 1995). Since the germplasm base of strawberries remains narrow, native germplasm can be injected into the lineage of cultivars relatively easily. However, identification of more wild clones and their use in strawberry improvement would be beneficial. We have spent the last decade cataloging horticulturally useful traits in native populations (Cameron et al., 1993; Hancock, 1999; Hancock ct al., 1990; Luby et al., 1991) and utilizing that variability (Dale et al., 1993; Hancock et al., 1993). Our primary goals have been to: 1) expand the germplasm base of F. xananassa by hybridizing it with elite native octoploid clones, 2) reconstruct F. xananassa using these clones, and 3) develop pure F. chiloensis cultivars. We would also like to construct a ''supercore" group of native F. virginiana and F. chiloensis clones that can be used by other breeders to expand their germplasm base and serve as a reference point for future collections.