Our Southern Strawberry Heritage: Fragaria chiloensis of Chile

The strawberry genus, Fragaria, is a polyploid series composed of nine diploids, three tetraploids, one pentaploid, one hexaploid, and four octoploids (Hancock and Luby, 1993). The primary species of international commerce is the octoploid F. ×ananassa Duch. (2x = 8n = 56), a hybrid of F. chiloensis L. and F. virginiana Duch. Native populations of F. chiloensis are found on the beaches and mountains of central and southern Chile, Hawaii, and in a narrow band along the coast of western North America from the middle of California to the Aleutian Islands. Wild F. virginiana is native to the woodlands and meadows of much of the United States and Canada. The evolutionary origin of the octoploid strawberry species is clouded. Cytogenetic data indicate that they are complex hybrids with the genomic constitution AAA’A’BBB’B’ (Bringhurst, 1990). The A genome donor has been identified as F. vesca L., but the other genomic contributors remain obscure. Although F. chiloensis and F. virginiana are restricted to the western hemisphere, the octoploids probably originated in the eastern hemisphere, as F. vesca is the only other species found in the United States and Canada. The point of origin is unclear, but the range of F. chiloensis extends north and west along the Aleutian Islands, almost to the Kuril Islands, where the only Asian octoploid, F. iturupensis Staudt, is found (Staudt, 1973). This suggests that the original octoploid arose in East Asia and then spread across the Bering Strait to North America. The ancestral octoploid species must have differentiated into F. chiloensis and F. virginiana as they moved south and developed differential adaptations to coastal and mountain habitats (Luby et al., 1992). In fact, the two species are completely interfertile and no significant differences between them have been identified in chloroplast DNA (Harrison et al., 1997a). Randomly amplified polymorphic DNA data suggest that they have remained relatively isolated, but the interspecific fertility and proximity of these groups have allowed for occasional introgression (Harrison et al., 1997b). The origin of Chilean and Hawaiian F. chiloensis is just as obscure, but presumably they were introduced from North America via bird migrations. Interestingly, the single Chilean species F. chiloensis has evolved multiple ecotypes that fill the habitats of both North American species, F. chiloensis and F. virginiana. At high elevations in Chile, plants occur that have the glaucous, thin leaves characteristic of F. virginiana ssp. glauca (Wats.) Staudt in the Rocky Mountains. On the beach in Chile, forms of F. chiloensis ssp. chiloensis f. patagonica Staudt can be found that resemble both the glossy, thick-leaved F. chiloensis ssp. pacifica Staudt found in the coastal fog belt of California and the more delicate F. chiloensis ssp. lucida (E. Vilm.) found on the coast of the Pacific Northwest (Cameron et al., 1991; Darrow, 1966; Lavin, 1997). DOMESTICATION OF THE CHILEAN STRAWBERRY utilized well over 1000 years ago by the indigenous Mapuches between the rivers Biobio and Tolten in south-central Chile, and by the more northern Picunches tribe between the rivers Itata and Biobio. The Picunches had contact with the northern-agrarian Inca invaders and were probably the first to transport elite plants from the wild to their home gardens. The Mapuches were primarily hunters and gatherers, but learned about agriculture from the Picunches (Aldunate, 1989). The Picunches grew mainly corn (Zea mays L.), quinoa (Chenopodium quinoa Willd.), dry beans (Phaseolus vulgaris L. and P. lunatus L.), squashes (Cucurbita maxima Duchesne ex Lam.), oca (Oxalis tuberosa Molina), pepper (Capsicum annuum L.), madi Madia chilensis (Nutt.) Reiche, and mango (Mangifera indica L.) (Montaldo, 1988). Strawberry fruits were used by the native Chileans fresh, dried, as a fermented juice or as medicinal infusions against indigestion, diarrhea, and bleeding (De Moesbach, 1992). The Mapuches made many other kinds of fermented juices, but their favorite was the one from the “llahuen” or “lahuene” (small, red-fruited wild strawberry) that was called “lahuene mushca” (Labarca, 1994). Most evidence indicates that the primary domesticants were the larger, white-fruited forms, called “kellen” or “quellghen” by the Mapuches. Albino-fruited types are rare in nature, but have been found at three southern locations. When subjected to a multivariate analysis, these forms were more closely associated with the cultivated white types than with the native wild red ones (de Pozo et al., unpublished; Lavin, 1997).