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Wild Fragaria supercore accessions from the U.S. Department of Agriculture (USDA) National Plant Germplasm System collection have been evaluated in temperate climates; however, there have been no characterizations of supercore accessions in nontemperate climates or in annualized production systems. Because Florida can serve as a model system for annualized winter and spring production worldwide, the objective of this study was to characterize an elite group of wild strawberry accessions under field and high tunnel production systems for mortality and the phenological responses of flowering and runner production. The wild accessions along with cultivars were planted in openfield and high tunnel production environments in a randomized complete block design within each environment with raised beds serving as blocks. Four replications of fiveplant plots were planted in each of two environments in 2 separate years. With the exception of Darrow 72, F. chiloensis accessions did not perform well in the minimumchill annualized winter production system. The accessions of this species generally did not flower and were prolific instead in runner production. The F. virginiana accessions performed better with F. virginiana subsps. grayana and virginiana accessions appearing more adapted for minimum-chill winter production because they flowered well and had few runners. We conclude that NC 96-48-1 (PI 612324), NC 95-21-1 (PI 612569), Darrow 72 (PI 236579), and RH 30 (PI 612499) would be attractive for inclusion in germplasm development in a minimal-chill, winter annual production system. In addition to producing many flowers and few runners, these accessions had low mortality. The modern cultivated strawberry, F. ·ananassa, is fully interfertile with its wild octoploid progenitor species F. virginiana and F. chiloensis. Thus, these species are in the primary germplasm pool for breeding purposes and are a repository of novel traits. A collection of 38 elite wild genotypes (Hancock et al., 2002) is housed at the National Clonal Germplasm Repository in Corvallis, OR. This collection, known as the Fragaria supercore, is a subset of a larger collection and represents the genetic diversity of the collection as a whole with a minimum of redundancy. The accessions within the collection, denoted by PI numbers, include F. chiloensis from North and South America that initiate flowers under short days (SD) and are male, female, or hermaphrodite and F. virginiana from North America that are both SD and remontant (RM) flowering and are also male, female, or hermaphrodite (Table 1). Since the cultivated strawberry resulted from an accidental hybridization of these two wild species in Europe 250 years ago (Hancock, 1999), attempts have been made to reconstruct the cultivated species using wild F. virginiana and F. chiloensis (Hancock et al., 2010; Luby et al., 2008; Stegmeir et al., 2010). Previously, F. virginiana glauca was crossed with F. ·ananassa for incorporating RM flowering (Bringhurst, 1976; Dale et al., 2002; Hancock et al., 2002), and F. chiloensis was used to improve fruit size of SD cultivars for California (Bringhurst and Voth, 1984). Since then, other important traits such as drought and salinity tolerance, red stele resistance, strawberry aphid resistance, and winterhardiness have been introgressed from wild sources (Barritt and Shanks, 1980; Daubeny, 1990; Galletta et al., 1989). Today breeders are using wild accessions of strawberry to improve early yields, achieve disease resistance, and enhance fruit quality attributes (Ludwig et al., 2013) such as flavor and aroma (Finn et al., 2013). A single-year multistate comparison of supercore accessions was conducted in five states in northern temperate latitudes. Data were collected on survival, cold tolerance, disease susceptibility, runner production, flowering and fruiting dates, and fruit size and quality in Maryland, Michigan, Minnesota, Oregon, and Pennsylvania (Hancock et al., 2001). Several accessions performed well overall environments including CA 1499 (PI 551735) for large early fruit and NC 95-19-1 (PI 612486), Frederick 9 (PI 612493), and RH 30 (PI 612499) for vigor and good fruit color. Accessions of the Fragaria supercore have been evaluated in temperate climates; however, supercore accessions have not been characterized in non-temperate climates or in annualized production systems. The annualized winter and spring strawberry production system used in Florida, California, and central Mexico provide most of the U.S. supply of fresh strawberries. Additionally, this approach to production is used around the world in the Mediterranean, Australia, and many other regions. Environmental conditions in spring/summer perennial production systems in northern latitudes are vastly different from these locales. In addition to the often humid conditions and dramatic temperature fluctuations in the subtropical Florida growing region, soils in central Florida are very low in organic matter and consist mainly of Myakka fine sand (USDA, NRCS, National Soil Survey Center, 2013). Thus, Florida is an extreme environment that can serve as an excellent testing ground for other winter and spring production regions of the world. In strawberry, the emergence and development of leaves, crowns, roots, runners, and inflorescences are influenced by temperature, light intensity, and light quality (Hancock, 1999). The most common environmental change used by plants to control seasonal behavior is photoperiod or daylength (Summerfield, 1999). Plants with RM flowering respond to a combination of daylength and temperature and can be quantitative long day (LD), qualitative LD, or truly day-neutral. SD plants initiate flower buds in the shortening days of summer and fall, winter, or early spring when days are short and temperatures are warm enough; however, high temperatures can inhibit bud formation in SD and RM plants as reviewed in Stewart and Folta (2010). In North American strawberry nursery production, two transplant types are typically used: bareroot and plug transplants. Plug plants are produced mainly in North Carolina and Canada for the Florida industry by rooting small runner plants in late summer in plug trays, and bareroot transplants are field propagated in the same regions and fresh dug in the fall. Both types of plants are established in October, and fruit harvest begins in late November and continues through March. Exposure to the combination of cooler temperatures and shortening days of September in the nurseries initiates flower buds in the transplant crowns before planting in the winter production fields. Stolon development usually occurs during the long days of summer when temperatures are warm. However, plants in the winter fruiting field continue to produce runners during the beginning of the fruiting season, although the amount of runnering differs among cultivars. Because early marketable yield is negatively affected by runner production (Albregts and Howard, 1986), runners are removed. Therefore, runnering in the fruiting field is considered an undesirable trait. Received for publication 3 Feb. 2014. Accepted for publication 1 May 2014. Partial funding for this project was provided under a USDA-ARS Specific Cooperative Agreement via the Small Fruits Crop Germplasm Committee. We acknowledge Dr. Kim Hummer and staff at the USDA-ARS National Clonal Germplasm Respository for their provision of propagules of the Fragaria supercore collection. To whom reprint requests should be addressed; e-mail vwhitaker@ufl.edu. 848 HORTSCIENCE VOL. 49(7) JULY 2014 The temperatures during the Florida production season can fluctuate dramatically. During planting season in October, the average high/low is 29/18 C. In December, when strawberries are in full production, the average high/low is 23/11 C. Temperatures fall to 22/10 C during the coldest month, January, and rise to 26/13 C at peak production in March. However, there are usually several nights with frost each season, and overhead irrigation is used to protect plants from freeze damage. Protective systems such as high tunnels are becoming more popular worldwide for season extension/optimization as well as for frost protection (Hancock and Simpson, 1995; Ogden and van Iersel, 2009; Salame-Donoso et al., 2010). Temperature difference in high tunnels compared with the open field affects flowering and other physiological responses. Donoso et al. (2009) found that plant diameter and total yield were higher in the high tunnel compared with the open field. In addition to temperatures during the production season, temperatures during transplant development are also important in strawberry. In an annual system, Durner et al. (1987) reported early yield differences in SD genotypes in response to differing levels of chilling in a North Carolina nursery. They found that with ‘Chandler’, slight chilling (less than 125 h) suppressed early yield and that increased chilling (greater than 125 h) enhanced early yield; on the other hand, chilling in ‘Tufts’ decreased early yields. Flowering in the temperate environment is strongly influenced by temperature and each cultivar has its own photoperiod · temperature interaction response curve with a minimum number of floral induction cycles required (whether SDs or low temperature) (Heide et al., 2013). In the University of Florida strawberry breeding program, plug plants of advanced selections are propagated over the summer in local greenhouses and do not receive any chilling before planting. This is done to select for cultivars that have very low or nonexistent chilling requirements for proper plant development and early flowering. Evaluation under these same conditions would allow similar observations of these important accessions. For wild germplasm to be usefully characterized, the material should be evaluated in multiple and diverse environments and production systems. Because Florida can serve as a model s

Characterization of Fragaria virginiana and F. chiloensis in a Minimal-chill, Winter Annual Production System