Royce S. Bringhurst and Victor Voth at the University of California-Davis (UC-Davis) revolutionized the strawberry industry in 1979 with the release of their first “day-neutrals” ‘Aptos’, ‘Brighton’, and ‘Hecker’ (Bringhurst and Voth, 1980). These day-neutrals could be programmed to produce fruit 3 months after planting and continued to fruit for up to 5 months regardless of daylength, greatly expanding the production season in California.
These unique cultivars were generated by backcrossing for three generations to conventional short-day types from a hybrid Bringhurst made between ‘Shasta’ and a Fragaria virginiana subsp. glauca clone from the Wasatch Mountains in Utah. Bringhurst continued backcrossing his elite day-neutral selections annually, releasing the very successful ‘Selva’ from the fourth generation and ‘Seascape’ from the fifth. This same strategy has been continued by Bringhurst’s replacements resulting in a string of day-neutral cultivar releases from the UC-Davis program.
As word spread about Bringhurst’s accomplishments, it did not take worldwide strawberry breeders long to begin using his day-neutral germplasm to generate new repeat flowering types. The standard approach was to hybridize a UC-Davis day-neutral selection or cultivar with their local short-day selections and then backcross like Bringhurst had done into their local breeding population. The USDA’s ‘Tristar’ and ‘Tribute’ were the first day-neutrals to be released outside of California in 1981. They were generated by Donald Scott in a 1974 cross using the parent of ‘Brighton’ and ‘Hecker’—Cal. 65.65-601 (Draper et al., 1981).
Over the last few decades, several day-neutral cultivars have been developed outside of California using Bringhurst’s source of day-neutrality, but none of these has achieved the commercial success of the UC-Davis cultivars. In general, their fruit are softer and smaller, and their floral development is inhibited by the hot summer temperatures common in temperate climates (Hancock et al., 2008). Because temperature has such a strong impact on performance, we have suggested that the day-neutrals are more appropriately called remontant (Bradford et al., 2010).
To facilitate the development of remontant cultivars outside of California, it is likely that local germplasm bases must be expanded. Levels of future success may be tied to incorporating new genetics into local breeding programs that are unique to the UC-Davis germplasm base. It might also be beneficial to incorporate genes specifically from genotypes that are known to be heat tolerant. Herein, we describe our efforts to generate such a diverse population that we would like to share with the breeding community.
Bradford, E., Hancock, J.F. & Warner, R.M. 2010 Interactions of temperature and photoperiod determine expression of repeat flowering in strawberry J. Amer. Soc. Hort. Sci. 135 102 107
Bringhurst, R.S. & Voth, V. 1980 Six new strawberry varieties released. Calif. Agr. February, p. 12–15
Finn, C., Hancock, J. & Heider, C. 1998 Notes on the strawberry of Ecuador: Ancient land races, the community of farmers and modern production HortScience 33 583 587
Hancock, J., Weebadde, C. & Serçe, S. 2008 Challenges faced by day-neutral strawberry breeders in the Continental climates of the Eastern USA and Canada HortScience 43 1635 1636
Hancock, J.F., Callow, P.W., Dale, A., Luby, J.J., Finn, C.E., Hokanson, S.C. & Hummer, K.E. 2001a From the Andes to the Rockies: Native strawberry collection and utilization HortScience 36 221 225
Hancock, J.F., Finn, C.A., Hokanson, S.C., Luby, J.J., Goulart, B.L., Demchak, K., Callow, P.W. & Hummer, K.E. 2001b A multistate comparison of native octoploid strawberries from North and South America J. Amer. Soc. Hort. Sci. 126 579 586
Hancock, J.F., Finn, C.E., Luby, J.J., Dale, A., Callow, P.W. & Serçe, S. 2010 Reconstruction of the strawberry, Fragaria ×ananassa, using genotypes of F. virginiana and F. chiloensis HortScience 45 1006 1013
Hancock, J.F., Hokanson, S.C., Finn, C.E. & Hummer, K.E. 2000 Introducing a supercore collection of wild octoploid strawberries Acta Hort. 567 77 79
Hancock, J.F., Luby, J.J., Dale, A., Callow, P.W., Serce, S. & El-Shiek, A. 2002 Utilizing wild Fragaria virginiana in strawberry cultivar development: Inheritance of photoperiod sensitivity, fruit size, gender, female fertility and disease resistance Euphytica 126 177 184
Mookerjee, S., Mathey, M.M., Finn, C.E., Zhang, Z. & Hancock, J.F. 2013 Heat tolerance plays an important role in regulating remontant flowering in an F1 population of octoploid strawberry (Fragaria ×ananassa) J. Berry Res. 3 151 158
Serçe, S. & Hancock, J.F. 2005 The temperature and photoperiod regulation of flowering and runnering in the strawberries, Fragaria chiloensis, F. virginiana, and F. ×ananassa Scientia Hort. 103 167 177
Stegmeir, T.L., Finn, C.E., Warner, R.M. & Hancock, J.F. 2010 Performance of an elite strawberry population derived from wild germplasm of Fragaria chiloensis and F. virginiana HortScience 45 1140 1145