‘Gumdrop’ is an open-pollinated offspring of female seedling ‘B15-69’, located in a selection plot near Famoso, CA, with 1410 seedlings, described in Chao et al. (1998). ‘B15-69’ was developed as part of the Parfitt, Kallsen, and Maranto breeding project in the 1990s (Kallsen et al., 2009), from a cross of female 2-35, originally selected by Dr. J. Crane in the 1970s, and ES2, an early flowering male of unknown parentage. ‘Gumdrop’ was selected as seedling S-43 (one of 35 seedlings from ‘B15-69’ seed) for precocity, early season nut maturity, and nut size in 2006 from a breeding selection plot, established near Bakersfield California in 2001. ‘Gumdrop’, ‘Kerman’, and ‘Golden Hills’ were grafted onto UCB1 rootstock and tested in a randomized block trial (three blocks, four to six trees per cultivar/block) established near Buttonwillow CA in 2007. This trial is located near the center of the major U.S. pistachio-growing region.
Administrative Committee for Pistachios 2014 Receipts/assessments/report instructions, Crop Year 2-14: 2015 Fresno, Calif. OMB no. 0581-0215. 16 June 2015. <https://www.ams.usda.gov/sites/default/files/media/ACP-1-PistachioReceiptAssessment.pdf>.
Chao, C.T., Parfitt, D.E., Ferguson, L., Kallsen, C. & Maranto, J. 1998 Breeding and genetics of pistachio: The California program. Proc. 2d Int. Symposium on Pistachios and Almonds, Aug. 24–29, 1997, Davis CA, USA Acta Hort. 470 152 161
Ghrab, M., Mimoun, M.B., Masmoudi, M.M. & Mechlia, N.B. 2014 Chilling trends in a warm production area and their impact on flowering and fruiting of peach trees Sci. Hort. 178 87 94
Kallsen, C.E., Parfitt, D.E., Maranto, J. & Holtz, B. 2009 New pistachio varieties show promise for California cultivation Calif. Agr. 63 18 23
Luedeling, E., Zhang, M. & Girvetz, E.H. 2009 Climatic changes lead to declining winter chill for fruit and nut trees in California during 1950–2099 PLoS One 4 E6166 doi: 10.1371/journal.pone.0006166
Parfitt, D.E., Kafkas, S., Batlle, I., Vargas, F.J. & Kallsen, C.E. 2012 Pistachio, p. 803–826. In: M.L. Badenes and D.H. Byrne (eds.). Fruit breeding. Springer, New York, NY
Royal Horticultural Society R.H.S. colour chart v. 3. R8 V. 1–4
Zhuang, W., Cai, B., Gao, Z. & Zhang, Z. 2016 Determination of chilling and heat requirements of 69 Japanese apricot cultivars Eur. J. Agron. 74 68 74