Environmental stresses such as chilling temperatures can reduce seed germination rate, seedling emergence rate, flower and fruit development, marketable yield, and postharvest fruit storage longevity in cucumber (Cucumis sativus L.) (Staub and Bacher, 1997; Staub and Wehner, 1996). Chilling temperatures occur in unpredictable patterns, making it difficult to implement management practices for crop protection. Moreover, response of cucumber seedlings to chilling depends on pre- and postchilling environment. Therefore, breeding for tolerance to chilling is an attractive management tool to minimize crop loss.
Chilling injury at the first true-leaf stage in cucumber is controlled by simple plastidic (maternal; Chung et al., 2003) and nuclear (parental; Kozik and Wehner, 2008) factors. While Chung et al. (2007) identified three putative plastidic single-nucleotide polymorphisms (SNPs) associated with chilling tolerance in processing cucumber ‘Chipper’, Kozik and Wehner (2008) characterized one dominant nuclear gene, Ch, in line NC-76 (derived from PI 246930). The response of chilling tolerant ‘Chipper’ and line NC-76 seedlings challenged at 4 °C for 5.5 h under 270 µmol·m−2·s−1 photosynthetic photon flux irradiance are similar (Gordon and Staub, 2011).
No chilling-tolerant U.S.-processing cucumber varieties are commercially available. Although the processing cultivar Chipper (released in 1968 from Clemson University, Clemson, SC) possesses plastid genes for chilling tolerance in the seedling stage, its yield and quality are substantially lower than current cultivars. Therefore, experiments were undertaken to introgress the plastid chilling tolerance of ‘Chipper’ (donor parent) into the commercially acceptable processing cucumber line M29 [recurrent parent; experimental inbred line (S11), North Carolina State University, Raleigh, NC] via backcrossing and self-pollination (Gordon and Staub, 2013). As a result, a series of three advanced backcross (ABL; BC5) and 10 inbred backcross (IBL; BC2S3–5) chilling-tolerant U.S. processing lines possessing acceptable yield and quality traits are being released by the Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA). The chilling tolerance of backcross progeny is characterized by their response to chilling stress (5.5 h at 4 °C in 270 µmol·s−2·m−2 cool white lighting) at the first true-leaf stage under controlled environmental conditions. These lines provide chilling-tolerant genetic stocks suitable for immediate use by cucumber improvement programs.
Chung, S.M., Staub, J.E. & Fazio, G. 2003 Inheritance of chilling injury: A maternally inherited trait in cucumber J. Amer. Soc. Hort. Sci. 128 526 530
Chung, S.M., Gordon, V.S. & Staub, J.E. 2007 Sequencing of cucumber (Cucumis sativus L.) chloroplast genomes identifies differences between chilling tolerant and susceptible cucumber lines Genome 50 215 225
Gordon, V.S. 2009 Characterizing plastome variation and its contribution to chilling injury tolerance in cucumber (Cucumis sativus L.). PhD Diss. University of Wisconsin, Madison (OCoLC: Ocn648006186). 20 July 2015. <http://search.proquest.com/docview/305029867?accountid=14761>
Gordon, V.S. & Staub, J.E. 2011 Comparative analysis of chilling response in cucumber through plastidic and nuclear genetic effects component analysis J. Amer. Soc. Hort. Sci. 136 256 264
Gordon, V.S. & Staub, J.E. 2013 Backcross introgression of plastomic factors controlling chilling tolerance into elite cucumber (Cucumis sativus L.) germplasm: Early generation recovery of recurrent parent phenotype Euphytica 195 217 234
Kozik, E.U. & Wehner, T.C. 2008 A single dominant gene ch for chilling resistance in cucumber seedlings J. Amer. Soc. Hort. Sci. 133 225 227
Staub, J.E. & Wehner, T.C. 1996 Noninfectious disorders: Temperature stress, p. 66. In: T.A. Zitter, D.L. Hopkins, and C.E. Thomas (eds.). Compendium of cucurbit diseases Part II. APS Press, St. Paul, MN
Staub, J.E. & Bacher, J. 1997 Cucumber as a processed vegetable. In: D.S. Smith, J.N. Cash, W.-K. Nip, Y.H. Hui (eds.). Processing vegetables: Science and technology IV. Technomic Publishing Co., Inc. Lancaster, PA