Quantitative trait loci for horticulturally important traits defining the Sikkim cucumber, Cucumis sativus var. sikkimen
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ORIGINAL ARTICLE
Quantitative trait loci for horticulturally important traits defining the Sikkim cucumber, Cucumis sativus var. sikkimensis Yuhui Wang1 · Biao Jiang1,2 · Ronald Dymerski1 · Xuewen Xu1,3 · Yiqun Weng1,4 Received: 5 June 2020 / Accepted: 18 September 2020 © This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2020
Abstract Key message QTL mapping identified simply inherited genes and quantitative trait loci underlying morphologically characteristic traits of the Sikkim cucumber, which reveals their genetic basis during crop evolution. The data suggest the Sikkim cucumber as an ecotype of cultivated cucumber not worthy of formal taxonomic recognition. Abstract The Sikkim cucumber, Cucumis sativus var. sikkimensis, is featured with some morphological traits like black spine, brown fruit with fine and heavy netting, as well as large hollow in mature fruit. Despite its establishment as a botanical variety ~ 150 years ago, and its wide use as an important source of disease resistances in cucumber breeding, little is known about its taxonomic status and genetic basis of those characteristic traits. Here we reported QTL mapping with segregating populations derived from two Sikkim-type inbred lines, WI7088D and WI7120, and identification of 48 QTL underlying phenotypic variation for 18 horticulturally important traits. We found that the fruit spine and skin colors in the two populations were controlled by the previously cloned pleiotropic B (black spine) locus. The fruit netting in WI7088D and WI7120 was controlled by the well-known H (Heavy netting) and a novel Rs (Russet skin) locus, which was delimited to a 271-kb region on Chr5 and ~ 736-kb region on Chr1, respectively. A single major-effect QTL was detected for flowering time in each population (ft1.1 for WI7088D and ft6.2 for WI7120). Fifteen, six and five QTL were identified for fruit size, hollow size and flesh thickness variation in the two populations, respectively. No major structural changes were found between the Sikkim and cultivated cucumbers. Except for the rare allele at the Rs locus, there seem no private QTL/alleles identified from this study supporting the Sikkim cucumber as an ecotype of C. sativus, not worthy of formal taxonomic recognition.
Introduction
Communicated by Sanwen Huang. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00122-020-03693-y) contains supplementary material, which is available to authorized users. * Yiqun Weng [email protected]; [email protected] 1
Horticulture Department, University of Wisconsin Madison, Madison, WI 53706, USA
2
Vegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
3
School of Horticulture and Plant Protection, Yangzhou University, Yangzhou 225009, China
4
USDA-ARS Vegetable Crops Research Unit, Madison, WI 53705, USA
Cucumber, Cucumis sativus L. (2n = 2x
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