The genus Cucurbita (Cucurbitaceae) includes a vast variety of fruits, including gourds, squashes, and pumpkins. One of the economically most important species of the genus is Cucurbita pepo L., which produces plants with a wide range of growth habits, fruit sizes, shapes, and colors. The edible round-fruited types of C. pepo are called “pumpkins,” the edible non-round types are called “squash,” whereas the non-edible sorts are called “gourds” (Paris et al., 2003). Based on fruit shape, the species is divided into eight edible-fruited cultivar groups and two cultivar groups of ornamental gourds: Pumpkin (round), Cocozelle (long, bulbous cylindrical), Vegetable Marrow (short, tapered cylindrical), Zucchini (uniformly cylindrical), Orange Gourd (small, round), Acorn (turbinate, furrowed), Scallop (flat, scalloped), Crookneck (long, narrow neck), Straightneck (short, thick neck), and Ovifera Gourd (small, various shapes) (Paris, 1986, 2000).
At the end of the 19th century, a mutation in the gene (genes) responsible for pumpkin seedcoat development occurred in Styria, and phenotypes with collapsed testa layers segregated from normal field pumpkins (Teppner, 2000). The absence of four lignified seedcoat layers revealed the dark green color of the innermost layer—the chlorenchyma—composed of cells with high levels of protochlorophyll pigment (Kreft et al., 2009). Since then, these genotypes have been cultivated and bred for the production of pumpkin seeds that are used as snacks and in the baking industry or further processed to extract the oil. The oil from roasted pumpkin seeds is particularly valued in central European cuisine as a result of its strong nut-like taste and dark green color. The seeds are also used in traditional medicine and are present in several medicinal products because of their demonstrated therapeutic properties against benign prostatic hyperplasia and other diseases (Gossell-Williams et al., 2006; Shirvan et al., 2014; Yadav et al., 2010). Despite the increasing economic significance of pumpkin cultivars for seed production, there is no information available about population structure within and among accessions with mutated seedcoats and the range of inbreeding present in these accessions. Previous genetic studies have been mainly focused on interspecific diversity within the genus Cucurbita or genetic diversity among C. pepo subspecies with an emphasis on other cultivar groups (Ferriol et al., 2003; Formisano et al., 2012; Gong et al., 2008a, 2012, 2013; Mady et al., 2013; Paris et al., 2003).
SSR (microsatellites) are very popular molecular markers because they are highly informative, multiallelic, polymerase chain reaction (PCR)-based, and codominant. In this study, SSRs were used to evaluate genetic variability within and among 51 C. pepo accessions with wild-type or mutated seedcoats, the latter commonly referred to as hull-less seeds, thin-coated seeds, or naked seeds. These accessions are valuable resources for breeding purposes and the obtained genetic information will complement phenotypic characterization during selection.
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