International Journal of Horticulture, 2024, Vol.14, No.4, 250-262 http://hortherbpublisher.com/index.php/ijh 257 Figure 2 (a) Haplotype network for two concatenated chloroplast regions (psbJ-petA and psbD-trnT(GGU); 1724 bp) depicting the relationship between 11 haplotypes found in C. pepo ssp. pepo, C. pepo ssp. fraterna and C. pepo ssp. ovifera from the current study, plus data reported by Kistler et al. (2015), including C. pepo ssp. fraterna archaeological sample (123Fra) as well as C. pepo ssp. fraterna modern sample (KFra). (b) Geographical distribution of 11 haplotypes considered in the haplotype network for the individuals analysed in this study (Adopted from Castellanos-Morales et al., 2019) The Approximate Bayesian Computation (ABC) analysis supported the hypothesis that Cucurbita pepo ssp. pepo originated through hybridization between C. pepo ssp. fraterna and C. pepo ssp. ovifera, although direct analysis suggested that C. pepo ssp. fraterna is more likely to be its ancestor. The study also revealed that the species underwent rapid population expansion and geographical diversification after domestication. This study provides important genetic evidence for understanding the domestication process of zucchini and its wild ancestors, offering valuable insights for future crop domestication studies. 8.2 Genetic diversity in pumpkin domestication Research has examined the genetic consequences of domestication in two independently domesticated pumpkin species—Cucurbita argyrosperma and Indian pumpkin Cucurbita maxima (Kates et al., 2021). Through the analysis of 15,000 SNPs, covering wild, landrace, and improved varieties, the study found that Cucurbita maxima did not exhibit a significant reduction in genetic diversity following domestication, whereas Cucurbita argyrosperma showed a marked decline in genetic diversity (Figure 3). This difference is primarily attributed to the distinct domestication processes of the two species and the varying degrees of gene flow between wild and cultivated populations. Cucurbita maxima was domesticated in South America and exhibits extensive morphological and genetic diversity, partly due to ongoing gene flow with its wild relatives. In contrast, Cucurbita argyrosperma was primarily domesticated in Mexico, with a more limited geographical distribution, and selection pressures were more focused on seed production rather than fruit diversity, leading to lower diversity and a significant genetic bottleneck. Cucurbita maxima has untapped genetic diversity potential that could be utilized for crop improvement, whereas Cucurbita argyrosperma may require strategies to mitigate the impact of reduced diversity (Kates et al., 2021; Liu et al., 2022). The research indicates that domestication does not uniformly reduce crop genetic diversity; rather, the genetic consequences are largely dependent on the specific domestication history and practices involved.
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