International Journal of Horticulture, 2024, Vol.14, No.4, 250-262 http://hortherbpublisher.com/index.php/ijh 253 maxima was domesticated in the Andes region of South America, and research has pointed out that domesticated varieties from this region are well adapted to cold, high-altitude environments (López-Anido, 2021). These regions offered the environmental conditions and cultural practices necessary to facilitate the domestication process. Genetic studies suggest that domestication events did not occur in isolation; there is evidence of gene flow between wild and domesticated populations, which helped maintain the genetic diversity and adaptability of domesticated pumpkins (Kistler et al., 2015; Kates et al., 2017; Barrera-Redondo et al., 2021). 4 Genetic Evidence of Pumpkin Domestication 4.1 DNA analysis of ancient pumpkin seeds The analysis of ancient pumpkin seeds provides critical insights into the domestication process of pumpkins. High-throughput sequencing of complete plastid genomes from ancient, modern wild, and modern domestic Cucurbita samples has revealed independent domestication events in different regions, such as eastern North America and northeastern Mexico. This sequencing also demonstrated the broad archaeological distribution of taxa currently unknown in the wild, suggesting a significant decline in wild-type populations coinciding with widespread domestication (Kistler et al., 2015). Additionally, the presence of pumpkin seeds in mastodon dung deposits indicates that large-bodied herbivores played a role in seed dispersal before their extinction, which may have influenced the domestication pathways of Cucurbitaspecies (Kistler et al., 2015). 4.2 Genetic markers for domestication traits Genetic markers have been instrumental in identifying domestication traits in pumpkins. For instance, the hull-less seed trait in Cucurbita pepo, controlled by a single recessive gene, has been mapped to a specific QTL on chromosome 12. This trait is highly valued in the industry as it eliminates the need for de-hulling seeds. Marker-assisted selection using SNP markers associated with this trait can significantly streamline breeding programs (Meru et al., 2022). Furthermore, comparative genomic analyses of wild and domesticated Cucurbita argyrosperma have identified candidate domestication genes involved in growth hormone regulation, plant defense mechanisms, seed development, and germination. These findings highlight the genetic basis of key domestication traits and their potential for crop improvement (Barrera-Redondo et al., 2020; 2021). 4.3 Comparative genomics of wild and domesticated pumpkins Comparative genomics has shed light on the genetic consequences of pumpkin domestication. Studies have shown that domesticated pumpkins exhibit reduced genetic diversity compared to their wild progenitors, although this reduction varies among species. For example, Cucurbita argyrosperma ssp. argyrosperma shows a significant reduction in genetic diversity relative to its wild counterpart, while other species like Cucurbita maxima do not exhibit the same pattern (Kates et al., 2021). Research has explored the domestication process of Cucurbita argyrosperma by comparing its genome with that of its wild relative, Cucurbita argyrosperma subsp. sororia, revealing the impact of domestication on the genome and variations associated with domestication traits (Barrera-Redondo et al., 2020; 2021). The findings suggest that the domestication of C. argyrosperma likely originated in the lowlands of Jalisco, Mexico, and that there was gene flow between domesticated and wild populations during the domestication process, which helped alleviate the domestication bottleneck effect (Figure 1). Furthermore, phylogenetic studies using nuclear loci have further clarified the relationships between wild and domesticated species within the Cucurbita genus, revealing close relationships and providing new evolutionary insights, which are crucial for understanding the domestication history of these crops (Kates et al., 2017).
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