Genetic Diversity and Evolution of Cucurbita Species

The genera Cucurbita comprises economically and culturally significant squashes and pumpkins, whose genetic diversity and evolutionary trajectories reveal insights into domestication, adaptation and crop improvement. Recent advances in genome sequencing and phylogenomic analysis have illuminated an ancient allotetraploid event that underpins modern diversity, with two progenitor lineages diverging over 25 million years ago and subsequent karyotype stability maintaining chromosomal architecture. Wild relatives across the Americas exhibit high levels of genetic differentiation shaped by climatic shifts and geographic isolation, while domesticated taxa experienced bottlenecks, selection for agronomic traits and recurrent gene flow with wild gene pools. Studies of population structure and demographic history have revealed centre-specific domestication pathways in Mesoamerica and South America, with multiple domestication events and ecotype diversification reflecting local adaptation to distinct environments. Such findings are crucial for exploiting genetic reservoirs in both wild and landrace populations, informing breeding strategies for resistance to biotic and abiotic stresses, and ensuring resilience under global climate change.

Research from Nature Portfolio

Recent studies have reconstructed early human interactions with cucurbits in the Americas through direct radiocarbon dating and morphological analysis of archaeological seeds and rinds. These analyses demonstrate initial utilisation of wild gourds for containers around 11,000 years ago, followed by the appearance of domesticated C. moschata and C. pepo varieties, underscoring selective breeding practices that fostered seed size diversification and varietal innovation. Parallel investigations of morphological and molecular diversity in pumpkin landraces collected in Turkey revealed extensive phenotypic variability correlated with Simple Sequence Repeat marker profiles, identifying distinct genetic clusters among locally adapted cultivars. Field assessments of C. moschata accessions in West Africa have further highlighted three ecotypes adapted to savannah, mountain and forest bioclimates, linking variation in fruit, leaf and flowering traits to rainfall and temperature regimes and informing conservation of in situ genetic resources.

Genetic Diversity and Evolution of Cucurbita Species publication trend

The graph below shows the total number of articles in genetic diversity and evolution of cucurbita species across all publications each year (not limited to Nature Index journals).

Technical terms

Single nucleotide polymorphism (SNP): A variation at a single base position in the DNA sequence among individuals of a species.

Polyploidization: The process whereby an organism acquires one or more additional complete sets of chromosomes.

Domestication bottleneck: A reduction in genetic diversity resulting from the selection of a limited number of individuals during the early stages of crop domestication.

Gene flow: The movement of genes between populations or species through interbreeding, affecting genetic diversity.

Population structure: The organisation of genetic variation into subgroups within a species due to factors such as geographic separation or selective breeding.

References

1. Karyotype Stability and Unbiased Fractionation in the Paleo-Allotetraploid Cucurbita Genomes. Molecular Plant (2017).
2. Targeted Sequencing Suggests Wild-Crop Gene Flow Is Central to Different Genetic Consequences of Two Independent Pumpkin Domestications. Frontiers in Ecology and Evolution (2021).
3. Archaeobotanical evidence supports indigenous cucurbit long-term use in the Mesoamerican Neotropics. Scientific Reports (2024).
4. Morphological and molecular characterization of some pumpkin (Cucurbita pepo L.) genotypes collected from Erzincan province of Turkey. Scientific Reports (2022).
5. Assessment of the variability of the morphological traits and differentiation of Cucurbita moschata in Cote d’Ivoire. Scientific Reports (2023).
6. Population Genomics of Domesticated Cucurbita ficifolia Reveals a Recent Bottleneck and Low Gene Flow with Wild Relatives. Plants (2023).
7. Conservation genomics of the wild pumpkin Cucurbita radicans in Central Mexico: The influence of a changing environment on the genetic diversity and differentiation of a rare species. Journal of Plant Research (2024).