Phylogeographic and population genetic analyses ofCucurbita moschatareveal divergence of two mitochondrial lineages linked to an elevational gradient

Abstract

Premise Domestication usually involves local adaptation to environmental conditions. Cucurbita species are a promising model for studying these processes. Cucurbita moschata is the third major crop in the genus because of its economic value and because it displays high landrace diversity, but research about its genetic diversity, population structure, and phylogeography is limited. We aimed at understanding how geography and elevation shape the distribution of genetic diversity in C. moschata landraces in Mexico. Methods We sampled fruits from 24 localities throughout Mexico. We assessed 11 nuclear microsatellite loci, one mtDNA region, and three cpDNA regions but found no variation in cpDNA. We explored genetic structure with cluster analysis, and phylogeographic relationships with haplotype network analysis. Results Mitochondrial genetic diversity was high, and nuclear genetic differentiation among localities was intermediate compared to other domesticated Cucurbita. We found high levels of inbreeding. We recovered two mitochondrial lineages: highland (associated with the Trans‐Mexican Volcanic Belt) and lowland. Nuclear microsatellites show that localities from the Yucatan Peninsula constitute a well‐differentiated group. Conclusions Mexico is an area of high diversity for C. moschata, and these landraces represent important plant genetic resources. In Mexico this species is characterized by divergence processes linked to an elevational gradient, which could be related to adaptation and may be of value for applications in agriculture. The Isthmus of Tehuantepec may be a partial barrier to gene flow. Morphological variation, agricultural management, and cultural differences may be related to this pattern of genetic structure, but further studies are needed.

Tracing back the origin of pumpkins (Cucurbita pepossp.pepoL.) in Mexico

“…Nuclear genetic structure was higher than values reported for wild C. argyrosperma ssp. sororia (R ST = 0.3 [67]) and domesticated C. moschata (F ST = 0.215 [68]), but similar to values reported for domesticated C. argyrosperma ssp. argyrosperma (R ST = 0.4 [67]).…”

“…pepo in Guatemala (H E = 0.5; 10 polymorphic loci [36]), and higher than those reported for C. argyrosperma ssp. argyrosperma (H E = 0.410; nine polymorphic loci [67]) and C. moschata (H E = 0.395; 12 polymorphic loci [68]). These results are consistent with previous isozyme analyses showing higher genetic variation in C. pepo ssp.…”

Brazilian germplasm of winter squash (Cucurbita moschata D.) displays vast genetic variability, allowing identification of promising genotypes for agro-morphological traits

“…Associated with its socio-economic importance, C. moschata germplasm commonly expresses high genetic variability in all regions where it occurs [15,16,17,18], especially in Brazil [19,20,21]. Archaeological evidence indicates that this species was present in Latin America prior to colonisation, and appears to have already been an important component in the diet of the native peoples living there [22,23,24].…”

Population Structure and Genetic Diversity of Cucurbita moschata Based on Genome-Wide High-Quality SNPs

“…Among them, C. moschata is considered as the second most diverse species of the genus after C. pepo, and is closely related to C. argyrosperma in genomic status [2][3][4][5]. C. moschata exhibits remarkable morphological diversity in its fruit and seed types, and is cultivated and consumed in many parts of the world in forms of mature and immature fruit, seeds, young stems, tendrils, and flowers [6,7]. C. moschata is a versatile food source, and it has also been used as rootstock for vegetable grafting, particularly in Asia [6].…”

“…C. moschata exhibits remarkable morphological diversity in its fruit and seed types, and is cultivated and consumed in many parts of the world in forms of mature and immature fruit, seeds, young stems, tendrils, and flowers [6,7]. C. moschata is a versatile food source, and it has also been used as rootstock for vegetable grafting, particularly in Asia [6].…”