Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Circuito Exterior s/n Anexo al Jardín Botánico, 04510, Ciudad de México, Mexico.
Programa de Doctorado en Ciencias Biomédicas, Instituto de Ecología, Universidad Nacional Autónoma de México, Circuito Exterior s/n Anexo al Jardín Botánico, 04510, Ciudad de México, Mexico.
Am J Bot. 2020 Mar;107(3):510-525. doi: 10.1002/ajb2.1424. Epub 2020 Feb 18.
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.
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.
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.
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.
驯化通常涉及对环境条件的局部适应。南瓜属物种是研究这些过程的有前途的模式。由于其经济价值和显示出高的地方品种多样性，南瓜属中的第三个主要作物是南瓜，但是关于其遗传多样性、种群结构和系统地理学的研究是有限的。我们旨在了解地理和海拔如何塑造墨西哥南瓜地方品种遗传多样性的分布。
我们从墨西哥各地的 24 个地点采集了果实。我们评估了 11 个核微卫星位点、一个 mtDNA 区域和三个 cpDNA 区域，但在 cpDNA 中没有发现变异。我们通过聚类分析探索遗传结构，并通过单倍型网络分析探索系统地理学关系。
线粒体遗传多样性很高，与其他驯化的南瓜相比，地点间的核遗传分化处于中等水平。我们发现高度的近亲繁殖。我们恢复了两个线粒体谱系：高地（与跨墨西哥火山带相关）和低地。核微卫星显示，尤卡坦半岛的地点构成了一个分化良好的群体。
墨西哥是南瓜属的一个高度多样性地区，这些地方品种代表了重要的植物遗传资源。在墨西哥，该物种的特征是与海拔梯度相关的分化过程，这可能与适应有关，并且可能对农业应用具有价值。特万特佩克地峡可能是基因流动的局部障碍。形态变异、农业管理和文化差异可能与这种遗传结构模式有关，但需要进一步的研究。
