Helena S Hernández-Rosales1,2, Gabriela Castellanos-Morales3, Guillermo Sánchez-de la Vega1, Erika Aguirre-Planter1, Salvador Montes-Hernández4, Rafael Lira-Saade5, Luis E Eguiarte1. 1. 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. 2. 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. 3. Departamento de Conservación de la Biodiversidad, El Colegio de la Frontera Sur, Villahermosa, Carretera Villahermosa-Reforma km 15.5 Ranchería El Guineo 2ª sección, 86280, Villahermosa, Tabasco, Mexico. 4. Campo Experimental Bajío, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarías, Km 6.5 carretera Celaya-San Miguel de Allende, C.P. 38110, Celaya, Guanajuato, México, Mexico. 5. UBIPRO, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Av. de los Barrios #1, Col. Los Reyes Iztacala, 54090, Tlanepantla, Edo. de Mex, Mexico.
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.
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.
Authors: Ronaldo Silva Gomes; Ronaldo Machado Júnior; Cleverson Freitas de Almeida; Rafael Ravaneli Chagas; Rebeca Lourenço de Oliveira; Fabio Teixeira Delazari; Derly José Henriques da Silva Journal: PLoS One Date: 2020-06-09 Impact factor: 3.240