AUTHOR=Sánchez-de la Vega Guillermo , Castellanos-Morales Gabriela , Gámez Niza , Hernández-Rosales Helena S. , Vázquez-Lobo Alejandra , Aguirre-Planter Erika , Jaramillo-Correa Juan P. , Montes-Hernández Salvador , Lira-Saade Rafael , Eguiarte Luis E. 

TITLE=Genetic Resources in the “Calabaza Pipiana” Squash (Cucurbita argyrosperma) in Mexico: Genetic Diversity, Genetic Differentiation and Distribution Models

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00400

DOI=10.3389/fpls.2018.00400

ISSN=1664-462X

ABSTRACT=<p>Analyses of genetic variation allow understanding the origin, diversification and genetic resources of cultivated plants. Domesticated taxa and their wild relatives are ideal systems for studying genetic processes of plant domestication and their joint is important to evaluate the distribution of their genetic resources. Such is the case of the domesticated subspecies <italic>C. argyrosperma</italic> ssp. <italic>argyrosperma</italic>, known in Mexico as <italic>calabaza pipiana</italic>, and its wild relative <italic>C. argyrosperma</italic> ssp. <italic>sororia</italic>. The main aim of this study was to use molecular data (microsatellites) to assess the levels of genetic variation and genetic differentiation within and among populations of domesticated <italic>argyrosperma</italic> across its distribution in Mexico in comparison to its wild relative, <italic>sororia</italic>, and to identify environmental suitability in previously proposed centers of domestication. We analyzed nine unlinked nuclear microsatellite loci to assess levels of diversity and distribution of genetic variation within and among populations in 440 individuals from 19 populations of cultivated landraces of <italic>argyrosperma</italic> and from six wild populations of <italic>sororia</italic>, in order to conduct a first systematic analysis of their genetic resources. We also used species distribution models (SDMs) for <italic>sororia</italic> to identify changes in this wild subspecies’ distribution from the Holocene (∼6,000 years ago) to the present, and to assess the presence of suitable environmental conditions in previously proposed domestication sites. Genetic variation was similar among subspecies (<italic>H</italic><sub>E</sub> = 0.428 in <italic>sororia</italic>, and <italic>H</italic><sub>E</sub> = 0.410 in <italic>argyrosperma</italic>). Nine <italic>argyrosperma</italic> populations showed significant levels of inbreeding. Both subspecies are well differentiated, and genetic differentiation (<italic>F</italic><sub>ST</sub>) among populations within each subspecies ranged from 0.152 to 0.652. Within <italic>argyrosperma</italic> we found three genetic groups (Northern Mexico, Yucatan Peninsula, including Michoacan and Veracruz, and Pacific coast plus Durango). We detected low levels of gene flow among populations at a regional scale (&lt;0.01), except for the Yucatan Peninsula, and the northern portion of the Pacific Coast. Our analyses suggested that the Isthmus of Tehuantepec is an effective barrier isolating southern populations. Our SDM results indicate that environmental characteristics in the Balsas-Jalisco region, a potential center of domestication, were suitable for the presence of <italic>sororia</italic> during the Holocene.</p>