Abstract
Mexico is the center of origin and genetic diversity of upland cotton (Gossypium hirsutumL.), the most important source of natural fiber in the world. Currently, wild and domesticated populations (including genetically modified [GM] varieties) occur in this country and gene flow among them has shaped the species’ genetic diversity and structure, setting a complex and challenging scenario for its conservation. Moreover, recent gene flow from GM cultivars to wild Mexican cotton populations has been reported since 2011.In situconservation ofG. hirsutumrequires knowledge about the extent of its geographic distribution, both wild and domesticated, as well as the possible routes and mechanisms that contribute to gene flow between the members of the species wild-to-domesticated continuum (i.e., the primary gene pool). However, little is known about the distribution of feral populations that could facilitate gene flow by acting as bridges. In this study, we analyzed the potential distribution of feral cotton based on an ecological niche modeling approach and discussed its implications in the light of the distribution of wild and domesticated cotton. Then, we examined the processes that could be leading to the escape of seeds from the cultivated fields. Our results indicate that the climatic suitability of feral plants in the environmental and geographic space is broad and overlaps with areas of wild cotton habitat and crop fields, suggesting a region that could bridge cultivated cotton and its wild relatives by allowing gene flow between them. This study provides information for management efforts focused on the conservation of wild populations, native landraces, and non-GM domesticated cotton at its center of origin and genetic diversity.
Highlights
Crop ferality can play an important role in gene flow between crops and their wild relatives and introgression from artificially selected sources can have significant evolutionary consequences (Ashiq Rabbani et al, 1998; Berville et al, 2005; Snow and Campbell, 2005; Devaux et al, 2007; Gering et al, 2019)
Our findings indicate that geographic distance measures in genetically modified (GM) release permits are not efficient to avoid transgene flow because wild-to-domesticated cotton niches are not isolated and previous genetic evidence shows that G. hirsutum’s gene flow patterns conforms to a long-distance model (Wegier et al, 2011; Hernández-Terán et al, 2019)
The eco-geographic niche of feral cotton should be considered in the design of future risk assessment and transgene monitoring studies to prevent further transgene flow
Summary
Crop ferality can play an important role in gene flow between crops and their wild relatives and introgression from artificially selected sources can have significant evolutionary consequences (Ashiq Rabbani et al, 1998; Berville et al, 2005; Snow and Campbell, 2005; Devaux et al, 2007; Gering et al, 2019). Recent research indicates that feralization is not a “reversal” from domestication, but rather a complex phenomenon that can involve several processes: adaptation to new habitats, novel selection pressures, admixture with wild relatives and other domesticated varieties, and even when feralization restores ancestral phenotypes, novel genetic mechanisms (Gering et al, 2019). Gene flow represents an important mechanism for the spread and establishment of domesticated genetic material (including transgenes) into the wild, which has several conservation implications for crop wild relatives, as is the case of upland cotton (Gossypium hirsutum L.) in Mexico
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