Recent long-distance transgene flow into wild populations conforms to historical patterns of gene flow in cotton (Gossypium hirsutum) at its centre of origin

Abstract

Over 95% of the currently cultivated cotton was domesticated from Gossypium hirsutum, which originated and diversified in Mexico. Demographic and genetic studies of this species at its centre of origin and diversification are lacking, although they are critical for cotton conservation and breeding. We investigated the actual and potential distribution of wild cotton populations, as well as the contribution of historical and recent gene flow in shaping cotton genetic diversity and structure. We evaluated historical gene flow using chloroplast microsatellites and recent gene flow through the assessment of transgene presence in wild cotton populations, exploiting the fact that genetically modified cotton has been planted in the North of Mexico since 1996. Assessment of geographic structure through Bayesian spatial analysis, BAPS and Genetic Algorithm for Rule-set Production (GARP), suggests that G. hirsutum seems to conform to a metapopulation scheme, with eight distinct metapopulations. Despite evidence for long-distance gene flow, genetic variation among the metapopulations of G. hirsutum is high (He = 0.894 ± 0.01). We identified 46 different haplotypes, 78% of which are unique to a particular metapopulation, in contrast to a single haplotype detected in cotton cultivars. Recent gene flow was also detected (m = 66/270 = 0.24), with four out of eight metapopulations having transgenes. We discuss the implications of the data presented here with respect to the conservation and future breeding of cotton populations and genetic diversity at its centre of crop origin.

Toward the Development of Novel Long-Term Pest Control Strategies Based on Insect Ecological and Evolutionary Dynamics

“…Several studies have shown that gene flow from transgenic to wild plants has already occurred. For example, Wegier et al (2011) confirmed the presence of transgenes in wild cotton plants in Mexico, which is the center of origin of this species. In this case, the evolutionary costs of this introgression should be evaluated, while a general question should be addressed: What would be the economic cost of losing the populations that gave rise to different crops used in agriculture today?…”

Cultivation-independent establishment of genetically engineered plants in natural populations: current evidence and implications for EU regulation

“…Outcrossing has been measured at distances of up to 1,625 m [21]. Thus, the findings of Wegier et al [16] showing that outcrossing has taken place are not entirely surprising. A potential cause for the spread of transgenic cotton could probably be the transport of cotton seed from the USA, which is used as livestock feed.…”

“…Based on genetic differences, eight metapopulations can be distinguished. In a pilot study published in 2011 [16], Wegier et al were able to show that transgene constructs from genetically engineered cotton have spread into these populations. Genetically engineered cotton has been planted in Mexico since 1996.…”

Biosafety and Environmental Releases of GM Crops in Mesoamerica: Context Does Matter

“…The possible sources and routes by which the genetic constructs might have arrived are unknown, this is also true in relation to the effects and consequences they might represent, targeted research is underway. Up to now, neither the proponents nor the competent authorities have openly reacted to the fi ndings [ 9 ] or to the warnings made by some scientifi c institutions (such as CONABIO has in its risk assessments).…”

“…In the case of GM cotton (level III), the fact is that recombinant proteins expressed from genetic constructs of GM cotton events have been detected in at least half the wild tetraploid cotton metapopulations present in Mexico [ 9 ]. The possible sources and routes by which the genetic constructs might have arrived are unknown, this is also true in relation to the effects and consequences they might represent, targeted research is underway.…”