Genetically engineered cotton in Mexico
Mexico is one of two centres of origin from which are all cotton varieties cultivated today originate. Wild cotton (Gossypium hirsutum) populations are found mainly in the coastal regions of the southern parts of Mexico. In a pilot study published in 2011, it was shown that transgene constructs from genetically engineered cotton have spread into these populations. Genetically engineered cotton has been planted in Mexico since 1996. Almost all commercially grown cotton is cultivated in northern Mexico, several hundred kilometres away from the regions where wild cotton grows. Nevertheless, every fourth sample proved positive for one or more transgenic constructs, and half of the populations were affected by the contamination. Several samples contained stacked constructs with up to four transgenes. Stacked events such as the ones found in the wild are not present in any commercialised genetically engineered cotton event worldwide. Therefore, it can be assumed that several individual transgenes have hybridised over time. This would mean that transgene constructs spread within the wild cotton populations. A main cause for the spread of transgenic cotton is probably the transport of cotton seeds. Nevertheless, it is not fully understood how transgenes introgressed.