Fitness correlates of crop transgene flow into weedy populations: a case study of weedy rice in China and other examples

Abstract

Whether transgene flow from crops to cross‐compatible weedy relatives will result in negative environmental consequences has been the topic of discussion for decades. An important component of environmental risk assessment depends on whether an introgressed transgene is associated with a fitness change in weedy populations. Several crop‐weed pairs have received experimental attention. Perhaps, the most worrisome example is transgene flow from genetically engineered cultivated rice, a staple for billions globally, to its conspecific weed, weedy rice. China's cultivated/weedy rice system is one of the best experimentally studied systems under field conditions for assessing how the presence of transgenes alters the weed's fitness and the likely impacts of that fitness change. Here, we present the cultivated/weedy rice system as a case study on the consequences of introgressed transgenes in unmanaged populations. The experimental work on this system reveals considerable variation in fitness outcomes ‐ increased, decreased, and none ‐ based on the transgenic trait, its introgressed genomic background, and the environment. A review of similar research from a sample of other crop‐wild pairs suggests such variation is the rule. We conclude such variation in fitness correlates supports the case‐by‐case method of biosafety regulation is sound.

Weedy rice in sustainable rice production. A review

“…According to De-Wet and Harlan (1975), weedy rice originated from the selection and adaptation of wild rice to agricultural habitats. In regions where no wild rice has been grown, weedy rice may instead originate from cultivated rice through de-domestication with adaptive mutations and the accumulation of beneficial mutants (Ishikawa et al 2005;Cao et al 2006;Reagon et al 2011;Thurber et al 2010;He et al 2014;Qiu et al 2014;Lu et al 2016;Li et al 2017;Qiu et al 2017). In the case of Brazil and Italy, where no wild Oryza types are indigenous, contamination of seed stocks with wild Oryza species has been proposed as a source of weedy rice (Carney 2004;Grimm 2014).…”

Fitness Cost of Transgenic cry1Ab/c Rice Under Saline-Alkaline Soil Condition

“…It might also reach common wild rice population via the same routes and have access to waste lots, saline-alkaline land and other sites outside the farmland (Jenczewski et al, 2003). Therefore, it could propagate in the natural ecosystem with unpredictable ecological consequences (Yang et al, 2015; Lu et al, 2016). …”

Genetically engineered rice endogenous 5-enolpyruvoylshikimate-3-phosphate synthase (epsps) transgene alters phenology and fitness of crop-wild hybrid offspring

“…Wild relative populations that have acquired a strongly fitted transgene through gene flow likely changes their evolutionary potential, resulting in unwanted environmental/ecological consequences 4–7 . It is therefore essential to properly assess the environmental impact of transgene flow before the commercialization of any GE crops.…”