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.
Highlights
Weeds are great challenges for crop production, those that are the same biological species as the crop they infest
We present the current state of development of genetically engineered (GE) cultivated rice for commercialization in China with emphasis on the two traits most likely to be first deregulated: insect resistance and herbicide tolerance
Some crop alleles can enhance the fitness of weedy rice, enabling it to adapt to and evolve rapidly in the cultivated rice agro-ecosystem
Summary
Weeds are great challenges for crop production, those that are the same biological species (conspecific) as the crop they infest. Whether or not an introgressed transgene will have similar negative consequences will depend on largely four factors: (i) the intended expressed transgene phenotype; (ii) the typical gene flow rates from the crop to the weed; (iii) the phenotype of weed with an introgressed transgene in terms of their ability to reproduce and increase relative to the nonintrogressed weed; and (iv) the introgressed weed’s relative ability to reduce the yield of their sympatric crop cultivar To address these factors, we examine the state of the art in China, is the primary site of GE rice development, for the various intended GE phenotypes being field released and in line for commercialization. If GE rice is involved in the crop-weed gene flow and introgression, the
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