title: 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.
authors.affiliation: Ministry of Education Key Laboratory for Biodiversity and Ecological Engineering Department of Ecology and Evolutionary Biology Fudan University Shanghai China.
authors.forename: Bao-Rong
authors.initials: BR
authors.lastname: Lu
authors.affiliation: Ministry of Education Key Laboratory for Biodiversity and Ecological Engineering Department of Ecology and Evolutionary Biology Fudan University Shanghai China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Botany and Plant Sciences Center for Conservation Biology University of California Riverside CA USA; Center for Invasive Species Research University of California Riverside CA USA.
authors.forename: Norman C
authors.initials: NC
authors.lastname: Ellstrand
keywords: Oryza sativa; conspecific weed; evolutionary potential; fitness; herbicide resistance; insect resistance; introgression; red rice