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Multiple transgene traits may create un-intended fitness effects in Brassica napus
Citation:
Londo, J. P., M. A. BOLLMAN, C. L. Sagers, E. LEE, AND L. S. WATRUD. Multiple transgene traits may create un-intended fitness effects in Brassica napus. Heredity. Genetics Society of America, Bethesda, MD, 107:328-337, (2011).
Impact/Purpose:
Increasingly, genetically modified crops are being developed to express multiple “stacked” traits for different types of transgenes, for example, herbicide resistance, insect resistance, crop quality and resistance to environmental factors.
Description:
Increasingly, genetically modified crops are being developed to express multiple “stacked” traits for different types of transgenes, for example, herbicide resistance, insect resistance, crop quality and resistance to environmental factors. The release of crops that express multiple traits could result in ecological changes in weedy environments if feral crop plants themselves or hybrids formed via cross-pollination with compatible weeds results in more competitive plants outside of agriculture. We developed a stacked transgenic line of canola (Brassica napus) that expresses genes for both glyphosate resistance (CP4 EPSPS) and lepidopteran insect resistance (Cry1Ac) from a segregating F2 population. Fitness associated traits were evaluated between this stacked genotype and five other Brassica genotypes in constructed mesocosm plant communities exposed to insect herbivores (Plutella xylostella) or glyphosate drift. Fitness measures of vegetative biomass, seed production, and relative fecundity were all reduced in stacked trait plants when compared with non-transgenic plants, indicating potential costs of expressing multiple transgenes. Costs of the two transgenes were not additive and were dependent on selective treatment; costs were offset under herbivory pressure, and increased under glyphosate-drift pressure. In contrast to fitness costs for stacked plants without selection, selection pressure increased the fitness of the stacked genotype. The increased fitness of the stacked genotype under selective pressure contributed to an increase in the number of seeds produced as well as a change in the proportion of seeds within the population with hitchhiking transgenes. These results demonstrate that fitness costs and benefits may occur when multiple transgenes are expressed in the same genetic background.