Jan. 2, 2003 While promising the possibility of hardier crops and a larger, more robust food supply for the world, worries continue over the effect genetically engineered plants might have on the environment. One fear is over the movement of altered genes from domesticated populations to the wild and the effect of these "escaped" genes on ecosystems. In a study published in the December issue of Ecological Applications, Charity Cummings (University of Kansas), Helen Alexander (University of Kansas), Allison Snow (Ohio State University), Loren Riesenberg (University of Indiana) and colleagues tracked the movement of three specific alleles, or genes, in wild and domesticated sunflowers to determine how often and to what extent these plant populations will hybridize and pass specific genes on to the next generation.
Domesticated sunflowers are commonly grown in the plains states of the US and California, and the wild sunflower is a native, annual weed that occurs throughout most of the US. Sunflower and other crops are currently under development for a variety of traits to make them more resistant to fungi and pests. Currently wild sunflowers pose a problem for farmers as a weed in domesticated sunflower crops. These already weedy plants could cause even more damage if a gene for insect resistance crossed into the wild population from the cultivated sunflowers.
Many undergraduate biology students conduct an experiment using daphnia, crickets or other small invertebrates, measuring the number of offspring produced, how many survive and several other factors to understand survivorship and other population concepts. The scientists used a similar approach to predict the likelihood of genes from hybrid crops entering wild populations and staying in the wild sunflowers. Starting with a hundred wild plants and a hundred crop-wild hybrids, the scientists set up three plots and observed the sunflowers for two growing seasons, collecting the seeds to analyze the protein and gene flow between generations of plants.
The team found wild and hybrids had similar survival rates, but the wild plants produced more flower heads, more seeds per head and more seeds overall than the hybrids, suggesting the wild plants would dominate by shear number when competing with the gene-altered hybrid plants. The hybrid seeds were also preferred by birds and other organisms that fed on the seeds, making the chances for these plants to reproduce successfully even lower.
The amount of the genetic markers passed on between generations varied, but the domesticated crop genes were likely to survive for many generations once they enter the wild population. This research could have larger implications for studying other organisms or to estimate the gene movement of other altered crops.
"We already knew that crop genes could spread, but now we know that direct measures of seed production can help predict the frequency of crop genes in wild populations. Also, this study shows that crop genes can persist even when the first generation of hybrids perform quite poorly compared to the wild plants," said Snow.
The group's research offers new ways for ecological science to predict the movement of genes among plant populations. Previous studies have shown that cultivated crops will cross-pollinate, sharing genetic material with wild plants. Other work indirectly estimated the likelihood of a gene lasting into mixed crop-wild populations while others directly measured gene flow in these hybrid populations. This study is the first to combine these approaches.
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