Gene Flow Patterns May Give Clues To Managing Genetically Modified Crops

FAYETTEVILLE, Ark. -Depending on whether genes travel by pollen or seed, different challenges arise in preventing genetic modifications from entering local weed populations, says a University of Arkansas researcher. Different methods of spreading genetic changes require different strategies to ensure that genetically modified crops do not create "super weeds" that become a major problem to agricultural production.

"In some part of its range, almost every crop species can hybridize with a native," said Cindy Sagers, associate professor in Fulbright College. She spoke on this subject at a recent meeting of ecologists, USDA plant specialists and representatives from the Environmental Protection Agency and industry at a meeting on the ecological and agronomic consequences of gene flow from transgenic crops to wild relatives at Ohio State University in Columbus.

Sagers studies the risk of modified genes from rice plants escaping into naturalized red rice populations. Red rice is already a leading weed pest of rice in the United States, and the concern is that introduced genes will make them a more serious threat to crops. Scientists have introduced about 40 novel rice genes to the commercial rice genome, with characteristics ranging from Roundup resistance to specific beetle or pathogen resistance. However, little to nothing is known about what might happen to weeds capable of cross breeding with rice if these genes are introduced into rice crops.

"We need to be cautious about releasing modified genes into nature," Sagers said.

Current examination of cross-contamination of genetically modified organisms involves looking at the characteristics of weed-crop hybrids in greenhouse laboratory studies. However, Sagers plans to reconstruct the history of hybridization by examining genetic relationships among cultivated and red rice populations. She and her colleagues also will track the gene flow in nuclear and chloroplast markers, because these markers differ depending upon how plants are fertilized.

"If the two markers contain differences in their genetic code, then we may deduce that gene movement is primarily through pollen," Sagers said. "If the two markers tell the same story, we may conclude that the gene movement is primarily through seeds."

These two different methods of gene flow pose different problems for people who want to manage the flow of modified genes. Rice seeds can lie dormant for up to 12 years in the soil and they are difficult to eradicate, meaning that managing modified gene flow in seeds may be difficult. To manage pollen, strips of buffer plants can be used to trap the pollen and keep modified genes from escaping into the weed population.

The major crops of current concern include canola, sorghum, rice and radishes because close relatives, and in some cases the same species, grow nearby. But questions still remain about genetically modified corn, cotton and soybean crops that have been released.

"By examining the gene flow, we’ll get better clues on how to manage these crops," Sagers said.

Gene flow is a new area for Sagers, whose primary work lies in ecology.

"Ecologists are taking a larger part in evaluating ecological risk in agricultural and urban environments," Sagers said. "Our understanding of genetics and population dynamics is coming to bear on critical issues of environmental policy."

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