How Far Does Wheat Pollen Flow? and Other Related Questions
How far does wheat pollen move? That is the subject of 4 year $900,000 grant funded by the Initiative for Future Agricultural and Food Systems, a federal research funding program. This grant is intended to address the problem that exists with hybridization between wheat and a common agricultural weed called jointed goatgrass (Aegilops cylindrica). Two recent studies have shown gene flow, including the transfer of herbicide resistance genes, from wheat and jointed goatgrass (Seefeldt et al., 1999; Mallory-Smith et al., 1999). These studies also have implications for growers, researchers, and decision makers concerned with transgenic contamination issues of seed and crops and the affects on marketability and farmers' livelihoods.
The possibility of herbicide-resistant wheat crossing with jointed goatgrass (JGG) is an issue, says Carol Mallory-Smith, a weed scientist at Oregon State University. Jointed goatgrass is a big weed problem in the United States. It costs growers millions of dollars a year in reduced production and grain value. Mallory-Smith's work isn't specific to Roundup Ready wheat. She started studying the occurrence and the nature of herbicide-resistant goatgrass, weeds that developed some resistance on their own, before genetically modified wheat became an issue. However, BASF's Clearfield System, a non-transgenic herbicide resistant wheat, is now licensed for commercialization and Monsanto's Roundup Ready spring wheat is on the horizon.
Mallory-Smith studied wheat pollen flow last summer using blue seeded winter wheat, along with white wheat cultivars to identify the potential for gene transfer to nonresistant wheat varieties. Working with a graduate student, Brad Hansen, to do wheat-to-wheat studies, they verified that pollen traveled 145 ft. according to a recent Farm Journal report [mid-February 2002]. Mallory-Smith told Farm Journal, "It's safe to assume the same would be true for pollen from herbicide-resistant varieties." The research is ongoing.
According to Martin Entz at the University of Manitoba, Pierre Hucl's research at the University of Saskatoon has shown that wheat pollen can move up to 800m [2,624 ft or about 1/2 mile].
According to a January 2000 report to the Soil Association in the UK, under certain conditions the distance of outcrossing could be considerably higher [than 60 m (197 ft.)] as previous research had indicated. Strong winds can not only disperse pollen widely but also increase the amount released by agitation of the anthers (Goss, 1968), while low temperatures and humidity can extend the viability of wheat pollen (deVries, 1971).
A degree of contradiction exists in the published studies on wheat pollen viability reviewed by deVries (1971). Estimates vary from 15 minutes up to 5 hours, most of the difference being due to different weather conditions. An estimate of one hour would seem to reflect wheat pollen viability in 'normal' field conditions [in the UK].
Hucl (1990; cf Anon 1999b) found that the frequency of outcrossing for 10 Canadian spring wheat cultivars varied according to the genotype, where the frequency was always lower than 9%. [Research results were compiled by National Pollen Research Unit, at the University College, Worcester, UK.]
According to the British publication, The Independent, an official EU study concludes genes will inevitably escape from genetically modified crops, contaminating organic farms, creating superweeds resistant to herbicides, and driving natural wild relatives of the crops to extinction through interbreeding. The report warns that "over time even small amounts of gene flow can have important effects on evolutionary change". For the full report in PDF format go to http://www.thecampaign.org/EEAPollenReport.pdf
In a paper presented at the 2001 Manitoba Agronomists Conference, researchers in Canada stated the following:
In conclusion, the paper stated, "Given the strong similarities between wheat and canola with respect to field persistence and outcrossing rate to 27m (88 ft) from pollen source, and the fact that spring wheat appears much more frequently in rotation than does canola it is apparent that there is a broad gene-bridge in spring wheat production in western Canada providing high risk for gene escape from Roundup Ready wheat. Gene escape will lead to both marketing and management problems with spring wheat and it may limit the sustainability of the valuable practice of direct-seeding in western Canada by increasing the cost and complexity of pre-seeding weed control and increasing the risk of glyphosate-resistant weed evolution." (R. van Acker and M. Entz, Dept. of Plant Science, University of Manitoba, Winnipeg)
According to Entz, "With the work that we have done on contamination with canola, where the pollen moves at least as far [as wheat-- 800m or 2,624 ft] and farther, our research indicates that it is the seed contamination issue that is the biggest culprit. Pollen flow is an issue. However, we just grow so much wheat that it is pretty hard to contain the seeds. In addition, because we have so much no-till, direct seeding, and Round-up use in ND, Manitoba and the rest of the Prairie region, we will be selecting for those [Round-up Ready] seeds that fall off the truck [escaping containment or segregation efforts]. So we are very concerned with the introduction of Round-up Ready wheat and its impact on farmers."
