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LETTERS TO THE EDITOR

^a Monsanto Company, 800 North Lindbergh Blvd., St. Louis, MO 63167
^b Monsanto Canada, Winnipeg, Manitoba
^c Dep. of Plant Sciences, Univ. of Saskatchewan, 51 Campus Dr., Saskatoon, SK S7N 5A8, Canada

^* Corresponding author (david.i.gustafson{at}monsanto.com)

Dear Editor:

We thank Willenborg and Van Acker for their interest in our recent paper entitled, "An Empirical Model for Pollen-Mediated Gene Flow in Wheat," (Gustafson et al., 2005). In their letter, they raise questions about our approach to which we respond here. Their primary critique involves the size of the pollen source plots in the various studies used to develop the model. We acknowledge that the pollen source plots were relatively small, but we conducted an exhaustive search for relevant data, and these were the only studies available. None of the other studies cited by Willenborg and Van Acker were for wheat, and we fail to see the relevance of canola and maize data to wheat, which is known to have a much lower out-crossing potential than these other crops.

Willenborg and Van Acker go on to criticize the specific mathematical model we employed in our study, claiming that it fails to describe the "tail of the gene flow." We respond simply that the wheat data do not have a "tail," and that our model fits all of the wheat data we have examined extremely well. We therefore stand by all of our conclusions regarding the minimal practical effects of scale and isolation distances in wheat.

Willenborg and Van Acker rightly point out that we failed to include standard errors for the various parameter estimates presented in the paper. We thank them for this helpful comment and plan to include this improvement in our subsequent work with other crops. We agree that proper characterization of overall model uncertainty is an excellent practice, although somewhat less necessary for a conservative (high estimates of gene flow) model of the type we proposed in our work.

We find ourselves puzzled by the comment that our assumptions concerning inter- and intraspecific gene flow on p. 1287 are "unusual." We believe they must have misunderstood the intent of our discussion. We agree with them that harvest losses of wheat grain occur and that any form of subsequent multigenerational population modeling should regard our gene flow estimates as being extreme upper-bound estimates (high estimates of gene flow) because most of the harvested grain is taken out of the environment. The remaining discussion in their letter speaks to a variety of issues not related to our paper. We stand by the conclusion that our model fits the observed wheat gene flow data very well.

REFERENCES

• Gustafson, D.I., M.J. Horak, C.B. Rempel, S.G. Metz, D.R. Gigax, and P. Hucl. 2005. An empirical model for pollen-mediated gene flow in wheat. Crop Sci. 45:1286–1294.[Abstract/Free Full Text]

This Article Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gustafson, D. I. Articles by Hucl, P. Search for Related Content PubMed Articles by Gustafson, D. I. Articles by Hucl, P. Agricola Articles by Gustafson, D. I. Articles by Hucl, P.