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[SANET-MG] Reproductive isolation in hybrid seed production



It is difficult to find good reports on the pollution of organic corn fields near GM corn production. The report below is on hybrid seed production and seed contamination by out crossing from nearby commercial corn fields shows that corn near the margins of fields may have as much as 21% contamination from the commercial crops. This suggests that non-GM or organic corn may be more extensively polluted by GM pollen than has previously been acknowledged. Off course, if 21% of the corn on field margins was polluted by GM pollen this would immediately lead to visits from roving bands of Monsanto lawyers (a major pest in corn country).
Published in Crop Sci 46:1445-1455 (2006)
DOI: 10.2135/cropsci2004.0007

Managing Reproductive Isolation in Hybrid Seed Corn Production
D. S. Irelanda, D. O. Wilson, Jr.b, M. E. Westgatec,*, J. S. Burrisd and M. J. Lauere
a Doebler's Pennsylvania Hybrids, Inc., daleireland@doeblers.com
b Landec Ag, Inc. 201 N. Michigan, Oxford, IN 47971, dwilson@landecag.com
c Department of Agronomy, Iowa State University, Ames, IA 50011
d Burris Consulting 1707 Burnett Ave, Ames, IA 50010, burrisconsulting@msn.com e Pioneer Hi-Bred International, Inc., 6900 NW 62nd Avenue, Johnston, IA 50131, Michael.Lauer@Pioneer.com Abstract:Production of hybrid corn (Zea mays L) depends on cross-pollination between male and female inbred parents. As such, reproductive isolation of seed fields is required to ensure genetic purity of the hybrid progeny. Customer demand for improved genetic purity prompted the seed industry to examine the level of genetic purity resulting from current isolation practices. A 3-yr study was conducted to monitor purity of hybrid seed produced in 315 fields from 24 seed companies in North America. Each field was near a commercial corn field shedding pollen synchronously with the seed parent: a worse case scenario. Seed samples were collected at five locations along a 200-m transect established perpendicular to the nearest potential adventitious pollen source, and 100 seed from each location were subjected to isozyme analysis to determine percent out-crossing. Isolation distance, seed field size, field block size, number of border rows, adventitious field size, male:female row ratio, male population, and male pollen class were analyzed as continuous predictors and as variable class predictors of out-crossing at the field margins and field midpoints. Year had a significant (p 0.05) impact on observed out-crossing. Isolation distance, border rows, and male pollen class were significant predictors of out-crossing at the field margin but not at the field midpoint. A significant interaction between isolation distance and border rows was observed at both the field margin and midpoint. There also was an interaction between male:female ratio and male pollen class on out-crossing at the field margin. These results indicate that current practices used to isolate hybrid seed fields often achieve the goal of producing 99% genetically pure seed, but much higher levels of out-crossing can and do occur. Because out-crossing generally was greater and more variable at the field margins than at the field midpoint, adjustments to field management that focus on minimizing out-crossing at the field margins should lead to consistently high levels of genetic purity from hybrid seed fields. From the report: "The distribution of out-crossing percentages for the nearly 1800 seed samples evaluated in this study. Across 3 yr of study, approximately 65% of the samples collected from the field margins and field midpoints had out-crossing levels of 1% or less. Out-crossing levels greater than 6% were rare, but levels as high as 21% out-crossing were reported. The extent of out-crossing varied by year and by location within the field. In 1998, for example, no out-crossing was detected in 60% of the field midpoint samples or in 56% of the field margin samples. None of the field midpoint samples collected in 1998 reported more than 4% out-crossing. The highest level of out-crossing observed at the field margin was 7%. In 1999 and 2000, fewer field midpoint and field margin samples had zero out-crossing, and the level of out-crossing was more variable along the field margins. Out-crossing values as high as 21% were observed at the field margin and up to 15% at the field midpoint. In general, out-crossing along the field margins was greater and more variable than that observed at the field midpoints."

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