Submitted to: Environmental Biosafety Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2003
Publication Date: 4/2/2003
Citation: Ray, J.D., Kilen, T.C., Abel, C.A., Paris, R.L. Soybean natural cross-pollination rates. Environmental Biosafety Research. 2:133-138
Interpretive Summary: Concerns about cross-pollination of transgenic crops with conventional crops has been a recent topic in public discussions. Natural cross-pollination rates were measured in soybean grown in the Delta region of Mississippi. Natural cross-pollination rates of 0.03% to 6.32% were measured in two experiments conducted at Stoneville, MS. The maximum rates reported are considerably higher than most previously reported rates. The results of these two experiments highlight the potential for within-crop transgene flow in soybean.
Technical Abstract: Recent concerns regarding within-crop transgene flow stimulated this research to update natural cross-pollination rates in conventional sowings of modern soybean in the Mississippi Delta. Two experiments were conducted in 2001 and 2002. Two soybean cultivars, 'Pace' (white-flowered) and 'DP3588' (purple-flowered) were used in the experiments. The cultivars were selected for their equivalent flowering dates. The experiments utilized the dominance of purple flower color over white flower color to identify natural cross-pollinations. In the first experiment, 20 rows 45 m in length and spaced 0.9 m apart were sown on 10 May 2001. The first 4 rows and the last 4 rows were sown to DP3588 and the middle 12 rows were sown to Pace. Seed were harvested by row from each of the Pace rows and examined for natural cross-pollinations in the next generation. In total, 73,512 potential hybrid plants were examined and natural cross-pollination rates ranged from 0.41% at 0.9 m from the pollen source to 0.03% at 5.4 m from the pollen source. These values were consistent with values previously reported in the literature. In the second experiment, seed of Pace and DP3588 were alternately sown 15.2 cm apart within a row in 2001. At maturity, 167 Pace plants were harvested and a total of 19,151 progeny were evaluated for natural cross-pollinations in the next generation. The progeny of 56 (33.5%) of the 167 parent plants showed no evidence of natural cross-pollination. The progeny of the remaining 111 plants exhibited natural cross-pollination rates ranging from 0.65 to 6.32% and averaged 1.8%. The maximum rates reported here are considerably higher than most previously reported rates. The results of these two experiments highlight the potential for within-crop transgene flow in soybean.