Papers on OSR Pollen Dispersion

National Pollen Research Unit, University College, Worcester 18may01

Selected papers on pollen dispersal over medium to long distances (>200m). Compiled by The National Pollen Research Unit, University College, Worcester ,WR2 6 AJ 8/3/01

The following selection of papers illustrate the fact that pollen from GM crops will spread far beyond the proposed separation distances. If commercial production takes place this will inevitably lead to an increase in plot size and number. It is reasonable to assume that the background concentrations of the pollen will rise and that the maximum 1% cross pollination guideline will be exceeded regionally.

Dispersal of pollen via Insects

The dynamics of insect foraging behaviour are vital in gaining an understanding of pollen dispersal and ultimately cross- pollination. Until recently it was thought that insects minimize the distance to obtain maximum of energy (optimal foraging) and consequently few studies have addressed the medium scale. Recent studies show that insects can follow complex foraging patterns at great distances.

Ramsey et al. (1999) Honey bees and wild bumble bees are important pollinators of oilseed rape (OSR). Honey bees were found to leave the hive with OSR pollen from different sources indicating that either the individual bees forage on different OSR crops or simply pick up loose pollen in the hive. In either case this would lead to the possibility of cross pollination between crops and the authors conclude that With most honeybee colonies foraging up to 2km from the hive, some pollen transfer and fertilization up to 4km must be expected.

Osborne et al.(1999) Individual Bumble bees have been tracked using harmonic radar. The foraging bees were fitted with lightweight radar trans- ponders and were found to far exceed their expected foraging range. Osborne et al.(1999) have shown, that most bees regularly fly over 200m (range 70-631 m) from the nest to forage. This was observed even when apparently plentiful food was available from an OSR crop adjacent to the bees nest. "The results support the hypothesis that Bumble bees do not necessarily forage close to the nest, and illustrate that studies on a landscape scale are required if we are to evaluate bee foraging ranges fully with respect to resource availability. Such evaluations are required to underpin assessments of gene flow in bee-pollinated crops and wild flowers."

Skogsmyr (1994) The pollen beetle, can play a role in medium range cross- pollination of crops. In potatoes grown for seed the pollen beetle was considered to be responsible for very high levels of cross-pollination between a GM and non-GM potato fields. Gene dispersal from the GM crop was highest (72% ) in the near vicinity of the source, decreasing to 36% at 100m, while at 1000m it had only fallen to 31% (Skogsmyr, 1994). "Thus gene dispersal occurred both over large distances and to a higher extent than had previously been shown ".

Free and Williams, 1978 In oilseed rape the pollen beetle is often very common (Free and Williams, 1978), although its role in cross-pollination between OSR crops has, to our knowledge, not been studied.

Dispersal of pollen by wind

Thompson et al. (1999) This study used male sterile bait oilseed rape plants spaced at 0-4000m from a pollen source to monitor gene flow on a regional basis. Seed set was observed at a rate of 5% at 4km. At one bait site the majority of the pollinated plants (<80%) were shown, by DNA profiling, to have been fertilised by pollen from the nearest crop, 900m distant. A smaller number were found to have been fertilised by pollen 4km from the nearest known source, probably by insects. These results illustrate potential gene flow. The pollination levels for male fertile bait plants are likely to be much lower, although many modern varietal associations have a high proportion of male sterility increasing the likelihood of external pollination. " Despite the predominance of non GM OSR crops in the immediate locality, all sites were pollinated by a mixture of GM and non GM sources. The results suggest that farm to farm spread of OSR transgenes will be widepsread ".

Squire et al. (1999). Many plants with pollen that becomes airborne show a very rapid decline in pollen concentrations near the source followed by a very slow decline with increasing distance. The absolute level of pollen in such a leptokurtic decline is a function of the scale of source emission. It would seem probable, therefore, that source scale is of more significance in cross pollination at the medium scale than is distance. The source scale is determined by size of source fields and also the interaction between such fields on a landscape level ( Squire et al., 1999). " The evidence indicates that large pollen sources, such as crop fields, interacted on a regional scale to increase gene flow".

Timmons et al. (1995) Oil seed rape is commonly both insect and wind pollinated (the relative importance of each is dependant on environmental conditions). In a two year study of pollen dispersal from isolated Rape fields Timmons et al. (1995) used emasculated bait plants and a volumetric pollen trap up to 2.5km from the nearest Rape field.. They found a frequency of pollination of 0.8% at 2.5 km. The petals of the bait plants were removed making insect pollination less likely, possibly explaining the lower levels of cross-pollination compared to Thompson et al. (1999). Airborne pollen concentrations were found to be 10% of those at the field margin at a distance of 360m. This study also highlights the extensive distribution of feral populations of OSR which can act both as additional pollen sources and recipients. " Oil seed rape pollen has greater capacity for long range dispersal than has been suggested by small scale field trials"

Jones and Brooks (1950) Pollination of Maize is by wind, although some insects, including bees, do collect pollen allowing for the possibility of inclusion in honey. According to MAAF (2000), the best body of data for estimating cross-pollination in maize is that of Jones and Brooks (1950). The 3-year means (and range) of cross- pollination at different separation distances are given below:

25m 14.2% (7 - 19.8%) 75m 5.8% (3.6 - 8.6%) 125m 2.3% (.8 - 3.7%) 200m 1.19% (0.4 - 2.5%) 300m 0.48% (0.15 - 0.99%) 400m 0.23% (0.15 - 0.32%) 500m 0.20% (0.12 - 0.32%)

Salamov (1940) A study by Salamov (1940 cf Jones and Brooks, 1950) shows relatively high cross-pollination at 600m and above:

10m 3.3% 50m 0.33% 100m 0.36% 150m 0.25% 200m 0.54% 400m 0.02% 500m 0.08% 600m 0.79% 700m 0.18% 800m 0.21%

The significance of these results is further increased as the recipient field was much larger than the source (effectively leading to a dilution of source pollen) and was in a direction opposite to that of the prevailing wind.

References: Free, J.B. and Williams, I.H. (1978) The responses of the pollen beetle, Meligethes aeneus, and the seed wevil, Ceuthorhychus assimilis, to oil seed rape, Brassica napus, and other plants. Journal of Applied Ecology. 15. 761-774

Jones, M.D. & Brooks, J.S. (1950) Effectiveness of distance and border rows in preventing outcrossing in corn. Oklahoma Agricultural Experimental Station. Bulletin no. T-38

Osborne, J.L., Clark, S.J., Morris, R., Williams, I., Riley, R., Smith, A., Reynolds, D. and A. Edwards. (1999) A landscape-scale study of bumble bee foraging range and constancy, using harmonic radar. Journal of Applied Ecology. 36, 519-533

Ramsey, G., Thompson, C.E., Neilson, S. and Mackay, G.R. (1999) Honeybees as vectors of GM oilseed rape pollen. In: Lutman, P.J.W. Gene flow and Agriculture: Relevance for Transgenic Crops. BCPC Symposium Proceedings no.72.

Skogsmyr, I. (1994) Gene dispersal from transgenic potatoes to conspecifics: A field trial. Theoretical and Applied Genetics. 88: 770-774

Squire, G.R., Crawford, J.W., Ramsey, G., Thompson, C. and Bown, J. (1999) Gene flow at the landscape level. In: Lutman, P.J.W. Gene flow and Agriculture: Relevance for Transgenic Crops. BCPC Symposium Proceedings no. 72.

Thompson, C.E., Squire, G., Mackay, G.R., Bradshaw, J.E., Crawford, J. and Ramsay, G. (1999) Regional patterns of gene flow and its consequence for GM oilseed rape. In: Lutman, P.J.W. Gene flow and Agriculture: Relevance for Transgenic Crops. BCPC Symposium Proceedings no. 72

Timmons, A.M., O'Brien, E.T., Charters, Y.M., Dubbels S.J. and Wilkinson, M.J. (1995) Assessing the risks of wind pollination from field of genetically modified Brassica napus ssp. oleifera. Euphytica 85 pp417-423

(To be released June 2001 in a Canadian scientific publication)