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Based on international findings, Irish co-existence guidelines for the
cultivation of GM potato stipulate that an isolation distance of 20 m is
required to minimize the spread of transgenic pollen in accordance with
required labeling thresholds. As potato tolerant to Phytophthora infestans is the most applicable GM
crop from an Irish context, we tested the efficacy of this isolation
distance under Irish environmental conditions using the conventional variety
Désirée as a pollen donor and the male-sterile variety British Queen
as a pollen receptor. Gene flow was determined by scoring for berry presence
on receptor plants and confirmed using a microsatellite marker system
designed to assess paternity in F1 seedlings. 99.1% of seedlings
recovered were identified as having Désirée paternity. Whereas
19.9% (140/708) of total berries formed on receptor plants occurred at a
distance of 21 m from the pollen source, only 4 of these berries bore viable
true potato seed (TPS), from which 23 TPS germinated. TPS-bearing berry
formation was negatively correlated with distance from the pollen source,
and although overall distribution of berries and seeds was non-random across
the plot, no significant correlation was evident with respect to wind
direction. Microsatellite markers were also used to confirm that the
foraging beetle Meligethes aeneus is a vector for the transmission of potato pollen, but a
more detailed statistical analysis of this dataset was limited by inclement
weather during the trial. To conclude, we recommend that a two-tiered system
be established in regard to establishing isolation distances for the
experimental trial and commercial cultivation of GM potato in Ireland, and
that responsible crop management be adopted to minimize the establishment of
TPS-derived volunteers, which we have noted will emerge through a rotation
as a result of pollen-mediated gene flow.
We have assessed the utility of morphological and microsatellite markers for tracing field hybridization between Lolium multiflorum and Lolium perenne in cereal-enclosed gene flow plots. The presence of awns on the inflorescence of F1 hybrids was found to be a reliable, but underscoring, indicator of L. multiflorum paternity in L. perenne derived seed as determined by inheritance of species-specific alleles at the microsatellite locus ‘H01 H06’ in these progeny. A positive correlation was evident in the experimental treatment between the number of pollen donor plants in a given plot and the frequency of hybrid F1 seed harvested from pollen receptor plants in that plot. These experiments have established the utility of naturally occurring heritable markers for the measurement of gene flow rates in field Ryegrass populations, with particular significance for risk assessment modeling of potential gene flow from transgenic grass cultivars.
Guidelines to ensure the efficient coexistence of genetically modified (GM) and conventional crops are currently being considered across the European Union. The purpose of this strategy is to describe the measures a farmer must adopt to minimize the admixture of GM and non-GM crops. Minimizing pollen / seed-mediated gene flow between GM and non-GM crops is central to successful coexistence. However no system is currently available to permit the numeric quantification of a crop’s propensity for pollen/seed-mediated gene flow. The provision of such a system could permit a background level of gene flow, specific for a particular conventional crop, to be calculated. Here we present a gene flow index model implemented using the principal arable crops in Ireland as a model dataset. The objective of this research was to establish a baseline gene flow data set for Ireland’s primary conventional crops through the provision of a simple numerical index. This Gene Flow Index (GFI) incorporates four strands of crop-mediated gene flow (crop pollen-to-crop, crop pollen-to-wild, crop seed-to-volunteer and crop seed-to-feral) into a format that permits the calculation of a crop’s gene flow potential. Responsive to regional parameters, we have applied the model to sugar beet, oilseed rape, potato, ryegrass, maize, wheat and barley. We propose that the attained indices will highlight those crops that require additional measures in order to minimize gene flow in accordance with anticipated coexistence guidelines.
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