Gene flow in birdsfoot trefoil (Lotus corniculatus) cultivations

Genetic engineering is becoming a useful tool in the improvement of plants but concern has been expressed about the potential environmental risks of releasing GM organisms into the environment. Attention has been focused on pollen dispersal as a major issue in the risk assessment of transgenic crop plants. Birdsfoot trefoil (Lotus corniculatus) is a perennial forage legume with high nutritive value used for pasture and hay. At this time, there are no data concerning the pollen diffusion from transgenic L. corniculatus field. The present communication wants to clarify the possibility, in central Italy, of gene escape, the frequency at which this occurs and the eventual cross pollination between birdsfoot trefoil and two related species, L. tenuis and L. pedunculatus. Plants of L. corniculatus transformed with either the E. coli asparagine synthetase gene asnA or the ?-glucuronidase gene uidA, have been used as pollen donor. Non-transgenic plants belonging to the species L. corniculatus L., L. tenuis and L. pedunculatus have been utilized as recipients. In the experimental field located in Perugia, two pollinating plots have been transplanted at the two opposite corners of a 64 x 40 m field. Sixteen recipient plots were distributed in the whole area of the field. In each plot, 4 non-transgenic plants for each of the three species considered were transplanted. In the experimental field in Rome, a 2 ha field trial was prepared to address the effect of field size on pollen. Ten recipients plots were distributed in the field. Seeds were hand-harvested at the end of summer in both fields and were sown in the greenhouse for DNA investigation. Gene flow was evaluated by PCR. For the uidA gene, the X-Gluc staining assay was also performed to confirm data obtained from PCR amplification. Gene flow was measured as the percentage of plants with a transgene-specific PCR product with respect to the totality of plants analysed. Plants carrying the uidA gene were partially sterile, therefore only the asnA gene was used as tracer marker. No transgene flow between L. corniculatus transformants and the non-transgenic L. tenuis and L . pedunculatus plants was detected. As regards non-transgenic L. corniculatus plants, while in Perugia the pollen diffusion was contained and occurred just for 18 meters away from the asnA pollinating plot with a frequency of 0,24%, in Rome the distance reached by the transgene is considerably higher, being the gene detectable till the distance of 120 m away from the source plot with a frequency of 0,74%. The results demonstrate that birdsfoot trefoil pollen can travels and that the percentage of gene flow is far from to be zero also at considerable distances.