转基因抗除草剂油菜对近缘作物的基因漂移

Studies on the gene flow from herbicide-tolerant GM rapeseed to its close relative crops

以转基因抗除草剂油菜 Q3和 HCN- 19为花粉供体材料 ,油菜近缘作物为花粉受体材料 ,在自然授粉条件下研究甘蓝型油菜与芸薹属近缘作物间的基因漂移频率。结果表明 ,油菜对芸薹属 6个种甘蓝、黑芥、埃芥、芥菜型油菜、白菜型油菜和甘蓝型油菜的基因漂移率分别为 0、0 .0 2 4 %～ 0 .2 4 3%、 0 .0 2 8%～ 0 .0 92 %、 0 .10 9%～ 0 .95 1%、 0 .4 79%～ 0 .879%、 1.2 5 2 %～2 .191%。且基因漂移频率受多种因素影响 ,其中与杂交亲和性、花期同步率、种植面积等高度相关。通过花粉将抗除草剂基因漂移给近缘作物 。

The rate and its determining factors of gene flow between two herbicide-tolerant GM rapeseed varieties and seven varieties from six Brassica species was studied under the paired growth and natural pollination conditions. This study will provide scientific evidence for the evaluation of the ecological safety of growing GM herbicide-tolerant rapeseed crop. At the year 2000/2001 season, the pollen donor glyphosate-tolerant GM rapeseed variety Q3 plants were grown in pairs with each of the seven pollen receptor varieties which are all close relative of the pollen donor. The row ratio is 4:2. The growth area for each pair is 20m^2. Following natural pollination, the seeds from receptor plants were harvested and pooled for each variety. Seeds were sown in the following autumn in the field condition in order to screen and identify the individual progenies with gained glyphosate-tolerance. Seedlings at the 4～5 leaves stage were spread with 0.2% glyphosate at 450 kg/hm^2. Both dead and survived seedlings were counted 15 days later and the rate of gene flow through pollen drift from the glyphosate-tolerant GM plants was calculated. Among the six Brassica species studied, only Brassica oleracea var. Rowara was not contaminated by gene drift owing to the its incompatible flowering period, while the rest six varieties from five species all contaminated by herbicide resistance gene through pollen drift to some extent. The rates of gene flow to B. carinata var. Dodolla and B. nigra var. UNS are the lowest among the six pairs, 0.091% and 0.243%, respectively. The rate of B. juncea var. Liyang Kucai and B. campestris var. Xinghua Youcai are relatively high, being 0.951% and 0.879%, respectively. The highest gene flow rates were observed in the two B. napus varieties, i.e. vars. Ningyou No.7 and Ningza No.1, with 1.252% and 2.191%, respectively. The same methodology was used to measure the rate of gene flow from glyfosinate-tolerant GM rapeseed HCN-19 and its close relative crops in the growing season of 2001～2002. The row ratio was 2:2 and the growth area for each pair was 30m^2. Mature seeds from each pollen receptor variety were harvested and sown in autumn to evaluate the rate of gene flow from the glyfosinate-tolerant GM pollen donor. The seedlings at 4～5 leaves stage were spread with 0.2% glyfosinate at 450 kg/hm^2. Except that B. oleracea var. Rowara, all the rest six varieties of five species have been contaminated by the gene flow from glyfosinate-tolerant GM pollen donor. The rate of gene flow to B. carinata var. Dodolla and B. nigra var. UNS was relatively low, being 0.028% and 0.024%, respectively. B. juncea var. Liyang kucai and B. campestris var. Xinghua youcai ranked in the middle, being 0.109% and 0.479%, respectively. The highest rate of gene flow was observed with B. napus var. Ningyou No.7 and Ningza No.1, up to 1.698% and 1.724%, respectively. The current research across two consecutive growing seasons has produced consistent results in relation to the trend of gene flow of two different herbicide-tolerance genes from rapeseed to its close Brassica relatives. It is clearly demonstrated that the rate of gene flow from rapeseed to other B.napus varieties is higher than to other Brassica species. It was also observed that the rate of gene flow from herbicide-tolerant rapeseed to B. juncea varieties or B. campestris varieties is higher than to B.nigra varieties or to B. carinata varieties. The true transgenic identity of the plants contaminated by gene flow has been further examined by PCR using primers derived from the respective herbicide-tolerence gene and all of these plants were confirmed positive. This clearly confirmed the high reliability of the current data. The current research also demonstrated that the flow rate of herbicide-tolerant gene from GM rapeseed to its Brassica relatives is determined by multiple factors among which the sexual compatibility between the pollen donor and recipients, synchronous flowering time are very important. It is the authors' belief that the rapeseed could transfer herbicide to