Beijing, China
August 22, 2012
Source: SciDev.Net
The spread of genes from genetically modified (GM) crops to neighbouring wild plants, although inevitable, may not happen as quickly as feared, according to a study conducted in Chinese rice fields.
GM crop genes, such as those designed for insect resistance, can spread through cross-pollination with wild plants surrounding farmers' fields — an issue considered to be of major environmental concern, as little is known of the ecological consequences of such gene spread.
But a study by Chinese scientists has found that gene flow of this type is unlikely to occur rapidly, as the transferred genes — or 'transgenes' — do not actually enhance the survival of wild plants. This is because the number of insect pests would have already been reduced in the local area due to the GM crops' insect-resistant genes.
The researchers from Fudan University and the Fuijan Academy of Agricultural Sciences crossed a rice strain that had been genetically modified to carry an insect-resistant gene with a wild, 'weedy rice' strain, and then tested the survival of their progeny four generations later in an experimental field setting in Fuzhou, in Fujian Province, China.
The scientists compared survival rates of progeny containing the insect-resistant transgene with those not containing it, and with survival rates of the original wild rice plant, under conditions of low and high insect pest numbers.
The results showed that when pressure from pests was high, the transgene gave the hybrid varieties a fitness advantage in all tested fitness traits, such as number of seeds produced. However, when the number of insect pests was lower — as is the case in areas surrounding GM fields — hybrids containing the transgene did no better than unmodified wild rice in most fitness traits.
Bao-Rong Lu, chairman of the ecology and evolutionary biology department at Fudan University in China, and a lead author of the study, said that by tracing the fitness of the first four generations of hybrids the researchers had shown that "GM rice will not cause serious environmental problems".
Wei Wei, an ecologist from the Institute of Botany at the Chinese Academy of Sciences, welcomed the study, but said further evidence was needed to confirm the findings.
Xue Dayuan, chief biodiversity scientist at the College of Life and Environmental Sciences at the Minzu University of China, told SciDev.Net the field tests were limited in what they can show.
"It's totally different with the open field. Under the different climate and ecological environments, the risk from the potential transgene flow or transgene pollution may be more likely to happen," Xue said.
And Bruce Tabashnik, a professor of zoology from the University of Michigan, United States, told SciDev.Net that the paper was correct in saying that it "is less likely that the transgenes will spread rapidly" when the pest population is slow.
But he added that some key questions remain, including the extent to which GM rice will reduce the number of pest insects.
The study was published in PLoS ONE last month (17 July).
Link to full article in PLoS ONE
转基因水稻的基因逃逸“不可避免但缓慢”
北京]基因从转基因（GM）作物向临近的野生植物的漂移尽管是不可避免的，但可能不像担心的那样快，根据在中国水稻田间展开的一项研究称。
转基因作物的基因，比如那些专为抗虫而设计的基因，能通过与农民田地周边的野生植物交叉授粉而传播出去——这曾被认为是影响环境的主要问题，因为人们对这种基因传播带来的生态后果知之甚少。
但中国科学家的一项研究发现，这种类型的基因流不可能发生的很快，因为转基因实际上不会提高野生植物的生存能力。原因在于当地害虫的数目已被转基因作物的抗虫基因而减少。
复旦大学和福建农科院的科研人员合作将一种带有抗虫基因的转基因水稻品系与一种野生‘杂草稻’品系杂交，然后在中国福建省福州市的实验田里已经追踪了几个代，论文中是追踪器其第四代的生存能力。
科学家们将含有抗虫转基因的后代、不含有的后代的生存能力与原始野生稻植物的生存率在高低病虫害数目的条件下作比较。
试验结果表明，当虫压力高时，转基因给杂交品种在所有测试适合度特点中一个适合度优势，比如产生种子的数目。然而，病虫害的数据较低的时候——就像在转基因作物田地周边地区的情况一样——含有输异基因的杂交品种在大多数适合度特点中并没有比未改变的野生稻表现的更好。
中国复旦大学生态学与进化生物学系主任、这项研究的主要作者卢宝荣称，通过跟踪杂交品种的前四代的适合度研究人员发现“转基因水稻不会造成严重的环境问题”。
中国科学院植物研究所的生态学家魏伟对这项研究表示欢迎，但也表示需要进一步的证据来确认这项发现。
中国中央民族大学生命与环境科学院的首席生物多样性科学家薛达元在接受科学与发展网络时表示，在田间实验研究生态风险毕竟有限。
“实验田地与野外田地完全不同。在不同的气候和生态环境下，潜在的基因流或基因污染的风险在野外田地发生的可能性更大，”薛达元表示。
而密歇根大学的动物学教授Bruce Tabashnik认为，这篇论文在表示当害虫种群增长缓慢时“基因漂移不太可能迅速扩散”方面是正确的。
但他补充道，一些关键问题仍然存在，包括转基因水稻降低病虫害数目的程度等。
这项研究发表于上月《PLoS ONE》（7月17日）。
链接到《PLoS ONE》全文
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