Gressel Jonathan
Plant Sciences, Weizmann Institute of Science, Rehovot, Israel.
Pest Manag Sci. 2015 May;71(5):658-67. doi: 10.1002/ps.3850. Epub 2014 Aug 15.
Genes regularly move within species, to/from crops, as well as to their con- specific progenitors, feral and weedy forms ('vertical' gene flow). Genes occasionally move to/from crops and their distantly related, hardly sexually interbreeding relatives, within a genus or among closely related genera (diagonal gene flow). Regulators have singled out transgene flow as an issue, yet non-transgenic herbicide resistance traits pose equal problems, which cannot be mitigated. The risks are quite different from genes flowing to natural (wild) ecosystems versus ruderal and agroecosystems. Transgenic herbicide resistance poses a major risk if introgressed into weedy relatives; disease and insect resistance less so. Technologies have been proposed to contain genes within crops (chloroplast transformation, male sterility) that imperfectly prevent gene flow by pollen to the wild. Containment does not prevent related weeds from pollinating crops. Repeated backcrossing with weeds as pollen parents results in gene establishment in the weeds. Transgenic mitigation relies on coupling crop protection traits in a tandem construct with traits that lower the fitness of the related weeds. Mitigation traits can be morphological (dwarfing, no seed shatter) or chemical (sensitivity to a chemical used later in a rotation). Tandem mitigation traits are genetically linked and will move together. Mitigation traits can also be spread by inserting them in multicopy transposons which disperse faster than the crop protection genes in related weeds. Thus, there are gene flow risks mainly to weeds from some crop protection traits; risks that can and should be dealt with.
基因经常在物种内部移动，在作物之间、与作物的同种祖先、野生和杂草形态之间移动（“垂直”基因流）。基因偶尔也会在作物与其远缘、几乎不进行有性杂交的亲缘物种之间移动，即在一个属内或密切相关的属之间移动（对角线基因流）。监管机构已将转基因流动视为一个问题，但非转基因除草剂抗性性状也带来了同样的问题，且无法缓解。基因流入自然（野生）生态系统与流入杂草丛生和农业生态系统的风险截然不同。如果转基因除草剂抗性渗入杂草亲缘物种中，会构成重大风险；而疾病和昆虫抗性带来的风险则较小。人们已提出一些技术来将基因限制在作物内部（叶绿体转化、雄性不育），但这些技术并不能完美地阻止花粉将基因传播到野外。限制措施并不能防止相关杂草给作物授粉。以杂草为花粉亲本进行反复回交会导致基因在杂草中确立。转基因缓解措施依赖于将作物保护性状与降低相关杂草适合度的性状串联构建。缓解性状可以是形态学上的（矮化、不散落种子）或化学上的（对轮作后期使用的某种化学物质敏感）。串联缓解性状在基因上是连锁的，会一起移动。缓解性状也可以通过将它们插入多拷贝转座子来传播，多拷贝转座子在相关杂草中的传播速度比作物保护基因更快。因此，一些作物保护性状主要对杂草存在基因流动风险；这些风险是可以且应该加以应对的。
