草甘膦抗性是北美和南美国家的农民普遍采用的转基因作物性状，目前全球1.2亿公顷转基因作物种植面积的80%是抗草甘膦性状作物。然而，由于受到包括劳动力市场、草甘膦残留等在内的诸多因素的影响，中国草甘膦抗性作物的种植并未得到相似的采用率。
来自中国农业科学院生物技术研究所的郭三堆研究员及其团队，通过共表达密码子优化的GR79 EPSPS基因和GAT基因创制获得两个转基因棉花株系GGCO2 and GGCO5，其草甘膦耐性提高了5倍，而草甘膦残留量降低了10倍。转基因株系GGCO2作为种质资源应用于棉花杂交育种，五个地点三个生长季的田间试验结果标明，转pGR79-pGAT基因棉花株系与对照非转基因常规棉花相比，其农艺性状表现无显著差异，但每公顷节约了390-495美元的人工除草成本。该研究表明，聚合EPSPS基因和GAT基因不仅能够提高草甘膦抗性而且可以降低草甘膦的残留量，对抗除草剂转基因作物的可持续发展具有重要的指导意义。药残留一直是食品安全的重要评价内容，2017年中国农业部新修订的转基因植物安全评价指南也明确指出，除草剂残留量是耐除草剂转基因作物安全评价的重要指标之一。
Plant Biotechnology Journal (2017), pp. 1–8
Co-expression of GR79 EPSPS and GAT yieldsherbicide-resistant cotton with low glyphosate residues
Authors
Chengzhen Liang, Bao Sun, Zhigang Meng, et al.
Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.
Summary
Glyphosate-resistant (GR) crops have been adopted on a massive scale by North and South American farmers.Currently, about 80% of the 120 million hectares of the global genetically modified (GM) crops are GR crop varieties. However, the adoption of GR plantsin China has not occurred at the same pace, owing to several factors including,among other things, labour markets and the residual effects of glyphosate intransgenic plants. Here, we report the co-expression of codon-optimized forms of GR79 EPSPS and N-acetyltransferase (GAT) genes in cotton. We found five times more resistance to glyphosate with 10-fold reduction in glyphosate residues in two pGR79 EPSPS-pGAT co-expression cotton lines, GGCO2 and GGCO5. The GGCO2 line was used in a hybridization programme to develop new GR cottons. Field trials at five locations during three growing seasons showed that pGR79-pGAT transgenic cotton lines have the same agronomic performance as conventional varieties, but were USD 390-495 cheaper to produce per hectare because of the high cost of conventional weed management practices. Our strategy to pyramid these genes clearly worked and thus offers attractive promise for the engineering and breeding of highly resistant low-glyphosate-residue cotton varieties.
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