转Xa21基因杂交水稻选育和评价

Breeding and Food Safety Evaluation of Transgenic Hybrid Rice Harboring Xa21 Gene

通过基因枪转基因方法和双质粒共转化体系将Xa21基因转入优良恢复系明恢63,得到转基因系M12和M22,并进一步做田间试验、新品种选育和食用安全性评价。结果显示:M12和M22对中国的所有白叶枯病小种都表现出高度抗性,但与原受体品种明恢63相比,农艺性状上有许多变异,主要表现在:结实率、千粒重等农艺性状变差,与珍汕97A的配合力显著降低;但与温敏不育系(X07S、056S)配组的F1有较好的田间表现。通过多代回交和分子标记辅助选择,成功地将Xa21基因从M12株系转到保持系80-4B和不育系80-4A中,得到抗白叶枯病的皖21B和皖21A。并利用皖21A不育系选育出优良杂交组合抗优97(皖21A×R-18),该组合在两年区域试验和一年生产试验中产量表现突出,米质优良。对不同世代和不同遗传背景的转基因品系进行白叶枯病鉴定和Southern分析表明:Xa21基因都能稳定遗传和正常表达,连续16代的种植并没使其白叶枯病的抗性减弱或丧失,而且不论Xa21基因是纯合的还是杂合的都有相同的抗性表现。对大鼠和小鼠的饲喂试验表明:转基因大米实质上等同于非转基因大米,是安全无害的。

Transgenic rice, events M12 and M22 in which a Xa21 gene inserted, derived from transformation of Minghui63, an elite restorer line, was developed for field evaluation, breeding and biosafety assessment in China. Result demonstrated that transgenic M12 and M22 were highly resistant to all Chinese races of rice bacterial blight （RBB）. Comparing M12 and M22 with the original recipient Minghui63, a lot of variations were found in agronomic characters. Seeding-setting capacity and 1 000 grains weight were lower than the recipient variety. Combining ability of M12 with a CMS （cytoplasmic male sterility） line, Zhenshan97A, was declined greatly, but combining ability of M12 with TGMS （temperature-sensitive genic male sterile） lines, X07S and 056S, was excellent. Through backcrossing and marker-aided selection, Xa21 gene was transferred from M12 to maintainer line 80-4B and it＇s CMS line 80-4A and produced Wan21B and Wan21A with high resistance to RBB. Finally, a superior hybrid rice （Wan21AxR-18） with Xa21 gene was developed which expressed high yields and excellent quality in two year＇s regional field test and pre-production test in Anhui. Results also indicated that Xa21 gene in different generation and genetic background could be stably inherited and presented sustained resistance to RBB and no resistance decline or loss were found in successive planting for 16 generations. Heterozygous Xa21 gene in hybrids and homozygous Xa21 gene in pure lines presented same RBB resistance. The acute oral toxicity in mice and rats,90-day feeding study, micronucles assay, sperm aberration test and Ames test have demonstrated that the transgenic rice grain is substantially equivalent to the non-transgenic rice grain in terms of the biosafety when consumed as food or feed.