回交次数对转Bt基因抗虫棉抗性及经济性状的影响

Effect of Back-crossing Times on Bollworm Resistance and Economic Traits of Transgenic Bt( Bacillus thuringiensis ) Cotton

以中国转Bt(Bacillusthuringiensis)基因棉GK3和美国转Bt基因棉33B为非轮回亲本,非抗虫品种中棉所17和中棉所19为轮回亲本,培育了两套回交世代材料。研究了回交材料各世代Bt基因棉杀虫蛋白含量和抗虫效果,以及回交次数与主要经济性状、Bt杀虫蛋白含量之间的关系。结果表明:杀虫蛋白含量随转Bt基因棉回交次数的增加,呈现下降趋势,两套材料表现较一致。以GK3为亲本的回交世代材料中,回交2次时,Bt杀虫蛋白含量下降到GK3的1/5～1/4,降低达显著水平。各世代室内生测抗虫效果,与Bt杀虫蛋白含量呈高度一致。回交次数与Bt杀虫蛋白含量、子、皮棉产量、单株铃数呈负相关,并达显著或极显著水平,与铃重、衣分呈正相关。选用的亲本材料纤维品质较一致,在回交各世代中,差异不明显。综合分析表明,在本文研究的回交材料中,回交次数少效果比较理想,主要性状已基本达到育种要求,回交次数多,虽然某些经济性状有所改善,但抗虫性已明显降低。

Utilizing summer in Anyang Henan and winter in Sanya Hainan as experiment field bred materials two generations in a year, 2 sets of cotton backcross generation were made by means of backcross, using transgenic Bt cotton lines GK3 and Nutn33B from China and U.S.A, respectively as non-recurrent parents, and CRI 17 and CRI 19 as recurrent parents, from 1997 to 2000. These 2 sets of back-crossing generation materials and parents were planted in experimental field in April 2000. At cotton flower and boll stage, the function leaves of cotton plants were chosed examined. Content of Bt insecticidal protein in each of the material, except CRI17 and CRI19 were examined by ELISA as designed according to Wang baomin,He zhongpei. The result of restance to ballworm was measured laboratory bioassay as designed by Ma lihua etc. The traits of lint yield and quality were obtained by field experiment. The field planting followed a random block design with three rows and three replications,the field management followed essentially the practice under normal agricultural conditions. The effect of bollworm resistance and Bt insecticidal protein content were studied in each backcross generation, and the relations were analyzed between backcross times, main economic traits and Bt insecticidal protein content. The results indicated content expressed of transgenic Bt plants was reduced as the increase of back-crossing times, which was consistent with the two materials. Content of Bt insecticidal protein significantly lowered to 1/4～1/5 of GK3's which was highly consistent with the result of laboratory bioassay utilizing GK3 as non-recurrent parent, when back-crossed to the second generation. Back-crossing times showed a significantly negative relativity with the content of Bt insecticidal protein, output of seed cotton and lint yield, boll numbers, and positive relativity with boll weight, lint percent, but not significantly. There were no differences in fiber quality between back-crossing generations, for the selected parents were uniform in their qualities. The result indicated there was an ideal effect by less back-crossing times, and main characters had reached breeding object. In sum, decision of back-cross times was a very important step in back-cross breeding, as to how many back-cross times were needed, which depended on whether the main traits reached cotton breeding object. According to this study, 1～2 times back-crossing were ideal. Although the more times of the back-crossing could improve some of the economic characters, the ability of the resistance bollworm could be greatly influenced and decreased.