Bt玉米秸秆还田对小麦幼苗生长发育的影响

以已进入中间试验阶段的Bt玉米及其亲本(非Bt玉米)秸秆为材料,与营养土及蛭石混合后培养小麦幼苗,同时以未使用秸秆的相应土为空白对照,在室内条件下研究了Bt玉米与亲本秸秆还田对后茬小麦的影响。结果表明:(1)不同秸秆还田对小麦幼苗出苗率、株高没有显著影响;(2)非转基因玉米与转Bt玉米秸秆拌土后地上部鲜重仅为对照鲜重的51%和65%,干重仅为对照的62%和72%,均达到差异显著水平;(3)Bt玉米秸秆还田降低小麦幼苗生长素(IAA)含量,郑58秸秆拌土增加了幼苗脱落酸(ABA)含量;(4)两种处理均提高了幼苗的超氧化物歧化酶(SOD)总活性。因此,秸秆拌土对小麦幼苗的处理效应一致,与秸秆类型无关,该研究可为评价转Bt玉米环境安全提供一定的理论依据。

Effects of maize straw with Bt gene return to field on growth of wheat seedlings

Fast popularization and widespread application of transgenic Bt corn have raised the issue of environmental safety. Despite considerable work in this field recently, no consensus on the effects of Bt corn on environmental safety has emerged, indicative of the complexity of this issue. Traditional study on environmental safety of transgenic crops often focused on the risks of weediness of genetic modified crop itself, gene flow, negative impact on useful insects or microbe in soil, while ignored the effect of transgenic crops on succeeding crops. Therefore, the major objective of this study is to investigate the effect of Bt corn straw incorporated into soil on growth of winter wheat (Triticum aestivum) seedlings. The chopped straw of transgenic Bt corn inbred (Bt-38) and non-Bt corn (Zheng 58, the receptor of Bt-38) was mixed with nutrient soil and vermiculite (1:3:3) to be as the growth media for winter wheat (cv. Duokang 1), with the media without corn straw as the control. The results showed that the emergence rate, shoot height and root length of seedlings were decreased by corn straw incorporated into media compared with the control. Similarly, corn straw reduced biomass of wheat seedlings. For example, the fresh and dry weight of wheat seedlings grown in media added with corn straw were only equal to 51%-65% and 62%-72% of those of control, respectively. The lower level of indole-3-acetic acid (IAA) and higher level of abscisic acid (ABA) in seedlings grown in media containing corn straw compared with the control partly explained the differences related to morphology and biomass. The corn straw added to media did not influence soluble protein and antioxidant enzymes such as peroxidase (POD) and catalase (CAT), as well as malondialdehyde(MDA), indicative of membrane damage, in wheat seedlings, however, increased the activity of superoxide dismutase (SOD ), which was probably associated with more reactive oxygen species (ROS) in seedlings grown in media containing corn straw. We did not find any significant differences in above results between Bt corn straw (Bt-38) and non-Bt corn straw (Zheng 58). Therefore, it was concluded that transgenic Bt corn had no environmental risk, referring in particular to the seedling growth of succeeding crop (winter wheat), under our experimental condition.