Portland State University, Department of Biology, Portland, Oregon 97207, USA.
Am J Bot. 2012 Apr;99(4):700-7. doi: 10.3732/ajb.1100529. Epub 2012 Apr 2.
Insect-resistant Bacillus thuringiensis (Bt) maize is widely cultivated, yet few studies have examined the interaction of symbiotic arbuscular mycorrhizal fungi (AMF) with different lines of Bt maize. As obligate symbionts, AMF may be sensitive to genetic changes within a plant host. Previous evaluations of the impact of Bt crops on AMF have been inconsistent, and because most studies were conducted under disparate experimental conditions, the results are difficult to compare.
We evaluate AMF colonization in nine Bt maize lines, differing in number and type of engineered trait, and five corresponding near-isogenic parental (P) base hybrids in greenhouse microcosms. Plants were grown in 50% local agricultural soil with low levels of fertilization, and AMF colonization was evaluated at 60 and 100 d. Nontarget effects of Bt cultivation on AMF colonization were tested in a subsequently planted crop, Glycine max, which was seeded into soil that had been preconditioned for 60 d with Bt or P maize.
We found that Bt maize had lower levels of AMF colonization in their roots than did the non-Bt parental lines. However, reductions in AMF colonization were not related to the expression of a particular Bt protein. There was no difference in AMF colonization in G. max grown in the Bt- or P-preconditioned soil.
These findings are the first demonstration of a reduction in AMF colonization in multiple Bt maize lines grown under the same experimental conditions and contribute to the growing body of knowledge examining the unanticipated effects of Bt crop cultivation on nontarget soil organisms.
抗虫苏云金芽孢杆菌（Bt）玉米被广泛种植，但很少有研究考察共生丛枝菌根真菌（AMF）与不同 Bt 玉米品系的相互作用。作为专性共生体，AMF 可能对植物宿主的遗传变化敏感。此前对 Bt 作物对 AMF 影响的评估结果不一致，而且由于大多数研究是在不同的实验条件下进行的，因此结果难以比较。
我们在温室微宇宙中评估了 9 种 Bt 玉米品系（在工程特性的数量和类型上有所不同）和 5 种相应的近等基因亲本（P）基础杂种的 AMF 定殖情况。植物在施肥水平较低的 50%当地农业土壤中生长，并在 60 和 100 天评估 AMF 定殖情况。Bt 种植对 AMF 定殖的非靶向效应在随后种植的作物 Glycine max 中进行了测试，将大豆种子播种到经过 60 天 Bt 或 P 玉米预处理的土壤中。
我们发现，Bt 玉米的根系中 AMF 定殖水平低于非 Bt 亲本系。然而，AMF 定殖的减少与特定 Bt 蛋白的表达无关。在 Bt 或 P 预处理的土壤中生长的 G. max 中，AMF 定殖没有差异。
这些发现首次证明了在相同实验条件下种植的多种 Bt 玉米品系中 AMF 定殖减少，并为研究 Bt 作物种植对非目标土壤生物的意外影响的知识体系不断增加做出了贡献。
