Naef Andreas, Zesiger Thierry, Défago Geneviève
Plant Pathology, Institute of Integrative Biology, ETH Zurich, 8092 Zurich, Switzerland.
J Environ Qual. 2006 May 31;35(4):1001-9. doi: 10.2134/jeq2005.0334. Print 2006 Jul-Aug.
Transformation of maize with genes encoding for insecticidal crystal (Cry) proteins from Bacillus thuringiensis (Bt) could have an impact on the saprophytic survival of plant pathogens and their antagonists on crop residues. We assessed potential effects on the mycotoxin deoxynivalenol (DON)-producing wheat and maize pathogen Fusarium graminearum and on the biocontrol agent Trichoderma atroviride. Purified Cry1Ab protein caused no growth inhibition of these fungi on agar plates. Cry1Ab concentrations above levels common in Bt maize tissue stimulated the growth of F. graminearum. The fungi were also grown on gamma-radiation-sterilized leaf tissue of four Bt maize hybrids and their non transgenic isolines collected at maize maturity on a field trial in 2002 and 2003. Both fungi degraded the Cry1Ab protein in Bt maize tissue. Fungal biomass quantification with microsatellite-based polymerase chain reaction (PCR) assays revealed differential fungal growth on leaf tissue of different maize varieties but no consistent difference between corresponding Bt and non-Bt hybrids. Generally, year of maize tissue collection had a greater impact on biomass production than cultivar or Bt transformation. The mycotoxin DON levels observed in maize tissue experiments corresponded with patterns in F. graminearum biomass, indicating that Bt transformation has no impact on DON production. In addition to bioassays, maize leaf tissue was analyzed with a mass spectrometer-based electronic nose, generating fingerprints of volatile organic compounds. Chemical fingerprints of corresponding Bt and non-Bt leaf tissues differed only for those hybrid pairs that caused differential fungal biomass production in the bioassays. Our results suggest that Cry1Ab protein in maize residues has no direct effect on F. graminearum and T. atroviride but some corresponding Bt/non-Bt maize hybrids differ more in composition than Cry protein content alone, which can affect the saprophytic growth of fungi on crop residues.
用编码苏云金芽孢杆菌（Bt）杀虫晶体（Cry）蛋白的基因转化玉米，可能会对植物病原体及其在作物残体上的拮抗物的腐生存活产生影响。我们评估了对产生霉菌毒素脱氧雪腐镰刀菌烯醇（DON）的小麦和玉米病原体禾谷镰刀菌以及生物防治剂绿色木霉的潜在影响。纯化的Cry1Ab蛋白在琼脂平板上对这些真菌没有生长抑制作用。高于Bt玉米组织中常见水平的Cry1Ab浓度刺激了禾谷镰刀菌的生长。这些真菌还在2002年和2003年田间试验中玉米成熟时采集的四个Bt玉米杂交种及其非转基因同型系的经γ射线灭菌的叶片组织上生长。两种真菌都能降解Bt玉米组织中的Cry1Ab蛋白。基于微卫星的聚合酶链反应（PCR）分析对真菌生物量进行定量，结果显示不同玉米品种的叶片组织上真菌生长存在差异，但相应的Bt和非Bt杂交种之间没有一致的差异。一般来说，玉米组织采集年份对生物量生产的影响大于品种或Bt转化。在玉米组织实验中观察到的霉菌毒素DON水平与禾谷镰刀菌生物量模式相对应，表明Bt转化对DON的产生没有影响。除了生物测定外，还使用基于质谱的电子鼻对玉米叶片组织进行分析，生成挥发性有机化合物的指纹图谱。相应的Bt和非Bt叶片组织的化学指纹图谱仅在生物测定中导致真菌生物量产生差异的那些杂交对中有所不同。我们的结果表明，玉米残体中的Cry1Ab蛋白对禾谷镰刀菌和绿色木霉没有直接影响，但一些相应的Bt/非Bt玉米杂交种在组成上的差异不仅仅在于Cry蛋白含量，这会影响真菌在作物残体上的腐生生长。
