Yang Fei, Kerns David L, Head Graham P, Leonard B Rogers, Levy Ronnie, Niu Ying, Huang Fangneng
Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, United States of America.
Macon Ridge Research Station, Louisiana State University Agricultural Center, Winnsboro, Louisiana, 71295, United States of America.
PLoS One. 2014 Nov 19;9(11):e112962. doi: 10.1371/journal.pone.0112962. eCollection 2014.
To counter the threat of insect resistance, Bacillus thuringiensis (Bt) maize growers in the U.S. are required to plant structured non-Bt maize refuges. Concerns with refuge compliance led to the introduction of seed mixtures, also called RIB (refuge-in-the-bag), as an alternative approach for implementing refuge for Bt maize products in the U.S. Maize Belt. A major concern in RIB is cross-pollination of maize hybrids that can cause Bt proteins to be present in refuge maize kernels and negatively affect refuge insects. Here we show that a mixed planting of 5% nonBt and 95% Bt maize containing the SmartStax traits expressing Cry1A.105, Cry2Ab2 and Cry1F did not provide an effective refuge for an important above-ground ear-feeding pest, the corn earworm, Helicoverpa zea (Boddie). Cross-pollination in RIB caused a majority (>90%) of refuge kernels to express ≥ one Bt protein. The contamination of Bt proteins in the refuge ears reduced neonate-to-adult survivorship of H. zea to only 4.6%, a reduction of 88.1% relative to larvae feeding on ears of pure non-Bt maize plantings. In addition, the limited survivors on refuge ears had lower pupal mass and took longer to develop to adults.
为应对昆虫抗性的威胁，美国种植苏云金芽孢杆菌（Bt）玉米的农户被要求种植结构化的非Bt玉米避难所。由于对避难所合规性的担忧，种子混合物（也称为袋中避难所，RIB）被引入，作为在美国玉米带实施Bt玉米产品避难所的一种替代方法。RIB的一个主要问题是玉米杂交种的异花授粉，这可能导致Bt蛋白存在于避难所玉米籽粒中，并对避难所昆虫产生负面影响。在此我们表明，5%非Bt玉米和95%含有表达Cry1A.105、Cry2Ab2和Cry1F的SmartStax性状的Bt玉米混合种植，对于一种重要的地上取食穗部害虫——玉米穗虫，即棉铃虫（Helicoverpa zea (Boddie)），并未提供有效的避难所。RIB中的异花授粉导致大多数（>90%）避难所籽粒表达≥一种Bt蛋白。避难所玉米穗中Bt蛋白的污染将棉铃虫从幼虫到成虫的存活率降低至仅4.6%，相对于取食纯非Bt玉米种植穗部的幼虫，降低了88.1%。此外，避难所玉米穗上有限的存活个体蛹重较低，发育至成虫所需的时间更长。
