Genetically Engineered Corn Rootworm Resistance: Potential for Reduction of Human Health Effects From Pesticides

Objective and Methods Insecticide use, grower preferences regarding genetically engineered (GE) corn resistant to com rootworm (CRW), and the health effects of using various CRW insecticides (organophosphates, pyrethroids, fipronil and carbamates) are reviewed for current and future farm practices. Results Pest damage to corn has been reduced only one-third by insecticide applications. Health costs from insecticide use appear significant, but costs attributable to CRW control are not quantifiable from available data. Methods reducing health-related costs of insecticide-based CRW control should be evaluated. As a first step, organophosphate insecticide use has been reduced as they have high acute toxicity and risk of long-term neurological consequences. A second step is to use agents which more specifically target the CRW. Conclusion Whereas current insecticides may be poisonous to many species of insects, birds, mammals and humans, a protein derived from Bacillus thurigiensis and produced in plants via genetic modification can target the specific insect of CRW (Coleoptra), sparing other insect and non-insect species from injury.

Synthesis of Southern Corn Rootworm Pheromone from S-Citronellol and Its Field Evaluation

Southern rootworm (Diabrotica undecimpunctata howardi) affects several plants such as soybean, sorghum, wheat, cucumber, alfalfa, cucurbits and it is most damaging to corn and peanuts. The pheromone based “attract and kill” strategy is one of the powerful ways to control pest population. To address our key objective of the practical utility of the synthetic pheromone, we have developed a simple synthetic strategy to produce gram scale southern corn rootworm pheromone in nine simple steps starting from S-Citronellol. The present strategy takes advantage of the existing chiral center of commercially available S-Citronellol. To get the basic carbon skeleton of the pheromone, the main step in the synthetic strategy is coupling of aliphatic units through Wittig reaction. The phosphonium salt from a non-functionalized aliphatic bromide followed by Wittig reaction improved the overall yield in the multistep synthesis of this pheromone. The large-scale production of pheromone enabled us to test it in the field.

Systemic RNAi in western corn rootworm, Diabrotica virgifera virgifera, does not involve transitive pathways

Western corn rootworm （WCR, Diabrotica virgifera virgifera LeConte） is highly sensitive to orally delivered double-stranded RNA （dsRNA）. RNAi in WCR is systemic and spreads throughout the insect body. This raises the question whether transitive RNAi is a mechanism that functions in WCR to amplify the RNAi response via production of secondary siRNA. Secondary siRNA production is achieved through RNA-dependent RNA polymerase （RdRP） activity in other eukaryotic organisms, but RdRP has not been identified in WCR and any other insects. This study visualized the spread of the RNAi- mediated knockdown of Dr v-ATPase C mRNA throughout the WCR gut and other tissues using high-sensitivity branched DNA in situ hybridization. Furthermore, we did not detect either secondary siRNA production or transitive RNAi in WCR through siRNA sequence profile analysis. Nucleotide mismatched sequences introduced into either the sense or antisense strand of v-ATPase C dsRNAs were maintained in siRNAs derived from WCR fed with the mismatched dsRNAs in a strand specific manner. The distribution of all siRNAs was restricted to within the original target sequence regions, which may indicate the lack of new dsRNA synthesis leading to production of secondary siRNA. Thus, the systemic spread of RNAi in WCR may be derived from the original dsRNA molecules taken up from the gut lumen. These results indicate that the initial dsRNA dose is important for a lethal systemic RNAi response in WCR and have implications in developing effective dsRNA traits to control WCR and in resistance management to prolong the durability of RNAi trait technology.

Elucidation of the MicroRNA Transcriptome in Western Corn Rootworm Reveals Its Dynamic and Evolutionary Complexity

Diabrotica virgifera virgifera(western corn rootworm,WCR)is one of the most destructive agricultural insect pests in North America.It is highly adaptive to environmental stimuli and crop protection technologies.However,little is known about the underlying genetic basis of WCR behavior and adaptation.More specifically,the involvement of small RNAs(s RNAs),especially micro RNAs(mi RNAs),a class of endogenous small non-coding RNAs that regulate various biological processes,has not been examined,and the datasets of putative s RNA sequences have not previously been generated for WCR.To achieve a comprehensive collection of s RNA transcriptomes in WCR,we constructed,sequenced,and analyzed s RNA libraries from different life stages of WCR and northern corn rootworm(NCR),and identified 101 conserved precursor mi RNAs(pre-mi RNAs)in WCR and other Arthropoda.We also identified 277 corn rootworm specific pre-mi RNAs.Systematic analyses of s RNA populations in WCR revealed that its s RNA transcriptome,which includes PIWI-interacting RNAs(pi RNAs)and mi RNAs,undergoes a dynamic change throughout insect development.Phylogenetic analysis of mi RNA datasets from model species reveals that a large pool of species-specific mi RNAs exists in corn rootworm;these are potentially evolutionarily transient.Comparisons of WCR mi RNA clusters to other insect species highlight conserved mi RNA-regulated processes that are common to insects.Parallel Analysis of RNA Ends(PARE)also uncovered potential mi RNA-guided cleavage sites in WCR.Overall,this study provides a new resource for studying the s RNA transcriptome and mi RNA-mediated gene regulation in WCR and other Coleopteran insects.

RNA-Based Biocontrols--A New Paradigm in Crop Protection

Modern agribusiness plays a vital role in safeguarding and improving the production,quality,and quantity of food,feed,fiber,and fuel.Growing concerns over the impact of chemical pesticides on health and the environment have stimulated the industry to search for alternative and greener solutions.Over the last years,the RNA interference(RNAi)process has been identified as a very promising new approach to complement the arsenal of foliar spray,soil,or seed treatments applied as chemical and biological pest control agents,and of plant-incorporated protectants(PIPs).RNA-based active ingredients(AIs)possess a unique mode of action and can be implemented via both genetic modification(GM)and biocontrol approaches.RNA-based AIs promise to deliver the selectivity and sustainability desired in future crop protection agents.This is due to their utilization of a natural process to exert control and their high level of selectivity,which leads to reduced risk for non-target organisms(NTOs).This review discusses the advantages and limitations of RNA-based solutions in crop protection and recent research progress toward RNA-based biocontrols against the Colorado potato beetle(CPB),corn rootworm(CRW),and soy stink bug(SSB).Many challenges still exist on the road to the implementation of a broad range of RNA-based products and their widespread use and application.Despite these challenges,it can be expected that RNA-based AIs will become valuable new tools complementing the current arsenal of crop-protection solutions.

Regional Risks for Biogas Production in Germany by the Maize Pest Diabrotica v. virgifera？

Caused by its multi purpose applicability in different areas of the energy system, biogas is an important source for the concept of ＂Energy Turnaround for Sustainability＂. To clarify the regional risks for biogas production due to Diabrotica virgifera virgifera （Coleoptera： Chrysomelidae） （Dw） results from the questionnaire on the current situation of the biogas plants in Germany are compared to our Dvv monitoring experiences and literature data. Maize silage is the main source for biogas production in Germany. Dvv is the most important maize pest within the United States. It also was monitored in different German States during the last years. The Dvv infestation risk and consequent damages are closely linked to the percentage of maize within the regional crop rotations scheme. Maize cropping within a monocultural production can lead to a significant harvest reduction of 30% to 80% after the outbreak of Dvv, especially in dry years. A high risk to the biogas production based on silage maize especially in some areas in North West and in southern Germany has been detected. Further research is needed focusing on （1） strategies to control Dvv, （2） development in alternative energy crops regarding their susceptibility to Dvv and （3） development of technologies along the process chains for using alternative substrates, especially residues from plant production.

玉米根萤叶甲的抗逆性与防治研究进展

玉米根萤叶甲(Diabrotica virgifera virgifera Leconte)在美国是最重要的玉米害虫。它不仅对一些环戊二烯、有机磷类和氨基甲酸盐类化学杀虫剂产生了很强的抗药性,还对玉米-大豆轮作和调整播期等农业防治措施产生了适应性。此外,该虫有较广的适生性和扩展性。在过去的60年内,它从美国中西部传到了东北部沿海地区,并入侵欧洲定殖为害。新近采用的防治方法主要是种植转Bt基因抗虫玉米。表达经生物工程改良并导入的某个Bt毒素基因如Cry3 Bb1、Cry34 Ab1/Cry35 Ab1或mCry3 A的转基因抗虫玉米可毒杀取食的玉米根萤叶甲。但在转Bt基因玉米使用数年后,田间观察和温室筛选研究显示,玉米根萤叶甲具有对转基因玉米的潜在抗性。本文对该叶甲与防治有关的生物学特性、抗逆性及其机制、防治措施做了综述和讨论,旨在对该害虫的检疫防除有所帮助。