Control of western corn rootworm via RNAi traits in maize: lethal and sublethal effects of Sec23 dsRNA.

Background: RNA interference (RNAi) triggered by maize plants expressing RNA hairpins against specific western corn rootworm (WCR) transcripts have proven to be effective at controlling this pest. To provide robust crop protection, mRNA transcripts targeted by double-stranded RNA must be sensitive to knockdown and encode essential proteins.

Results: Using WCR adult feeding assays, we identified Sec23 as a highly lethal RNAi target.

RNAi targeting of rootworm Troponin I transcripts confers root protection in maize.

Western corn rootworm, Diabrotica virgifera virgifera, is the major agronomically important pest of maize in the US Corn Belt. To augment the repertoire of the available dsRNA-based traits that control rootworm, we explored a potentially haplolethal gene target, wings up A (wupA), which encodes Troponin I. Troponin I, a component of the Troponin-Tropomyosin complex, is an inhibitory protein involved in muscle contraction.

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.

RNAi induced knockdown of a cadherin-like protein (EF531715) does not affect toxicity of Cry34/35Ab1 or Cry3Aa to Diabrotica virgifera virgifera larvae (Coleoptera: Chrysomelidae).

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is an important maize pest throughout most of the U.S. Corn Belt.

RNAi as a management tool for the western corn rootworm, Diabrotica virgifera virgifera.

The western corn rootworm (WCR), Diabrotica virgifera virgifera, is the most important pest of corn in the US Corn Belt. Economic estimates indicate that costs of control and yield loss associated with WCR damage exceed $US 1 billion annually. Historically, corn rootworm management has been extremely difficult because of its ability to evolve resistance to both chemical insecticides and cultural control practices.

Differential Probing Behavior of Blissus insularis (Hemiptera: Blissidae) on Resistant and Susceptible St. Augustinegrasses.

Southern chinch bug, Blissus insularis Barber, is a severe pest of St. Augustinegrass throughout the southern United States. Host plant resistance is an environmentally friendly method to manage chinch bug infestations and is increasingly important, as the southern chinch bug develops resistance to insecticides.

Parental RNA interference of genes involved in embryonic development of the western corn rootworm, Diabrotica virgifera virgifera LeConte.

RNA interference (RNAi) is being developed as a potential tool for insect pest management and one of the most likely target pest species for transgenic plants that express double stranded RNA (dsRNA) is the western corn rootworm. Thus far, most genes proposed as targets for RNAi in rootworm cause lethality in the larval stage. In this study, we describe RNAi-mediated knockdown of two developmental genes, hunchback (hb) and brahma (brm), in the western corn rootworm delivered via dsRNA fed to adult females.

A combinatorial bidirectional and bicistronic approach for coordinated multi-gene expression in corn.

Transgene stacking in trait development process through genetic engineering is becoming complex with increased number of desired traits and multiple modes of action for each trait. We demonstrate here a novel gene stacking strategy by combining bidirectional promoter (BDP) and bicistronic approaches to drive coordinated expression of multi-genes in corn. A unidirectional promoter, Ubiquitin-1 (ZMUbi1), from Zea mays was first converted into a synthetic BDP, such that a single promoter can direct the expression of two genes from each end of the promoter.

Estimating the frequency of Cry1F resistance in field populations of the European corn borer (Lepidoptera: Crambidae).

Background: Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) have suppressed European corn borer populations and reduced the pest status of this insect throughout much of the US corn belt. A major assumption of the high-dose/refuge strategy proposed for insect resistance management and Bt corn is that the frequency of resistance alleles is low so that resistant pests surviving exposure to Bt corn will be rare.

Results: The frequency of resistance to the Cry1F Bt toxin was estimated using two different screening tools and compared with annual susceptibility monitoring based on diagnostic bioassays and LC50 and EC50 determinations.

Validation of RNA interference in western corn rootworm Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) adults.

Background: RNA interference (RNAi) is commonly used in insect functional genomics studies and usually involves direct injection of double-stranded RNA (dsRNA). Only a few studies have involved exposure to dsRNAs through feeding. For western corn rootworm (Diabrotica virgifera virgifera) larvae, ingestion of dsRNA designed from the housekeeping gene, vacuolar ATPase (vATPase) triggers RNAi causing growth inhibition and mortality; however, the effect of dsRNA feeding on adults has not been examined.

Efficacy of genetically modified Bt toxins against insects with different genetic mechanisms of resistance.

Transgenic crops that produce Bacillus thuringiensis (Bt) toxins are grown widely for pest control, but insect adaptation can reduce their efficacy. The genetically modified Bt toxins Cry1AbMod and Cry1AcMod were designed to counter insect resistance to native Bt toxins Cry1Ab and Cry1Ac. Previous results suggested that the modified toxins would be effective only if resistance was linked with mutations in genes encoding toxin-binding cadherin proteins.

Evaluation of five methods for total DNA extraction from western corn rootworm beetles.

Background: DNA extraction is a routine step in many insect molecular studies. A variety of methods have been used to isolate DNA molecules from insects, and many commercial kits are available. Extraction methods need to be evaluated for their efficiency, cost, and side effects such as DNA degradation during extraction.

Oxidative responses of St. Augustinegrasses to feeding of southern chinch bug, Blissus insularis Barber.

Southern chinch bug, Blissus insularis Barber (Hemiptera: Blissidae), is a serious insect pest of St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze, a turfgrass commonly grown in the southeastern United States.

Role of leaf sheath lignification and anatomy in resistance against southern chinch bug (Hemiptera: Blissidae) in St. Augustinegrass.

Southern chinch bug, Blissus insularis Barber (Hemiptera: Blissidae), is the most serious insect pest of St. Augustinegrass Stenotaphrum secundatum (Walter) Kuntze, a common lawngrass grown in southeastern U.S.

Arsenic hyperaccumulation in the Chinese brake fern (Pteris vittata) deters grasshopper (Schistocerca americana) herbivory.

Brake fern, Pteris vittata, not only tolerates arsenic but also hyperaccumulates it in the frond. The hypothesis that arsenic hyperaccumulation in this fern could function as a defense against insect herbivory was tested. Fronds from control and arsenic-treated ferns were presented to nymphs of the grasshopper Schistocerca americana.