Source: AgAnswers, an Ohio State University and Purdue Extension Partnership

Ohio State University scientists are on their way to creating the perfect bio-weapon. But fear not. This killer is harmless to all manner of living things except those we already spend billions of dollars and massive amounts of toxic chemicals trying to exterminate: Insect pests that terrorize valuable agricultural crops, urban-landscape greenery, livestock and yes, even humans and their pets.

The National Institutes of Health (NIH) and the U.S. Department of Agriculture have awarded $1.8 million for sequencing the genome of insect-parasitic nematodes -- microscopic roundworms that have proven to be highly effective biological insecticides against a wide variety of pests. Leading the multi-institutional project is Parwinder Grewal, an entomologist with the university's Ohio Agricultural Research and Development Center (OARDC) in Wooster, Ohio.

The three-year project will specifically sequence and interpret the genome of Heterorhabditis bacteriophora, one of the most effective insect-parasitic nematodes known. The project's goal is to access novel genetic tools that would revolutionize biological control by boosting the effectiveness of nematodes as insect killers, increasing the number of their target pests and the environments where they could be applied, and making them cheap enough so they can be cost-effective for use in high-acreage crops such as corn and cotton.

Applied through sprayers or irrigation systems, nematodes are available for insect control in citrus, strawberry, cranberry, nursery plants and turfgrass; they have also shown promise against animal and human pests such as ticks and lice.

Here's how these unique bio-weapons work: Juvenile nematodes, which form symbiotic associations with disease-causing bacteria, enter the body cavity of insects and release the bacteria, which in turn multiply and kill the host within one or two days. The nematodes then feed on the bacteria, reproduce and migrate in search of new hosts to infect.

"Insect-parasitic nematodes have been used very successfully in the past two decades as environmentally benign alternatives to chemical insecticides," Grewal said. "Lots of research has been conducted to make nematodes commercially available, but there are limitations that have kept them from going mainstream in the insecticide market. Genome sequencing will help us get rid of those hurdles."

Since they are living organisms, nematodes have a short shelf life compared to synthetic pesticides. They also are sensitive to light, run the risk of drying up and must be kept in refrigerated conditions during shipping and storage. All of these factors prevent their use for other than soil-dwelling insects and make them expensive, especially for large farming operations.

That's where genetics comes in.

"This research project will open up the door to functional genomics," Grewal said. "We'll know the genes and their functions, which will allow us to identify nematodes with desired traits in the field. It will also enable us to switch genes on and off to improve certain characteristics that are important in biological control. If we can develop transgenic nematodes that can be stored longer and are more virulent so that consumers will need fewer nematodes to achieve desired results, that would reduce the price significantly. In addition, if their UV and desiccation sensitivity can be limited, nematodes could also be used against above-soil insects such as soybean loopers, corn earworm and tomato hornworm."

Such advances could turn insect-parasitic nematodes, currently a $10 million industry worldwide, into a billion-dollar business, Grewal said. But more importantly, increased use of these biocontrol agents would help reduce the environmental and human-health risks of chemical insecticides, while contributing to deter global crop losses due to insect pests -- estimated at 13 percent to 16 percent, or $244 billion per year.

Nematodes, for example, are the only control available for black vine weevil and cranberry girdler in North American cranberry bogs, and are the most effective killers of white grubs in turfgrass.

In addition to pest control, NIH's National Human Genome Research Institute sees tremendous scientific value in sequencing the genome of H. bacteriophora, as detailed knowledge about this organism could provide fresh insights into different areas of biological research.

For instance, H. bacteriophora is a unique model for the study of parasitism and pathogenicity, as emerging data suggests an association between invertebrate and vertebrate parasitism. This nematode also could break new ground in the study of mutualism between bacteria and animal cells, as little is known about this type of relationship and not many symbiotic-interaction models are as conducive for lab research as H. bacteriophora and its associated bacterium, Photorhabdus luminescens.

Moreover, Grewal said, this insect-parasitic nematode represents a bridge between the well-studied free-living nematodes, such as the Caenorhabditis elegans, and the much harder to work with parasitic nematodes, which cause disease in plants, animals and humans.

Other institutions involved in this project include Washington University's Genome Sequencing Center in St. Louis, which has sequenced the two previous nematode genomes of C. elegans and C. briggsae; Rutgers, The State University of New Jersey; Michigan State University; and the California Institute of Technology.