WOOSTER, Ohio -- The National Institutes of Health and the USDA 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 Ohio State University's Ohio Agricultural Research and Development Center in Wooster.



The goal of the three-year project -- which will specifically sequence and interpret the genome of Heterorhabditis bacteriophora, one of the most effective insect-parasitic nematodes known -- is to access novel genetic tools that would "revolutionize" biological control. They hope to boost the effectiveness of nematodes as insect killers, increase the types of target pests and the environments where they could be applied, and make 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," said Grewal, an internationally renowned nematologist and lead editor of the recently published book "Nematodes as Biocontrol Agents."



"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," Grewal said. "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 are also 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," explained Grewal, also a specialist with Ohio State University Extension. "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.



Genome project goes beyond controlling insects



In addition to pest control, NIH's National Human Genome Research Institute - which funded the project - 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 could also break new ground in the study of mutualism between bacteria and animal cells, as little is known about this type of relationships.



Not many symbiotic-interaction models are as conducive for lab research as H. bacteriophora and its associated bacterium, Photorhabdus luminescens, and the fact that the genome of P. luminescens has already been sequenced is a big benefit.



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 (C. elegans and C. briggsae); Rutgers, The State University of New Jersey; Michigan State University; and the California Institute of Technology.



OARDC and OSU Extension are part of Ohio State's College of Food, Agricultural and Environmental Sciences.



SOURCE: News release from Ohio State University's College of Food, Agricultural and Environmental Sciences.