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EC-sponsored Research on Safety of Genetically Modified Organisms - A Review of Results
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image Risk assessment: field release of genetically manipulated baculoviruses

Background and objectives

Baculoviruses are a group of viruses that kill particular insects including crop pests. The value of wild type baculoviruses as sprayable, environmentally safe, biopesticides has been well established. However, their commercial competitiveness with chemical insecticides would be further improved by genetic engineering to incorporate genes which would lead to swifter death or cessation of host insect feeding. It is also perceived that the practical use of genetically modified baculoviruses depends on a satisfactory outcome to thorough assessment of the risks of release.

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Approach and methodology

Assessing the risk of release of a genetically modified baculovirus depends on a sound knowledge of the ecology of the wild type from which it was derived. Ecological deviations in the recombinant virus can thus be identified. The wild type baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) and its recombinant clone (AcNPC/p1OZ) were studied. The wild-type and recombinant were both infective in both a pest of pine forests (Pine beauty moth) and a pest of agricultural crops (Cabbage moth). Extensive field observations identified ecological aspects suitable for study in severely contained simulated ecosystems (microcosms) specially developed for the purpose. The behaviour of wild type viruses and the recombinant were studied in microcosms.


Main findings and outcome

Cabbage moth and Pine beauty moth NPVs were infective in 4 of the 14 Lepidoptera families. Each of four NPV clones had different infectivity levels which were up to four and a half times greater than those of the wild type.

In the field, baculoviruses can persist in the soil for at least 3 years. Opilionids are the main agents of local dispersal, they excrete active viruses for 100 hours after ingestion. Birds are a second major pathway by which baculoviruses are spread; 40% of individuals and 9 out of 15 bird species studied excreted active virus. Cabbage moth virus was recovered 20 km from the point of introduction. In microcosms containing field crops, simulated rain also dispersed baculoviruses. Between 1 and 10% of baculoviruses remained on plants but the soil contained the remaining 90 to 99%. No baculoviruses were found in percolation water. Air flow, rain splash, parasites and aphids all dispersed viruses. Despite similar levels of infectivity of wild type and recombinant viruses, less recombinant baculoviruses were produced in microcosms. Recombinant baculoviruses were less persistent than the wild type.


Conclusions

Despite baculoviruses having many alternative lepidopteran hosts, field infections were not found in alternative hosts, suggesting little risk of environmental disturbance. In vivo cloning of Pine beauty moth NPV gave many distinct clones, which allowed selection for recombinant work. Recombinant baculoviruses were less productive and persistent in a microcosm than the wild type: Higher NPV doses gave lower progeny NPV yields in microcosms.

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imageResearch project
 

Contract number
BAP-0192/0201

Period
April 1987 - December 1989

Coordinator
P.F. Entwistle
NERC
Institute of Virology and Environmental Microbiology
Oxford (UK)

 
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Partner


J. Huber
Biologische Bundesanstalt für Land- und Forstwirtschaft
Darmstadt (DE)

 
 
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