2012 Annual Report
1a.Objectives (from AD-416):
The long-term objective of this project is to develop improved strains of beneficial insects and baculoviruses through traditional breeding techniques. The specific objectives are to:.
1)select and develop beneficial lines of a predator, the spined soldier bug, Podisus maculiventris, for improved bionomic traits such as increased female fecundity, sex ratio, development time, and shelf life,.
2)select and develop baculovirus lines for important biopesticide traits such as increased speed of kill, persistence, and broadened host range, and.
3)in partnership with small and urban vegetable growers, develop novel beneficial insect and baculovirus delivery systems for application, using such strategies as chemical attractants, artificial diets, and release mechanisms.
1b.Approach (from AD-416):
The goal of this research is to select biological control agents with improved traits for controlling pest insects in greenhouse, organic and small field applications. This project will generate a highly fecund line of the spined solder bug, Podisus maculiventris (and if time permits, a line tolerant to cold storage) and naturally occurring stable, efficacious strains of the celery looper baculovirus, Anagrapha falcifera nucleopolyhedrovirus. We will measure genetic variation within and between the predator populations and the virus populations to assess their potential for selection procedures. Initially we will use egg production traits to direct the selection of predator lines and virulency to direct the selection of virus lines. For the predator lines, genetic variation will be assessed and polymorphisms will be used to identify and confirm associations between genotype and the high fecund phenotype. For the virus strains, genetic variation will be assessed and variable regions will be sequenced to identify genes related to efficacy and stability. Together, this research will produce significant advancements in knowledge of the genomic basis underlying complex traits. It also will build our capability to breed lines of insects and strains of viruses with enhanced production traits and pest control efficacy. We have established collaborations to test the improved lines of predators and viruses at the greenhouse and small plot levels. Two key end products, which we will transfer to industry and producers, will be improved beneficial agents with increased value to commercial insectaries and producers and the technology required to achieve these improved agents.
For Objective 1 field collections of a beneficial predatory insect were subjected to selection based on high and low reproductive capacity. The selection protocol generated lines with high and low reproductive capacity in sufficient quantity for predation and genetic tests. The predatation tests will assess protection of agricultural and horticultural crops using natural enemies, and the genetic tests will assess biomarkers associated with the most effective beneficial insects. The selection process will be completed this calendar year.
For milestone 2, six celery looper baculovirus isolates collected from Missouri were tested in budworm and fall armyworm bioassays. Smaller bioassays were also run for related lepidopteran species. The six isolates were tested with a contaminant cypovirus co-isolated from the field and also without the cypovirus. The six isolates without the cypovirus were further purified in cell culture and twelve purified isolates were selected based in tissue culture cells. These isolates will be tested in laboratory bioassay to identify changes in host range and eventually the most promising isolates will be field tested. A previously developed fast acting fall armyworm virus was field tested. It is a highly effective biocontrol agent and environmentally stable. Potential formulations of the virus were field tested to identify ways to protect the virus from UV degradation in the field.
For Objective 3 pest insect plant preference tests have identified preferred and non-preferred cabbage cultivars. A leaf bouquet assay has been developed and integrated with caged tests for leaf consumption and predation rates. A software program has been adapted for leaf measurements enabling consumption to be quantified. Preliminary results show reduced consumption resulting from predation, supporting the feasibility of accomplishing the goals of the objective.
Improved baculovirus delivery for biocontrol. Lignin is a readily available, inexpensive, and renewable resource that could be used as an alternative to costly UV-protectants for naturally occurring baculoviruses selected for faster kill of crop-damaging caterpillars. ARS researchers at Columbia, Missouri and Peoria, Illinois explored lignin as an encapsulating agent that protects the baculoviruses from exposure to destructive ultraviolet (UV) light. In greenhouse and field experiments with cabbage, the researchers used a spray-dried lignin formulation to encapsulate a highly effective natural baculovirus and compare its persistence, rate of kill and replication to the wild-type strain. While the wild-type baculovirus proved more adept at replicating inside the caterpillars than the natural baculovirus, the caterpillars infected by the natural baculovirus died a day sooner than those infected by the wild-type strain. The lignin-encapsulated natural baculovirus killed the pests as quickly as lignin-free isolates, and lasted longer than lignin-free ones when exposed to UV radiation (27 versus 8 hours). This additional evidence of the formulation’s commercial potential will benefit growers by improving pest insect control and consumers who prefer organic and insecticide-free foods.
Selecting highly fecund lines of beneficial insects. The concept of biological control of insects is a potentially powerful alternative to classical insecticides. A major challenge is, however, the high cost of mass-producing beneficial insects restricts global use of these agents. ARS scientists at Columbia, Missouri, in collaboration with researchers at the University of Nebraska, Lincoln, Nebraska, are working to reduce mass-production costs by selecting lines of predatory insects with increased egg-laying capacity. These selection programs depend on substantial genetic variability among individuals within the species of predatory insects. The researchers confirmed high genetic variability between populations from different geographic locations, providing the foundation for future work to breed a strain of spined soldier bugs with high reproductive capacity. Ultimately, this research will benefit growers who use biological control agents to reduce insect pest damage to their crops and consumers seeking food having reduced pesticide levels.
Breitenbach, J.E., Shelby, K., Popham, H.J. 2011. Baculovirus induced transcripts in hemocytes from Heliothis virescens. Viruses. 3(11):2047-2064.
Grasela, J.J., McIntosh, A.H., Ringbauer Jr, J.A., Goodman, C.L., Carpenter, J.E., Popham, H.J. 2012. Development of cell lines from the cactophagous insect: Cactoblastis cactorum (Lepidoptera: Pyralidae) and their susceptibility to three baculoviruses. In Vitro Cellular and Developmental Biology - Animals. 48:293-300.
Kneeland, K., Coudron, T.A., Lindroth, E., Stanley, D.W., Foster, J.E. 2012. Genetic variation in field and laboratory populations of the spined soldier bug Podisus maculiventris. Entomologia Experimentalis et Applicata. 143:120-126.
Coudron, T.A., Mitchell, L.C., Sun, R., Robertson, J.D., Pham, N.V., Popham, H.J. 2012. Dietary composition affect levels of trace elements in the predator Podisus maculiventris (Say) (Heteroptera: Pentatomidae). Biological Control. 61:141-146.
Greenstone, M.H., Weber, D.C., Hu, J.S., Coudron, T.A., Payton, M.E. 2012. Removing external DNA contamination from arthropod predators destined for molecular gut-content analysis. Molecular Ecology Resources. 12(3):464-469.
Popham, H.J., Sun, R., Shelby, K., Robertson, D. 2012. Changes in trace metals in hemolymph of baculovirus-infected noctuid larvae. Biological Trace Element Research. 146:325-334.
Behle, R.W., Popham, H.J. 2012. Laboratory and field evaluations for efficacy of a fast-killing baculovirus isolate from Spodoptera frugiperda. Journal of Invertebrate Pathology. 109:194-200.
Harrison, R.L., Popham, H.J., Breitenbach, J.E., Rowley, D.L. 2012. Genetic variation and virulence of Autographa californica multiple nucleopolyhedrovirus and Trichoplusia ni single nucleopolyhedrovirus isolates. Journal of Invertebrate Pathology. 110(1):33-47.
Chang, C.L., Coudron, T.A., Goodman, C.L., Stanley, D.W. 2012. Larval dietary wheat germ oil influences age-specific protein expression in adults of the oriental fruit fly. Journal of Insect Physiology. 58:690-698.