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United States Department of Agriculture

Agricultural Research Service

2008 Annual Report

1a.Objectives (from AD-416)
(1) Determine the genetic and evolutionary basis for host specificity of insect parasitoids and herbivores; (2) Determine the importance of climatic adaptation for establishment and growth of introduced populations of insects; and (3) Screen, introduce, and evaluate impact of candidates for biological control introductions, based on host specificity and climatic tolerances.

1b.Approach (from AD-416)
For the first objective, we will determine the genetic basis for a host shift in the specialist herbivore, Heliothis subflexa, and for differences in host specificity between species in the Aphelinus varipes complex using crosses, quantitative trait loci mapping, and differences in gene expression. We will confirm gene function by silencing with RNA interference. Climate matching is frequently used to decide where to collect biocontrol agents for introduction. However, three hypotheses can explain climatic adaptation:(1) populations in different regions are adapted to local climates, (2) single populations have the full range of genetic variation in traits affecting climatic adaption, and (3) physiological plasticity is sufficient for local adaptation. These hypotheses have very different implications for collection strategies. The second objective is to test these hypotheses using the A. varipes complex. In the third objective, we will use the knowledge and methods developed under objectives 1 and 2 to screen candidates proposed for introduction to control Diuraphis noxia and Aphis glycines, introduce the most promising candidates, evaluate their impact on target and non-target species, and determine whether the screening was useful in improving the success and safety of biocontrol introductions.

3.Progress Report
We continued with development of genetic maps for analysis of host specificity in APHELINUS species and HELIOTHIS species. We continued to establish laboratory cultures in quarantine and test host specificity of parasitoids of soybean aphid. We have started cultures of additional aphid species in the genus APHIS to more precisely determine the host specificity of promising candidates for introduction against soybean aphid. We determined that soybean aphid was under attack by a variety of predators and parasitoids on its overwintering host plant, RHAMNUS SPP. We submitted three proposals to the USDA NRI competitive grants program and one proposal to NSF; one of these proposal is pending. This research relates to National Program 304 Problem Statements A - Understanding Complex Interactions under National Program Component III - Plant, Pest, and Natural Enemy Interactions and Ecology; and Problem Statement A - Traditional Biological Control under National Program Component V - Pest Control Technologies.

1. Plasticity in genetic make-up may allow insects to switch host plants. A major question in biological control is whether a plant-feeding insect imported to control a weed is likely to switch to attack other plants and adversely affect agriculture or the environment. Using genetic markers mapped to 31 chromosomes in two closely related moth species, we found that genes on different chromosomes enabled moths to develop on a novel host plant, showing that the same behavior can be produced by changes in different genes. These results suggest that the likelihood of host plant shifts in plant-feeding insects are greater than previously thought and have implications not only for the safety of biological control introductions but also for shifts in the ability of pests to feed on previously unattacked plant species. This accomplishment relates to National Program 304 Problem Statement A - Understanding Complex Interactions under National Program Component III - Plant, Pest, and Natural Enemy Interactions and Ecology; Problem Statement A - Traditional Biological Control under National Program Component V - Pest Control Technologies; and Problem Statement A - Agent Discovery and Selection and Risk Assessment under National Program Component IX – Biological Control of Weeds.

5.Significant Activities that Support Special Target Populations

6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings1

Review Publications
Miao, J., Wu, K., Hopper, K.R., Li, G. 2007. Population dynamics of APHIS GLYCINES (Hompotera: Aphididae) and impact of natural enemies in northern China. Environmental Entomology. 36:840-848.

Ulrichs, C., Hopper, K.R. 2008. Predicting insect distributions from climate and habitat data. BioControl. 10.1007/s10526-007-9143-8, 1-14.

Last Modified: 5/5/2015
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