Start Date: May 25, 2005
End Date: May 24, 2010
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.