Project Number: 5440-21000-030-05
Project Type: General Cooperative Agreement

Start Date: Feb 01, 2011
End Date: Jan 31, 2016

Objective:
(1) Develop efficient phenotyping tools for insect resistance of switchgrass to greenbugs, chinch bugs and other key piercing-sucking insects and determine the categories of resistance; (2) Obtain biochemical, physiological and anatomical insights into insect-bioenergy grass interactions and determine potential insect resistance mechanisms among defined switchgrass populations; (3) Generate and evaluate diverse segregating populations of switchgrass to assess for insect herbivory using phenotyping tools; (4) Use selected susceptible and resistant switchgrass genotypes to define transcriptional changes before and during insect feeding in order to identify candidate resistance genes; (5) Perform association mapping on developed switchgrass population to correlate candidate resistance genes with insect feeding; and (6) Utilize methods in RNA profiling of insects to uncover key transcriptional regulatory mechanisms that govern host range in grass-feeding insects.

Approach:
The research goals of this project are to identify plants with enhanced resistance to piercing-sucking insects using defined populations of switchgrass and new screening protocols to identify sources of both resistant and susceptible genotypes using five populations of tetraploid switchgrasses and two piercing-sucking insects. During Obj. 1 we will develop the protocols to identify resistant and susceptible switchgrass genotypes to the green bug and the chinch bug. Selected plants will be clonally propagated to obtain materials for Obj. 2. Anatomical, physiological, biochemical and molecular tools will be used to assess insect-plant interactions. Select plants will also be intermated to develop F1 populations for Obj. 3. In this objective (3), marker populations will be screened for insect resistance at the seedling stage. Resistant and susceptible plants will be identified, removed from insect pressure and allowed to grow to obtain clonally propagated materials. During Obj. 4 harvested plant materials will be pooled for biochemical analyses and for the generation of mRNA with subsequent next-generation DNA sequencing to obtain potential candidate genes using a combination of studies conducted in the previous Objectives along with detailed bioinformatic analyses. These data will be used to perform associating mapping on switchgrass marker populations to correlate candidate resistance genes to insect feeding to support Obj. 5. For Obj. 6 insects reared on appropriate switchgrass and/or other control plants will be collected. mRNA isolated from these insects will be subjected for RNA profiling to uncover key transcriptional regulatory mechanisms that govern host range in grass-feeding insects.