Project Number: 5442-21000-033-06
Project Type: Specific Cooperative Agreement

Start Date: Sep 15, 2006
End Date: Oct 31, 2009

Objective:
At least six pest resistance genes (e.g. tan spot, insect resistance) originally derived from Aegilops tauschii were recently localized on chromosome 3D in synthetic hexaploid wheat. The objectives of this project are to characterize the chromosomal intervals harboring these resistance genes using genomic resources currently available in wheat and model species, to develop user-friendly molecular markers for marker-assisted selection in breeding, and to provide a better understanding of the mechanisms underlying pest resistance in wheat.

Approach:
We will precisely position the resistance genes on chromosome 3D using molecular markers. A novel strategy will be adopted to quickly develop four doubled haploid (DH) populations for mapping these genes and for followup high resolution mapping. This will be done by crossing susceptible Ae. tauschii accessions with four resistant Ae. tauschii accessions, then crossing the F1¿s to the durum `Langdon¿, followed by embryo rescue and chromosome doubling. These populations segregate only at the loci on D-genome chromosomes. The A and B genomes are identical across the entire populations. We will phenotype the populations, then use bulked segregation analysis to identify SSR and TRAP markers closely linked to the genes. Polymorphic SSRs/TRAPs will be used to construct linkage maps of the genes in the DH populations. Physical and comparative mapping will be also carried out to determine the physical location of the resistance genes on chromosome 3D and to identify chromosomal regions collinear with the intervals harboring the resistance genes from model species, such as rice. We will explore the structural and functional genomic resources from model species to enhance knowledge of the resistance genes and the genomic regions spanning the genes in wheat. Accomplishment of this project will enhance our understanding of the defense system encoded in this chromosome and facilitate efficient use of the host defense system against pests in wheat.