2010 Annual Report
1a.Objectives (from AD-416)
A major goal of wheat improvement is to identify, isolate, and characterize genes and gene complexes that control value-added traits that can be introduced into commercial cultivars to improve production. Historically, once such gene complexes were identified and characterized they were manipulated into a hexaploid wheat background for improved production. Once the options for trait improvement genes in the available wheat germplasm were exhausted wheat geneticists turned to other members of the Triticeae tribe (cereals) as desirable genetic resources for trait exploitation. However, to date only a few gene complexes from non-wheat related species and genera have been characterized, manipulated and introduced into wheat. The lack of advancement in this area results from an undesirable linkage drag, resulting in low yields, that is associated with the transference of gene complexes from related species. This laboratory has developed methods for the efficient transferring of value-added gene complexes, without linkage drag, from rye into wheat for wheat improvement. This project will utilize these previously developed technologies of chromosomal centric-break and fusion translocations to transfer the value added traits of disease resistance and abiotic stress tolerance from rye and wheat-rye hybrids (triticales) to commercially useful hexaploid wheat cultivars. In particular the project will focus on 1. Identifying novel genetic elements associated with resistance to new strains of stem rust linked to rye chromosome 1R within local and world stock collections of triticales and spring ryes for transfer into hexaploid wheat, and 2. Identifying, characterizing and transferring novel genetic elements, regardless of chromosomal location, for resistance to stem and leaf rusts and tolerance to low pH and saline soils for transfer into hexaploid wheat. Objective 1: Develop, evaluate, and distribute wheat-rye aneuploid stocks. Objective 2: Use rye genes and gene complexes to improve stem and leaf rust resistance and abiotic stress tolerance in wheat.
1b.Approach (from AD-416)
To create and characterize wheat containing 1RS/1BL wheat/rye translocations. The present discovery-driven objective was designed to screen all newly developed wheat/rye translocation stocks, from every rye chromosome arm, for resistance to new races of leaf and stem rust, as well as screen for new levels of tolerance to select abiotic stresses.
The project has created four new wheat/rye hybrids utilizing newly characterized rye accessions that were found to be resistant to all forms of stem rust including UG99. The project has initiated the creation of fertile hybrids from the original wheat/rye haploid hybrids and one fertile hybrid has been established. The transfer of rye chromosome arms containing rye stem rust resistant genes into a common wheat background will be initiated this coming fall. The project is continuing to maintain and distribute wheat-rye genetic stocks and the USDA-Sears Collection of wheat aneuploids. The project has completed the stem rust screening of a rye germplasm collection in collaboration with the USDA-ARS Cereal Disease Laboratory located at the University of Minnesota, St. Paul, MN. The screened rye accessions resistant to stem rust have been crossed to hexaploid wheat. Screening of three newly developed triticale haploid hybrids for stem rust resistance by the USDA-ARS Cereal Disease Laboratory was completed. Additional stem rust screening in the USDA-ARS Cereal Disease Laboratory will be completed, but the rust screening is seasonal due to demands on that facility. The rye accessions were sent to the International Center for Maize and Wheat Improvement (CIMMYT) in East Africa for field testing in the environment where the new UG99 stem rust race was first identified and this coming fall the triticale hybrids will be sent to CIMMYT in East Africa for field evaluation of their UG99 stem rust resistance. East Africa is the center of origin of UG99.
In 2010 geneticists of the Plant Genetics Research Unit in Columbia, MO stabilized three haploid hybrids that exhibit UG99 resistance by treatment with colchicine. This treatment rendered them fertile, a prerequisite for breeding. A fourth rye stem rust resistant haploid triticale has been created, but has not yet been screened for UG99 resistance. It will be screened in the winter of 2010. The new ARS wheat/rye hybrids will be further screened for UG99 resistance, and constitute a new and valuable gene pool of stem rust resistance for incorporation into wheat cultivars. This is very important for wheat production on a world scale. The research is part of an expanded project to incorporate value-added traits of interest for wheat breeders from rye without involving the techniques associated with the molecular approaches of genetic engineering. This research is also a critical component of an overall ARS strategy to combat new strains of wheat rust pathogens.
Bento, M., Gustafson, J.P., Viegas, W., Silva, M. 2010. Genomes Behave as Social Entities: Alien Chromatin Minorities Evolve Through Specificities Reduction. Theoretical and Applied Genetics. 121(3):489-497. 10.1007/s00122-010-1325-6.