Location: Plant Genetics Research2011 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.
3. Progress Report
The project created four new wheat/rye haploid hybrids utilizing newly characterized rye accessions found to be resistant to all forms of stem rust including Ug99 when tested by the USDA-ARS, Cereal Disease Laboratory, St. Paul, MN. The project created two fertile amphidiploids from the original wheat/rye haploid hybrids and two haploid hybrids were repeatedly sterile. The rye parents used in making the sterile hybrids were crossed to a hexaploid triticale in order to allow the rye chromosomes to recombine in the hope of transferring the rye gene complex controlling Ug99 resistance to a rye compatible with wheat. The transfer of rye chromosome arms containing rye stem rust resistant genes into a common wheat background will continue this fall. The project continues 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, 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, St. Paul, MN was completed. Additional stem rust screening in the United Nations, International Atomic Energy Agency, Food and Agriculture Organization, (UN-IAEA-FAO) East Africa, Cereal Disease field Evaluation Program will be completed, but rust screening is seasonal. The rye accessions were sent to East Africa for field testing, along with wheat germplasm lines from around the world, in the environment where the new UG99 stem rust race was first identified. This past fall the triticale and wheat mutant hybrids were grown and evaluated in East Africa for field evaluation for UG99 stem rust resistance. East Africa is the center of origin of UG99.
1. New sources of stem rust resistance for wheat. Ug99, a new stem rust strain, threatens world wheat production and global food security. An ARS scientist in Columbia, Missouri created four wheat/rye hybrids using a combination of stem rust susceptible wheat 'Chinese Spring' accessions and four different rye accessions that were previously screened for stem rust resistance as parental lines. In collaboration with ARS scientists in St. Paul, Minnesota three of the wheat/rye hybrids were screened for stem rust resistance. The hybrids were stabilized by a chemical treatment that resulted in a doubling of their chromosomes to give them the normal chromosomal compliment of commercial varieties. Two of the hybrids became fertile by this stabilization treatment. Two stem rust resistant triticale (rye/wheat hybrid) were also created, but no viable seed was obtained as the rye parent chromosomes proved to be incapable of combining with wheat. These ARS wheat/rye hybrids constitute a new and valuable gene pool of Ug99 stem rust resistance for incorporation into wheat cultivars. This is very important for world scale wheat production as Ug99 expands into the major commercial growing regions of the world and threatening food security. This research is part of an expanded project to incorporate value-added traits from rye.