2012 Annual Report
1a.Objectives (from AD-416):
The main objective of this project is to develop improved winter wheat and barley germplasm and cultivars with stem rust resistance that will be winter-hardy with high yield and end-use quality, environmentally stable in production, and provide an increased return per grower input. Stem rust resistant plant materials adapted to both conventional and organic production systems will be developed.
1b.Approach (from AD-416):
Crosses will be made in the greenhouse using selected wheat and barley germplasm parents possessing various combinations of adequate winter-hardiness and heat and drought tolerance, high yield, resistance to Ug99 stem rust and other races of rust prevalent in the northern Great Plains, other disease and insect resistance or tolerance, improved end use quality attributes, and good straw strength. Germplasm will include locally adapted lines and cultivars, introduced materials from private programs, other regions or countries having unique characteristics, and, when necessary, derivatives from related species and genera developed by more basic germplasm programs. Marker assisted selection will be used for allele enrichment in the early generations and genotyping advanced lines for line characterization. F1 seed will be increased in the greenhouse or Yuma, AZ to create a large number of populations of ample size. F2 and F3 populations will be grown at Lincoln or Mead, NE. F3 derived lines will continue to be selected with statewide testing beginning in the F6. Field testing will be supplemented with greenhouse testing for leaf and stem rust testing at Lincoln, NE and St. Paul, MN (USDA ARS Cereal Disease Laboratory). Standard and molecular genetic analytical procedures to determine the inheritance of the traits that are useful to enhance adapted cultivars. Agrobase GenII software, SAS or GENSTAT will be used to analyze data.
Wheat breeding lines from University of Nebraska Small Grains Breeding Program were screened in the greenhouse for responses to stem races QFCS and TPMK. These races serve as surrogates and can predict responses to Ug99 stem rust. More than 2000 lines were tested at the University of Nebraska, with a subset of sixty lines also tested at the USDA-ARS Cereal Disease Lab in St. Paul, MN. Approximately 36% of the tested lines were eliminated from further consideration as they proved susceptible. To ensure a very high frequency of Ug99 stem rust resistance, crosses were made to germplasm carrying Srtmp, Sr39, Sr2, Sr25, SrCadillac, as well as other unknown minor genes from CIMMYT. The ultimate goal is to pyramid genes to build a stronger base of resistance among Nebraska-adapted lines. The elite triticale nursery from the University of Stellenbosch, RSA (where Ug99 has spread and lines were selected for field stem rust resistance) was used to make crosses to Nebraska-adapted triticales in 2012. The F1 seed of finished crosses of wheat, barley, and triticale were sent to Yuma, AZ (726 rows). The F2 seed will be planted and inoculated with stem (race TPMK). The Yuma seed increase was returned in June, 2012. A genetic study is being conducted to analyze the exceptional stem rust resistance of ‘Gage’ wheat. Gage, ‘Lancer’, and ‘Scout 66’ carry Sr2 (an adult plant resistance gene), but Gage always displays higher levels of resistance. Gage was crossed to ‘Bill Brown’ (a highly susceptible cultivar), and resultant F2:4 lines screened for stem rust resistance. The population has been submitted for DNA sequence analysis to identify the source of Gage’s novel resistance. Finally, the stem rust resistance of two synthetic wheat lines was analyzed. Both lines were found to have combined drought tolerance with two novel dominant stem rust resistance genes.