2013 Annual Report
1a.Objectives (from AD-416):
The main objective of this project is to develop wheat germplasm with genes for resistance to stem rust race Ug99 and currently encountered races of wheat stem rust. Attention will focus on the introduction of new genes to Great Plains adapted wheats, and pyramiding these genes with genes for resistance to additional pathogens.
1b.Approach (from AD-416):
The USDA-ARS Grain, Forages and Biofuels Research Unit at Lincoln, NE, is developing Great Plains adapted winter wheat germplasm with resistance to Ug99 and other races of stem rust. Stem rust resistance is being pyramided with genes conferring resistance to additional pathogens, including leaf and stripe rusts, and wheat streak mosaic and soilborne mosaic viruses. The Department of Plant Pathology at the University of Nebraska will identify breeding lines carrying stem rust resistance. Newly developed wheat breeding lines (F5 or F6 generations) derived from crosses with resistant donor parents will be assayed for stem rust resistance at the seedling stage via inoculations in the greenhouse, and for adult plant resistance, after inoculation at the University of Nebraska Agricultural Research and Development Center near Mead, NE.
The objective of this project is to identify wheat germplasm lines with resistance to stem rust, coupled with additional disease resistance and quality related traits. During the winter of 2013, 245 advanced breeding lines were tested in greenhouse and field screens against stem rust race TPMK, a surrogate race for Ug99, a potentially highly virulent race of east African origin not yet present in the U.S. TPMK also was used to inoculate the same 245 lines in field-grown materials to determine adult plant responses. Field inoculation also was used to score all breeding lines entered in the 2013 USDA-ARS coordinated Regional Germplasm Observation Nursery (RGON). Of the 245 USDA-ARS developed experimental breeding lines, 145 were scored as highly resistant, resistant, or moderately resistant. Field inoculation with TPMK during the summer of 2013 verified these results at the adult plant stage. Approximately 66% of the RGON entries displayed either resistance, or moderate resistance, to field inoculation with TPMK. A subset of thirty of the 245 ARS lines was tested for field responses to stem rust in Kenya; nine were found to be resistant. These materials will be useful to wheat breeding programs across the nation as sources of resistance to Ug99. Several of these Ug99 resistant lines will be entered in advanced regional testing trials in the fall of 2014.