Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2003
Publication Date: 2/11/2003
Citation: BROWN GUEDIRA, G.L., SINGH, S., FRITZ, A.K. PERFORMANCE AND MAPPING OF LEAF RUST RESISTANCE TRANSFERRED TO WHEAT FROM TRITICUM ARMENIACUM. PHYTOPATHOLOGY, Vol.93, No 7, 2003. p784-789 Interpretive Summary: Foliar diseases of wheat continue to be the most important cause of yield loss in wheat in the Central Plains of the U.S. and other regions of the world. Leaf rust causes average annual yield losses of more than 5% in the Central Plains of the U.S., translating into a loss of more than 20 million bushels ($60 million) each year in Kansas alone. The wheat germplasm lines KS96WGRC35, KS96WGRC36, and U2657 were found to be resistant to leaf rust in multiple years of field testing in KS and TX. Genetic analyses determined that these lines have two different genes for resistance to leaf rust that were transferred to hard winter wheat from accessions of wild timopheevi wheat. Molecular markers Xgwm382 and Xgdm87 were linked to one of the resistance genes, indicating that this gene is located on the long arm of wheat chromosome 2B. This new leaf rust resistance gene is designated Lr50. It is the first named gene for leaf rust resistance transferred from wild timopheevi wheat and is the only Lr gene located on the long arm of wheat group 2 chromosomes. Availability of markers linked to Lr50 will allow breeders to use marker-assisted selection to build pyramids of leaf rust resistance genes that include Lr50.
Technical Abstract: Host plant resistance is an economical and environmentally sound method of control of leaf rust, caused by the fungus Puccinia triticina Eriks, which is one of the most serious diseases of wheat (Triticum aestivum L.) worldwide. Wild relatives of wheat, including the tetraploid Triticum timopheevii (Zhuk.) Zhuk. ssp. armeniacum (Jakubz.) van Slageran (hereafter referred to as T. armeniacum), represent an important source of genes for resistance to leaf rust. The objectives of this study were (1) to evaluate the performance of leaf rust resistance genes previously transferred to wheat from three accesssions of T. armeniacum, (2) determine inheritance and allelic relationship of the new leaf rust resistance gene(s) and (3) to determine the genetic map location of one of the T. armeniacum-derived genes using microsatellite markers. The leaf rust resistance genes transferred to hexaploid wheat from accession TA 28 of T. armeniacum exhibited slightly different infection types (ITs) to diverse races of leaf rust in inoculated tests of seedlings compared to the gene transferred from TA 870 and TA 874. High ITs were exhibited when seedlings of all the germplasm lines were inoculated with P. triticina races MBRL and PNMQ. However, low ITs were observed on adult plants of all lines having the T. armeniacum-derived genes for resistance in the field at locations in Kansas and Texas. Analysis of crosses between resistant germplasm lines showed that accessions TA 870 and TA 874 donated the same gene for resistance to leaf rust and TA 28 donated an independent resistance gene. The gene donated to germplasm line KS96WGRC36 from TA 870 of T. armeniacum was linked to microsatellite markers Xgwm382 (6.7 cM) and Xgdm87 (9.4 cM) on wheat chromosome arm 2B long. This new leaf rust resistance gene is designated Lr50. It is the first named gene for leaf rust resistance transferred from wild timopheevi wheat and is the only Lr gene located on the long arm of wheat homoeologous group 2 chromosomes.