Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2008
Publication Date: 5/1/2008
Citation: Zhang, X., Singh, R.P., Kolmer, J.A., Huerta-Espino, J., Jin, Y., Anderson, J.A. 2008. Genetics of leaf rust resistance in CIMMYT "Brambling" wheat. Plant Disease. 92:1111-1118.
Interpretive Summary: A wheat cultivar called “Brambling” that was developed by the International Wheat Breeding Center in Mexico, was studied in a genetic analysis to identify what genes it has that provide resistance to the leaf rust disease that is caused by the fungus Puccinia triticina. Leaf rust resistance genes Lr14a and Lr23 were determined to be in “Brambling”. This cultivar also had the very important gene Lr34, and an additional gene that is best expressed in mature adult plants, that has not been previously identified. The leaf rust resistance of Brambling was due to the combination of genes Lr23, Lr34, and the unidentified gene. Gene Lr14a did not give resistance to the current leaf rust races. Since “Brambling” has a new gene for leaf rust resistance, it can be used in crosses to improve U.S. cultivars for diversity of leaf rust resistance genes.
Technical Abstract: The CIMMYT-developed spring wheat ‘Brambling’ has a high level of adult plant resistance (APR) to leaf rust, caused by Puccinia triticina. Our objectives were to determine the genetic basis of resistance in seedlings and adult plants, and the magnitude of genotype x environment effects on the expression of APR. Brambling was crossed with the spring wheat ‘Jupateco 73S’ that is highly susceptible to current predominant P. triticina races in Mexico and USA. The F1, F2:3, F4:5, F4:6 and F5:7 recombinant inbred lines (RILs) were evaluated under artificial field epidemics in Mexico and St. Paul, MN. The RILs also were tested with five isolates of P. triticina in greenhouse seedling experiments. A DNA marker was used to postulate the presence of slow-rusting gene Lr34 in the RILs. The proportion of homozygous susceptible lines in each generation indicated the presence of three effective resistance genes in adult plants of Brambling in tests in Mexico and four genes in tests at St. Paul. The RILs segregated for seedling genes Lr14a and Lr23 and adult plant slow-rusting gene Lr34 derived from Brambling and Lr17a from Jupateco 73S. Gene Lr23 conferred APR to P. triticina races present in the St. Paul nursery and accounted for the additional effective gene at this location. One of the remaining two new slow-rusting APR genes had larger effects than those from the other two known slow-rusting genes Lr34 and Lr46, and this gene was temporally designated as LrBram1. Expression of APR was influenced by the environment in the RILs, even though Brambling displayed a consistent response indicating that stability of APR can be achieved by combinations of slow-rusting resistance genes.