Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 11, 2011
Publication Date: June 1, 2011
Citation: Lowe, I., Jankuloski, L., Chao, S., Chen, X., See, D.R., Dubcovsky, J. 2011. Mapping and validation of Yr48 and other QTL conferring partial resistance to broadly virulent post-2000 North American races of stripe rust in hexaploid wheat. Theoretical and Applied Genetics. 123:143-157. Interpretive Summary: Stripe rust, a fungal disease, has been a historical and continuing threat to wheat production throughout the world including the US, capable of causing significant reductions in both grain quality and yield. The development and timely deployment of genetic resistance to this important disease is complicated by the fast evolving pathogen that consists of a population of distinctive races. Since the year 2000 more than 60 new races were identified in the western region of the US that overcome some of the previously effective resistance genes. Therefore, there is an urgent need for novel resistance genes that can provide durable resistance, particularly in combination with genes that are still effective. The purpose of this study was to identify, characterize, and ultimately deploy genetic sources of partial resistance to stripe rust. A population of 188 progeny lines segregating for disease resistance was developed by crossing two wheat germplasm with moderate resistance. One is UC1110, an adapted California spring wheat, and the other, PI610750, is a synthetic derivative from CIMMYT's wide-cross program. These materials were evaluated for their responses to current California races of stripe rust in replicated field trials over four seasons (2007-2010) in the northern Sacramento Valley. The genetic analysis has revealed the presence of four major genes located on chromosomes 3BS, 5AL, 2A and 2B that contributed large genetic effects on stripe rust resistance. The two genes on 3BS and 5AL having the largest effects were further validated using independent genetic populations and disease evaluations. Additional genetic tests also suggested that the resistance genes detected in this study were novel. The 5AL gene, in particular, carrying a previously unreported partial stripe rust resistance gene was designated here as Yr48. The lines carrying these novel genes identified in this study are publicly available, and can be readily used for wheat breeding and research applications.
Technical Abstract: A mapping population of 188 recombinant inbred lines developed from a cross between UC1110, an adapted California spring wheat, and PI610750, a synthetic derivative from CIMMYT's wide-cross program, was evaluated for its response to current California races of stripe rust (Puccinia striiformis f.sp. tritici) in replicated field trials over four seasons (2007-2010) in the northern Sacramento Valley. A genetic map was constructed consisting of 1,494 polymorphic probes (SSRs, DArTs, and ESTs) mapped to 559 unique loci; and QTL analysis revealed the presence of four stripe rust resistance QTL segregating in this population, two from UC1110 (on chromosomes 3BS and 2B) and two from PI610750 (5AL and 2A). The two QTL of largest effects (on 3BS and 5AL) were validated in independent populations and their intervals narrowed to 2.5 cM and 4.7 cM, respectively. The 3BS QTL is shown, by allelism test and genotype, to carry a gene different from the Yr30/Sr2 complex. Mapped position also suggests that the 3BS QTL carries a gene different from either Yrns-B1 or YrRub, two other stripe rust resistance genes mapped in other studies to this region. The 5AL QTL carries a previously unreported partial stripe rust resistance gene, designated here as Yr48. This paper presents a preliminary characterization of all four QTL and discusses their potential in durable resistance strategies based on combinations of partial resistance genes.