Identification of Quantitative Trait Loci for Resistance to Crown Rust in Oat Line MAM17‐5

Abstract

Crown rust, caused by the fungus Puccinia coronata Cda. f. sp. avenae Eriksson, is the most damaging disease of oat (Avena sativa L.). Breeding for resistance to crown rust has been an efficient and economical means to control the disease. Most of the resistance genes in recently released oat cultivars have been introgressed from the hexaploid, wild oat species A. sterilis L. The number of effective resistance genes has been rapidly decreasing. Characterization and utilization of new resistance sources are needed to ensure adequate resistance in future oat cultivars. Crown rust resistance in diploid, wild oat accessions was transferred to the hexaploid, cultivated oat line MAM17‐5. The objective of this study was to identify the number, position, and effect of quantitative trait loci (QTL) and digenic QTL epistasis controlling crown rust resistance in MAM17‐5. A linkage map of 272 molcular markers was used for this analysis. Reaction type and rust severity data were collected on field‐grown adult plants from 152 F5:6 recombinant inbred lines derived from the cross, ‘Ogle’/MAM17‐5. Composite interval mapping was conducted to identify genomic regions associated with crown rust resistance. Overall, two QTL, Pcq1 on linkage group 28 and Pcq2 on 29, were consistently identified for crown rust resistance in different years. Pcq1 and Pcq2 explained 48.5 to 70.1% and 9.6 to 14.0%, respectively, of the total phenotypic variation for crown rust resistance. Significant digenic, epistatic interactions were detected for QTL controlling rust severity but not reaction type. Marker‐assisted selection targeting the major QTL, Pcq1, should be useful for efficient selection of crown rust resistance.