Genetic Analysis of Puccinia coronata Corda f.sp. avenae Resistance in Oat (Avena sativa L.)

In Western Canada, oat crown rust (caused by Puccinia coronata Corda f. sp. avenae Eriks) is considered the most economically important disease of cultivated oat (Avena sativa L.). Resistant oat varieties are an important control method for crown rust. Avena sterilis L. accessions have been the main source of crown rust resistance genes due to their reproductive compatibility with A. sativa. In order to discover new seedling resistance genes in Avena sterilis accessions, six genetic populations were generated by crossing AC Morgan (Reg. no.CV-369, PI 629113) with six A. sterilis accessions (PI311623-4, PI333561, PI334672-5, PI335562, PI375506 and PI375547). All F2 populations and partial F3 families were inoculated with isolate CR259 (race LQCB-91; virulent on Pc35/38/39/40/55/59/60/61/63/91) at the two leaf stage and rated 11 or 12 days post-inoculation. Resistance in PI334672-5 was the result of two resistance genes with one dominant resistance gene and one recessive resistance gene. Two dominant resistance genes were likely present in PI375547. Current F2 tests revealed that both PI311623-4 and PI335562 contained two dominant genes, resulting in duplicate dominant epistasis. Based on current F2 and F3 data, resistance genes present in PI375506 are most likely one dominant resistance gene or one dominant resistance gene and one recessive resistance gene. In F2 tests, PI333561 appeared to be heterogeneous. Assuming no heterogeneity, PI333561 would carry two resistance genes, one or both of which are incompletely dominant. PI333561 is the only accession resistant to all crown rust isolates contained in the Cereal and Flax Pathology Lab (University of Saskatchewan, Saskatoon, SK) and Cereal Research Centre (Agriculture and Agri-Food Canada, Winnipeg, MB) collections. As such, this accession likely carries valuable new seedling crown rust resistance genes. Extensive use of seedling genes in breeding programs corresponds with high virulence frequency to those genes. Adult plant resistance (APR) is believed to be a durable rust management strategy. The crown rust resistance in the oat line MN841801 has been effective for more than 20 years. Research was conducted to detect APR quantitative trait loci (QTLs) contributed by MN841801. A genetic map was generated in a population of 167 F7-derived recombinant inbred lines (RILs) from a cross AC Assiniboia x MN841801 (AM). The map containing mostly Diversity Arrays Technology (DArT) markers consisted of 30 linkage groups spanning 955 cM. Two field environmental tests under a lattice design were conducted in Saskatoon, Saskatchewan. Only one QTL contributed by AC Assiniboia was detected on 2010 Saskatchewan field data. This detected QTL was the result of the seedling resistance gene Pc68, since it was mapped 4 cM away from the sequence characterized amplified region (SCAR) marker Pc68-300. No QTL contributed by MN841801 were detected in this study. Low oat genome coverage in the current genetic map of the AM population is the primary limitation to detecting APR QTLs contributed by MN841801. Single nucleotide polymorphism (SNP) markers from the first complete oat map will be important for improving the genetic map of this population and detection of APR QTL from MN841801. Additional field testing of the AM population with P. coronata isolate CR251 is recommended to improve the precision and accuracy of the phenotypic data