Genetic Analysis of Loose Smut (Ustilago avenae Pers. (Rostr.)) Resistance in Oat (Avena sativa L.)

Abstract

Oat (Avena sativa L.) is a widely grown cereal crop that is used for human consumption and livestock feed. Canada is the second largest producer of oat worldwide, with Saskatchewan leading annual Canadian production with 1.7 million tonnes. As market prices for oat are usually lower than other cereals, growers tend to forgo the use of certified seed or crop inputs (e.g. seed treatment) when growing oat. This can have significant repercussions when it comes to diseases that affect both the quality and quantity of the crop. One such disease is loose smut of oat, caused by the basidiomycete pathogen Ustilago avenae (Pers.) Rostr. This study investigated loose smut resistance present in ‘CDC Dancer’ using an F4:7 recombinant inbred line (RIL) population derived from the cross ‘CDC Dancer’ x ‘AC Morgan’ (DM). The goals were to: 1) phenotypically characterize, linkage map and identify putative marker(s) linked to loci governing resistance, and 2) to assess whether resistance from this population conferred a negative yield effect in the absence of the pathogen. A linkage map was constructed with data from single nucleotide polymorphism (SNP) genotyping of the population, in conjunction with both field and greenhouse the phenotypic disease assessments. The map was comprised of 34 linkage groups (LGs), with a major resistance gene mapping to the terminus of linkage group (LG) 11 and a minor resistance gene mapping to LG19. Investigation of allelic effects underlying each QTL revealed that lines possessing the ‘CDC Dancer’ allele at either QTL had a lower loose smut disease reaction score. Analysis of both QTL indicated an interaction (P < 0.05) in disease reaction scores. The markers linked to these two QTL will be useful to oat breeders wishing to incorporate this resistance into future oat cultivars. Evaluation of two genetically similar RILs from the DM population, which differed in their reaction to loose smut, indicated no difference in mean yield between the lines. As such, the absence of yield effects from the U. avenae resistance gene investigated in this study means that incorporation of this source of loose smut resistance is a viable option for oat breeders.