Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/26/2007
Publication Date: 1/9/2008
Citation: Jackson, E.W., Obert, D.E., Hu, G., Menz, M., Bonman, J.M. 2008. Qualitative and Quantitative trait loci conditioning resistance to Puccinia coronata races NQMG and LGCG in the oat (Avena sativa L.) cultivars Ogle and TAM O-301. Theoretical and Applied Genetics.v116:517-527 Interpretive Summary: Because of the health benefits of oats in the human diet, there is renewed interest in this crop. Crown rust disease is the most important disease of oats worldwide and breeding for resistance is the primary means of controlling the disease. Quantitative disease resistance, where the pathogen is not completely inhibited by the host, can be longer lasting in crop cultivars and therefore valuable to plant breeders. In this study we used new methods of measuring disease to identify regions of the oat genome where quantitative resistance to oat crown rust is located. This knowledge will ultimately help scientists breed better crown rust resistance and thus help oat growers produce crops at lower cost and without the use of chemical fungicides.
Technical Abstract: Accurately mapping disease resistance loci is dependent on the type and precision of phenotypic measurements. For crown rust of oat, phenotypic measurements are commonly based on visual ratings of infection types (IT) and/or diseased leaf area (DLA) of infected plants in the greenhouse or field. These data can be affected by several variables including; i) non-uniform disease development in the field, ii) atypical symptom development in the greenhouse, iii) the presence of multiple pathogenic races in the field, and iv) rating bias. We sought to accurately map a crown rust resistance phenotype in TAM O-301 using an Ogle/TAM O-301 (OT) recombinant inbred line (RIL) population and detailed measurements of IT, uredinia length (UL), and q-PCR-generated fungal DNA (FDNA) estimates. The measurements were taken on OT parents and recombinant inbred lines (RIL) inoculated with Puccinia coronata races NQMG and LGCG in separate greenhouse and field tests. Qualitative mapping identified an allele conferred by TAM O-301on linkage group (LG) OT-11, which produced a bleached fleck IT to races NQMG and LGCG. Quantitative mapping identified two major quantitative trait loci (QTL) originating from TAM O-301 on LGs OT-11 and OT-32 which reduced UL and FDNA of both races in all experiments. Additionally, minor QTLs that reduced UL and FDNA were detected on LGs OT-15 and OT-8, originating from TAM O-301 and LG OT-27, originating from Ogle. Detailed assessments of the OT population using multiple races in both the greenhouse and field provided comprehensive information to effectively map the genes responsible for crown rust resistance in Ogle and TAM O-301 to races NQMG and LGCG.