Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/2/2005
Publication Date: 5/26/2005
Citation: Portyanko, V.A., Chen, G., Rines, H.W., Phillips, R.L., Leonard, K.J., Ochocki, G.E., Stuthman, D.D. 2005. Quantitative trait loci for partial resistance to crown rust, Puccinia coronata, in cultivated oat, Avena sativa L. Journal of Theoretical and Applied Genetics. 111(2):313-324. Interpretive Summary: Oat crown rust is the major disease in the cereal oat in the Upper Midwest, the primary region of oat grain production in the U.S. In most currently available oat varieties, resistance to this fungal disease is imparted by single major genes that cause strong selection within the rust population leading to a rapid build-up of rust strains not sensitive to the resistance genes. Thus, the resistance becomes ineffective within 1 to 3 years once an oat variety is widely grown. An alternative type of resistance has been identified which does not prevent rust infection, but greatly reduces the rate of development and spread of the disease regardless of the rust race involved. The incorporation of such partial resistance into an oat cultivar should make its rust resistance more long lasting, or durable. The problem a plant breeder faces in trying to incorporate this partial resistance into a new oat variety is that the resistance is inherited in a complex fashion with several genes contributing to its effect. We have used molecular genetic techniques combined with field testing to develop information and tools to facilitate the transfer of this multi-gene trait from a donor oat line into recipient lines that may include a potential new oat variety. We identified DNA sequences termed molecular markers that are genetically linked or associated with oat genetic regions or quantitative trait loci that specify resistance. Assays of these DNA markers in small samples of tissue taken from young plants enable the indirect selection for the plants with the right combination of quantitative trait loci for the desired rust resistance. The identification of relevant DNA marker associations to quantitative trait loci in an oat donor line with good partial rust resistance provides oat breeders and geneticists tools to more efficiently and effectively develop oat varieties with durable crown rust resistance.
Technical Abstract: To facilitate the detection of quantitative trait loci (QTLs) for partial resistance to oat crown rust, Puccinia coronata f. sp. avenae Eriks, a genetic map was generated in a population of F6-derived oat recombinant inbred lines (RILs) from a cross of a partial resistance line MN841801-1 by a susceptible cultivar selection Noble-2. The map was developed using RFLP (Restriction Fragment Length Polymorphism) and AFLP (Amplified Fragment Length Polymorphism) markers and spanned 1509 cM (Haldane) arranged into 30 linkage groups of 2-18 markers each. Four consistently detected major QTLs for partial rust resistance, Prq1a, Prq1b, Prq2, and Prq7, and three minor QTLs, Prq3, Prq5, and Prq6, were found in tests involving three field and two greenhouse environments. Also, two major QTLs for flowering time, Ftq1 and Ftq7, and five weaker QTLs, Ftq2, Ftq3, Ftq4, Ftq5, Ftq6, were revealed. Overlapping of the map regions of Ftq1 and Prq1 and of Ftq7 and Prq7 suggest either linkage between the flowering time QTLs and resistance QTLs or a pleiotropic effect of the Ftq QTLs on rust resistance. Relatively low heritability estimates (0.30) obtained for partial resistance to crown rust in the field indicate a potential value for marker-assisted selection.