Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/1995
Publication Date: N/A
Interpretive Summary: Progress in plant breeding depends on successful detection and exploitation of genetic variability. In many cases, the rate of progress has been hindered by the lack of knowledge of important characteristics and the factors that influence them. Puccinia coronata, the causal agent of crown rust, is the most important fungal pathogen of cultivated oat. The primary means of control of the crown rust is through the use of cultivars that are resistant to this disease. A large number of factors that determine resistance to this pathogen have been identified. These factors are called genetic loci. However, the relationship of one locus to another has been unclear, as well as the location of these loci on the oat chromosomes. In this investigation, we identified and confirmed a group of five loci for resistance to the crown rust disease in a wild relative of cultivated oat. We also identified a locus which interferes with the function of one of the resistance loci in this group. This is one of the first reports of five loci determining resistance that are clustered and originate from a single accession. These types of resistance clusters are useful in the breeding of resistant oats. The results of this work will be of interest to plant breeders, plant pathologists, and researchers interested in investigating host-pathogen interaction in cereals.
Technical Abstract: A set of 100 recombinant inbred lines (RILS) was produced from a cross of diploid (n=7) Avena strigosa (CI 3815) with A. wiestii (CI 1994), resistant and susceptible, respectively, to Puccinia coronata, the causal agent of crown rust. This set of RILS was inoculated with 11 isolates of P. coronata. Infection type reactions to nine isolates (PC54, 263, 290, PC62, 202, 258, 325a, PC58, and PC59) fit a 1 resistant:1 susceptible ratio expected for traits controlled by single genes. Reaction to isolate 264B fit a 3 resistant:1 susceptible ratio suggesting control by dominant alleles of two genes. Reaction to isolate 276 fit a 1 resistant:3 susceptible ratio suggesting control by dominant alleles of two genes, whereby one allele inhibits the resistance conferred by the other. All isolates detected resistance specificities that mapped to the Pca region in A. strigosa for resistance to P. coronata. Pca is positioned between the oat RFLP marker, Xisu2192, and a new RAPD marker, XisuC18, near the end of linkage group A. Five unique specificities within the Pca region were differentiated by recombination. The observation of five specificities conferring disease resistance that are linked in coupling is unusual, because such genes are generally linked in repulsion and inherited from multiple donor parents.