Mapping Gray Leaf Spot Resistance Genes in St. Augustinegrass.

While St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) is a valued turfgrass in the southern United States for its superior shade tolerance and vigorous growth, the grass is susceptible to damage from diseases such as gray leaf spot [GLS, Magnaporthe grisea (T.T. Hebert) Yaegashi & Ugadawa]. In the warm, humid summers that characterize the Southeast, GLS is especially pervasive and damaging. Development of cultivars with genetic resistance to the fungus could provide an alternative management strategy for the disease.  Plant introduction 410353 has been identified as having good levels of resistance to the fungus and can therefore be used in breeding for GLS resistance. Identification of molecular markers linked to quantitative trait loci (QTL) conferring resistance to GLS in this genotype could accelerate breeding efforts via marker assisted selection (MAS). In this study, a pseudo-F₂ population consisting of 129 individuals was developed from crosses between cultivar ‘Raleigh’ and PI 410353. Genotypes were assessed for GLS response under controlled environmental conditions at the Southeastern Environment Laboratory (Raleigh, NC). Simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers were used to genotype the population and to create the first linkage map of St. Augustinegrass. Subsequently, genotypic and phenotypic data were analyzed in order to identify QTL associated with GLS resistance.