Association of SSR and Candidate Gene Markers with Genetic Variations in Summer Heat and Drought Performance for Creeping Bentgrass

Identification of molecular markers linked to physiological traits for stress tolerance is important for understanding the underlying genetics and breeding for improving plant stress tolerance. The objectives of the current study were to evaluate genotypic variations in a population of creeping bentgrass (Agrostis stolonifera L.) germplasm for summer performance and drought tolerance under field conditions, and to validate candidate gene and quantitative trait locus (QTL) markers associated with physiological traits for stress tolerance in two locations differing in climate conditions. The trials were conducted in 2014 and 2015 in field plots covered under automatic rainout shelters in Georgia and New Jersey. Phenotypic and physiological traits, including visual turf quality ratings, membrane stability, chlorophyll content, normalized difference vegetative index, and leaf water content, were evaluated for heat tolerance during summer months and for drought tolerance. Using association analysis, phenotypic and physiological traits were measured to confirm linkage to 29 simple sequence repeat (SSR) markers and five candidate gene markers. Significant associations between traits and markers were found for 24 of the 34 molecular markers for the bentgrass population exposed to summer heat stress or drought stress. Those markers with significant associations may be useful in marker-assisted selection and understanding how specific genetic regions influence abiotic stress tolerance in creeping bentgrass.