Genetic diversity for pink snow mold resistance in greens-type annual bluegrass
Unseeded annual bluegrass (Poa annua L.) is an important component of golf greens in many regions of Canada and the United States. Although this turfgrass species has desirable playing attributes, it suffers from susceptibility to environmental and biological stresses including subfreezing temperatures and snow molds. In this study, we compared 29 genotypes collected from golf greens located in Québec and Ontario for their resistance to pink snow mold (SM). Plants were inoculated with Microdochium nivale [(Fries) Samuels & Hallett], causal agent of SM, and incubated under controlled conditions. High levels of variation in SM resistance were detected within the collection and between genotypes. Analysis of the relationship between climatic parameters at the sites of origin and SM susceptibility revealed that level of resistance was positively correlated to the duration of snow cover. Genetic diversity within the Poa collection was estimated using the sequence related amplified polymorphism (SRAP) technique. The UPGMA (unweighted-pair group method arithmetic average) dendrogram yielded two main clusters that differed markedly in their proportion of SM-resistant genotypes. Our results show that SM disease is a major selection pressure for the generation of genetic diversity among annual bluegrass biotypes that evolved on golf greens in northern climates. SRAP polymorphisms between bulked genotypes with contrasting resistance to SM were identified and could be used as markers for SM resistance in annual bluegrass.