Genetic diversity of Kentucky bluegrass genotypes in morphological, agronomic, and abiotic stress tolerance characteristics

Kentucky bluegrass (Poa pratensis L.) is a perennial turfgrass species that is widely adapted to many distinct environments. Kentucky bluegrass reproduces through an asexual process called apomixis, resulting in many unique and distinctly different cultivars with specific niche uses. Therefore it is important to quantify and classify the broad range of adaptations within this species. The objectives of this study were to: (i) Classify Kentucky bluegrass genotypes based on morphological and agronomic traits and determine their inheritance patterns, (ii) Evaluate the range of variability Kentucky bluegrass cultivars and selections exhibit in response to a novel annual bluegrass control, bispyribac-sodium herbicide, (iii) Determine the effects of fertilizer on the response of Kentucky bluegrass cultivars and selections to bispyribac-sodium herbicide, and (iv) Evaluate the diversity of Kentucky bluegrass cultivars and selections in their rooting ability under heat stress. To do this a number of experiments were designed between the summers of 2004 and 2008 at the Rutgers University Plant Science Research Farms in Adelphia and New Brunswick, NJ. There is variation in morphological and agronomic traits in Kentucky bluegrass leading to a 12 group classification system based on the cultivars and selections evaluated. The traits that define these types are highly heritable. There is a differential response among Kentucky bluegrass cultivars and selections to bispyribac-sodium herbicide with some exhibiting almost complete tolerance and others complete susceptibility. Fertilizer can offset the injury associated with bispyribac-sodium herbicide on some cultivars, but actually increases the injury seen on others. There is variation in the rooting ability of Kentucky bluegrass cultivars under heat stress and based on the work of others it should be possible to select for and improve upon this trait. Kentucky bluegrass is a high quality turfgrass species with many distinct uses and based on these results the selection and management of Kentucky bluegrass cultivars is greatly simplified leading to proper cultivar use and long-term persistence.