Determination of the Level of Variation in Polyploidy among Kentucky Bluegrass Cultivars by Means of Flow Cytometry

Abstract

Kentucky bluegrass (Poa pratensis L.) is an important cool-season grass species in the turfgrass and forage industries. Understanding the genetics of Kentucky bluegrass is useful in developing improved cultivars and hybrids. However, studying the genetics of Kentucky bluegrass can often be difficult because of the high variation in ploidy level that results from its facultative apomictic reproductive nature. Flow cytometry provides an easy and accurate method for assessing this variation by quantifying DNA content. The purpose of our study was to determine the level of variation in ploidy in Kentucky bluegrass by analyzing its DNA content using flow cytometry. In addition, DNA content was compared with genetic similarity derived from DNA marker data, and was also correlated with chromosome number. Twenty-two cultivars of Kentucky bluegrass were selected for the study by considering the range of variability in morphological traits and genetic distance derived from DNA marker data. We found that the DNA content of Kentucky bluegrass genotypes from the 22 cultivars ranged from 5.39 to 17.69 pg of DNA/2C and that a majority of the genotypes had a DNA content value in the range of 7 to 13 pg. A significant correlation between DNA content and chromosome number was detected. Euploid chromosome numbers (x = 7) with a range from the pentaploid (2n = 5x = 35) to the quindecaploid (2n = 15x = 105) were found along with aneuploid numbers. The results of this research could aid both breeders and researchers in studying the genetics of the species and in improving Kentucky bluegrass cultivars via intra- and interspecific hybridizations.