Genotypic variation in germination rate, seedling vigor, and seed phenotype of Kentucky bluegrass cultivars

Kentucky bluegrass (Poa pratensis L.) is the most widely used cool-season turfgrass for athletic fields, but its seeds germinate slowly. The objective was to determine the germination rate, seedling vigor, and seed phenotype of Kentucky bluegrass cultivars. Germination and seedling vigor tests were conducted using a seed incubator set at alternating 25/15 & DEG;C (day/night) temperatures and an 8 h day(-1) photoperiod. Twenty-one cultivars were tested using two seed lots for each. Germination was most rapid among the experimental genotype PST-T15-44 and the commercial cultivar "After Midnight, as they took the minimum days to reach 50% germination in only 7.9-8.0 or 8.8 days, respectively. Cultivars Tirem and Volt required >12 days in both lots to reach 50% germination (12.0-13.7 days). There was a difference of 5-6 days in 50% germination between cultivars. Seedling vigor was also measured but few differences between cultivars were noted. Data on seed phenotype including seed length, width, area, circularity, and thousand seed weights (TSW) all varied by cultivar. ''After Midnight'' had the longest seeds (3.065 mm). ''Moonlight SLT'' seeds were the shortest in length (2.366 mm), narrowest in width (0.717 mm), and smallest in area (1.328 cm(2)). Across all cultivars, seed length and circularity were correlated with germination rate (r = 0.62, p = 0.0025; r = -0.53, p = 0.0141). Seed phenotyping could be an important tool in breeding for improved germination rate. By identifying and using rapidly germinating Kentucky bluegrass cultivars, it may be possible to establish turf more rapidly.