Abstract

See also: Key to St. Augustinegrass cultivars

A vegetatively propagated crop such as St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] should consist of distinctive, easily identifiable cultivars.  The purpose of this study was to improve identification criteria for this species and measure the frequencies of various St. Augustinegrass cultivars in Florida.    Morphological traits were recorded in 242 unknown Florida St. Augustinegrass lawn and turf samples, which had been transplanted and grown outdoors in containers with 16 known clonal cultivars and taxonomic representatives.  Lawn and turf samples conformed mostly to the expected morphological distributions of 'Floratam', 'Bitterblue' and a heterogeneous 'Roselawn'-like complex.  The latter clones were distinctive because of their intermediate-sized (4.6 to 4.8 mm) spikelets, relatively long floral regions (measured from the base of the lowermost spikelet to the tip of the inflorescence), and long, narrow internodes.   Therefore, they were named the Longicaudatus ("long-stemmed") Race.  Clones with short (<4.5 mm) spikelets were also distinctive and were named the Breviflorus Race, however, this race was virtually absent in Florida.  Spikelet length and length of the floral region separated known cultivars in 84 of 91 pairwise comparisons (P<0.05), and these two traits showed no detectable environmental variance between containers and field plots.   Inclusion of floral traits in discriminant analysis increased the proportion of unknown clones that could be identified from 49% (with vegetative traits only) to 95%.  Keys using vegetative field traits and replicated container measurements were 93% accurate in identification of known, and 86 to 96% consistent with discriminant analysis in identification of unknowns.