Genetic Diversity and Vulnerability of St. Augustinegrass

St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze, expanding rapidly as a lawn grass, due especially to urban development in warm coastal areas, where it is best adapted. Although first discovered in South Carolina, in 1788, St. Augustinegrass may not be native to North America. The six other species of the genus are endemic to the Old World, and are still confined mainly along shorelines from Africa to the South Pacific. The first recorded use of St. Augustinegrass was in 1880, as a lawn in Florida. Cultivars were named beginning in the 1920s. The first cultivar of known parentage was released in 1980. Genetic diversity in the urban landscape is reduced by reliance on a few vegetatively propagated cultivars. Among breeding collections of St. Augustinegrass, considerable diversity exists for diploids, but not for polyploids. A related species, pembagrass, S. dimidiatum (L). Brongn., is resistant to the southern chinch bug, Blissus insularis Barber, and the sting nematode, Belonolaimus longicaudatus Rau., which are pests of St. Augustinegrass. Currently, only 26 foreign introductions of Stenotaphrum are found in the National Plant Germplasm System. Untapped germplasm potential of polyploid St. Augustinegrass and related species should be explored in southern Africa, where potential sources of resistance to chinch bugs and drought, and shade tolerance might be found. For new problems that will be discovered, genetic diversity must be deployed so as to deter resistance‐breaking pest strains. This will require better knowledge of the biological relationships.