Wear and Shade Tolerance in St. Augustinegrass Genotypes.

Wear and shade are environmental stresses affecting turfgrasses in the landscape that are not easily measured. The objectives were to measure wear and shade resistance in 25 genotypes of St. Augustinegrass, Stenotaphrum secundatum, and to determine if these traits were associated with morphological variables. Named cultivars Bitterblue, Delmar, Floralawn, Floratam, FX-10, Jade, Mercedes, Raleigh, Seville, and Sunclipse, and 15 experimental genotypes in the 1989 National Turfgrass Evaluation Program were grown in a commercial sod farm and transplanted as sod to a shade area and a wear track area. The shade area was covered with a dome with 27% transmission shade cloth which was doubled during the experiment to reduce sunlight transmission to 6% and there were four replications of each genotype that were evaluated visually for turfgrass quality each week for 11 months. The mean quality in the shade was used as the surrogate for shade resistance. The road track area was a dirt roadway, absent of all living vegetation, which received golf car traffic, about 30 passes per work day, plus about 5 passes per day traffic from pickups, vans, and other passenger vehicles. Visual evaluations were 1=bare to 9=healthy, no damage. Morphological variables included unmown plant height, internode length, stolon thickness, leaf thickness, and root dry weight density per area, measured in the shade area. Wear resistance was highly positively correlated (r2 = 0.51) with turfgrass quality in the shade. Internode length and some other traits were negatively associated with wear resistance and turfgrass resistance in the shade, with the dwarf type St. Augustinegrasses having the greatest wear resistance and shade resistance. Polyploid St. Augustinegrasses such as Floralawn and Floratam tended to have the poorest wear and shade resistance.