'FX-10' ST. AUGUSTINEGRASS [Stenotaphrum secundatum (Walt.) Kuntze] (Reg. no. CV-153, PI 561856) is an asexually propagated clone that was developed at the Fort Lauderdale Research and Education Center, University of Florida.  It was released by the University of Florida in April 1990.  FX-10 was selected from second-generation progeny produced through controlled pollination among African germplasm. The pedigree of FX-10 was (PI 290888 X PI 293666) X (PI 300127 X PI 300130).  Planting stock of FX-10 has been increased and maintained by vegetative propagation of stolon cuttings.

FX-10 is sparsely pubescent on both surfaces of the youngest leaf blades.  The 0.5 to 1.0 mm long hairs are more numerous (mean = 21) on the adaxial surface than on the abaxial surface (mean = 12) and are discernible to the unaided eye.  Except for FX-33, other recognized cultivars of St. Augustinegrass have no hairs on the leaf blade surfaces, although hairs are present in all cultivars on the ligule and collar region.  Adaxial leaf color of FX-10, based on Munsell color notation (1), varies between 7.5 GY 5/4 (approximately grass green) and 7.5 GY 4/4 under typical fertilization levels, and the overall color, when viewed in a plot, is more blue and less saturated than other cultivars.  Leaf texture of FX-10 is very coarse, with individual leaf blades varying from 8 to 14 mm wide.  Leaf dimensions and other vegetative traits of St. Augustinegrasses vary greatly in response to age, light level, and other environmental factors.  Spikelet length in St. Augustinegrass is adequately free of environmental effects for use in cultivar description and identification (2).  Spikelets of FX-10 average 4.5 mm long, which is much shorter than 'Floratam' and 'Floralawn' and slightly shorter than 'Bitterblue' and 'FX-33'.  Anther color of FX-10 is approximately 10YR 7/10 (approximately orange-buff) and stigma color is 5RP 3/10 (approximately true purple).  FX-10 produces more inflorescences per unit ground area than Floratam or Floralawn.  The unreduced chromosome number of FX-10 is 2n=30 and chromosomes associate in diakinesis principally as bivalents with regular disjunction (3).

In southern Florida, FX-10 survives seasonal drought with greater canopy coverage compared with other cultivars of St. Augustinegrass [Author's note added later:  See Busey, 1996].  FX-10 roots penetrate the 1.4 m aquifer, thus it is drought resistant due to avoidance.  FX-10 survived well in Fort Lauderdale test plots for 2 yr without irrigation, but died during the third year.  In another experiment at Fort Lauderdale, a lawn of FX-10 remained alive and provided acceptable turf quality when it received an average of four irrigations per year. While irrigation would thus be necessary to maintain FX-10, the grass is usable as a sparingly irrigated turfgrass in southern Florida.  The unmown height of FX-10 is shorter than Floratam and Floralawn, and it can be maintained with a rotary mower set at 6 cm height.  Fertilization can best be accomplished in two to three applications per year, totaling 5.0 to 7.5 g N m^-2 yr^-1, in a complete formulation that includes adequate P.

While Floratam is susceptible, FX-10 is resistant to the PDP (Polyploid Damaging Population) southern chinch bug (Blissus insularis Barber) based on laboratory (3) and field evaluation [Author's note added later:  See Busey, 1995].  The PDP southern chinch bug has damaged Floratam in Florida since 1985 (4).  FX-10 is also resistant to the STD (Standard) southern chinch bug, a race which is not adapted to Floratam (5).  FX-10 has moderate resistance to gray leaf spot disease, caused by Pyricularia grisea (Cke.) Sacc., as evidenced by reduced leaf spot damage ratings compared with Bitterblue, Floratam, and FX-33.  In sandy soil, and under irrigation, FX-10 has exhibited slower ground coverage than other cultivars and is more prone to weed infestation than Floratam.  FX-10 has shown moderate damage from atrazine when the herbicide is applied to sandy soil.  Under 5% relative outdoor illumination deriving from neutral shade cloth, FX-10 has shown unacceptable turf quality.  The critical range for field survival of FX-10 plugs in the winter of 1989 was between -5 and -9^o C.

Clonal breeder stock of FX-10 is maintained by the University of Florida and small quantities are available for experimental purposes.  Foundation planting stock is available to licensed producers from the Florida Sod Growers Cooperative, Inc., Box 745, Murdock, FL 33938.  U.S. Plant Patent 7852 has been issued for FX-10.

References and Notes

1. Anonymous.  1977.  Munsell Color Charts for Plant Tissues, Munsell Color, Baltimore, MD.

2. Busey, P.  1986.  Morphological identification of St. Augustinegrass cultivars.  Crop Sci. 26:28-32.

3. Busey, P. 1990.  Polyploid Stenotaphrum germplasm: Resistance to the polyploid damaging population southern chinch bug.  Crop Sci. 30:588-593.

4. Busey, P. and B. J. Center.  1987.  Southern chinch bug (Hemiptera: Heteroptera: Lygaeidae) overcomes resistance in St. Augustinegrass.  J. Econ. Entomol. 80:608-611.

5. Busey, P. and E. I. Zaenker.  1992.  Resistance bioassay from southern chinch bug (Heteroptera: Lygaeidae) excreta.  J. Econ. Entomol. 85:2032-2038.

6. Philip Busey, Fort Lauderdale Res. and Educ. Ctr., University of Florida, 3205 College Ave., Fort Lauderdale, FL 33314.  Agric. Exp. Stn., Journal Series no. R-02020.  Registration by CSSA.  Accepted 31 July 1992.