Registration of `Liberator' Kentucky Bluegrass.
Liberator was developed from a highly apomictic, singleplant selection from hybrid cross number 90-0336, hybridized in the greenhouse during winter of 1990. Pollen from `Glade' Kentucky bluegrass (1) was used to pollinate plants of breeding line `50-14.' Breeding line 50-14 originated from a collection by the late Arden Jacklin made in the northeastern USA during the 1970s.
Seed harvested from plants of 50-14 were individually sown into cells of greenhouse flats during the spring of 1992. The resulting plants were transferred to a field nursery of 28 800 plants near Post Falls. Offspring with characteristics dissimilar to 50-14, the female parent, were flagged during maturation in spring of 1992. Plant number 92-2572 was identified as being different from 50-14 by its leaf color and texture prior to heading. Seed harvested from this plant was used to establish a turf trial in September 1992, a replicated seed yield trial in August 1993, and a plant variety protection (PVP) trial in June 1994 near Post Falls.
Liberator is most similar in form and appearance to the cultivar, `Midnight' (2); however, Liberator can be differentiated from Midnight based on 10 botanical measures (as recorded in the U.S. PVP application for Liberator, no. 9800188), which include a longer culm internode length, longer flag leaf sheath length, and a later reproductive maturity. Liberator demonstrated a significantly longer culm length (P = 0.001) than Midnight in two years of field evaluations.
Progeny trials were conducted in spaced-plant nurseries established near Post Falls in May 1994 to determine the level of apomixis. Of 478 Liberator plants, 1.7% were variants in the vegetative (preheading) stage, 4.8% were heading maturity variants, 0% seedhead variants, 0% miniature plants, and 0% were headless plants. Most of the variants are similar to common Kentucky bluegrass in appearance, averaging nearly 1 m in culm length with susceptibility to leaf spot [caused by Drechslera poae (Baudys) Shoem]. There is also a variant with a nearly identical plant form, but with droopier leaves and much droopier seedheads. But because of its similar height and maturity, it may be inconspicuous in seed production. In spaced-plant nurseries, Liberator averaged 93% apomictic but varied from 90 to 99% depending upon weather and year. Aberrant progeny are rogued from seedstock fields to ensure continued uniformity and stability, but they will continue to occur in every generation.
Liberator was equal to the top-rated cultivar in overall turf quality in the National Turfgrass Evaluation Program (NTEP) trials for Kentucky bluegrass established in 1995 (3). In the same trial, Liberator demonstrated improved drought tolerance (dormancy), resistance to leafspot and melting out (caused by Drechslera spp.), necrotic ring spot (caused by Leptosphaeria korrae J. Walker and A.M. Smith), leaf rust (caused by Puccinia coronata Corda var. coronata), stem rust (caused by P. graminis Pers.:Pers.), dollar spot (caused by Lanzia Sacc. or Moellerodiscus Henn. spp.), and summer patch (caused by Magnaporthe poae Landschoot and Jackson), and susceptibility to powdery mildew (caused by Erysiphe graminis DC. ex Merat).
In five years of commercial seed production, Liberator has shown the potential for high yields of quality seed with freedom from ergot [caused by Claviceps purpurea (Fr.) Tul.] honeydew and sclerotia. Liberator has exhibited no adverse reactions to labeled Kentucky bluegrass pesticides.
Liberator is recommended for lawns, golf courses, parks, and sports turf in areas where Kentucky bluegrass is well adapted for turf. It can be grown in full sun or some shade. Liberator is compatible in blends and mixtures with other cool-season turfgrasses.
Breeder seed, first harvested in 1995, is maintained by Simplot Turf and Horticulture. Seed propagation is limited to four cycles of increase: Breeder, Foundation, Registered, and Certified. U.S. Plant Variety Protection status for Liberator has been applied for (PVP certificate no. 9800188).
References and Notes
(1.) Jacklin, A.W., J.H. Thorne, R.E. Engel, W.K. Dickson, and C.R. Funk. 1977. Registration of `Glade' Kentucky bluegrass, reg. no. 12. Crop Sci. 17:187.
(2.) Meyer, W.A., B.L. Rose, J.M. Johnson-Cicalese, and C.R. Funk. 1984. Registration of `Midnight' Kentucky bluegrass. Crop Sci. 24:822-823.
(3.) Morris, K.N. 1999. National Kentucky bluegrass test 1995-medium-high maintenance. NTEP no. 99-8. National Turfgrass Evaluation Program, USDA-ARS, Beltsville, MD.
(4.) A. Douglas Brede, Simplot Turf and Horticulture, West 5300 Riverbend Ave., Post Falls, ID 83854-9499. Registration by CSSA. Accepted 30 Sept. 2000. A. (*) Corresponding author (dbrede@ simplot.com).
Published in Crop Sci. 41:583-584 (2001).
A. DOUGLAS BREDE(*)