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Simplot/Jacklin Seed, West 5300 Riverbend Ave., Post Falls, ID 83854-9499
* Corresponding author (dbrede{at}simplot.com)
‘Explorer’ Kentucky bluegrass (Poa pratensis L.) (Reg. no. CV-69, PI 599227) is a turf-type cultivar released in August 1996, by Pickseed West, Tangent, OR, under a license agreement from the developer, the J.R. Simplot Co., Jacklin Seed, Post Falls, ID. Experimental designations for Explorer were 91-3561 and Pick-3561.
Explorer originated from a highly apomictic, single-plant selection from hybrid cross 89-1033, made in the field at Post Falls in July 1989 using pollen from ‘Limousine’ (Alderson and Sharp, 1994) to pollinate plants of ‘Midnight’ (Meyer et al., 1984). Seed harvested from Midnight mother plants were individually sown into cells of greenhouse flats during the spring of 1990 and later transplanted to a spaced-plant field nursery of 33 500 plants. Offspring with characteristics dissimilar to Midnight were flagged during maturation in the spring of 1991. Plant number 91-3561 differed from Midnight for turf characteristics before heading. It produced 13 g of seed from a single spaced plant, which is typical for a Kentucky bluegrass spaced plant in North Idaho.
Progeny trials were conducted in spaced-plant nurseries, established May, 1994, to determine the level of apomixis. The spaced-plant apomixis rate of Explorer averages 95%, but can vary by 5% based on growing conditions. A survey of 1117 Explorer plants showed that 2.1% were variants in the vegetative (preheading) stage, 0.9% were heading maturity variants, 0.5% seedhead variants, and 0% were headless plants. Approximately 1% of Explorer plants are a taller growing, earlier maturing, light-green variant, resembling common Kentucky bluegrass, but with better leaf spot [caused by Drechslera poae (Baudys) Shoem] resistance. This particular variant has culms up to 75 cm in length, with light greenish-yellow panicles with no hint of purple. Approximately 1% of the plants have a panicle devoid of the normal purple color. Culm length of these plants is similar to the majority plant form. Some of these variants may not appear in commercial seed production due to the masking effect of bulk populations. Aberrant progeny are rogued from Breeders, Foundation, and Registered seed fields to ensure continued uniformity and stability, but they will continue to occur in every generation.
In seed production, Explorer is a low-growing, very late maturing, dark-green plant, with first-year culm length averaging 54 cm at maturity, and second year culm length averaging 43 cm. Culm length is greatest at the center of a clonal plant, tapering 10 cm shorter toward the perimeter of the plant. Rhizome growth in 1 yr from a single tiller averages 42 cm.
Explorer is most similar to ‘Glade’ Kentucky bluegrass (PI 599227) (Alderson and Sharp, 1994), its grandparent. However, it can be differentiated from Glade based on 14 botanical traits, documented in the United States Plant Variety Protection (PVP) application for Explorer. These traits include a later reproductive maturity than all other cultivars tested.
In the 1995 National Turfgrass Evaluation Program (NTEP) trials for Kentucky bluegrass (Morris, 2001), Explorer ranked 32nd in overall turfgrass quality out of 103 cultivars. Explorer displayed a medium-dark green color, medium-fine leaf texture, good spring and summer density, and good resistance to stem rust (caused by Puccinia graminis Pers.:Pers), crown rust (caused by P. coronata Corda.), pink snow mold {caused by Microdochium nivale (Fr.) Samuels and Hallett [teleomorph: Monographella nivalis (Schaf) E. Muller]}, and chinch bug (Blissus leucopterus hirtus Montandon). Explorer had moderate resistance to spring melting out (D. poae). In 7 yr of commercial seed production, Explorer has demonstrated the potential for high yields of quality seed, relative freedom from ergot [Claviceps purpurea (Fr.) Tul.], and no adverse reactions to labeled Kentucky bluegrass pesticides.
Explorer is recommended for golf course tees, fairways, and roughs, and for lawns, parks, and sports turf, in full sun or some shade, in areas where Kentucky bluegrass is well adapted for turf. It is compatible in blends and mixtures with other cool-season turfgrasses.
Breeder seed, first harvested in 1995, is maintained by Simplot/Jacklin Seed. Seed propagation is limited to one generation of increase for Foundation, Registered, and Certified seed. United States Plant Variety Protection application no. 9700387 has been filed for Explorer.
NOTES
Accepted for publication December 31, 2002.
REFERENCES
This article has been cited by other articles:
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  A.D Brede Registration of 'Chicago II' Kentucky Bluegrass Crop Sci., November 1, 2004; 44(6): 2267 - 2268. [Full Text] [PDF]
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