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USDA-ARS, Forage and Range Res. Lab., Utah State Univ., Logan, UT 84322-6300
* Corresponding author (kevin{at}cc.usu.edu)
RS-H hybrid wheatgrass (Elymus hoffmannii Jensen & Asay) germplasm (Reg. no. GP-8, PI 631392) was developed by the USDA-ARS, Forage and Range Research Laboratory in cooperation with the Utah Agricultural Experiment Station and released on 10 May 2002. It was derived from a collection made in 1979 by J. A. Hoffmann (USDA-ARS, Logan, UT) and R. J. Metzger (USDA-ARS, Corvallis, OR) from the edge of a wheat field approximately 56 km northwest of Eleskirt, Erzurum Province, Turkey. The original seedlot, MH-114-1085, described in the collection notes as Agropyron sp., was identified as quackgrass [Elymus repens (L.) Gould, ( = Agropyron repens (L.) P. Beauv. and Elytrigia repens (L.) Nevski] (D.R. Dewey, unpublished). It was included in the National Plant Germplasm System as Elytrigia repens (PI 593438).
Although the original collection was predominantly rhizomatous, approximately 5% of the plants were nearly caespitose. In 1984, open-pollinated (OP) progenies from these caespitose plants were subjected to a cycle of mass selection for bunch-type growth habit to generate a cycle-1 breeding population. In 1988, controlled crosses were made among 20 selections from 1260 cycle-1 plants. These parental plants were selected on the basis of caespitose growth habit, vegetative vigor, leafiness, seed set, plant color, and freedom from plant pests. Space-planted nurseries of cycle-2 progeny were established at Nephi, UT (2400 plants; mean annual precipitation 350 mm) and at Evans research farm near Logan, UT (3000 plants; mean annual precipitation 425 mm) in 1993 and 1995, respectively. In 1997, OP seed was harvested from 24 plants from the Nephi and 28 plants from the Logan nurseries that were selected for improved seed yield, individual seed weight, and seedling emergence from deep (7.6 cm) plantings. Plants with reduced vigor and rhizome development were removed before anthesis during cycle 3. In 1998, 100 plants from each of 52 cycle-3 half-sib families were established at Evans research farm near Logan, UT, and evaluated for bunch-type growth habit, vegetative vigor, leafiness, plant color, seed yield, individual seed weight, and seedling emergence. On the basis of superior performance, OP seed of 60 plants (cycle-4 selections) were established in a 1360-plant nursery at Evans research farm near Logan, UT, in 1999. Inferior plants (20%) were rouged before pollination in 2001. On the basis of total seed yield (g), seed of the top 30 plants (cycle-5 selections) was bulked and designated as Breeder seed.
RS-H is cytologically similar to and interfertile with the cultivar NewHy (Asay et al., 1991; Jensen and Asay, 1996), which is an advanced-generation hybrid between quackgrass and bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Löve]. Results from morphological and cytological studies of NewHy, RS-H, quackgrass, and their hybrids indicate that RS-H originated from a natural hybrid between quackgrass and an Asian relative of bluebunch wheatgrass (Jensen and Asay, 1996). Because of its morphological divergence from quackgrass and similarity to NewHy, both RS-H and NewHy are now classified as a new species, Elymus hoffmannii (Jensen and Asay, 1996). As with NewHy, RS-H has a chromosome number of 2n = 6x = 42 and a genomic constitution of StStStStHH. Genetic interchange likely occurred between the St genomes of the two parental species.
RS-H is less rhizomatous (58 vs. 83 cm), taller in stature (1007 vs. 934 mm), and has longer flag leaves (213 vs. 164 mm) than NewHy. Its rate of phenological development is similar to NewHy with anthesis occurring from mid- to late-June in nurseries near Logan, UT. RS-H is fully fertile and produces from 350 to 450 kg ha-1 of seed under limited irrigation on semiarid sites. The germplasm has shown tolerance to salinity that is comparable to NewHy, but less than tall wheatgrass [Thinopyrum ponticum (Podp.) Barkworth & D. R. Dewey]. Observed genetic variation within RS-H should allow selection for improved salinity tolerance.
On a saline site near Roosevelt, UT, forage yields of RS-H were similar to NewHy, tall wheatgrass, and intermediate wheatgrass and significantly greater than Russian wildrye [(Psathyrostachys juncea (Fisch.) Nevski], ‘Garrison’ creeping foxtail (Alopecurus arundinaceus Poir), Great Basin wildrye [Leymus cinereus (Scribn. & Merr.) A. Löve], and Altai wildrye [Leymus angustus (Trin.) Pilger]. Under irrigation, it yielded significantly less than orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), or meadow brome (Bromus riparius Rehm.) (Jensen et al., 2001); however, it is significantly more resistant to drought than these grasses (Jensen et al., 2001; Waldron et al., 2002). Forage quality of RS-H is comparable to NewHy. It begins growth early in the spring and its leaves remain green and succulent longer in the growing season than most other wheatgrasses.
Seed of RS-H is maintained by the USDA-ARS, Forage and Range Research Laboratory, Utah State University, Logan, UT 84322-6300, and 25-g seed lots will be provided to researchers and other interested parties on request. This germplasm qualifies for commercial production in accordance with the "Tested Class Pre-variety Germplasm Certification Standards" adopted by the Association of Official Seed Certifying Agencies (AOSCA, 2001). Seed of this germplasm has been provided to the National Plant Germplasm System, where it will be made available for research purposes, including the development and commercialization of new cultivars. It is requested that appropriate recognition be given if this germplasm contributes to the development of a new breeding line or cultivar.
NOTES
Utah Agric. Exp. Stn. Journal Article No. 7484. Registration by CSSA.
Accepted for publication October 31, 2002.
REFERENCES
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