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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)
‘Mustang’ Altai wildrye [Leymus angustus (Trin.) Pilger], (Reg. no. CV-240, PI 634756) was developed by a research team at the USDA-ARS, Forage and Range Research Laboratory at Utah State University, Logan, UT, and was released on 4 March 2004 in cooperation with the Utah Agricultural Experiment Station. Mustang was evaluated in field trials as M5 and DT-3185. Mustang is recommended for use on arid and semiarid rangelands as a winter forage and a revegetation grass in the Intermountain Region and Northern Great Plains of western USA.
The parental germplasm from Mustang was derived from selections within PI 499650 (DT-3185; 79%), ‘Prairieland’ (7%) (Lawrence, 1976), ‘Eejay’ (7%) (Lawrence et al., 1991a), and ‘Pearl’ (7%) (Lawrence et al., 1991b). PI 499650 was collected 10 Aug. 1983 by Drs. Douglas R. Dewey and William Tai approximately 50 km southwest of Urumqi on the road to South Mountain, Xinjiang Province, People's Republic of China, at an elevation of 1600 m.
PI 499650 was identified as a superior accession from an evaluation nursery in 1989 near Logan, UT, that contained collections from Russia and all Plant Introductions of Altai wildrye in the National Plant Germplasm System. Spaced-plant source nursery of PI 499650 consisting of 825 plants was established at Bluecreek, UT, in 1990. On the basis of vegetative vigor in 1991, open-pollinated (OP) seed from 112 plants were selected. On the basis of a selection index that included total seed yield and 100-seed weight, seed from 14 single OP plants were selected and 58 seedlings from each plant were established in 1992 at the Evans Research Farm, Logan, UT, in a completely randomized design with 58 replications to initiate cycle-2 selection.
On the basis of vegetative vigor and retention of green leaves under drought, OP seed from 84 cycle-2 plants were selected in 1994. With additional emphasis placed on seed yield, 100-seed weight, and seedling emergence from a 7.6-cm planting depth (Maguire, 1962), this number was reduced to 66 selected plants. Open-pollinated progeny from these 66 plants were established with representative plants of cultivars Prairieland, Eejay, and Pearl at Richmond, UT, in 1995. On the basis of vegetative vigor in 1997, OP seed from 65 cycle-3 plants were selected (7%), which included selections from Prairieland, Eejay, and Pearl. These selections were subsequently screened for seedling vigor (emergence from a deep planting depth) in 1997. On the basis of superior emergence from a deep planting depth, 723 seedlings were recovered representing the 14 best plants and were subsequently established in 1998 at Bluecreek, UT, where equal quantities of seed was bulked from each plant to produce Breeder seed starting in 1999. Breeder seed was produced as described above in 2000, 2001, 2002, and 2003.
Mustang is significantly taller, with longer flag leaves that are oriented higher on the culm than Prairieland, Eejay, and Pearl. In addition, Mustang is green in color with wider flag leaves and longer inflorescences. Mustang Altai wildrye is a dodecaploid (2n = 12x = 84) and has the same ploidy level as the commercially available cultivars Prairieland, Eejay, and Pearl.
Amplified fragment length polymorphisms (AFLP) (Vos et al., 1995) were used to compare Mustang with other released cultivars of Altai wildrye. The neighbor-joining tree demonstrated that all but one of the 24 Mustang samples group together relative to Prairieland, Eejay, and Pearl (Page, 1996; DeHaan et al., 2002). The average number of fragments detected in Mustang was not significantly different from Eejay or Pearl (Excoffier et al., 1992; Leonard et al., 1999). However, the average number of fragments in Mustang was significantly less than Prairieland. Mustang displays more DNA variation than Eejay, Pearl, or Prairieland. The E.ACAG//M.CTTG primer combination distinguished Mustang from the other cultivars.
Mustang Altai wildrye was evaluated in the Northern Plains Regional Trials (NPA) at Bluecreek, UT; Green Canyon, UT; Mead, NE; Sidney, NE; Mandan, ND; and Miles City, MT, for dry matter forage production, initial stand, and persistence. When combined over six locations and 3 yr, Mustang Altai wildrye (3026 kg ha–1) produced significantly more forage dry matter than cultivars Prairieland (2394 kg ha–1) and Pearl (2247 kg ha–1) Altai wildrye, Magnar (2220 kg ha–1) and Trailhead (2214 kg ha–1) basin wildrye [Leymus cinereus (Scribn. & Merr.) A. Love], and Bozoisky-Select (2525 kg ha–1), Mankota (2434 kg ha–1), and Tetra-1 (2118 kg ha–1) Russian wildrye [Psathryostachys juncea (Fisch.) Nevski]. Within locations, Mustang Altai wildrye consistently produced (not always significant) more dry matter forage than commercially available Altai wildrye cultivars. Combined over six locations and 3 yr in the NPA trials, Mustang Altai wildrye had superior seedling establishment (83%) compared to Pearl (68%) and Prairieland (64%) Altai wildrye. After 4 yr at Mead and Sidney, NE; Mandan, ND; and Miles City, MT, Mustang (71%) Altai wildrye was more persistent than Prairieland (39%) and Pearl (50%).
Seedling vigor of Mustang Altai wildrye, as indicated by seedling emergence from a deep planting depth (7.6 cm), was better than Prairieland and comparable to Pearl. Individual seed weight of Mustang was comparable to Prairieland and Eejay, but significantly lighter than Pearl. At 100% purity, there are approximately 138888 seeds kg–1.
Breeder, Foundation, and Certified seed classes will be recognized. Breeder seed will be maintained by the USDA-ARS Forage and Range Research Laboratory at Logan, UT. Foundation seed will be produced by the USDA-ARS at Logan and made available for certified seed production on a nonexclusive basis to seed producers by the Utah Crop Improvement Association. U.S. Plant Variety Protection will not be pursued for Mustang. It is requested that appropriate recognition be made if this cultivar contributes to the development of a new breeding line or cultivar.
NOTES
Utah Agric. Exp. Stn. Journal Article No. 7593. Registration by CSSA.
Accepted for publication July 31, 2004.
REFERENCES
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