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USDA-ARS, Forage and Range Research Lab., 695 North 1100 East, Logan, UT 84322-6300. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the USDA or Utah State University
* Corresponding author (kevin.jensen{at}ars.usda.gov).
ABSTRACT
‘Hycrest II’ crested wheatgrass (Agropyron cristatum L.) (Reg. No. CV-31, PI 653685) was released by the USDA-ARS and the Utah State Agricultural Experiment Station and was developed for reseeding disturbed rangelands dominated by annual weeds as a result of severe disturbance, frequent wild fires, and soil erosion. Hycrest II is one of the original parents to the cultivar Hycrest and originated by intercrossing 10 induced tetraploid plants of ‘Fairway’ crested wheatgrass. Selection emphasis in Hycrest II was on seedling establishment on disturbed rangelands. When planted at a rate of 1 pure live seed cm–1, Hycrest II had more seedlings per unit area during the establishment year than Hycrest at Blue Creek, UT, Green Canyon, UT, Mandan, ND, Miles City, MT, Dugway, UT, and Stone, ID. At Dugway, UT, Hycrest II had more seedlings per unit area than ‘CD II’ crested wheatgrass. Foundation seed of Hycrest II is available through the Utah Crop Improvement Association.
Abbreviations: AMOVA, analysis of molecular variance
It has been estimated that cheatgrass (Bromus tectorum L.) has displaced approximately 10 million ha of perennial vegetation within the Great Basin (Menakis et al., 2003). Over the past 20 years, the frequency and size of cheatgrass infestations have continued to increase, which enhances fire frequency, destroys soil structure (Norton et al., 2004), and reduces economic profitability on western rangelands (Mosely et al., 1999). The control of cheatgrass without replacement by desirable perennial species frequently results in the reestablishment of cheatgrass or other noxious weeds on disturbed rangeland (Mosely et al., 1999). Rapid seedling growth and ability to compete against cheatgrass are two characteristics that perennial grasses must have for successful establishment on semiarid western rangelands (Aguirre and Johnson, 1991).
Artificial seeding of perennial species such as crested wheatgrass (Agropyron cristatum L.) and Siberian wheatgrass [A. fragile (Roth) Candargy] is commonly performed following disturbance of managed lands receiving less than 300 mm of annual precipitation to preclude the development of undesirable cheatgrass stands and to meet other management objectives (Asay et al., 2001; Evans and Young, 1978; MacDonald, 1999; Ott et al., 2001). In recent studies on six range sites, crested and Siberian wheatgrass were among the easiest to establish and were more productive, more persistent, and more defoliation tolerant under severe water stress compared with other rangeland revegetation grasses (Asay et al., 2001). ‘Hycrest’ crested wheatgrass seedlings were more effective competitors with cheatgrass than ‘Whitmar’ bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Á. Löve] (Aguirre and Johnson, 1991). Native grasses are more difficult to establish, less persistent, and less productive than nonnative grasses on sites with less than 300 mm of annual precipitation (Asay et al., 2001).
Crested wheatgrass is indigenous to the Steppe region of European Russia and southwestern Siberia (Kirk, 1932). Most early seedings of crested wheatgrass were made with unimproved introductions or mixes consisting of both ‘Fairway’ (A. cristatum) and Standard [A. desertorum (Fisch. ex Link) Schultes] types (Asay and Jensen, 1996). The breeding history of crested wheatgrass was reviewed in Asay and Jensen (1996). In rangeland reclamation, ‘Nordan’ (Rogler, 1954) and Hycrest (Asay et al., 1985) are the two most widely used. Known for its large seeds and seedling establishment, Nordan was released in 1953 and remained the predominant crested wheatgrass on rangeland revegetation projects until the release of Hycrest in 1984. Hycrest consistently produced more forage than Nordan on semiarid range sites and is particularly noted for its vigor during and immediately after stand establishment under conditions of environmental stress (Asay et al., 1985, 1986). To combat the increasing spread of cheatgrass and other invasive annual weeds on western rangelands, it is critical to develop improved plant materials with increased seedling establishment (Asay et al., 2003). The principle objective of this research was to develop a crested wheatgrass cultivar with increased establishment characteristics under harsh dry environments.
‘Hycrest II’ crested wheatgrass (Agropyron cristatum L.) (Reg. No. CV-31, PI 653685) was released by the USDA-ARS and the Utah State Agricultural Experiment Station and is intended for use on arid and semiarid rangelands as a rapid establishing revegetation grass in the Intermountain Region and Northern Great Plains of the western United States. Hycrest II was selected for improved seedling establishment under drought and has been evaluated on rangeland sites in the western United States for seedling establishment compared to commercially available cultivars Hycrest, CD-II, and Nordan. Hycrest II was tested under the experimental designation I-28.
Methods
Breeding History
The original parental germplasm of Hycrest II was generated by intercrossing 10 induced tetraploid plants of Fairway crested wheatgrass (PI 279802) between 1960 and 1961 (Tai and Dewey, 1966; Dewey and Pendse, 1968). This tetraploid population was one of the parents of the hybrid cultivar Hycrest released in 1984, while the other hybrid parent was the natural tetraploid A. desertorum (Asay et al., 1985). From 1976 to 1985, the induced tetraploid population under went three cycles of recurrent phenotypic selection for seedling vigor (emergence from a 7.6 cm planting depth; Maguire 1962), seed yield, and visual plant vigor at Stone, ID, and Blue Creek and Logan, UT. Within each cycle, the top 5% were selected from approximately 2000 spaced plants, and open-pollinated seed from each selected genotype was bulked equally by weight to initiate the next cycle of selection.
In 1997, open-pollinated progenies from cycle 3 were established in a 1600-plant source nursery on a range site in northwest Utah. On the basis of 100-seed weight, seedling vigor (Maguire, 1962), and visual plant vigor in 1998, 17 genotypes (entries) were selected. In 1999, open-pollinated seed from these 17 entries were established in a RCBD with 10 plants per plot and 10 replications at Nephi, UT. During 2000 and 2001, these 17 entries were evaluated for seedling vigor, total seed yield, and dry matter forage yield. Six top-performing entries were identified. On the basis of visual plant vigor within each entry, eight plants per entry were selected. These 48 plants were moved to the greenhouse during fall 2002 and allowed to intercross. Seed was equally bulked by weight within each entry. In 2003, 660 plants per entry, 3960 total plants, were spaced-planted in a completely randomized design near Logan, UT, and designated as Breeder seed.
Seeded Trials
Between 2000 and 2005, fall-seeded evaluation trials were established to compare seedling establishment of Hycrest II, Hycrest, CD-II, and Nordan at Blue Creek, UT (41°56'02'' N, 112°26'20'' W; elevation 1563 m); Green Canyon, UT (412°46'21'' N, 111°46'57'' W; elevation 1520 m); Mandan, ND (46°49'35'' N, 100°53'22'' W; elevation 510 m); Miles City, MT (46°24'30'' N, 105°50'27'' W; elevation 721 m); Dugway, UT (40°15'51'' N, 112°49'69'' W; elevation 1614 m); and Stone, ID (42°01'15'' N, 112°39'09'' W; elevation 1432 m). Plots were arranged in a randomized complete block with four replications. Entries were seeded at a rate of one pure live seed cm–1 in five rows. Plot size was 1.5 m wide by 8 m long.
Seedling Establishment
Seedling establishment in seeded trials was measured as a plant density frequency using the grid system described by Vogel and Masters (2001) at Blue Creek, UT; Green Canyon, UT; Mandan, ND; Miles City, MT; Dugway, UT; and Stone, ID. Frequency was determined by laying a grid of 5.1-cm by 5.1-cm quadrants over the drilled rows and determining the percentage of quadrats containing at least one seedling. If a plant occurred in every quadrant, establishment was considered to be 100%. This was repeated three times along the 8-m row for a total of 144 quadrants.
Morphological Characterization
Twelve morphological characters were evaluated from at least 40 different plants each of Hycrest II, Hycrest, CD-II, Douglas, and Nordan at Nephi (39°38'43'' N 111°52'11'' W; elevation 1600 m) and Blue Creek, UT. The experimental design at each location was a RCBD with four replications at Nephi and six replications at Blue Creek with 10 plants per replication. All data were subjected to analysis of variance using GLM procedures as a fixed model. Unless otherwise noted, all mean separations were made on the basis of least significant differences at the 0.05 probability level (SAS Institute, 1999).
Characteristics
Seedling Establishment
Selection for improved seedling establishment followed the methods reviewed by Johnson and Asay (1993), where they showed a strong correlation between a plant's ability to emerge from a deep planting depth in the greenhouse and its ability to germinate and establish rapidly when planted 0.63 cm deep under dryland conditions. Hycrest II had more seedlings per unit area (m2) during the establishment year than Hycrest at Blue Creek, UT (76 vs. 65%; P < 0.05); Green Canyon, UT (78 vs. 61%; P < 0.05); Mandan, ND (78 vs. 69%; P < 0.05); Miles City, MT (85 vs. 72%; P < 0.05); Dugway, UT (35 vs. 10%; P < 0.05); and Curlew Valley, ID (72 vs. 56%; P < 0.05) (Table 1
). At Dugway, UT, Hycrest II (35%) had more seedlings per unit area than did CD II (13%). Due to Hycrest II's increased seedling establishment potential, particularly under harsh dry environments, it is intended to replace Hycrest for reseeding of severely disturbed range sites on heavier soils receiving less than 300 mm of annual precipitation. It is recommended that Hycrest II be planted as a component of seed mixes and not as a monoculture.
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Seed Availability
Breeder, Foundation, Registered, and Certified seed classes of Hycrest II will be recognized. Breeder and Foundation seed will be maintained by the USDA-ARS Forage and Range Research Laboratory at Logan, UT. Protection under the U.S. Plant Variety Protection Act of 1994 will be applied for, with the requirement that seed of Hycrest II can be marketed only as a class of Certified seed. All seed requests should be sent to the corresponding author during the period of protection by the Plant Variety Protection Certificate. No seed will be distributed without written permission for 20 yr from the date of release, 10 Apr. 2008, by the USDA-ARS, at which time seed will also be available from the National Plant Germplasm System. Foundation seed is be available through the Utah Crop Improvement Association (435-797-2082; sayoung{at}mendel.usu.edu).
Footnotes
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication April 25, 2008.
References
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