REGISTRATION OF 'NEWHY' RS HYBRID WHEATGRASS
Crop Sci. 31: 1384-1385 (1991)

K. H. Asay, D. R. Dewey, W. H. Horton, K. B. Jensen, P. O. Currie, N. J. Chatterton, W. T. Hansen II, and J. R. Carlson

'NewHy' RS Hybrid [quackgrass (Elytrigia repens, L., Nevski, 2n=6x=42)) X bluebunch wheatgrass (Pseudoroegneria spicata, Pursh, A. Love, 2n=4x=28) (Reg. no. Cv-18, PI 538763) was developed and released December 1989 by the USDA-ARS in cooperation with the Utah Agricultural Experiment Station, and the USDA-SCS. The new hybrid cultivar is recommended for range sites with moderate salinity problems and that receive at least 33 cm of annual precipitation. The initial RS hybrid population was established in 1962 (2). The F₁ hybrid was a pentaploid (2n=5x=35), meiotically irregular, beset with chlorophyll deficiencies, and in general, had poor vegetative vigor. Although the hybrid plants were only partially fertile, adequate seed set permitted selection for improved fertility without chromosome doubling. From the F₁ to F₅ generation, selection was based largely on fertility (seeds/spike) and only plants with characteristics of both parental species and moderate to no rhizome development were retained for generation advance. More intense selection for agronomic performance and adaptation to semiarid range conditions was initiated in the F₅ generation. The objectives were to combine the vigor, productivity, salinity tolerance, and persistence of quackgrass with the drought resistance, caespitose growth habit, seed quality, and forage quality of bluebunch wheatgrass.

NewHy is meiotically stable with a chromosome number of 2n=6x=42 and fully fertile. Dewey (3) concluded that the genome constitution of the parental species was S₁S₁S₂S₂XX for quackgrass and SSSS for bluebunch wheatgrass, and that genetic exchange in the RS hybrid had occurred between the S genomes of the two species. Rate of phenological development is intermediate to the parental species and anthesis occurs from mid to late June in nurseries near Logan. The hybrid produced 560 kg seed ha^-1 on an irrigated site near Miles City, MT. (Currie unpublished). Degree of rhizome development in the hybrid breeding population readily responds to selection pressure (4). Essentially caespitose types have been derived after two cycles of selection. Rhizome development of the NewHy cultivar, as measured by clone diameter, ranges from less than 0.1 m to approximately 1.0 m per year on range sites receiving from 33 to 38 cm annual precipitation. On these sites, over 85% of the plants had a vegetative spread of less than 0.5 m during the season.

NewHy has demonstrated excellent resistance to excess soil salinity (5). In greenhouse trials (Horton unpublished), salinity resistance of NewHy approached that of tall wheatgrass (Thinopyrum ponticum, Podp., Barkworth & D. R. Dewey). Agronomic performance of the cultivar has been evaluated on several range sites in the Intermountain West and to a lesser extent in the Great Plains of the USA. It is most productive on slightly saline or alkaline range sites receiving at least 33 cm of precipitation annually or supplemental irrigation. Results from a trial on a range site in northwest Utah, which receives an average of 36.6 cm annual precipitation, are typical. Poor seed germination resulted in stands of less than 50% during the establishment year. As stands improved through tillering and rhizome development during the third and fourth years, NewHy produced more forage than any of the other 16 entries included in the trial. It is noteworthy that NewHy, unlike its quackgrass parent, did not spread beyond its plot borders into adjacent plots. Similar trends were observed in a trial established in the foothills of the LaSal Mountains in Southern Utah, at an altitude of 1,900 m and with an annual average of 33 cm precipitation.

Forage quality of NewHy, based on neutral detergent fiber (NDF) and percent crude protein, compared favorably to intermediate wheatgrass (Thinopyrum intermedium, Host, Barkworth & D. R. Dewey) under semiarid conditions (W. H. Horton, 1990, personal communication). Although NewHy begins growth early in the spring, it remains more succulent and palatable for livestock later in the growing season than most other wheatgrasses, especially on dryland range sites. In a trial in central Utah, cattle grazed NewHy in preference to all other entries in the trial including intermediate wheatgrass and crested wheatgrass (Agropyron desertorum, Fisch. ex Link, Schultes). The hybrid is resistant to moderate grazing pressure after establishment and it recovers rapidly after grazing or defoliation.

Although considerable variation exists among seedlots, seed quality tends to be somewhat lower than grasses such as crested wheatgrass and intermediate wheatgrass. Improved seed quality continues to be a breeding objective; however, until this deficiency is corrected it is recommended that seeding rates from 9 to 12 kg ha^-1 be used in its areas of adaptation. After emergence, seedlings are vigorous and establish themselves rapidly under relatively harsh conditions.

Breeders seed will be maintained by the USDA-ARS at Logan, UT. Foundation seed is being produced from breeders seed by USDA-ARS at Logan and USDA-SCS at Los Lunas, NM. Foundation seed will be distributed by the Utah Crop Improvement Association and the USDA-SCS. Because of the morphological similarity of NewHy seed to that of quackgrass, protection has been applied for under the Plant Variety Protection Act of 1970. Conditions of this license specifies that NewHy seed can be marketed only as a class of certified seed.

References

Dewey, D. R. 1967. Synthetic hybrids of new world and old world Agropyrons: III. Agropyron repens X tetraploid Agropyron spicatum. Am J. Bot. 54:93-98.

Dewey, D. R. 1976. Derivation of a new forage grass from Agropyron repens X Agropyron spicatum hybrids. Crop Sci. 16:175-180.

Asay, K. H. and W. T. Hansen, II. 1984. Prospects for genetic improvement in the quackgrass X bluebunch wheatgrass hybrid. Crop Sci. 24:743-745.

Currie, P. O., T. O. Hilken, and R. S. White. 1986. field evaluation of five grasses grown on a saline soil. J. Range Manage. 39:386-388.

K. H. Asay, D. R. Dewey (deceased), W. H. Horton, K. B. Jensen, N. J. Chatterton, and W. T. Hansen, USDA-ARS, Forage and Range Res. Lab., Utah State Univ., Logan, UT 84322-6300; P. O. Currie, USDA-ARS (retired) Ft. Keogh Livestock and Range Res. Stn. Miles City, MT 59301; and J. R. Carlson, USDA-SCS, West National Technical Center, Portland, OR 97209-3489. Utah Agric. Exp. Stn. Journal Article No. 4046. Registration by CSSA.