Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 21, 2005
Publication Date: August 1, 2005
Citation: Jensen, K.B., Peel, M., Waldron, B.L., Horton, W.H., Asay, K.H. 2005. Persistence after three cycles of selection in newhy rs-wheatgrass [elymus hoffmannii k. b. jensen & asay] at increased salinity levels. Crop Science 45:1717-1720. Interpretive Summary: Excess soil salinity is a major factor limiting the establishment, persistence, and productivity of forage grasses in the Intermountain West. One approach to improving salt affected lands is to establish species or cultivars that have been bred for persistence under saline conditions. The cultivar NewHy combines the vigor, productivity, salinity tolerance, and persistence of quackgrass with the drought resistance, bunch growth habit, and seed and forage quality of bluebunch wheatgrass. If the persistence of NewHy under saline conditions could be increased, it will provide a source of forage with increased quality over that of tall wheatgrass and persist at high levels of soil salinity than other irrigated pasture grasses. The study comparing the relative ability of plants to persist in increasing salt concentrations of NewHy, Cycle-1, Cycle-2, Cycle-3, and quackgrass was conducted in a greenhouse in Logan, UT in 2002 and 2003. Six weeks after germination, plants were subjected to increasing salt concentrations starting at an EC of 6 dS m-1 and increased 6 dS m-1 increments every 1 to 2 weeks until an EC level of 42 dS m-1. We found that the greenhouse salt screening method effectively improved plant persistence under increased levels of salinity in NewHy.
Technical Abstract: The cultivar NewHy RS-wheatgrass resulted from hybridization between quackgrass (Elytrigia repens, L., Nevski, 2n=6x=42) and bluebunch wheatgrass (Pseudoroegneria spicata, Pursh, A. Love, 2n=4x=28) and is recommended for use on range sites with moderate salinity problems that receives at least 35 cm of annual precipitation. The lack of high quality forage on salt affected soils is often associated with the inability of plants to establish and persist at elevated soil salinity levels. Objectives of this study were to evaluate 1) the ability to improve plant persistence in NewHy over three Cycles of greenhouse selection at increased salinity levels and 2) corresponding changes in seedling vigor and germination under non-saline conditions. Plants were irrigated every 3 days with a complete nutrient solution and salt levels increased by an EC of 6 dS m-1 every 1 to 2 weeks until an EC level of 42 dS m-1 was reached and remained there until plant mortality in 2002 and 2003. Probit analysis was used to estimate the time and salt concentration required to kill 50% of the plants (LD50) in each Cycle. Significant differences for LD50 were found among the different Cycles of NewHy selected for persistence under saline conditions and the quackgrass parent with a resulting ranking of Cycle-3 > Cycle-2 > Cycle-1 > quackgrass > NewHy (Cycle-0). The largest single gain was achieved from NewHy to Cycle-1, which required an additional 145 EC days to reach an LD50 level with smaller increases observed between Cycles-1 and 2 and between Cycles-2 and 3. Selection for persistence under a saline environment did not reduce seedling germination rate or vigor.