A method to differentiate summer-dormant from summer-active tall fescue and orchardgrass accessions at germination stage
Dariusz P. Malinowski A D , David P. Belesky B , Betty A. Kramp A , Joyce Ruckle B , Jaime Kigel C and William E. Pinchak AA Texas AgriLife Research, POB 1658, Vernon, TX 76385, USA.
B USDA-ARS, Appalachian Farming Systems Research Center, 1224 Airport Rd, Beaver, WV 25813, USA.
C The Hebrew University of Jerusalem, Faculty of Agriculture, POB 12, Rehovot 76100, Israel.
D Corresponding author. Email: d-malinowski@tamu.edu
Australian Journal of Agricultural Research 59(12) 1092-1102 https://doi.org/10.1071/AR08084
Submitted: 5 March 2008 Accepted: 11 September 2008 Published: 10 November 2008
Abstract
Summer-dormant, cool-season perennial grasses are being used in place of traditional, summer-active cultivars for high-quality winter forage. One reason for this change is the ability of cultivars with summer-dormant attributes to tolerate increasing annual temperature, decreasing precipitation, and repeated severe summer droughts. The mechanism of summer dormancy is still not understood in detail. Cultivar development for summer dormancy typically is conducted under field conditions in environments where summer-active types do not survive summer weather conditions. We developed a method based on germination responses to photoperiod to differentiate summer-dormant from summer-active types of tall fescue [Lolium arundinaceum (Schreb.) S. J. Darbyshire] and orchardgrass (Dactylis glomerata L.). Seed of cultivars with known summer dormancy characteristics was germinated at a constant temperature of 24°C under a range of photoperiods (0–24 h) for 14 days. Total germination, modelled cumulative germination, instantaneous rate of germination, and relative germination (to that in the dark) were analysed. Germination of summer-dormant orchardgrass was similar in the dark and short photoperiods (4–12 h), but it was inhibited by a photoperiod longer than 12 h. Germination of summer-active orchardgrass was promoted by any photoperiod compared with the control (0 h). Short photoperiods (4–12 h) promoted germination of summer-dormant tall fescue, while long photoperiods (>12 h) inhibited germination compared with germination in the dark. Summer-active types of tall fescue did not respond to photoperiod, regardless of length. A validation test using two Mediterranean origin cultivars of orchardgrass with contrasting summer dormancy characteristics and experimental lines of Mediterranean origin tall fescue with known expression of summer dormancy characteristics supported the use of seed germination analysis to differentiate among lines for this trait.
Additional keywords: cool-season grasses, dormancy, drought, southern Great Plains.
Acknowledgments
We appreciate the cooperation of the following seed companies and research institutions who donated seed of tall fescue and orchardgrass cultivars for this and our other ongoing experiments on the mechanisms of summer dormancy in cool-season grasses: AgResearch USA, Ltd, Barenbrug USA, DFL International Seeds, Inc., Round Butte Seed (USA), Seed Technology and Marketing Pty (Australia), and United Agro Products N.W. Seeds. We especially thank Dr Florence Volaire (INRA, France) and Dr Allen Newman (Heritage Seeds, Australia) for donating Medly and Currie orchardgrass, respectively. We also appreciate the cooperation of Juan Amadeo, Gentos Argentina, in evaluation of the experimental tall fescue lines. We thank Matt Angerer, Michael Burnett, and Royce Hammonds (technicians), and Ashley Bain and Josh Arismendez (summer student workers) for help with conducting the experiments. We appreciate the comments and suggestions of anonymous reviewers on an earlier version of the manuscript. This research project was funded by Texas AgriLife Research (The Texas A&M System) and Research Grant No. TB-8012-04 from BARD, The United States–Israel Binational Agricultural Research and Development Fund.
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