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Title: FIVE DECADES OF ALFALFA CULTIVAR IMPROVEMENT: IMPACT ON FORAGE YIELD, PERSISTENCE, AND NUTRITIVE VALUE

Author
item Lamb, Joann
item SHEAFFER, CRAIG - UNIVERSITY OF MINNESOTA
item RHODES, LANDON - UNIVERSITY OF MINNESOTA
item SULC, R - UNIVERSITY OF MINNESOTA
item UNDERSANDER, DANIEL - UNIVERSITY OF MINNESOTA
item BRUMMER, E - UNIVERSITY OF MINNESOTA

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2005
Publication Date: 3/1/2006
Citation: Lamb, J.F., Sheaffer, C.C., Rhodes, L.H., Sulc, R.M., Undersander, D.J., Brummer, E.C. 2006. Five decades of alfalfa cultivar improvement: impact on forage yield, persistence, and nutritive value. Crop Science. 46:902-909.

Interpretive Summary: Alfalfa plant breeding programs in the U.S. started releasing and marketing improved cultivars in the mid-1900s. Most breeding programs focused on releasing cultivars with increased levels of disease and pest resistance. Newer cultivars with multiple disease resistance had superior forage yield compared to older, susceptible cultivars when grown in fields infested with disease. However, recent reports have implied that forage yield in released alfalfa cultivars declined slightly between 1978 and 1996. Increasing forage yield has once again become a focus for discussion among alfalfa researchers. Alfalfa researchers need to know if the plant enhancement procedures used to produce improved cultivars over the past 60 years has increased, decreased, or had no effect on forage yield in alfalfa. A study was conducted to compare the forage yield and assess nutritive value and plant stand of alfalfa cultivars released between 1940 and 1995 for 5 years at four Upper Midwest locations. The most recently released cultivars showed improved forage yield and stand survival at locations with disease infestations (WI and OH) but not at locations that were disease free (MN and IA). Modern cultivars with multiple disease resistance demonstrated improved yield protection and stand survival compared to older cultivars but no improvement in forage yield as such. Nutritive value traits were similar among cultivars released between 1940 through 1995. Results of this research demonstrated that plant enhancement procedures used to produce improved alfalfa cultivars over the past 60 years had no effect on forage yield in alfalfa. This information can be utilized by both public and commercial plant breeding programs to modify current breeding procedures and give higher priority to direct selection for increased forage yield. New alfalfa cultivars with improved forage yield or nutritive value can only be produced if plant breeding programs adjust their focus to these plant characteristics.

Technical Abstract: Previous research has implied that forage yield in released alfalfa cultivars declined slightly between 1978 and 1996. Our objective was to compare alfalfa cultivars released over the past five decades side by side in replicated yield trials to test for any changes in forage yield over time. At least three consecutive year averages at Rosemount, MN, Ames, IA, and Arlington, WI, were used to select cultivars representative of the 1950s, 1960s, 1970s, 1980s, and the 1990s. Ten cultivars, two from each of the five decades, four more recently released cultivars (Wintergreen, DK 127, Jade II, and WL 324), and two check cultivars (Vernal and 5454) were compared for forage yield, persistence, and nutritive value at four locations. Cultivars were established in a randomized complete block design in May 1999 at Ames, IA, Arlington, WI, Columbus, OH, and Rosemount, MN. Forage was harvested once or twice in the establishment year and three to four times in each of four subsequent production years depending on location. Plots were sub-sampled for nutritive value analyses for the first and third harvests in 2000 and 2001 at MN, OH, and WI. Year x location x cultivar-release date interactions demonstrated that forage yield and final stand densities differed among the cultivars in each year of the experiment at each location. Recently released cultivars showed improved forage yield and stand survival at locations with disease infestations (WI and OH) but not at locations that were essentially disease free (MN and IA). Modern cultivars with multiple disease resistance demonstrated improved yield protection and stand survival compared to older cultivars but no enhancement in yield per se. Nutritive value traits were similar among cultivars released between 1940 through 1995. We suggest that targeted selection directly for improved yield be given a higher priority in alfalfa breeding programs.