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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #157978
Title: GERMPLASM VARIABILITY AND ENVIRONMENTAL EFFECTS ON STEM CELLULOSE AND LIGNIN CONCENTRATIONS IN ALFALFA

Author
item SCHWAB, P - CSREES
item Lamb, Joann
item SHEAFFER, C - UNIVERSITY OF MINNESOTA
item BARNES, DONALD - RETIRED ARS

Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2004
Publication Date: 10/1/2005
Citation: Schwab, P.M., Lamb, J.F., Sheaffer, C.C., Barnes, D.K. 2005. Germplasm variability and environmental effects on stem cellulose and lignin concentrations in alfalfa. Journal of Agronomy and Crop Science. 191:386-392.

Interpretive Summary: Dairy cows need large amounts of forage in their diet to maintain health of their four stomachs and to promote milk fat production. Unfortunately, forages such as alfalfa have stems that are rich in poorly digested fiber components, such as cellulose and lignin, which limits feed consumption and does not support high levels of milk production. In order to both protect dairy cow health and achieve high levels of milk production, the forage quality of alfalfa stems must be improved. In support of efforts to improve alfalfa stem quality, studies were conducted to evaluate the potential to modify stem lignin and stem cellulose concentrations in alfalfa. Differences in stem cellulose and stem lignin were found among the alfalfa genetic sources evaluated. Stem cellulose concentration was found to be more stable and repeatable across environments than stem lignin concentration. We concluded that selecting for changes in stem cellulose concentration would have the greater impact in improving forage quality than stem lignin in alfalfa. These results are being utilized to guide our group's on-going efforts to improve alfalfa through breeding and selection, and to identify specific gene targets for molecular approaches to improving alfalfa stem quality. Feeding alfalfa cultivars with altered stem cellulose concentration could maintain dairy cow health and improve milk production and profitability for dairy producers.

Technical Abstract: Stem cellulose and lignin concentrations are major determining factors of alfalfa (Medicago sativa L.) forage quality. Limited information is available on the genetic variability and the influence of environmental effects on these two stem quality traits. Our objectives were to: evaluate the variability for stem cellulose and lignin concentrations in modern alfalfa germplasms across several harvests; observe the environmental stability of these two quality traits in 32 alfalfa clones selected high or low for either stem cellulose or lignin concentration; and examine the relationships between these two stem quality traits and leaf and stem crude protein (CP). Fifty alfalfa entries (cultivars and experimental populations) were established May 1993 and sampled for stem acid detergent lignin (SADL), stem acid detergent cellulose (SADC), and stem CP (SCP) in Sept 1993 and in June and Aug 1994. Clones were vegetatively propagated from individual plants selected for extremes in SADL and SADC and transplanted into blocks at two locations in May 1994 and sampled for quality analysis in September 1994. For all samples leaves were hand separated from stems and SADL, SADC, SCP, and leaf CP (LCP) were determined using Near Infrared Reflectance Spectroscopy (NIRS). Entry differences for SADL and SADC were detected only at the June 1994 harvest date in the cultivar study. Spearman ranked correlations over years in the clonal study demonstrated greater environmental stability for SADC (r=0.70, P>0.01) than for SADL (r=0.54, P>0.05). Environmental effects impacted both traits, but SADC showed greater potential for improving forage quality. Simple correlations showed that decreasing SADL or SADC would have minimal effect on LCP and may increase SCP.