Conclusions About Alfalfa Persistence 1925-1995

Edwin T. Bingham
Dept. of Agronomy, Univ. Wisconsin-Madison, 53706

Conclusions about alfalfa persistence are based on project experiments, and the writings and communications of R.A. Brink, L.F. Graber, Dale Smith, R.P. Murphy, Pat Palmer, Derek Woodfield, and R.B. Ipson. The list is not complete and is continuously refined.

• Persistence is essentially adaptation.
• Adaptation is the most fundamental trait in the perenniality of alfalfa, and perenniality requires persistence.
• Persistence has its own genetic base. The base is not necessarily the same for all materials with equivalent persistence. And, there is much interaction with specific traits.
• The genetic base is not fixed in most materials and requires selection to maintain it.
• Persistence usually decreases over sexual generations for other traits.
• The more intervening sexual generations for other traits, the greater the potential for loss in persistence.
• The loss in persistence over generations fits classical population genetic theory and may be due to genetic drift, negative genetic linkages with other traits being selected, and/or more complicated factors associated with lack of selection pressure.
• Winter hardy plant materials may be fall dormant or relatively non-fall dormant.
• Winter hardy plant materials are not always persistent. Hence, some materials may overwinter one or two winters just fine, and then crash due to lack of persistence.
• Persistent plant materials may be fall dormant or relatively non-fall dormant.
• The benefits of pest resistance are best obtained in persistent alfalfa. High levels of multiple pest resistance do not necessarily ensure persistence.
• The best method to ensure persistence is to select for persistence. But, selection of plants persisting in depleted stands with little or no competition is often ineffective. Selection of plants persisting in competitive stands is most efficient.
• Selection for persistence lengthens the breeding cycle. Nonetheless, if a new cycle is started every year there is only one lag-phase and eventually a new product can be selected every year.

• Brink R.A., F.R. Jones, and H.R. Albrecht. 1935. Genetics of resistance to bacterial wilt in alfalfa. J. Agric. Res. 49:635-642.
• Ipson, R.B. 1991. Thirty years at Wisconsin Alfalfa Variety Trials. M.S. Thesis, Univ. Of Wisconsin-Madison.
• Holland, J.B. and E.T. Bingham. 1994. Genetic Improvement for yield and fertility of alfalfa cultivars representing different eras of breeding. Crop Sci. 34:953-957.

1995 Central Alfalfa Improvement Conference Proceedings