and Persistence in Alfalfa Varieties
Edwin T. Bingham
Agronomy Department, University of Wisconsin, Madison, WI 53706
This project is evaluating the bacterial wilt resistance (BWR) of field survivors after 4 years. As reported at NAAIC in 1998, progeny of field survivors of Vernal, Wrangler and Oneida (pre 1980 varieties) were more BWR resistant than the original variety (1). However, progeny of field survivors of a sample of varieties from the mid-1980s were lower in BWR than the original variety (1). This indicated that some BWR plants in these varieties lacked persistence, and this helped explain the persistence problem (2,3). Now we report that a sample of varieties from the mid 1990s is back to the traditional expression of higher BWR in field survivors. This indicates that we may be recovering the desired relationship between BWR and persistence.
The varieties from the mid-199Os were 'Legendairy', 'Magnum III', and 'Pioneer 5262'. Field survivors of each variety (50 plants each) were dug in fall 1998 from yield trial plots after 3 winters and 4 production years. Seed for testing was produced by hand intercrossing in the greenhouse during the winter. BWR was evaluated by Crop Characteristics, Inc., Farmington, MN 55024. BWR percentages for Legendairy, Magnum III, and 5262 were 74%, 57%, and 60%, respectively. These percentages are well above the minimum HR rating and suggest that most field survivors are BWR, and that the level of BWR should be adequate for persistence.
References
1. Bingham, E. T. 1998. The relationship between BWR and persistence is not the same among alfalfa varieties. Report of the 36th NAAIC. 36: 28.
2. Ipson, R. B., D. A. Rohweder, E. T. Bingham, C. R. Grau and D. J. Undersander. 1991. 30 years of Wisconsin alfalfa variety trials. Central Alfalfa Impr. Conf. 22: 19.
3. Volenec, J. 1993. Selection for disease resistence: Are we improving alfalfa persistence? Central Alfalfa Impr. Conf. 23: 17.