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United States Department of Agriculture

Agricultural Research Service

Research Project: Enhanced Alfalfa Germplasm and Genomic Resources for Yield, Quality, and Environmental Protection

Location: Plant Science Research

Title: Protecting the (alfalfa) crown jewels

Authors
item Samac, Deborah
item Lamb, Joann

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: July 26, 2013
Publication Date: August 1, 2013
Citation: Samac, D.A., Lamb, J.F. 2013. Protecting the (alfalfa) crown jewels. Forage Focus. August 2013. Pages 7-9.

Technical Abstract: Strategies are needed to reduce the mechanical damage to the crown of the alfalfa plant that occurs with each harvest resulting in injury to the buds producing stems and allowing entry of pathogens causing decay of the crown and tap root. Selection and breeding for crown rot resistance has been slow and no cultivars with resistance to crown rot are currently available. An experiment was done in Saint Paul, MN and Becker, MN to investigate whether incorporation of green plant material (green manure) from buckwheat and sorghum-sudangrass could increase the population of soil microbes that inhibit Fusarium and Phoma, two crown rot organisms. Wheel traffic stress was applied to all plants in a treatment two days after each harvest. Incorporation of green manures at Becker increased the population of pathogen inhibitors significantly, but inhibitor populations were not significantly increased in St. Paul. The green manure treatments did not significantly reduce crown rot or increase plant counts. However, green manure treated plots in which wheel traffic was applied had greater forage yields than control fallow plots. Wheel traffic reduced forage yield 12% to 17% depending on year and location, significantly reduced plant counts, and increased crown rot compared to the no traffic control. The cultivar selected for grazing tolerance performed better with wheel traffic compared to the other cultivars tested indicating that selection and breeding for wheel traffic tolerance is possible. Increasing populations of pathogen antagonists and development of traffic tolerant cultivars will increase alfalfa stand life and productivity while reducing inputs.

Last Modified: 10/30/2014
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