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United States Department of Agriculture

Agricultural Research Service

Title: Enhancement of Root Elongation Rate in Alfalfa

Authors
item Lamb, Joann
item Russelle, Michael

Submitted to: North American Alfalfa Improvement Conference
Publication Type: Abstract Only
Publication Acceptance Date: July 16, 2000
Publication Date: N/A

Technical Abstract: Alfalfa (Medicago sativa L.) is a deep-rooted perennial that may be able to remove nitrate-N from subsoil beneath the rooting zone of annual crops. Research goals include development of a breeding methodology for increased root elongation rate in alfalfa under field conditions. Previous research has shown that using the herbicide fluridone {1-methyl-3-phenyl-5-[3- (trifluromethyl) phenyl]-4(1H)-pyridinone} as a root activity marker can indicate alfalfa root penetration in soil. Objectives include evaluating the influence of either genetic source or root morphology on root elongation rate in alfalfa under field conditions. In 1994 a field site for selection of alfalfa populations for rapid root elongation rate was constructed. An 18 x 61 m sloped area was excavated to a maximum depth of 2.96 m. Fluridone was applied to the excavated surface and then the site was refilled with the unearthed soil to represent the original landscape. Experimental alfalfa populations were randomly established in replicate blocks across the surface of the experimental site. Planting dates were recorded and survey techniques were used to calculate the depth to fluridone for each block. The date of onset of fluridone bleaching symptoms for the first 20 to 30 plants in each block were recorded and plants were dug and taken to the greenhouse for crossing. Two cycles of selection were conducted and root elongation rate data were recorded for approximately 5,000 individual plants. Mean root elongation rate was significantly different among the experimental populations for both cycles of selection. Root morphology was shown to influence root elongation rate in some genetic backgrounds but not in others.

Last Modified: 4/19/2014
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