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United States Department of Agriculture

Agricultural Research Service

Title: Selection for Geotropic Root Elongation Rate in Alfalfa under Field Conditions

Authors
item Lamb, Joann
item Russelle, Michael

Submitted to: Central Alfalfa Improvement Conference
Publication Type: Abstract Only
Publication Acceptance Date: July 17, 1997
Publication Date: N/A

Technical Abstract: Previous research demonstrated that fluridone {1-methyl-3-phenyl-5-[3- (trifluromethyl) phenyl]-4(1H)-pyridinone} caused distinctive bleaching of alfalfa leaves without being fatal and can be used as a marker for root activity when placed at predetermined depths in the soil. Under greenhouse conditions, individual plants within alfalfa germplasms differed by 56 d in nonset of symptoms, indicating a similar difference in root activity at 32 inch depth in the soil. A field site for selection of individual plants for root elongation rate was excavated and topsoil was stockpiled separately from subsoil. The total area excavated was 60 x 200 ft with a maximum depth of 10 ft. Fluridone readily bonds to organic matter, therefore, to minimize movement of the herbicide in the soil a 2 inch layer of peat moss was applied. The peat layer was disced and fluridone was applied at a rate of 50 ppm. The subsoil and top soil were replaced and alfalfa populations differing in root architecture were seeded and thinned to 3 inches between plants. Seven 3 x 4 ft blocks (208 plants per block) were established on the north and south facing slopes of the site where depth to the fluridone layer ranged from 1.8 to 6.5 ft. The first 30 symptomatic plants per block were dug, tagged for identification, and brought back to the greenhouse. Cuttings were taken from each plant and transplanted for crossing. The mean root elongation rate of the first 30 plants per block were significantly different among the experimental alfalfa populations with different root architectures. Selection for or against the number of lateral or amount of fibrous roots had an effect on root elongation rate in some germplasms sources but not in others. A second cycle of selection for root elongation rate was begun in May 1997.

Last Modified: 10/1/2014
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