Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/4/2002
Publication Date: 11/4/2002
Citation: LAMB, J.F., RUSSELLE, M.P. A NEW SELECTION METHOD CREATES ALFALFA POPULATIONS THAT DIFFER IN NITRATE-NUPTAKE. ASA-CSSA-SSSA ANNUAL MEETING ABSTRACTS. 2002. CD-ROM. PAPER NO. C06-LAMB135716-ORAL.
Technical Abstract: New alfalfas that reduce nitrate-N losses to groundwater would be environmentally and economically beneficial to sustainable cropping systems. The 15N isotope is a reliable way to measure and distinguish N2- fixing plants that differ in nitrate-N uptake but is too expensive for plant breeding programs. We developed a method under field conditions using gbromide (Br) as an alternative tracer to select alfalfa plants that differ in nitrate-N uptake. Two cycles of divergent selection for nitrate-N uptake in alfalfa have been completed. In 1999 unselected and selected alfalfa populations for either high or low Br concentration or uptake were established at two locations. A solution of Br and 15N were applied to all populations for one regrowth period in both 1999 and 2000. All plots were harvested for herbage yield and analyzed for Br and 15N isotope content. Populations selected for high Br concentration or high Br uptake were significantly greater in Br concentration, Br- uptake, and nitrate-N uptak compared to populations selected for low Br concentration or uptake. Using this selection method, we have created alfalfa populations that differ in their ability to take up nitrate-N from the subsoil.