ARS | Publication request: Nitrogen supplementation does not affect level of an Alkaloid swainsonine in four locoweeds

Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 7, 2011
Publication Date: March 13, 2011
Citation: Klypina, N., Maruthavanan, J., Delaney, K.J., Lange, C.L., Sterling, T.M. 2011. Nitrogen supplementation does not affect level of an Alkaloid swainsonine in four locoweeds. Western Society of Weed Science Meeting Proceedings. 64: 52.

Technical Abstract: Locoweeds are legumes that can be highly poisonous to livestock and wild animals. Locoweed toxicity depends on the association of a plant and a fungal endophyte which produces the alkaloid swainsonine (SWA); however, environmental factors affecting SWA synthesis are unknown. Additionally, locoweeds can be associated with a bacterial symbiont, nitrogen-fixing Rhizobium spp. that provides reduced nitrogen for plant growth and may alter SWA synthesis. We examined responses of SWA production, photosynthetic activity, pigment levels, and plant growth to nitrogen supplementation in four locoweed taxa which differ in average leaf SWA concentrations. Plants were grown in a greenhouse environment and provided 0 to 4 mM of ammonium nitrate; leaves were collected several times over a three-month period and analyzed for SWA. Shoot and root mass, leaf photosynthetic rate and pigment concentrations had positive N dose responses and supplemental N increased shoot growth more than root growth in all four locoweeds. A small, temporary increase of SWA with increasing N was detected only in the very low SWA producer (0.001 % SWA in leaves) A. moll. var. matthewsii. SWA levels in moderately high producers (0.15-0.20 % SWA) O.sericea and A. mollissimus var. bigelovii had negative dose response to N, while the highest SWA producer (0.35 % SWA) A. mollissimus var. mollissimus did not have a significant response. Our results demonstrate that N supplementation, even at levels which promote locoweed growth and photosynthesis, does not have a consistent effect on SWA production.