Locoweeds (Astragalus and Oxytropis) are leguminous plants that are toxic due to a symbiotic association with the endophytic fungus Undifilum oxytropis. The fungus produces the alkaloid swainsonine, an α-mannosidase-inhibitor that causes serious damage to mammals when consumed. A real-time PCR technique was developed to quantify the colonization extent of Undifilum in locoweeds and to compare it to the swainsonine concentration in the plants. Amplification of the endophyte nuclear ITS region allowed reliable quantification of Undifilum DNA from field plants and in vitro cultures. Swainsonine concentration was highly correlated (ρ = 0.972, P < 0.001) with the proportion of Undifilum DNA during the first 4 weeks of in vitro culture growth. Species of Astragalus and Oxytropis were sampled seasonally in New Mexico and Colorado for two years. High swainsonine concentration in plant samples was associated with high levels of endophyte DNA, except in plant reproductive tissues.
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We thank Dr Jose Valdez-Barillas and David Graham for their guidance during field seasons, and Dr Steve Hanson, Dr Champa Sengupta-Gopalan, and Dr Tracy Sterling for allowing the use of their lab facilities and equipment. We acknowledge USDA Special Grant # 59-5428-1-327 and the New Mexico State University Agricultural Experiment Station for supporting this work.
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Achata Böttger, J., Creamer, R. & Gardner, D. Seasonal Changes in Undifilum Colonization and Swainsonine Content of Locoweeds. J Chem Ecol 38, 486–495 (2012). https://doi.org/10.1007/s10886-012-0120-z
- Quantitative PCR