Detection of swainsonine-producing endophytes in Patagonian Astragalus species

Authors: MARTINEZ, AGUSTIN - National Institute Of Agricultural Technology(INTA); ROBLES, CARLOS - National Institute Of Agricultural Technology(INTA); Roper, Jessie; Gardner, Dale; NEYAZ, MARWAH - New Mexico State University; JOELSON, NATALIA - Universidad Del Comahue; Cook, Daniel

Submitted to: Toxicon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2019
Publication Date: 12/5/2019
Citation: Martinez, A., Robles, C., Roper, J.M., Gardner, D.R., Neyaz, M., Joelson, N., Cook, D. 2019. Detection of swainsonine-producing endophytes in Patagonian Astragalus species. Toxicon. 117:1-6. https://doi.org/10.1016/j.toxicon.2019.09.020.
DOI: https://doi.org/10.1016/j.toxicon.2019.09.020

Interpretive Summary: Swainsonine has been identified as the toxin in some legumes belonging to the genera Astragalus and Oxytropis throughout the world including China, North America, and South America. Several South American Astragalus species have been reported to contain swainsonine; however, data is lacking supporting the presence of a fungal symbiont in South American Astragalus species as has been shown for North American and Chinese Astragalus and Oxytropis species. The objective of this paper was to investigate several South American species that have been reported to contain swainsonine for the presence of the fungal symbiont using culturing and PCR based techniques. Swainsonine was detected in field collections of A. pehuenches, A. illini and A. chamissoni but not A. moyanoi consistent with reports of toxicity regarding these species. The symbiont Alternaria section Undifilum was detected by PCR in all three species that contained swainsonine but not in A. moyanoi. A seed transmitted fungal symbiont was isolated from seeds of Astragalus pehuenches and A. illini. The isolated symbiont from both respective species produced swainsonine in vitro, and was demonstrated to belong to the genus Alternaria section Undifilum by analysis of the nuclear ribosomal DNA. It seems highly probable that Alternaria section Undifilum isolates will be associated with other South American Astragalus species that are reported to contain swainsonine and this merits further investigation.

Technical Abstract: Swainsonine has been identified as the toxin in some legumes belonging to the genera Astragalus and Oxytropis throughout the world including China, North America, and South America. Several South American Astragalus species have been reported to contain swainsonine; however, data is lacking supporting the presence of a fungal symbiont in South American Astragalus species as has been shown for North American and Chinese Astragalus and Oxytropis species. The objective of this paper was to investigate several South American species that have been reported to contain swainsonine for the presence of the fungal symbiont using culturing and PCR based techniques. Swainsonine was detected in field collections of A. pehuenches, A. illini and A. chamissoni but not A. moyanoi consistent with reports of toxicity regarding these species. The symbiont Alternaria section Undifilum was detected by PCR in all three species that contained swainsonine but not in A. moyanoi. A seed transmitted fungal symbiont was isolated from seeds of Astragalus pehuenches and A. illini. The isolated symbiont from both respective species produced swainsonine in vitro, and was demonstrated to belong to the genus Alternaria section Undifilum by analysis of the nuclear ribosomal DNA. It seems highly probable that Alternaria section Undifilum isolates will be associated with other South American Astragalus species that are reported to contain swainsonine and this merits further investigation.