First report of the production of mycotoxins and other secondary metabolites by macrophomina phaseolina (Tassi)goid isolates from soybeans (Glycine max L.) symptomatic with charcoal rot disease

Authors: KHAMBHATI, VIVEK - Mississippi State University; Abbas, Hamed; SULYOK, MICHAEL - University Of Natural Resources & Applied Life Sciences - Austria; PETERSON, MARIA - Mississippi State University; SHIER, THOMAS - University Of Minnesota

Submitted to: The Journal of Fungi
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2020
Publication Date: 12/3/2020
Citation: Khambhati, V.K., Abbas, H.K., Sulyok, M., Peterson, M.T., Shier, T.W. 2020. First report of the production of mycotoxins and other secondary metabolites by macrophomina phaseolina (Tassi)goid isolates from soybeans (Glycine max L.) symptomatic with charcoal rot disease. The Journal of Fungi. 6:332.

Interpretive Summary: The fungus Macrophomina phaseolina causes charcoal rot disease in soybean and causes various other diseases in more than 500 other commercially important plants, particularly during hot, dry growing conditions. In many years, charcoal rot is a major cause of yield losses in Arkansas, Louisiana and Mississippi. A study was conducted to measure the production in culture of known mycotoxins and other secondary metabolites by 89 isolates of M. phaseolina from soybean plants symptomatic for charcoal rot. Six mycotoxins and other metabolites were observed at relatively high frequencies (19.1 to 84.3% of cultures), including the previously reported mycotoxins, botryodiplodin and mellein, as well as four previously unreported substances, namely kojic acid, moniliformin, orsellinic acid and cyclo[L-proline-L-tyrosine]. In addition, the study identified an additional nine previously unreported metabolites that were observed at relatively low frequency (<5% of cultures), including cordycepin, emodin, endocrocin, citrinin, gliocladic acid, infectopyron, methylorsellinic acid, monocerin, and N-benzoyl-L-phenylalanine. Further studies are needed to investigate possible effects of these mycotoxins and metabolites on pathogenesis by M. phaseolina and on food and feed safety, if any of them are found to contaminate the seeds of infected soybean plants at toxic levels.

Technical Abstract: Macrophomina phaseolina (Tassi) Goid., the causal agent of charcoal rot disease of soybean is capable of causing disease in more than 500 other commercially important plants. This fungus produces several secondary metabolites in culture, including (-)-botryodiplodin, phaseolinone and mellein. Given that independent fungal isolates may differ in mycotoxin and secondary metabolite production, we examined a collection of 89 independent M. phaseolina isolates from soybean plants with charcoal rot disease using LC-MS/MS analysis of culture filtrates. In addition to (-)-botryodiplodin and mellein, four previously unreported metabolites were observed at relatively high frequency (>19% of cultures), including kojic acid (84.3% of cultures at 0.57 - 79.9 µg/L), moniliformin (61.8% of cultures at 0.011-12.9 µg/L), orsellinic acid (49.4% of cultures at 5.71-1,960 µg/L) and cyclo[L-proline-L-tyrosine] (19.1% of cultures at 0.012-0.082 µg/L). In addition, nine previously unreported metabolites were observed at relatively low frequency (<5% of cultures), including cordycepin, emodin, endocrocin, citrinin, gliocladic acid, infectopyron, methylorsellinic acid, monocerin, and N-benzoyl-L-phenylalanine. Further studies are needed to investigate possible effects of these mycotoxins and metabolites on pathogenesis by M. phaseolina and on food and feed safety, if any of them contaminate the seeds of infected soybean plants.