Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2006
Publication Date: 1/6/2007
Citation: Ranezabu, M., Shier, W.T., Abbas, H.K., Tonos, J.L., Baird, R.E., Sciumbato, G. 2007. Production of (-)-Botryodiplodin, but not Phaseolinone, by the Soybean Charcoal Rot Disease Fungus Macrophomina phaseolina in Mississippi. Journal of Natural Products. 70:128-129. Interpretive Summary: Charcoal rot disease causes significant crop losses in soybean, especially in hot climates. A toxin produced by the fungus (mold) that causes this disease has been reported, but its structure was not identified. The fungus that causes charcoal rot disease was found in this research to produce the toxin called botryodiplodin which was previously found in tropical fruit infected with another fungus. Earlier, some scientists reported that the toxin phaseolinone was involved in the charcoal rot disease. However, no phaseolinone was found in this research. This new discovery will allow us to apply the knowledge about botryodiplodin to charcoal rot disease and hopefully lead to ways to control this problem.
Technical Abstract: Charcoal rot disease, which causes significant losses in crops grown in hot, relatively dry areas, is caused by the fungus Macrophomina phaseolina. M. phaseolina produces a phytotoxin believed to play a role in helping establish infections. Siddiqui et al. [Experentia 35, 1222 (1979)] purified and partially characterized a phytotoxin from cultures of M. phaseolina. The phytotoxin was named phaseolinone, and assigned the structure of an epoxidized derivative of phomenone, making it a member of an extensive family of phytotoxic eremophilane sesquiterpenoids. The phytotoxin produced by cultures of M. phaseolina isolated from soybean [Glycine max (L.) Merr.] with charcoal rot disease in Mississippi has been purified in a manner similar to that of Siddiqui et al., 1979. However, the phytotoxic activity in the extracts was shown by electrospray ionization high resolution mass spectrometry and other spectroscopic methods to be (-)-botryodiplodin. No phaseolinone was found. (-)-Botryodiplodin is a ribose-analog mycotoxin isolated previously from cultures of Botryodiplodia theobromae, a fungus which causes rot in tropical fruits, and various other fungi, including Penicillium roqueforti, but not previously from M. phaseolina. (-)-Botryodiplodin exhibits properties in solution, including the presence of anomeric forms and the generation of oligomeric impurities on standing, which make structure determination by spectroscopic methods unusually difficult. However, the properties of (-)-botryodiplodin are a better match for the properties reported by Siddiqui et al. for the phytotoxin from M. phaseolina, than are the properties expected from a substance with the structure phaseolinone, notably the ability to react with Somogyi’s reagent for reducing sugars.