Submitted to: Fungal Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/24/2010
Publication Date: 2/20/2011
Citation: Wicklow, D.T., Rogers, K.D., Dowd, P.F., Gloer, J.B. 2011. Bioactive metabolites from Stenocarpella maydis, a stalk and ear rot pathogen of maize. Fungal Biology. 115(2):133-142. Interpretive Summary: In this research we identified toxins produced by a unique fungal pathogen of corn called Stenocarpella maydis. This fungus causes a severe dry-rot of corn ears resulting in substantial losses to the U.S. corn crop. It is also associated with a common nerve disorder in cattle grazing harvested corn fields in southern Africa. A leaf puncture wound assay revealed that diplodiatoxin, heretofore the only natural product reported from S. maydis, was phytotoxic to corn seedlings. Chemical studies of S. maydis culture extracts exhibiting toxicity to other fungi and fall armyworm larvae revealed that the metabolites accounting for this activity were chemicals called chaetoglobosins K and L. Veterinary toxicologists now will recognize that the toxins diplodiatoxin, chaetoglobosins and a bisdienediol are produced by S. maydis in solid fermentation culture, and may have contributed to some of the reported symptoms of toxicity in experimental animals fed such rations.
Technical Abstract: Stenocarpella maydis is a fungal pathogen of major importance that causes a dry-rot of maize ears and is associated with a neuromycotoxicosis in cattle grazing harvested maize fields in southern Africa and Argentina. In an effort to investigate the potential roles of S. maydis metabolites in the fungal disease cycle, ethyl acetate extracts of solid substrate fermentations of several S. maydis isolates from maize grown in the United States were found to exhibit significant phytotoxic, antifungal and antiinsectan activity. Chemical investigations of extracts of S. maydis isolates from Illinois and Nebraska led to the isolation or detection of the known metabolites diplodiatoxin, chaetoglobosins K and L and (all-E-) trideca-4, 6,10,12-tetraene-2,8 diol as major components. A culture of S. macrospora from maize grown in Zambia produced diplosporin and chaetoglobosins K and L as major components that were isolated. Diplodiatoxin produced significant lesions in a maize leaf puncture wound assay. Diplosporin and chaetoglobosin K displayed moderate antiinsectan activity in dietary assays against the fall armyworm Spodoptera frugiperda, while chaetoglobosin K exhibited significant antifungal activity against Aspergillus flavus and Fusarium verticillioides. Using LC-HRESITOFMS and 1H NMR data, diplodiatoxin was detected as a major component in S. maydis rotted grain, stalks, and stalk residues. This consititutes the first report of of chaetoglobosins K and L from S. maydis, of (all-E) trideca-4, 6,10,12-tetraene-2,8 diol from Stenocarpella, and the first reported detection of diplodiatoxin, or any other Stenocarpella metabolite, in diseased maize seeds and stalk tissues.