Phytotoxin production and phytoalexin elicitation by the phytopathogenic fungus Sclerotinia sclerotiorum

• Published in: Journal of chemical ecology 2004-11, Vol.30 (11), p.2163-2179
• Main Authors: Pedras, M.S.C, Ahiahonu, P.W.K
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; antifungal properties; Artemia; Artemia salina; Ascomycota - physiology; Autoecology; Bioassays; Biological and medical sciences; Biological Assay; Biomarkers; Brassica napus; Brassicaceae; Brassicaceae - chemistry; Brassicaceae - microbiology; Crop diseases; disease resistance; Drug Resistance; Erucastrum; Erucastrum gallicum; Fundamental and applied biological sciences. Psychology; Genetics; Indoles - isolation & purification; Indoles - pharmacology; Larva - drug effects; Larva - metabolism; Larvae; Oleic Acid - isolation & purification; Oleic Acid - pharmacology; phytoalexins; Phytotoxins; Plant Extracts - isolation & purification; Plant Extracts - pharmacology; Plant Leaves - chemistry; plant pathogenic fungi; Plants and fungi; Sclerotinia sclerotiorum; Sesquiterpenes; Sinapis alba; Species Specificity; Spiro Compounds - isolation & purification; Spiro Compounds - pharmacology; stem rot; Terpenes; Thiazoles - isolation & purification; Thiazoles - pharmacology
• ISSN: 0098-0331; 1573-1561
• DOI: 10.1023/B:JOEC.0000048781.72203.6c

The fungus Sclerotinia sclerotiorum (Lib.) de Bary causes rot disease in a vast range of plant families, including Cruciferae (Brassicaceae). We investigated the production of phytotoxins by S. sclerotiorum by using a bioassay-guided isolation, as well as the phytoalexins produced by the resistant wild crucifer Erucastrum gallicum under elicitation by S. sclerotiorum and other agents. We established for the first time that S. sclerotiorum produces a somewhat selective phytotoxin, sclerin, which is phytotoxic to three cruciferous species (Brassica napus, B. juncea, and Sinapis alba) susceptible to Sclerotinia stem rot disease, causing severe necrosis and chlorosis, but not to a resistant species (Erucastrum gallicum). In addition, we have shown that oleic acid, the major fatty acid isolated from sclerotia of S. sclerotiorum is responsible for the toxic activity of extracts of sclerotia to brine shrimp larvae (Artemia salina). Phytoalexin elicitation in leaves of E. gallicum led to the isolation of three known phytoalexins: indole-3-acetonitrile, arvelexin, and 1-methoxyspirobrassinin. Considering that resistance of E. gallicum to S. sclerotiorum is potentially transferable to B. rapa, a susceptible canola species, and that arvelexin, and 1-methoxyspirobrassinin are not produced by B. rapa, these phytoalexins may become useful markers for resistance against S. sclerotiorum.