Characterization of sirodesmins isolated from the phytopathogenic fungus Leptosphaeria maculans

Abstract

Pathogenicity of phytopathogenic fungi is accociated with phytotoxins, especially with their chemical nature and quantity. Sirodesmins are phytotoxins from epipolythiodioxopiperazines group, produced by fungi Leptosphaeria maculans that is a cause of blackleg and stem canker in oilseed rape (Brassica napus L.). The aim of this work was to obtain a detailed chemical profile of sirodesmins in five fungal isolates (four from Vojvodina and one from UK). Sirodesmins showing different phytotoxicity on treated cotyledons of cv. Quinta were separated and detected by thin layer chromatography in all analysed isolates (L.m, C-3, St-5, S-11) except K-113, which did not contain sirodesmin congeners nor exhibited activity. By use of high performance liquid chromatography coupled with tandem mass spectrometer, it was possible to identify total of 10 sirodesmins, together with their precursor - phomamide. It was found that dominant epipolythiodioxopiperazines of investigated L. maculans isolates were sirodesmin PL, sirodesmin C, and their deacetylated derivatives.