The phytopathogenic fungi Leptosphaeria maculans and Leptosphaeria biglobosa: chemotaxonomical characterization of isolates and metabolite production in different culture media.

Previous molecular chemotaxonomic analyses of isolates of the plant pathogenic fungus Leptosphaeria maculans (Desm.) Ces. et de Not. (asexual stage Phoma lingam (Tode ex Fr.) Desm.) in a chemically defined medium suggested that this species complex was composed of at least three distinct groups. Subsequently, a group within L. maculans was classified as Leptosphaeria biglobosa, on the basis of morphologic characteristics and the lack of sexual crossing. To obtain clarification regarding the metabolite profiles of the various groups or species of blackleg fungi, the objectives of this work were (i) to determine the chemical structures of metabolites produced by Canadian V isolates and Polish-type isolates in potato dextrose broth (PDB) and (ii) to determine the chemotaxonomic relationship among French isolates of L. biglobosa and among Canadian W isolates and Thlaspi isolates of L. maculans. Here, we report for the first time that Canadian V isolates grown in PDB produced 2,4-dihydroxy-3,6-dimethylbenzaldehyde, a metabolite never reported from L. maculans, but none of the usual phytotoxins (sirodesmins). In addition, we report a new metabolite, 2-[2-(5-hydroxybenzofuranyl)]-3-(4-hydroxyphenyl)propanenitrile, from Polish-type isolates of L. maculans grown in PDB and the metabolite profiles of 16 Thlaspi isolates. The metabolite profiles of Thlaspi isolates indicate that these are part of two distinct groups, the Polish W group and the Canadian W group, i.e., L. biglobosa. Finally, we demonstrate that the metabolite profiles of the French isolates classified as L. biglobosa are similar to those of Canadian W isolates.