INTRASPECIFIC VARIATION IN SOLUBLE MYCELIAL PROTEIN AND ESTERASE PATTERNS OF LEPTOSPHAERIA-MACULANS FRENCH ISOLATES

Thirty-six single-ascospore isolates of Leptosphaeria maculans were obtained from eight stubbles of diseased Brassica napus plants collected from two locations in France. The isolates were assessed for (i) their sirodesmin PL and phomenoic acid production in vitro; (ii) their esterase profiles following native polyacrylamide gel electrophoresis; and (iii) their protein patterns obtained by isoelectric focusing. Two groups of isolates could be discriminated according to their toxin production, i.e. isolates producing both sirodesmin PL and phomenoic acid, termed Tox+, and those producing neither of these compounds, termed Tox0. The same dear-cut separation between Tox+ and Tox0 isolates was observed when analysing esterase or soluble protein profiles. In the latter case, the mean similarity index between isolates was 46 % when belonging to different groups, and 88-92 % when belonging to the same group. Esterase patterns were highly polymorphic within the Toxo group, and factorial correspondence analysis of soluble protein profiles showed that one individual dearly departed from the main cluster. Within the Tox+ group all the isolates displayed the same five esterase bands. Within this group a high degree of homology between protein profiles was also observed. Nevertheless, three major bands could be used to further characterize Tox+ isolates and discriminate them into subgroups. Both Tox0 and Tox+ isolates were present in each of the collection areas, and even on the same stubble.