Effect of age on the fatty acid content of Blumeria graminis conidia

Blumeria (= Erysiphe) graminis f.sp. tritici (Bgt), the causal agent of whe at powdery mildew, is responsible for an important disease leading to consi derable yield reductions in wheat worldwide. Conidia of the obligate plant pathogen Bgt were analysed for their total fatty acid (FA) composition as a function of their ontogeny. A total of 17 FAs were detected (C-12-C-24 sat urated and unsaturated ones), including the presence of unusual long-chain monoenoic FAs. In young conidia, the major FAs were C-18:2 (23 %), C-16:0 ( 16 %), C-18:0 (15.2 %) and C-18:1 (14.3 %). In old conidia, the main FAs we re C-24:1 (20.7 %), C-22:0 (15 %), C-22:1 (13.5 %) and C-24:0 (9.7 %). The amount of total FA was about 39 mug.mg of dry weight(-1) in young conidia a nd decreased clearly to 18 mug.mg of dry weight(-1) in older conidia. For t he first time, we have demonstrated that the FA composition of conidia chan ges greatly with age. Medium-chain FAs (C-12-C-18) are predominant in very young conidia (75 %), whereas long-chain FAs (C-22-C-24) are the major comp ounds in old conidia (74%). This study showed a significant elongation of F As and a drastic decrease in the total FA amount during the ontogeny of con idia.