T. KOUSSA*, Monique CHERRAD**, D. ZAOUI*** et M. BROQUEDIS**
*Laboratoire de Physiologie et Pathologie Végétales ; *** Laboratoire de Biochimie Métabolique. Département de Biologie, Université Chouaïb Doukkali, Faculté des Sciences, 24000 El Jadida (Maroc).
**Institut de la Vigne de Bordeaux, Laboratoire des Sciences de la Vigne,
Université Bordeaux I, Avenue des Facultés, 33405 Talence cedex (France).
Abstract : On Cabernet sauvignon, eutypiosis sensible variety, we have compared fatty acids content in healthy leaves (S: leaves beared by healthy vine stock), in leaves seeming healthy (Ap.S: leaves beared by arm without symptoms, the other arm is diseased) and in diseased leaves (M: leaves beared by diseased arm). The results show that disease does not alter the fatty acids order. Linolenic acid (C18:3) content is always the most important, followed by palmitic (C16:0) and linoleic acids, then by stearic (C18:0) and oleic acids and at last by arachidic acid (C20:0). During the three stages studied (flowers buds: H, flowering: I and closed cluster: L), only the development of C18:3 content was modified by disease. It increases in healthy leaves at stage I, while in Ap.S and M leaves there is a decrease from H to L stages. Otherwise, development of fatty acids proportions does not seem to be changed by eutypiosis.
Proportions and content comparison in S, Ap.S and M leaves show a decrease of C18:3 synthesis benefit of C18:2. This increases is important as well as the symptoms are evident. These results seem to be in relationship with decrease of leaves size caused by eutypiosis. At the end, the disease induces a desaturation decrease of C18:0 and C18:2 as well as an aliphatic chain lengthening of C16:0 . These inhibitions are showed by more increase of C16:0 and C18:2 in diseased leaves than in healthy leaves. No action is observed in C18:1 desaturation.
Key words : Eutypiosis (Dying arm disease), Vitis vinifera L., fatty acids, leaves