INVOLVEMENT OF A PLANT DEFENSES ENHANCER FOSETYL-AL IN FLOWERING INDUCTION: FROM THE FIELD TO THE GENES

Fosetyl-Al is a well-known anti-oomycetes fungicide with efficacy based on an indirect action as stimulation of the natural plant defenses. Field phenotypic observations in apple, pear and cherry orchards have revealed very positive effect of fosetyl-Al on flowering the year following treatment. An advantageous effect was noticed both on quantity as on the quality of flower buds. Flower cluster of trees treated with Aliette in the previous season had more flowers and a tendency of being surrounded by more well developed rosette leaves. Fosetyl-Al’s mode of action analysis was conducted in parallel and independently on the vine-downy mildew patho-system to elucidate the effect as stimulator of natural plant defense. Transcriptomic analysis clearly showed involvement of fosetyl-Al in defense response with genes deregulation in chalcone synthase biosynthetic pathway and in stilbenes accumulation. Those pathways are the most frequently and best characterized defense mechanisms described in vine. Besides that, 3 clusters of genes corresponding to auxine responsive proteins were found slightly up-regulated with fosetyl-Al preventative treatment. Speculation on the role of those genes induced by fosetyl-Al and consequently the input on flowering quality on apples and pears could be discussed.