EXOGENOUS ABSCISIC ACID INCREASES BUD FREEZING TOLERANCE OF
VITIS VINIFERA "PINOT GRIS" GROWN IN COLD REGIONS OF THE UNITED STATES
Economic losses due to cold weather events are a major constraint to the expansion of premium but cold sensitive winegrape cultivars in cold regions of the United States. The purpose of this study was to determine whether a foliar application of abscisic acid (ABA) could increase the freezing tolerance (FT) of field-grown, Vitis vinifera «Pinot gris» grapevines, and whether the effectiveness of ABA treatments can be influenced by the phenological timing of the application. Mature, « Pinot gris » grapevines were treated with a foliar application of ABA at a concentration of 0 mg·L-1 (control), or 400 mg·L-1 at vine phenological stages corresponding to véraison, post-véraison, and post-harvest. ABA application did not affect yield components or fruit composition, but caused early leaf senescence, leaf abscission, and advanced dormancy that led to increased FT of « Pinot gris » during the dormant season. The phenological timing of application influenced ABA effectiveness, and spray applications made at véraison and post-véraison decreased LT50 (increased FT) the most by 2 oC to 4 oC as compared to the untreated control vines. Furthermore seasonal changes of bud FT were linked with changes in soluble sugars particularly raffinose. It is concluded that a foliar application of ABA increased bud FT during the dormant season and thus ABA is a potential cultural practice for mitigating economic losses from cold injury in production regions with damaging cold events.
Keywords : freezing tolerance, dormancy, thermal analysis, low temperature exotherm, cold injury
Les pulvérisations foliaires d’acide abscissique – ABA (400 mg/l) à la véraison et en post-véraison n’affectent pas le rendement ni la composition des raisins, mais avancent la sénescence et la chute des feuilles, ainsi que la dormance des bourgeons ce qui augmente finalement la tolérance au froid de 2 à 4°C. Ceci présente un intérêt dans les zones sujettes fréquemment aux dégâts de gel en automne et hiver.
Mots-clés : Tolérance au froid, dormance, analyse thermique, exotherme, dégât de froid