Agronomie 11 (1991) 169-174
DOI: 10.1051/agro:19910303

Analyse de la gélivité des bourgeons de vigne. Expérimentation in situ sur le vignole champenois

B. Itier^a, D. Flura^a, O. Brun^b, J. Luisetti^c, JL Gaignard^c, C. Choisy^d, G. Lemoine^d, B. Durand^a, S. Masson^a, M. Devaux^c and JC Lhotel<sup>e

a</sup>  INRA, station de bioclimatologie, 78850 Thiverval-Grignon
^b  GCEV MUMM vignobles et recherches, 11 avenue de Champagne, 51200 Epernay
^c  INRA, station de pathologie végétale et phytobactériologie, route de Saint-Clément, Beaucouzé, 49000 Angers
^d  Faculté de pharmacie, laboratoire de microbiologie, 52 rue Cognacq-Jay, 51096 Reims Cedex
^e  INRA, station de bioclimatologie, domaine de Saint-Paul, BP 91, 84140 Montfavet, France

Résumé - Une étude expérimentale de la gélivité des bourgeons de vigne in situ a été entreprise sur le vignoble champenois (Vitis vinifera L Chardonnay) de 1987 à 1989 en utilisant l'analyse thermique différentielle dans des chambres de refroidissement. L'analyse de la gélivité a consisté à étudier l'influence sur la température de rupture de surfusion de facteurs tels que le stade phénologique, le mouillage des organes végétaux et la teneur en bactéries dites glaçogènes. Au vu des résultats il apparaît que stade phénologique et mouillage sont des variables déterminantes, tandis que l'action des bactéries est beaucoup plus ténue et difficile à interpréter. Les informations recueillies doivent permettre à terme d'élaborer un modèle probabiliste du risque de rupture de surfusion dans le bourgeon.

Abstract - An analysis of sensitivity to spring frost in vine buds. An experiment on sensitivity to spring frost in vine buds was undertaken in the champagne vineyard (Vitis vinifera L Chardonnay) during the springs of 1987-1989 by means of differential thermal analysis (first exotherm) performed in freezing chambers, providing either convective cooling (on vine directly in the field) or radiative cooling on twigs. The sensitivity of buds was analysed in terms of bud phase, surface wetness and ice nuclei bacteria (Pseudomonas syringae) concentration. Figure 1 shows the evolution with phenological phase of mean freezing point of dry buds for 3 yr independently of ice nuclei concentration. Figure 2 reports this freezing point for dry vine buds which contain < 10³ bacteria, ie quasi-free of ice nuclei. Figure 3 reports for stage 9 of Eichhhorn and Lorenz the freezing point of dry buds versus ice nuclei concentration. The evolution of the mean freezing point at different stages is plotted on figure 4 versus mean ice nuclei bacterial concentration for both dry and wetted vine buds. From this figure, one can see that frost sensitivity of buds is increased not only by phenology but also by wetness of bud surface. On the contrary, the influence of ice nuclei bacteria is not so obvious. It seems that this bacterial influence could be different depending on the origin of the bacteria. In figure 5 at stage 7, the freezing point of contaminated buds (x) is higher than that of buds which contain the same amount of bacteria (Δ). The only minor effect of natural ice nuclei bacteria concentration on buds was observed on the percentage of surviving buds for a given temperature : the concentration of bacteria observed on killed buds (□) is a little higher in figure 6 than those in surviving buds (+).

Key words: frost / sensitivity / bud / Vitis vinifera = vine / bacteria / phenology / wetness

Mots clés : gel / sensibilité / bourgeon / Vitis vinifera = vigne / bactérie / phénologie / mouillage