Pseudomonas syringae pv. syringae as one of the factors affecting the ice nucleation of grapevine buds in controlled conditions

Ice nucleation in grapevine buds (cv. Pinot noir) was studied in freezing chamber in container grown plants. The ice nucleation of individual 278 buds at different stages of their development (between stage B and stage E according to Baggiolini scale) was measured by differential thermal analysis. Treatments were applied to plants to modify the Pseudomonas syringae pv. syringae content of buds and alter their water potential. Based on the results it was pointed out that (i) the ice nucleation temperatures of buds were generally normally distributed, (ii) the probability of bud nucleation at a given temperature was, to a certain extent, dependent on the amount of Pseudomonas present, (iii) the modification of water potential following an artificial rain led to a signification increase of the probability of bud nucleation and (iv) the nucleation probability did not increase significantly with the bud development between stage B and stage E.