Xanthan gum as adjuvant in controlling table grapes rots with Aureobasidium pullulans A

The results of a two-year investigation aimed at evaluating the activity of the yeast-like fungus Aureobasidium pullulans, isolate L47, in combination with Xanthan gum (0.05% w/v) (Xg) against sour and Botrytis rots of table grapes are reported. The antagonist was also applied in combination with CaCl2 (1% w/v) or with Procymidone at 1/10 of full dose. The antagonist alone or in combination was sprayed on bunches in the field 40 (first year) and 21 (second year) days before harvest. Untreated bunches or those treated with Procymidone at full dose (100 g hl-1) served as controls. Rots were evaluated at harvest and after 30 days cold storage (0°C, 95-98% RH). The epiphytic population of yeasts (including yeast-like fungi) and filamentous fungi on the berries was evaluated at harvest and after cold storage. Control of Botrytis rot and survival of isolate L47 at harvest were significantly enhanced when the antagonist was applied in combination with Xg; the improvement was less evident after cold storage. L47 was more active in combination with CaCl2 than alone, but not significantly so. A significant improvement of L47 activity was observed at harvest when the antagonist was applied in combination with Procymidone at 1/10 of full dose. Sour rot, appreciable only in the field at harvest, was significantly reduced by all treatments, with the lowest values on bunches treated with Xg. The improved activity of isolate L47 in combination with Xg seems to be associated with its greater survival on the berries.