Pollination of <i>Vitis vinifera</i> L. cv. Pinot noir as influenced by <i>Botrytis</i> fungicides

Abstract

The effects of fungicides on grape (Vitis vinifera L. cv. Pinot noir) pollen germination and tube growth were studied in vitro, and a related field trial examined effects of time of fungicide application during flowering on seed number and fruitset. Fungicides pyrimethanil, cyprodinil + fludioxonil and chlorothalonil incorporated into in vitro germination medium at the recommended mixing rate for field application all prevented pollen germination. When the fungicides were diluted to 10 % of the recommended mixing rate, pollen grain germination was still completely inhibited. Further dilution to 1 %, resulted in some pollen grains germinating but the level was significantly less than the control, and the grains that did germinate had stunted pollen tubes (< 100 μm in length), compared with controls not exposed to fungicide (800 μm in length). In a 0.1 % dilution of the fungicides, germination percent was not significantly different to untreated control, however pollen tube length was still slightly suppressed in media containing pyrimethanil (523 μm) and cyprodinil + fludioxonil (366 μm). In spite of these marked effects on pollen germination and tube growth in vitro, plants sprayed with pyrimethanil at either 5 or 80 % cap fall, resulted in no significant reduction in fruitset. Seed set however was affected, with seed number per berry being significantly reduced on inflorescences that were sprayed at 5 % cap fall.