CHANGES IN COMPOSITION AND COLOUR DEVELOPMENT OF ´TEMPRANILLO´ GRAPES DURING RIPENING INDUCED BY ETHEPHON TREATMENTS AT VERAISON

The aim of this work was to evaluate the influence of the application of ethephon (2-chloroethylphosphonic acid) at evasion on composition and colour of ‘Tempranillo’ grapes throughout their ripening. The experiment was carried out in a full production vineyard located in the ‘Cigales’ Appellation d’Origine area (northwest Spain) during three years: from 2001 to 2003. Vines were sprayed at veraison (75% berries coloured) with ethephon at 0, 700 and 1400 mg•L-1 in a randomized complete block design with three replications. Must composition, polyphenols and anthocyanins content in the skin, and chromatic characteristics of grapes were measured regularly from 100% berries coloured to harvest (almost six points of control every year). The experimental treatments did not significantly affect vigour (pruning weight) and yield of vines. Ethephon increased the pH and reduced titratable acidity of must in relation to the untreated control, with significant differences from the first point of ripening monitoring (ten days after application) until harvest. Total polyphenols index was higher in treated vines, but the significant differences did not appear until 20 days after spraying. Ethephon treatment al 1400 mg•L^-1 increased colour intensity, absorbance at 520 nm and the red component of must colour. The anthocyanins content of berry skins in treated vines was significantly higher than untreated from the first points of ripening monitoring.