The effect of bunch shading on berry development and flavonoid accumulation in Shiraz grapes

• Autores: John S. Harvey, Mark O. Downey, Simon P. Robinson
• Localización: Australian journal of grape and wine research, ISSN 1322-7130, Vol. 10, Nº 1, 2004, págs. 55-73
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Dialnet Métricas: 4 Citas
• Resumen

  • Opaque boxes were applied to bunches of Shiraz grapesprior to flowering to determine the effect of sunlight on berry developmentand accumulation of flavonoids. The boxes were designed to maintain airflowwhile excluding light and thus to minimise changes in temperature andhumidity. There was no significant effect of shading on sugar accumulationand in two of the three seasons studied there was no effect on berryweight. Chlorophyll concentration was much lower in the shaded fruit, whichappeared pale yellow until veraison. The fruit coloured normally in theshaded bunches and in two of the three seasons there was no significantchange in anthocyanin content. Expression of the gene encoding UDP-glucoseflavonoid-3-O-glucosyl transferase (UFGT), a key gene in anthocyaninsynthesis, increased after veraison and was similar in both shaded andexposed fruit. Anthocyanin composition was altered in the shaded fruit,which had a greater proportion of the dioxygenated anthocyanins, theglucosides of cyanidin and peonidin. Shading had no significant effect onthe levels of condensed tannins in the skin or seeds of ripe fruit. Shadingsignificantly reduced the levels of flavonols in the grape skin. In theexposed fruit, flavonol concentration was highest around flowering thendeclined as the berries grew, but there was an increase in flavonols perberry during ripening. When the boxes were applied before flowering, shadedfruit had much lower levels of flavonols throughout berry development andat harvest the level of flavonols were less than 10% of that in exposedfruit. A gene encoding flavonol synthase (FLS) was expressed at floweringand during ripening in exposed grapes but its expression was greatlyreduced in shaded fruit. The results indicate that shading had littleeffect on berry development and ripening, including accumulation ofanthocyanins and tannins, but significantly decreased flavonol synthesis.