WINETECH Technical Yearbook 2020

TABLE 5. Proportions of mean grape skin proanthocyanidin extension subunit in 2010/2011 and 2011/2012 season. Means in columns followed by a different letter are significantly different within one season. 2010/2011 2011/2012 Treatment C EC ECG EGC Treatment C EC ECG EGC Standard (Control) 1.9 b 41.2 0.3 ab 56.6 Standard (Control) 1.2 b 39.3 ab 0.7 b 58.8 Leaf Removal West 2.1 a 40.1 0.4 a 57.4 Leaf Removal West 1.3 b 38.8 b 0.7 b 59.2 STD-UV-B 1.9 ab 40.6 0.2 b 55.0 LR (-UV-B, 2xOp50) 1.3 a 39.4 ab 0.6 c 58.8 LRW-UV-B 2.0 b 42.2 0.2 b 55.5 LR (-UV-B, 2xUHI) 1.2 b 39.7 a 0.8 a 58.3 Significance ** ns *** ns Significance *** * *** ns Percent composition of proanthocyanidin extension skin subunits C, (+)-catechin; EC, (−)-epicatechin; ECG, (−)-epicatechin-3-O-gallate; EGC, (–)-epigallocatechin. STD (Shaded/Control); LRW (Leaf Removal West); STD with decreased UV-B radiation (STD-UV-B); LRW with decreased UV-B radiation (LRW-UV-B); LR-UV-B, 2xOp50 (Leaf removal with decreased UV-B radiation and 2xOp50 UV-sheets added on both sides of the bunch zone); LR-UV-B, 2xUHI (Leaf removal with decreased UV-B radiation and 2xUHI UV-sheets added on both sides of the bunch zone ). Significance (*, ** and *** indicate significance at p ≤ 0.05, 0.01, 0.001 respectively; ns: not significant).

than the individual treatments applied to alter the light quantity and quality. Therefore, seasonal differences should be taken into account. These results contribute to a better understanding of the light and seasonal interaction on flavonoid composition. Furthermore, additional studies performed in a greenhouse or growth chamber, to control the temperature and light con­ ditions to have a clearer understanding of the abiotic factors influencing flavonoid composition in the berry, could be bene­ ficial. REFERENCES Adams, D. 2006. Phenolics and ripening in grape berries. American Journal of Enology and Viticulture . 57, 3, 249-256. Cohen, S. D., Tarara, J. M., Kennedy, J. A. 2008. Assessing the impact of temperature on grape phenolic metabolism. Analytica Chimica Acta 621, 57–67. doi: 10.1016/j. aca.2007.11.029 Chorti, E., Guidoni, S., Ferrandino, A., Novello, V. 2010. Effect of different cluster sunlight exposure levels on ripening and anthocyanin accumulation in Nebbiolo grapes. American Journal of Enology and Viticulture 61, 23-30. De Freitas, V.A.P., Glories, Y. & Monique, A. 2000. Developmental changes of procyanidins in grapes of red Vitis vini­

TABLE 6. Mean skin tannin structural characteristics in 2010/2011 and 2011/2012 season. 2010/2011

2011/2012

Skin % G 0.8 a

Skin % P mDP avMM Treatment

Skin % G

Skin % P mDP avMM

Treatment

Standard (Control) Leaf Removal West

Standard (Control) Leaf Removal West LR (-UV-B, 2xOp50) LR (-UV-B, 2xUHI)

54.3 26.2 c 7824.1 c

0.8 c 57.5 ab 46.4 a 13837.0 a

0.6 b 55.3 29.9 b 8899.4 b

0.7 c 1.4 a

57.8 a 42.3 b 12620.5 b 56.7 c 32.6 c 9740.8 c

STD-UV-B LRW-UV-B Significance

0.4 c

53.9 31.4 b 9330.5 b 54.7 35.6 a 10614.2 a

0.5 bc

0.9 b 56.9 cb 46.5 a 13895.6 a

*** *** Means in columns followed by a different letter are significantly different within one season. Mass conversion based on percent recovery of proanthocyanidin by phloroglucinolysis; mDP, mean degree of polymerisation; %G, percentage galloylation; %P, percentage prodelphinidins; avMM, average molecular mass. STD (Shaded/Control); LRW (Leaf Removal West); STD with decreased UV-B radiation (STD-UV-B); LRW with decreased UV-B radiation (LRW-UV-B); LR-UV-B, 2xOp50 (Leaf removal with decreased UV-B radiation and 2xOp50 UV-sheets added on both sides of the bunch zone); LR-UV-B, 2xUHI (Leaf removal with decreased UV-B radiation and 2xUHI UV-sheets added on both sides of the bunch zone ). Significance (*, ** and *** indicate significance at p ≤ 0.05, 0.01, 0.001 respectively; ns: not significant). ns *** *** Significance *** *** ***

WINETECH TECHNICAL YEARBOOK 2020 63