WINETECH Technical Yearbook 2020

TABLE 3. Mean seed tannin structural characteristics in 2010/2011 and 2011/2012 season. 2010/2011

the LR (-UV-B, 2xUHI) treatment can be a result of the high PAR (Blancquaert et al. , 2019) that may have been above optimal levels. However, this is not supported by LRW treatment that had similar high PAR values combined with higher tempera- tures in 2010/2011. Chorti et al. (2010) reported that excessive sunlight exposure could result in excessive sunburn, which could influence skin proanthocyanidins in the grape berry. Where similar mDP values were obtained between the seeds in the respective seasons, skin mDPs were higher in 2011/2012 when compared with 2010/2011 (table 6). CONCLUSIONS From this study, it can be concluded that tannin composition is influenced by complex interactions within a par­ ticular season. These interactions in­ clude seasonal climatic patterns and particularly the light quality and quantity from flowering until harvest which have a direct impact on the berry size and seed number, as well as the accumulation of flavonoids. There was no clear impact of treatment and thus light quality and quantity on either seed tannin content or concentration (Part 1). In the case of skin tannin there was an indication of increased skin tannin with l ight exposure, but this was only visible in the 2010/2011 seasons indicating that seasonal variability had a larger impact

2011/2012

Seed % G 5.5 a 2.7 b 0.6 d 1.6 c

Seed % G

Treatment

mDP

avMM

Treatment

mDP

avMM

Standard (Control) Leaf Removal West

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

6.1 a 5.4 b 4.5 c 5.1 b

1804.1 a 1582.5 b 1309.0 c 1499.2 b

7.8 7.5 7.6 7.9

5.0 b 5.2 a 4.8 b 5.3 a

1518.6 cb 1581.6 ab 1456.4 c 1587.9 a

STD-UV-B LRW-UV-B Significance

*** *** Means in columns followed by a different letter are significantly different within one season. Mass conversion based on percent recovery of proanthocyanidin by phloroglucinolysis; %G, percentage galloylation; mDP, mean degree of polymerisation; 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). TABLE 4. Proportions of mean grape skin terminal subunits 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 Treatment C EC ECG Standard (Control) 79.2 b 9.9 b 10.4 a Standard (Control) 83.9 a 15.5 3.1 b Leaf Removal West 79.6 b 14.6 a 5.8 b Leaf Removal West 81.7 ab 15.3 3.1 b STD-UV-B 84.8 a 8.8 b 6.4 b LR (-UV-B, 2xOp50) 61.2 c 15.6 21.6 a LRW-UV-B 86.4 a 3.9 c 8.7 a LR (-UV-B, 2xUHI) 79.8 b 17.0 3.2 b Significance *** *** *** Significance *** ns *** Percent composition of proanthocyanidin terminal skin subunits C, (+)-catechin; EC, (−)-epicatechin; ECG, (−)-epicatechin-3-O-gallate. 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). *** *** Significance ns ***

WINETECH TECHNICAL YEARBOOK 2020 62