The effect of variation in berry size on berry composition was studied in irrigated Syrah/R99 grapevines, located in a temperate area of South Africa. Berries from 45 clusters, sampled from both sides of the canopy (east and west), were weighed to create four categories: 1. less or equal to 1.5 g; 2. between 1.51 g and 2.00 g; 3. between 2.01 g and 2.50 g; 4. more than 2.50 g. Berry physical characteristics were determined and total anthocyanins and seed flavonoids were analysed by spectrophotometry and anthocyanin profiles by HPLC. The ratio of skin weight:berry weight did not change with increasing berry size, but the ratio of seed weight:berry weight increased. For total anthocyanins, varying results were obtained if values were expressed in mg/berry, mg/g skin, mg/kg grape and mg/cm2 skin. The quantity of total anthocyanins changed positively with increasing berry weight if expressed in mg/berry and remained almost similar if expressed in mg/cm2 of skin. In contrast, total polyphenols decreased with berry weight if the values were expressed in mg/kg grape and in mg/g skin. Total anthocyanins expressed in mg/kg grape and in mg/g skin were correlated positively to the number of berries as well as to the total skin surface in one kilogram of grape. In this study, the largest berries seemed to have lower quality characteristics. In order to obtain better wine quality, it seems important to reduce berry weight and, in general, berry size variability of Syrah. The obtainment and continuity of a particular wine style may be affected by berry variability.

Terroir factors and vineyard practices largely determine canopy and root system functioning. In this study, changes in soil conditions, multi-level (vertical, horizontal) light interception (quantitative, photographic, schematic, 3D modelled), leaf water potential and photosynthetic activity were measured during the grape ripening period on NS, EW, NE-SW, and NW-SE orientated (Southern Hemisphere) vertically trellised Shiraz grapevine canopies. It was hypothesised that the spatial radiation interception angle and radiation distribution of differently orientated and vertically trained grapevine rows would affect soil conditions and vine physiological activity. Soil water content showed an increase and soil temperature a decreasing gradient with soil depth. In the afternoon, soil layers of EW orientated rows reached their highest temperature. This, along with measured photosynthetic active radiation received by canopies, complimented the diurnally-captured photographic, constructed and 3D modelled images (also schematically) of canopy and soil exposure patterns. The top, bottom and outside of NS canopies mainly received radiation from directly above, from the E and the W; during midday, high radiation was only received from above. The EW rows received the highest radiation component from above and from the N. The NE-SW rows received high levels of radiation from above, from the SE until 10:00, and from the NW from 13:00. A similar profile can be described for NW-SE rows, but with high radiation received from the NE up to 13:00 and from the SW from 16:00. Overall, lowest leaf water potential occurred for NE-SW canopies, followed by those orientated NW-SE, NS and EW. Photosynthetic activity reflected the positive radiation impact of the sun azimuth during the grape ripening period; best overall performance seemed to occur for E and N exposed canopy sides. This was largely driven by the responsiveness of the secondary leaves to radiation. Photosynthetic output decreased from apical to basal canopy zones with low, erratic values in the light-limited canopy centre. The NS and EW orientated canopies generally showed the highest average photosynthesis, while it was lower for the sides facing S, SE and SW. The results provide a better understanding of the physiological functioning of horizontal and vertical leaf layers in differently orientated grapevine canopies, as affected by climatic conditions. The study contributes to the longstanding challenges of capturing the complexity of parallel microclimatic and physiological output of grapevine canopies under open field conditions. The results can be directly applied to the selection of vineyard practices and seasonal management to ensure the attainment of yield, grape composition and wine quality objectives.

To optimise the functioning of the grapevine in a specific environment and to improve grape and wine quality, suitability of climatic parameters for key grapevine physiological processes needs to be assessed at fine scales. This paper presents methodology using hourly weather data in three wine producing regions of South Africa (Coastal Region – Stellenbosch district; Breede River Valley – Robertson district; Central Orange River Region – Upington district) during the pre- (November to December) and post-véraison (January to February) periods. Durations inside and outside an optimum climatic range and of extreme climatic conditions were calculated over a 5-year period (1999/2000 to 2003/2004) to quantify a climatic profile related to grapevine physiological requirements. Climatic requirements for optimum photosynthetic activity were defined as follows: temperature 25°C to 30°C, windspeed <4 m/s, relative humidity 60% to 70%. Unsuitable climatic periods for vine performance were calculated as 35°C, >4m/s, 80%. A coefficient was assigned to each climatic parameter according to an assumed importance level for physiological processes. Optimum temperature requirements for other physiological parameters were also investigated. A diurnal minimum/maximum temperature range of 25°C to 30°C was used for sugar content and organic acid levels and a maximum night/day temperature range of 15°C/25°C for colour and flavour. Light intensity was accepted as being sufficient. Stations were classified according to their potential for meeting the climatic requirements of each physiological parameter. Marked variation in climatic profiles and available time for optimal physiological functioning occurred between regions. All factors considered, the climatic profile of the Coastal Region (Stellenbosch district) seemed to best satisfy the climatic requirements of the physiological parameters studied.

Berry size has always been a quality factor in wine production. In this study, Syrah grapes from a single vineyard were classified into different size groups according to diameter: small (< 13 mm), medium (13 < diameter < 14 mm) and large (> 14 mm). Smaller berries were present in the highest and larger berries in the lowest numbers. Size distributions were similar in both seasons (2010/2011 and 2011/2012). Berry physical characteristics (mass, volume and skin area) increased with size, showing the same tendency in both years. Positive correlations between berry mass, volume and skin area were found, whereas these variables were negatively related with berry number/kg grapes. Berry volume was negatively correlated with dry skin weight. Skin surface area/berry volume seems to be an indicator of the “dilution” effect associated with increasing size, as larger berries presented the lowest values. In 2012 the grapes were harvested at a higher soluble solid level than in the previous year; large-sized berries presented the lowest levels in both years. The whole-berry analysis of total anthocyanins showed a decrease in concentration and increase in content per berry, from smaller to larger berries. Small berries and the control (naturally occurring berry size mixture) showed a higher extractability of anthocyanins and phenolic compounds than the medium and large berries. Sensorially, wines from medium berries were more consistent over the two years, scoring higher than the rest. Berry sizes were related to wine style differences, and knowing the population of berry sizes in the vineyard close to harvest would offer a possibility to predict wine styles.

Seasonal variation in the water, sugar, organic acid and cation contents of developing grape berries ( Vitis vinifera L. ‘Grenache noir’) under different levels of water supply (with and without deficit irrigation) and leaf:fruit ratios (18, 10 and five leaves per primary shoot, with one bunch per shoot), was investigated over two successive years in Mediterranean conditions (South of France). Fourteen shoots per vine were left for each leaf:fruit ratio level, and each vine was considered as having homogeneous primary shoots. The growth rate of the berries was increased with irrigation. Total dry matter content of the berry was not affected by leaf:fruit ratios, but the sugar loading decreased during berry development with a lower leaf:fruit ratio (five leaves per bunch). Treatments had little effect on organic acid contents and pH. Berry cation accumulation depended on vine water status and not on the total leaf area of the vine. Under irrigated conditions, calcium continued to accumulate in the berries after véraison. This confirms a partial functioning of the berry xylem during the post-véraison period. The seasonal variation in berry composition was less dependent on the leaf:fruit ratio than on the water status of the vine (mainly cations and sugar). This study provides evidence for the importance of plant water status effects on berry composition, irrespective of the leaf:fruit ratio. Vine water status is a major regulating factor for source-sink relationships.