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w i n e G R O WIN G 40 µmols-1m-2 280 µmols-1m-2 Figure 3: Leaf removal performed on Sauvignon Blanc vines at phenological stage berry pea size. Left: The shaded treatment (no leaf and lateral shoot removal) with a mean daily PAR (photosynthetically active radiation) of 40 µmols-1m-2. Right: The morning side exposed treatment with a mean daily PAR of 280 µmols-1m-2. itself and not transported to the berry from either the leaves or shoots.9 This is not in agreement with D. Roujou de Boubée who has reported that deuterated analogue of IBMP was translocated from the leaves to grape clusters.14 Abiotic factors such as light and temperature in the fruit zone and the vine water status, and various viticultural practices such as leaf removal, irrigation and vine training system can influence 28 p r acti c al w i ne ry & v i n e yard JANUARY 20 14 the concentration of IBMP in the berry and wine.2,14,17 It has been shown that grapes and wines from cooler climatic regions contain higher concentrations of IBMP than grapes grown in warmer regions. Recent studies have shown the importance of the timing and severity of leaf removal on the final concentration of IBMP in the mature grapes. J.J. Scheiner et al., have shown that early leaf removal, performed 10 days after flowering, significantly reduced the IBMP concentration in Cabernet Franc grapes, while the same treatment, applied 40 and 60 days after flowering, had a less significant effect.18 Leaf removal performed after veraison had little or no effect on the IBMP concentration in grape berries. Bunch exposure pre-veraison is therefore crucial for reducing IBMP concentration in grape berries at harvest, affecting mainly the synthesis. However, light exposure after veraison does not influence IBMP degradation.16,18,19 To understand the effect of sunlight exposure to bunches on the IBMP concentration in grape berries during maturation and the resulting concentration in the wine, leaves and lateral shoots were removed on Sauvignon Blanc and Merlot vineyards in the Overberg and Stellenbosch regions (South Africa). MATERIALS and METHODS Sauvignon Blanc The experiment was performed in a Vitis vinifera L. cv. Sauvignon Blanc (clone 316, grafted onto 101-14 rootstock) vineyard in the Overberg region of the western coastal area, South Africa (34°S; 19°E). The row orientation is northwest to southeast with