151 1. Introduction Summer pruning is a fairly broad term comprising a set of practices performed on the canopy during the growing season with an array of aims, including regulation of size, vigour and crop and reduction of the susceptibility to biotic and abiotic stress. If it is considered that at least two such operations, e.g. selective shoot and cluster thinning, still re- quire manual execution, the total amount of necessary sea- sonal labour, calculated as man × hr/ha, readily exceeds the demand for winter pruning and becomes a primary determi- nant of vineyard economics (Intrieri and Poni, 1995). While it is commonly heard that the ‘perfect’ vineyard needs no summer pruning, perfect in reality has proved to be a very rare occurrence. Yet, we should certainly like to see vine- yards of the future moving towards a more focused appli- cation of summer pruning operations. The major change is that a given summer cut is not solely or exclusively seen as something the grower “has to do”, say, to accommodate adjustments for excessive shoot growth or canopy density. Rather it should also be viewed as something that the grow- er may ‘use’ to head vine and cluster growth towards bet- ter grape composition or to specific features consonant with adjustments needed because of climate change. Along with traditional summer pruning operations, which define the grapevine canopy management strategy and include cluster and shoot thinning, shoot positioning and hedging, elimination of lateral shoots and late season basal leaf removal, over the last few years innovative sum- mer techniques such as pre-flowering leaf removal (Poni et al., 2006; Intrieri et al., 2008; Poni et al., 2008; Diago et al., 2010 a; Palliotti et al., 2011 b) or early and late season anti-transpirant sprays (Palliotti et al., 2010 and 2011 a) have been introduced. These latter management practices are useful in any situation where the main aims are to re- duce the vine yield and improve both technological and phenolic maturation. Moreover, global warming is leading to a progressive shift toward sub-tropicalization of several viticulture areas, shorter time intervals between pheno- logical stages (Schultz, 2000; Jones et al., 2005) as well as increased probability for berry sunburn (Spayd et al., Traditional and innovative summer pruning techniques for vineyard management A. Palliotti*, S. Poni** * Dipartimento di Scienze Agrarie e Ambientali, Università degli Studi di Perugia, Borgo XX Giugno, 74, 06121 Perugia, Italy. ** Istituto di Frutti-Viticoltura, Università Cattolica del Sacro Cuore, Via Emilia Parmense, 84, 29100 Piacenza, Italy. Key words: cluster thinning, grape composition, leaf removal, shoot hedging, shoot thinning, vegetative growth. Abstract: This review paper highlights physiological and vine performance effects of widely adopted summer pruning operations such as leaf removal, shoot trimming and positioning and cluster thinning. Leaf removal is addressed either under its traditional configuration, i.e. removing in dense canopies some or all leaves around clusters usually pre-veraison to improve fruit microclimate and facilitate spraying and early (pre-flowering) defoliation primarily aimed at inducing looser clusters via a concurrent reduction of fruit-set and berry size. Time consuming and still non mechanisable cluster thinning is evaluated primarily in terms of response variability vs. season and intensity with emphasis on lack of signifi- cant reduction of final yield per vine in thinned treatments when large crop compensation occurs. Variability of expected final grape composition improvements in thinned vines is also discussed based on the actual vine balance when the opera- tion is performed. Although fully mechanisable, shoot trimming is still a debated choice in terms of timing and severity. While severe (i.e. fewer than six or seven main leaves retained) and late (i.e. several weeks after bloom) cuts should pos- sibly be avoided, the effects of shoot trimming on final grape composition is discussed as a function of seasonal changes in leaf area development, demography, fraction of lateral leaves from the total and leaf to fruit ratio. It is indicated that, for vertically shoot-positioned trellises, if the support trellising is correctly designed and vine vigour is balanced, timing and severity of trimming are dictated by the vine “itself” rather than by grower choices. Overall, this review underscores the importance of leading the vineyard to a “natural” control of vegetative growth, which would minimise the need for an extensive use of summer pruning. In other words, such vineyard operations should be viewed not just as something the growers “have to do”, instead as specific tools used to achieve targeted final grape composition. Adv. Hort. Sci., 2011 25(3): 151-163 Received for publication 9 May 2011 Accepted for publication 6 June 2011 152 2002; Tarara and Spayd, 2005; Greer et al., 2006). Finally, clear evidence does exist for faster ripening leading to sig- nificant increases in grape sugar concentration at harvest (Dokoozlian, 2009). 2. Leaf removal This operation has been historically defined as “the re- moval of some leaves from the fruiting area between fruit set and veraison” (Smart, 1973) with the prevailing aim to ameliorate bunch microclimate and reduce rot incidence in canopies that are too dense (Gubler et al., 1991). Ongoing research has provided knowledge to distinguish two types of leaf removal aimed at quite distinct goals. Traditional leaf removal Although this practice may have different purposes, it is usually employed from fruit set to veraison on high-den- sity canopies to improve light exposure and air circulation around the clusters, with substantial benefits in terms of pigmentation and tolerance to rot (Smart, 1985; Bledsoe et al., 1988; Gubler et al., 1991; Percival et al., 1994; Reyn- olds et al., 1996). This operation can be done manually, requiring up to about 60 hr/ha, although increasing labour costs nowadays strongly advise a mechanical approach which can be easily performed in less than 2 hr/ha. The best timing for machine use is about one to two weeks prior to veraison when berries are still hard while specific bunch weight is already much higher than that of leaves. Yield may not change (Bledsoe et al., 1988; Smith et al., 1988; Hunter et al., 1995) or might even occasionally increase as compared with non-defoliated vines (Zoeck- lein et al., 1992). The variability of the impact that leaf removal has on yield and their components is likely depen- dent upon the negative effects on fruit set and berry growth in the current year and positive effects on bud induction and differentiation for the next year’s crop via an improve- ment in canopy microclimate. Although this type of leaf removal usually leads to undeniable improvements in fruit composition, which more frequently are a slight increase in sugars and ripe fruit characters and a decreased malic acid content and attenuated herbaceous and grassy wine characters (Smart, 1985; Reynolds et al., 1996; Zoechlein et al., 1992; Scheiner et al., 2010), its popularity has prob- ably decreased over the last two decades due to either ad- vancement in leaf and whole-canopy physiology and new pressure from global warming. A study from Petrie et al. (2003) found that leaf re- moval from the lower quarter of the canopy during the lag phase of berry growth caused a significant decrease of whole-vine photosynthesis, even on a per-unit leaf area basis, thus suggesting that the lower portion of the canopy contributed more than the upper portion to the whole-vine carbon budget. A possible explanation of this finding is that although basal, and hence older leaves are removed by defoliation, they are also the largest leaves along the shoot and their size can offset lower photosynthetic rates (Poni et al., 1994). Therefore, lowering shoot photosyn- thesis might not be negligible especially for leaf removals performed after fruit set. Removal of all the leaves from the fruiting area, which thereby exposes the clusters to full sun, might lead in warm climates to compromised fruit composition because of excessive berry temperatures, which can hinder colour formation and cause a sharp drop in malic acid concentra- tions (Spayd et al., 2002; Tarara et al., 2008). For such rea- sons and in association with increasing concern for berry sunburn, criteria for applying leaf removal have become more restrictive and more often conceive retaining some leaf cover around the fruiting area. Differentiation in the actual need and/or severity of leaf removal also depends upon specific planting choices. For instance, no or very light defoliation is usually applied on the south facing side of an east-west oriented row, whereas more severe leaf stripping might be required on the north facing row side; basically the same applies for west- and east facing sides of north-south oriented rows, respectively. More physiological insights have also been provided about “why” a traditional leaf removal might become man- datory. Backward to the still shareable rule indicated from Dr. Shaulis in that “no leaf removal is needed if while stand- ing in front of a canopy at veraison about 50-60% of the clus- ters are visible”, other more recent findings have shown that in a significant number of cases, excessive canopy crowding in the bunch zone leading, in turn, to the need of stripping leaves, is caused by other wrong or rushed vineyard man- agement choices (Fig. 1). One example is worthwhile above all: spur pruned vertically shoot positioned (VSP) cordon- trained canopies are usually prone to leaf removal due to too high shoot density per meter of canopy length. Yet, this often happens as vines burst many either secondary or base bud originated shoots casting additional shade in the bunch area. More equilibrated vines would better comply with the shared requirement that, on average, one shoot is expected from each single retained node and, if so, the subsequent leaf removal would become quite likely unnecessary. Fig. 1 - Interrelationships of excessive shoot vigour stimulated by a too narrow within-row vine spacing and related consequences on summer pruning needs (drawn by Authors). 153 Early leaf removal This practice has mainly been inspired from long-standing knowledge according to which carbohydrate supply at flow- ering is a primary determinant of fruit set (Coombe, 1959; May et al., 1969). The temporary source limitation induced by removing an average of six main basal leaves before flow- ering has led, under a broad array of genotypes and growing conditions, to a significant decrease in fruit-set, which in turn increases cluster looseness and tolerance to rot (Gubler et al., 1991; Poni et al., 2006; Intrieri et al., 2008; Poni et al., 2008; Diago et al., 2010 a). Yet, the most important outcome is that, irrespective of genotype, this early leaf removal markedly improves grape composition and wine sensory properties as compared to non-defoliated shoots (Poni et al., 2006; Diago et al., 2010 a; Palliotti et al., 2011 b). There are multiple mechanisms involved in such a pos- itive response. Defoliated shoots generally have a higher final leaf-to-fruit ratio than control, thus implying that the yield reduction induced by defoliation was more than pro- portional to the leaf removal constraint due to a fruit-set and berry-size effect (Poni et. al., 2006). Furthermore, it is known that a precocious source limitation carried out in the form of defoliation or darkening the basal shoot zone hastens translocation of assimilates towards the cluster (Quinlan and Weaver, 1970). Improved grape composi- tion in the defoliated shoots also relates to the ‘quality’ of the source. For example, it is indeed true that removing the main six basal leaves at pre-bloom causes an abrupt and severe decrease in vine photosynthesis [75% less than with not-defoliated (ND) according to Poni et al., 2008]. However, removing source leaves around bloom also trig- gers a series of dynamic changes in canopy growth, age and photosynthesis. Defoliated vines have a ‘younger’ canopy at veraison since median and apical shoot leaves at this time are now mature and more lateral leaves may be present as a compensating reaction to early main leaf re- moval, while some, albeit temporary, photosynthetic com- pensation usually occurs in both main and lateral leaves of defoliated plants. Poni et al. (2008) have recently shown that whole canopy net CO2 exchange rates (NCER) moni- tored uninterruptedly for three months in defoliated (D) vs. non-defoliated Sangiovese vines indicated no differ- ences in data expressed on a per-vine basis. Yet when the same data were given on a per-unit leaf area basis, defoli- ated vines showed higher rates than ND vines (4.75 µmol m-2 s-1 vs. 4.16 µmol m-2 s-1) and, most importantly, NCER/ yield increased by 38% in D vines, thus resulting in en- hanced carbohydrate supply for ripening (Table 1). However, the most intriguing outcome from these ear- ly-season defoliation tests is that a significant increase in relative skin mass has consistently been found in separate field studies conducted on a three-year basis in cv. Barbera (Poni and Bernizzoni, 2010), regardless of absolute berry mass (Fig. 2). It is reasonable to think that such an early Table 1 - Effects of early defoliation on yield components and whole shoot net CO2 exchange rate (NCER)/fresh fruit mass Treatment Flowers/cluster (no.) Fruit set (%) Total berries/ cluster (no.) Cluster weight (g) Berry weight (g) NCER shoot/yield (nmol/s x g) Cluster compactness (rating) Control 435 38.8 169 334 1.98 2.43 6.60 Defoliated 487 21.0 103 207 2.01 3.31 4.25 Significance ns ** ** ** ns ** ** **, ns= significant at P ≤ 0.05 or not significant, respectively. Fig. 2 - Correlation between relative skin and berry mass in 2006, 2007 and 2008 for non defoliated and defoliated Barbera grapevines (from Poni and Bernizzoni, 2010). 154 basal leaf removal, besides favouring berry hardening in the long run, would also impose more favourable microcli- mate conditions for cell division and berry skin deposition, which typically takes place within four to five weeks after flowering. Mescalchin et al. (2008) have shown in Pinot Gris that the earlier the defoliation, the lesser the incidence of skin burning on VSP and pergola-trained varieties due to both more time allowed for cluster cover after treatment and adaptation towards the formation of a thicker skin. Mechanization is feasible by preferably using at pre- flowering (i.e. closed-flower stage) an air pressure blowing machine which can run two passages per row in about 5-7 hr/ha (Intrieri et al., 2008). Best performance is obtained on canopies characterized by vertical and well positioned shoots and on cultivars having mostly erect inflorescences. It has to be kept in mind that early leaf removal is specif- ically recommended in highly productive vineyards which often present heavy, thick bunches very susceptible to rot. Based on the constancy of the results obtained under the above circumstances, this practice is nowadays an interest- ing alternative to traditional methods of crop control such as bunch thinning. Advantages are feasibility of mechaniza- tion, hence cost saving, and different mechanisms by which the crop level on the vine is adjusted. If early leaf removal is chosen, the primary regulation for crop restriction is via a decrease in fruit set with or without a significant reduction in berry size. Therefore, cluster number is unchanged, yet each bunch is smaller and looser. Conversely, hand bunch- thinning, besides being time consuming, drastically lowers bunch number per vine and favours undesirable yield com- pensation mechanisms such as larger berries and heavier clusters (Ough and Nagaoka, 1984; Keller et al., 2005). Anti-transpirant applications A very recent development of the above work inves- tigated whether the precocious, albeit temporary, source limitation sought with early leaf removal can be induced through the non-invasive and easy-to-do application of anti-transpirants (Palliotti et al., 2010). Their use could sort out the inherent limitations of high labour demand for manual work while eliminating the risks of direct damage to the inflorescences linked to the use of a leaf plucker. Re- sults reported for cvs. Sangiovese and Ciliegiolo subjected to pre-bloom treatment of anti-transpirant Vapor Gard® (a.i. di-1-p-menthene at 3% concentration, Intrachem Bio Italia, Grassobbio, BG, Italy) show similar reductions of net photosynthesis (from 30% to 70%) over several weeks after spraying as compared to control vines (Fig. 3). The treated Sangiovese vines showed reduced yield, berry weight, cluster compactness and, on a two-year ba- sis, lower vigour and unchanged vine capacity per year. At harvest, the treated vines showed higher °Brix in all seasons and higher anthocyanin concentration two years out of three. Overall, early-season applications of a film- forming anti-transpirant caused a leaf function limitation strong enough to reduce yield and cluster compactness through smaller final berry size. Over the last decade, climate change along with im- provements in vineyard management and clonal selection have exerted a strong impact on vine yield and grape and wine composition. Among the most important effects, the increase in grape sugar concentration at harvest, is to be considered, which resulted in wines with high alcohol con- Fig. 3 - Seasonal trends of air vapour pressure deficit (VPD) and total photo- synthetic active radiation (PAR) (a), assimilation rate (b), transpira- tion rate (c) and intrinsic water use efficiency (d) recorded on fully expanded, median Sangiovese (top image) and Ciliegiolo (bottom image) leaves sprayed twice with anti-transpirant Vapor Gard® at 3% (T) or left unsprayed (C). Bold arrows indicate the time of ap- plication. Data are means ± se (from Palliotti et al., 2010). 155 tent (Vierra, 2004; Duchêne and Schneider, 2005; God- den and Gishen, 2005). There is a surge of interest from the wine industry in tools suitable to lower wine alcohol content such as the de-alcoholisation process which also agrees with the EU legislative measure No 606/2009. Conversely, it would thus be helpful to find strategies able to reduce grape sugar concentration in the vineyard, thus limiting the need to operate in the winery without detri- mental effects on wine characteristics. In association with traditional management practices which can be used to slow down the accumulation of sugars in the grape ber- ry, interest is growing in late season applications of an- ti-transpirants. In a recent contribution by Palliotti et al. (2011 a), the anti-transpirant Vapor Gard® sprayed about one month before harvest significantly delayed sugar ac- cumulation in Sangiovese, Tocai rosso and Trebbiano Toscano berries which, at harvest, had -1.2 to -2.7 less °Brix than the un-sprayed control according to genotype and crop load. The temporary reduction of photosynthesis, due to the film formed by the anti-transpirant, limited the amount of assimilates translocated into the ripening berry, thus lowering must sugar concentration with a potential effect on wine alcohol content. 3. Cluster thinning The achievement of an adequate balance between growth and fruiting can be obtained by the regulation of crop level through cluster thinning treatments. Despite ad- ditional labour costs, cluster thinning might play an im- portant role in all cases where over cropping occurs (e.g. excess of vigour due to cultivar and rootstock, high soil fertility, low planting density, use of drip fertigation, etc.) and in cases where winter pruning severity has not over- come cropping due to high bud fertility. The negative ef- fects of over cropping include delay in grape maturation, worsening of overall grape quality, increased susceptibil- ity to biotic disease and poor wood maturity (Winkler et al., 1974). Furthermore, different environmental param- eters, particularly air temperature, light intensity, photope- riod and soil water content, together with phyto-hormones and the availability of mineral ions are known to influence bud fertility and fruit-set (Srinivasan and Mullins, 1981). Therefore, it is not always possible to regulate the yield level by solely adjusting bud load, especially in vineyards with low planting density and in years and areas character- ized by unfavourable environmental conditions. However, the results regarding the effects of high yield levels on fruit composition (sugar, acidity, colour, etc.) and wine quality (taste, flavours, colour and potential for ag- ing) are quite contradictory. For example, some authors found an increase in anthocyanin concentration upon clus- ter thinning (Bravdo et al., 1984 a, Reynolds, 1989; Gui- doni et al., 2002), whereas no improvement in anthocy- anin content or wine colour in cluster-thinned vines were found by Bravdo et al. (1984 b) and Ough and Nagaoka (1984). Location, application time and intensity of clus- ter thinning treatment significantly affected the results and can therefore justify, at least in part, the discrepancy of the experimental results in literature. The results of a three-year trial on the effects of three levels of cropping (0%, 20% and 40% cluster thinning treatments) applied just before veraison in Sangiovese, Merlot and Cabernet Sauvignon showed that this manage- ment practice caused a significant reduction of yield only at the 40% severity and in two out of the three seasons studied (Table 2) (Palliotti and Cartechini, 1988). In each cultivar, in 1995 and 1996, yield was linearly correlated with cluster thinning intensity. Cluster thinning treatment at the 40% level caused a reduction of vine yield that ranged from 22% to 47%. The reduction of yield observed was, in general, not proportional to the cluster thinning intensity due to a significant increase of berry and clus- Table 2 - Effects of cluster thinning on yield and cluster characteristics in Sangiovese, Merlot and Cabernet Sauvignon grapevine cultivars Cultivar Thinning Yield (kg/vine) Cluster/vine (n°) Cluster weight (g) Berry weight (g) 1995 1996 1997 1995 1996 1997 1995 1996 1997 1995 1996 1997 Sangiovese 0% 12.4 11.3 10.1 40.6 46.4 39.9 306 245 251 2.30 2.36 2.33 20% 11.8 9.5 10.0 35.1 34.3 32.9 340 271 300 2.47 2.60 2.68 40% 9.5 6.9 9.5 25.2 22.6 24.3 381 308 387 2.70 2.82 3.38 Significance ** *** ns ** *** ** *** *** *** *** *** *** r2 0.76 0.92 --- 0.76 0.94 0.75 0.90 0.89 0.92 0.87 0.94 0.96 Merlot 0% 8.1 8.7 8.7 57.8 64.1 60.5 147 137 149 1.70 1.82 2.03 20% 7.7 8.0 8.2 49.5 52.1 50.5 159 154 160 1.76 1.83 2.12 40% 6.1 6.6 7.9 35.4 38.8 37.5 172 170 212 1.92 1.94 2.53 Significance * *** ns *** *** *** *** *** *** *** * ** r2 0.47 0.87 --- 0.84 0.91 0.83 0.89 0.91 0.84 0.85 0.46 0.73 Cabernet S. 0% 7.2 7.9 6.2 56.1 58.9 51.6 131 135 123 1.35 1.94 1.39 20% 7.4 7.0 6.1 44.2 47.6 42.2 167 146 146 1.60 2.02 1.57 40% 5.6 4.2 6.0 32.2 27.9 30.5 176 154 198 1.70 2.06 1.89 Significance * *** ns *** *** *** *** *** *** ** ** *** r2 0.42 0.84 --- 0.90 0.93 0.92 0.85 0.87 0.84 0.72 0.70 0.84 *,**,***, ns= linear component significant at P ≤ 0.05, 0.01, 0.001, or not significant, respectively. 156 ter weight. At the 20% intensity of cluster thinning, vine self-regulation warranted full yield compensation through significantly increased berry size and cluster weight. In 1997, due to quite favourable environmental conditions for ripening, +156 and +143 degree-days, base 10°C, as compared to 1995 and 1996, respectively, and lower rain- fall during the two months prior to harvest, the impact of the 40% cluster thinning on vine yield was negligible. Total soluble solids, anthocyanins and phenolics in- creased linearly with thinning severity in two out of the three seasons (Tables 3 and 4). Juice pH and titratable acidity (TA) were rather variable, although cluster thin- ning tended to reduce TA and increase pH (Table 3). In 1995 and 1996, improvements in soluble solids content in cluster-thinned vines were consistent with lower yield levels (Table 3) whereas the reduction of titratable acid- ity and the slight increase of juice pH were probably at- tributable to an earlier ripening. Similar results have also been reported by Looney (1981), Bravdo et al. (1984 a) and Reynolds (1989). Table 4 - Effects of cluster thinning on anthocyanins, polyphenols and total nitrogen content at harvest in Sangiovese, Merlot and Cabernet S. grapevine cultivars Cultivar Thinning Anthocyanins (mg/cm2 berry skin) Polyphenols (mg/cm2 berry skin) Total nitrogen (% s.s.) 1995 1996 1997 1995 1996 1997 1996 1997 Sangiovese 0% 0.412 0.453 0.602 1.42 1.95 1.34 0.35 0.56 20% 0.580 0.596 0.652 1.89 2.37 1.84 0.56 0.56 40% 0.610 0.692 0.639 1.94 2.42 1.87 0.49 0.70 Significance *** *** ns ** * ns ns ** r2 0.83 0.96 --- 0.80 0.57 --- --- 0.65 Merlot 0% 0.491 0.487 0.576 1.51 1.63 1.24 0.42 0.49 20% 0.571 0.554 0.641 1.73 2.00 1.46 0.63 0.49 40% 0.824 0.742 0.653 2.10 2.37 1.56 0.49 0.53 Significance *** *** * ** ** ns ns ns r2 0.90 0.91 0.49 0.68 0.77 --- --- --- Cabernet S. 0% 0.652 0.786 0.691 1.80 1.91 2.08 0.38 0.29 20% 0.670 0.772 1.021 2.10 2.60 2.52 0.70 0.42 40% 1.024 0.942 1.073 2.70 2.84 2.55 0.56 0.56 Significance ** * *** *** ** ns ns *** r2 0.78 0.62 0.83 0.81 0.79 --- --- 0.95 *,**,***, ns= linear component significant at P ≤ 0.05, 0.01, 0.001, or not significant, respectively. Table 3 - Effects of cluster thinning on soluble solids, titratable acidity and pH at harvest in Sangiovese, Merlot and Cabernet Sauvignon grapevine cultivars Cultivar Thinning Soluble solids (°Brix) Titratable acidity (g/l) Juice pH 1995 1996 1997 1995 1996 1997 1995 1996 1997 Sangiovese 0% 17.3 17.1 21.4 8.5 8.2 6.3 3.01 3.08 3.26 20% 18.0 18.9 21.8 8.8 7.5 6.1 3.04 3.11 3.22 40% 18.4 21.1 22.0 8.0 7.2 5.9 3.04 3.12 3.21 Significance * *** ns ns ** ns ns ns ns r2 0.54 0.94 --- --- 0.71 --- --- --- --- Merlot 0% 20.6 21.0 21.4 9.7 6.8 6.5 3.13 3.29 3.32 20% 21.4 21.2 22.8 9.5 6.7 6.3 3.15 3.27 3.28 40% 22.6 22.8 22.6 8.8 6.5 6.4 3.18 3.44 3.36 Significance ** ** ns ** ns ns *** ns ns r2 0.79 0.67 --- 0.64 --- --- 0.85 --- --- Cabernet S. 0% 20.2 21.0 21.6 9.7 8.0 7.6 3.05 3.21 3.22 20% 20.0 21.4 22.2 9.5 7.9 7.1 3.09 3.19 3.23 40% 22.0 23.2 22.0 8.8 7.5 7.2 3.13 3.25 3.27 Significance * ** ns * ns ns * ns ns r2 0.55 0.74 --- 0.55 --- --- 0.46 --- --- *,**,***, ns= linear component significant at P ≤ 0.05, 0.01, 0.001, or not significant, respectively. 157 Data pooled from cultivars and years resulted in nega- tive correlations between total soluble solids and yield level, while positive linear relationships were found between an- thocyanins in berry skin and soluble solids in berry juice (Fig. 4). Overall, regulation of yield through cluster thin- ning is strictly dependent on year; the grape composition is generally improved and this assumes particular importance in seasons marked by unfavourable environmental condi- tions or in very productive vineyards due to either high fertility cultivars (i.e. Sangiovese) or soils. The increase of polyphenols and anthocyanin content recorded in both 20% and 40% cluster-thinned vines is of great significance for the production of high quality red wine, especially when targeted to aging. Since manual cluster thinning is a very expensive operation due to large labour requirements, its mechanization is a very needed, yet largely unresolved is- sue. In Grenache and Tempranillo grapevines trained to vertical, shoot-positioned mechanical berry thinning per- formed with a grape harvester was effective to reduce yield while achieving more ripened grapes and wines with higher alcohol and pH values, more intense colour and increased phenolic compounds (Diago et al., 2010 b). 4. Shoot hedging Practices aimed at manipulating vegetative growth dur- ing late-spring and summer, particularly in vigorous vine- yards, can substantially influence yield and grape compo- sition (Intrieri et al., 1983; Kliewer and Bledsoe, 1987; Reynolds and Wardle, 1989). Hedging is a common man- agement practice used to maintain canopy shape, reduce vine vigour, improve the microclimate in the fruiting zone, increase the efficiency of disease treatments and facili- tate harvest and access of machines to the vineyard rows. Compared with other summer management practices used for similar purposes, such as leaf removal and pulling of lateral shoots, hedging is commonly used because it can Fig. 4 - Relationship between yield per vine and total soluble solids (left) and total soluble solids and anthocyanins content in the berry skin at harvest (right). 158 be done completely mechanically and therefore is easy, fast and cheap. The effects of hedging on yield and fruit quality, considering the variables of timing and severity of application, are strictly associated to the ability of the cultivar to develop lateral shoots and their photosynthetic capacity from veraison to harvest (Cartechini et al., 1998). The impact of hedging severity on vine performance is well known; severe hedging, i.e. less than six main leaves retained per shoot, generally reduces grape quality (Kliewer and Bledsoe, 1987; Reynolds and Wardle, 1989; Palliotti, 1992), whereas the time of application is rather controversial because other factors may also influence these effects such as bud load, shoot orientation, training system, environmental conditions, soil characteristics, wa- ter availability, and so on (Intrieri et al., 1983; Reynolds and Wardle, 1989). Vertical shoot positioned (VSP) training systems are normally trimmed when their shoots exceed the wires placed at the top of the canopy. Therefore, the timing is poorly dependent on grower’s decisions and it is instead a function of intrinsic shoot vigour and vine balance. A balanced vineyard would reach the height suitable for trimming around fruit set, whereas an excessively vigor- ous one would get to the same growth stage much earlier, therefore making shoot trimming more likely to be repeat- ed again later in the season. Timing of trimming follows different rules when performed on sprawl canopies (i.e. a single high wire trellis) where an early (pre-flowering) shoot trimming might be made necessary by the need to induce mostly upright shoot growth habits. A two-year trial, aimed at assessing the effect of tim- ing of hedging (one and five weeks after full bloom, AFB) on yield and grape composition in different red and white grapevine cultivars grown on fertile clay soil and trained to a single high wire trellis, showed that hedging at the 9-10th node on primary shoots, carried out one week AFB, mark- edly changed canopy characteristics, yield and grape com- position (Fig. 5 and Tables 5, 6, 7 and 8) (Cartechini et al., 1998). In untrimmed Sangiovese, Cabernet Sauvignon and Verdello vines, leaf area build up progressed rapidly from about 30 to 120 days after bud burst (Fig. 5). The develop- ment of laterals and relative leaf area occurred from 60 to 110 days after bud burst in Sangiovese and from 60 to 140 days after bud burst in Cabernet Sauvignon and Verdello. Fig. 5 - Development of primary and lateral leaves in Sangiovese, Cabernet Sauvignon and Verdello grapevine cultivars hedged one and five weeks after full bloom (AFB) as compared to the untrimmed control (n = 3 ± se). 159 In all the cultivars, from flowering to veraison, the total leaf area increased more than three-fold. At the end of canopy growth, the Sangiovese had less total leaf area than Cab- ernet Sauvignon and Verdello (-1.5 and -2.0 m2/vine, re- spectively) and the laterals represented 18, 32 and 22% of the total leaf area in Sangiovese, Cabernet Sauvignon and Verdello, respectively. Up to the end of canopy growth, San- giovese, Cabernet Sauvignon and Verdello hedging one and five weeks AFB produced about 1.1, 3.9 and 3.5 and 0.9, 3.4 and 3.1 m2 of new leaves per vine, respectively, derived mainly from lateral development. In all cultivars, early-hedging, one week AFB, gener- ally increased the contents of soluble solids, total nitrogen and total polyphenols (Tables 6, 7 and 8) as well as antho- cyanins content in the red cultivars (Table 8). Early-hedg- ing significantly reduced the titratable acidity and juice pH in all the cultivars (Table 6 and 7). Late-hedging, five weeks AFB, instead significantly reduced yield in Sangio- vese and, except for Sauvignon blanc, the soluble solid content was significantly reduced as well as anthocyanins content in both red cultivars. The positive outcomes of the early-hedging were likely dependent upon a cultivar’s ability to develop lat- eral shoots after trimming (Fig. 5). All the cultivars with a good capacity to produce laterals, such as Cabernet Sauvignon, Verdello, Drupeggio and Sauvignon blanc, responded better to early summer pruning as shown by the increased cluster weight and yield and improved con- tents of soluble solids, total polyphenols and nitrogen content. Trimming vines increased lateral growth and Table 5 - Yield and average cluster weight at harvest in vines of different grapevine cultivars hedged one and five weeks after full bloom (AFB) and control (n= 60) Cultivar Yield (kg/vine) Cluster weight (g) Control Hedged 1 week AFB Hedged 5 weeks AFB Control Hedged 1 week AFB Hedged 5 weeks AFB Sangiovese 7.4 b 7.3 b 6.0 a 279.8 b 292.4 b 253.5 a Cabernet S. 6.0 a 7.8 b 5.5 a 122.9 a 143.7 b 110.5 a Verdello 7.0 a 8.2 b 6.9 a 215.6 a 276.6 b 218.7 a Drupeggio 7.4 a 9.1 b 7.2 a 238.7 a 275.7 b 235.4 a Sauvignon b. 4.0 a 5.2 b 3.9 a 106.5 a 129.3 b 103.8 a For each grapevine cultivar, the means followed by different letters are significantly different at P ≤ 0.05. Table 6 - Soluble solids content and titratable acidity at harvest in different grapevine cultivars hedged one and five weeks after full bloom (AFB) and control Cultivar Soluble solids (°Brix) Titratable acidity (g/l) Control Hedged 1 week AFB Hedged 5 weeks AFB Control Hedged 1 week AFB Hedged 5 weeks AFB Sangiovese 23.2 b 23.9 b 21.8 a 6.6 b 6.1 a 6.8 b Cabernet S. 23.4 b 23.7 b 22.9 a 7.1 b 6.6 a 7.3 b Verdello 19.4 b 21.0 c 17.8 a 8.5 b 8.0 a 8.6 b Drupeggio 20.3 b 21.9 c 18.1 a 8.4 b 7.8 a 8.3 b Sauvignon b. 20.5 a 23.1 b 20.4 a 8.8 b 8.2 a 9.0 b For each grapevine cultivar, the means followed by different letters are significantly different at P ≤ 0.05. Table 7 - Juice pH and berry nitrogen content at harvest in vines of different grapevine cultivars hedged one and five weeks after full bloom (AFB) and control Cultivar Juice pH Total nitrogen (% d.w.) Control Hedged 1 week AFB Hedged 5 weeks AFB Control Hedged 1 week AFB Hedged 5 weeks AFB Sangiovese 3.42 b 3.35 a 3.36 a 0.48 a 0.63 b 0.45 a Cabernet S. 3.40 b 3.22 a 3.29 a 0.63 a 0.98 b 0.55 a Verdello 3.06 b 3.00 a 2.99 a 0.42 a 0.59 b 0.41 a Drupeggio 3.08 b 3.03 a 3.04 a 0.44 a 0.68 b 0.38 a Sauvignon b. 3.07 b 3.01 a 3.02 a 0.51 a 0.66 b 0.45 a For each grapevine cultivar, the means followed by different letters are significantly different at P ≤ 0.05. 160 the total final leaf area was always less than that record- ed in control vines (from 15 to 49% less). At harvest, in all the grapevines tested, early-hedging reduced the leaf/ fruit ratio from 33 to 45% in comparison to the control vines and improved the soluble solids content (from 0.3 to 1.6°Brix), whereas late-hedging caused a reduction of both leaf/fruit ratio and soluble solid accumulation in the berries (Fig. 6). The rejuvenation of leaf area in the canopy following early-hedging and their high pho- tosynthetic efficiency from veraison to harvest of the newly formed lateral leaves (Fig. 7) likely reduced the leaf area per gram of fruit required to achieve adequate ripeness. These laterals also translocate assimilates to the subtending clusters very efficiently (Candolfi-Vas- concelos and Koblet, 1990). Negative results found on late-hedged vines, also reported by other authors (Intri- eri et al., 1983; Palliotti, 1992), are probably linked to the fact that lateral shoots compete with the developing grapes for carbohydrates, causing delayed berry growth and sugar accumulation. Early-trimming reduced titratable acidity as compared to control vines due to greater cluster exposure to sunlight Table 8 - Anthocyanins and total polyphenol content at harvest in the berry skin of different grapevine cultivars hedged one and five weeks after full bloom (AFB) and control Cultivar Anthocyanins (mg/cm2 berry skin) Polyphenols (mg/cm2 berry skin) Control Hedged 1 week AFB Hedged 5 weeks AFB Control Hedged 1 week AFB Hedged 5 weeks AFB Sangiovese 0.754 b 0.958 c 0.412 a 1.65 b 2.24 c 1.09 a Cabernet S. 1.095 b 0.998 b 0.773 a 2.07 a 2.96 b 1.90 a Verdello --- --- --- 0.88 a 1.25 b 0.80 a Drupeggio --- --- --- 0.91 a 1.19 b 0.81 a Sauvignon b. --- --- --- 0.82 a 1.12 b 0.75 a For each grapevine cultivar, the means followed by different letters are significantly different at P ≤ 0.05. Fig. 6 - Relationship between must total soluble solids and leaf/fruit ratio at harvest in vines of Sangiovese, Cabernet Sauvignon and Verdello either untrimmed or trimmed one (A) and five (B) weeks after full bloom (AFB). Fig. 7 - Evolution of net photosynthesis of primary and lateral leaves from veraison to leaf fall in Sangiovese, Cabernet Sauvignon and Verdello grapevine cultivars (n = 8 ±se). 161 and a consequent decrease of malic acid content due to respiration activity. In addition, the reduced must pH with early-hedging is probably linked to the reduction of both the malic acid and potassium contents in the must in as- sociation with lower total leaf area. Bledsoe et al. (1988) found a significant positive correlation between these two parameters and juice pH. In all the grapevine cultivars that develop many laterals after hedging, the greater transpiration rate (from +15 to 35%, data not shown) assessed in these leaves, compared with primary ones, particularly in August and September, may aggravate susceptibility to vine water stress especially in hot environments and in particularly dry years. During the first two weeks of November, the laterals on the vines had net photosynthesis values that ranged from 0.7 to 1.6 µmol CO2 m -2 s-1 (Fig. 6), in a period when all the carbo- hydrates fixed are very useful for the reserve accumula- tion, and therefore for increased cold hardiness (Wample and Bary, 1992) and even for budbreak and initial shoot growth the following season. Thus, at the end of the sea- son care must be taken to maintain the integrity of these leaves until total abscission occurs. Early winter pruning, practiced in some viticulture areas, should be avoided. 5. Shoot positioning In VSP canopy trellis systems, shoot positioning is performed to maintain canopy form and shoot separation, to create a uniform distribution of leaves that minimizes cluster shading as well as to optimize canopy light inter- ception and allowing the transit of mechanical equipment between rows. Shoot positioning also exerts a positive effect on disease incidence and severity; usually disease pressure is lessened due to increased air flow and sunlight penetration inside the vine canopy. Another important ef- fect of this canopy management technique is that it has a positive impact on the development of fruitful buds and therefore for the vine yield in the following year. The way shoot positioning is performed depends mainly on the training systems. In a VSP system the process con- sists of directing the shoots growing up between a set of catch wires as they develop. The vertically positioning of shoots can be done manually or using movable wires and done several times during the growing season. Mechanical shoot positioning on VSP trellis systems with specialized equipment has undergone a notable increase in recent years. On Geneva Double Curtain (GDC) training system the shoots are positioned downward and separated out from the permanent cordon in order to reduce the vigour of shoots and attain optimal canopy density. In the GDC trel- lis, shoot positioning is performed on the interior part of the canopy to maintain two distinct canopies avoiding ex- cessive shading in the central part of the canopy. Usually, in most training systems, shoot positioning is performed one or two weeks after bloom, before tendrils have be- come firmly attached. For best results, however, two or three shoot positioning runs during the season are needed. 6. Conclusions Vineyard management should aim to achieve and main- tain high efficiency over time, which is closely dependent on the ability to control the competition both between-and intra-vine. This approach would warrant a fair and fruitful balance between vegetative and productive activity of the vines and the best expression of grape quality (Smart and Robinson, 1991) without costly additional inputs. Since the “perfect” vineyard able to reach and maintain this equilibrium in a natural way during the season is generally utopia, summer pruning often plays a crucial role. In light of the climate change in progress, an important challenge for old and new vineyards will be the match- ing of tradition and innovation. This raises the question of new techniques of canopy management, availability of rootstocks of low-to-moderate vigour, new cultivars bet- ter adapted to higher temperatures and water shortage and more intense mechanization. The latter assumes particular importance especially when the wines produced must be sold in un-bottled form or within large organized distribu- tion (LOD) chains, like supermarkets, hypermarkets and discount markets. Currently, at least in Italy, LOD com- mercialize about 70% of the entire Italian wine production (which corresponds to about 48-50 million hl per year) (ISMEA, 2007), where the binomial “adequate quality”- “moderate selling price” is still dominant. Global warming requires rapid adaptation and poses the crucial question of ripening modulation. In white grape va- rieties, the major challenge is the preservation of organic acids and primary grape flavours; whereas in black-berried cultivars the priority is producing wines with moderate al- cohol content without modifying colour intensity and wine sensory. 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