Rootstock Effects on Primary Bud Necrosis, Bud Fertility, and Carbohydrate Storage in Shiraz
============================================================================================

* Catherine M. Cox
* Ana Carolina Favero
* Peter R. Dry
* Michael G. McCarthy
* Cassandra Collins

## Abstract

Shiraz grapevines (*Vitis vinifera* L.) grafted to three different hybrid (American *Vitis*) rootstocks at two sites were used to evaluate the effect of rootstock on primary bud necrosis (PBN), fruitfulness, and carbohydrate storage. Buds were dissected during winter dormancy and assessed for the number of inflorescence primordia and incidence of primary bud necrosis. Trunks, canes, and roots were sampled at dormancy for carbohydrate concentration. A water deficit treatment was also applied at one of the two locations. Fruitfulness and yield were affected by water deficit. Rootstock type influenced the incidence of primary bud necrosis, fruitfulness, and carbohydrate concentration at both sites.

*   *Vitis vinifera* L.
*   rootstocks
*   water supply
*   fruitfulness
*   primary bud necrosis (PBN)
*   carbohydrate

The use of grapevine rootstocks (American *Vitis*) in phylloxera-free regions of South Australia has increased steadily over the past 30 years, yet rootstock use still accounts for only ~20% of total plantings (Dry 2007). It is well known that rootstocks affect both vegetative growth and yield of the scion variety (Keller et al. 2001, Sommer et al. 2001, Dry 2007). However, at present, comparisons between grafted rootstocks and nongrafted *Vitis vinifera* scions for fruitfulness are limited or often lack a comparison with a nongrafted control. Fruitfulness assessed at dormancy is a measure of the number of inflorescence primordia within a compound bud that have the potential to develop into bunches the following season (Dry 2000). This is distinct from actual fruitfulness, which is a measure of the number of inflorescences per node after budburst (Williams 2000).

Primary bud necrosis (PBN) is a physiological disorder that results in the death of the primary bud within the compound bud during bud initiation (Collins et al. 2006, Collins and Rawnsley 2008). A decrease in bunches per node and a reduction in bunch weight has been shown to occur as the secondary buds, which arise to compensate for the loss of the primary bud, are considered to be less fruitful and smaller in size (Dry and Coombe 1994, Dry 2000). Criteria found to influence both fruitfulness and PBN relevant here include excessive shoot growth (Lavee et al. 1981, Dry and Coombe 1994) and canopy shading (May 1965, Perez and Kliewer 1990, Wolf and Cook 1992). The effects of rootstock type on fruitfulness and PBN are not well understood and results are often contradictory. According to one study, there was no influence of rootstock on the incidence of PBN (Dry et al. 2003), whereas another study observed significant differences in the incidence of PBN due to rootstock for the cultivars Shiraz and Cabernet Sauvignon (Collins and Rawnsley 2004). Therefore, it remains unclear whether rootstock has an effect on the incidence of PBN.

Cultivars and viticultural practices are known to influence PBN (Dry and Coombe 1994). The cultivar Shiraz is reported to have one of the highest incidences of PBN in Australian vineyards (Dry 2000, Dry and Coombe 1994, Dry et al. 2003). A survey of the incidence of PBN in Australian vineyards found that deficit irrigation may also influence the incidence of PBN (Collins and Rawnsley 2004). However, literature on the effect of deficit irrigation on fruitfulness is varied. Water deficit has been shown to reduce fruitfulness (Buttrose 1969, Williams et al. 2010), whereas a mild water deficit has been shown to promote fruitfulness through reduction in vine vigor and improved canopy microclimate (Collins and Rawnsley 2005, Keller 2010).

Carbohydrates are supplied to developing shoots and leaves of grapevines during budburst through the remobilization of carbohydrates from the perennial parts of the vine prior to and during anthesis (Lebon et al. 2004, 2008, Bates et al. 2002, Bennett et al. 2005). The development of reproductive organs and vegetative growth in grapevines occur simultaneously, and competitive requirements for carbohydrate reserves may exist between the vegetative and reproductive structures under stress (Nuzzo and Matthews 2006). The perennial parts of the vine, such as roots and trunk, are the major storage organs for carbohydrates with maximum concentrations of starch reached at leaf fall (postharvest) within the perennial organs (Bates et al. 2002). This postharvest period is important and recognized as the carbohydrate replenishment or recovery period (Bates et al. 2002). Typically, values of carbohydrate reserves in the trunk range from 2.5 to 11.4% dry weight, with variation dependant on climate and variety (Bennett et al. 2005). Carbohydrate reserves of less than 2% dry weight in the roots have been shown to reduce cane weight, fruitfulness, and yield (Bennett et al. 2005). Trunk and cordon volume as influenced by rootstock may affect the potential of the vine to overwinter carbohydrates for early season growth (Koblet et al. 1994). A reduction in truck starch concentration for deficit-irrigated relative to well-watered grapevines at budburst, veraison, and postharvest has also been observed (Edwards et al. 2011). Moreover, postharvest water deficits that result in early defoliation can reduce carbohydrate replenishment in the perennial parts of the vine (Bennett et al. 2005, Candolfi-Vasconcelos et al. 1994). Significant stress periods can affect carbohydrate accumulation differently for both scions and rootstocks. Riesling and Müller-Thurgau grapevines were observed to increase carbohydrate accumulation in the roots under stress, yet this accumulation decreased for rootstock 5BB Kober due to a restriction of carbohydrate concentration through reduced shoot growth (Rühl and Alleweldt 1990).

A comparative investigation was undertaken in Shiraz to examine the effects of rootstock cultivar on fruitfulness, PBN, and carbohydrate accumulation at two sites in South Australia. A water-stress treatment was also applied at one of the sites to examine the relationship between rootstocks and water deficit. In addition, the inclusion of a *Vitis vinifera* control enabled further examination of the differences in fruitfulness, incidence of PBN, and carbohydrate accumulation between grafted and nongrafted vines.

## Materials and Methods

### Experimental sites.

The study was conducted in two vineyards located in South Australia, Australia: one vineyard at the Waite Agricultural Research Institute in Adelaide (34°97′S, 138°63′E) and the second at Nuriootpa in the Barossa Valley (34°48′S, 139°01′E). The Adelaide vineyard was planted in 1993 at 1133 vines per hectare and trained to a bilateral vertical shoot-positioned canopy. Vines were spaced 2.8 m apart and rows 3.15 m. The Nuriootpa vineyard was planted in 2001 at 1481 vines per hectare and trained to a bilateral cordon. Vines were spaced 2.25 m apart and rows 3.0 m. Both vineyards were drip-irrigated, with scheduling based on soil moisture probes. In the 2009–2010 season, the Adelaide and Nuriootpa vineyards received 150 mm and 50 mm of irrigation, respectively. Class A pan evaporation rates at Adelaide for the 2009–2010 growing season were 1335 mm with a growing season rainfall (September 2009 to May 2010) of 281 mm. At Nuriootpa, the corresponding Class A pan evaporation was 1336 mm and the growing season rainfall totaled 386 mm ([http://www.bom.gov.au/climate/data/](http://www.bom.gov.au/climate/data/)).

### Experimental design.

Four treatments were applied at both vineyards in a single season: an own-rooted Shiraz (Shiraz OR) control and a Shiraz (BVRC12 clone at Adelaide and BVRC30 clone at Nuriootpa) scion grafted to three rootstocks: Ramsey (*Vitis champinii*), Schwarzmann (*Vitis riparia* x *Vitis rupestris*), and 140 Ruggeri (*Vitis berlandieri* x *Vitis rupestris*). A completely randomized design of four rootstock treatments with six replicates was used in the Adelaide vineyard. The Nuriootpa vineyard had the same four rootstock treatments (whole plots) plus the addition of an irrigated and unirrigated treatment for each rootstock (subplots), each with three replicate blocks consisting of nine vines (split-plot design). The unirrigated treatment was established in August 2008 before the start of the 2008–2009 growing season. Treatments undergoing zero irrigation had their drip-irrigation lines bypassed using polyethylene piping. Vines 1 and 9 in the unirrigated plots were used as buffer vines, and adjacent panels in rows on either side also had their irrigation bypassed to act as buffer rows.

### Experimental protocol.

During July 2010 at winter dormancy the vines were spur-pruned to approximately 40 nodes/vine as two-bud spurs in both vineyards. At this stage, cane number and pruning weights were recorded per meter of canopy. Twenty canes from each plot were also collected at this time to assess bud fertility. Compound buds at node positions 1 to 4 on each cane were dissected and scored for the number of inflorescence primordia (IP) and the presence of PBN using a binocular microscope (model MS5; Leica, Heerbrugg, Switzerland) at 10 to 40× magnification. The number of IP per compound bud was recorded in the primary (N+2) bud; however, if the primary bud was necrotic, then the largest secondary (N+3) bud was scored. An average of the number of IP in nodes 1 to 4 was determined to give an indication of the potential fruitfulness per node. PBN incidence was expressed as a percentage. Actual fruitfulness per node was determined after budburst when inflorescences were visible on shoots. The number of inflorescences per vine were counted and divided by the number of buds retained at pruning time to give a mean number of inflorescences per node. Due to high disease pressure in the Adelaide vineyard in 2011, yield, bunch weight, and bunch number (per meter of canopy) were only recorded for the Nuriootpa vineyard.

For carbohydrate analysis, wood samples from canes, trunks, and roots were taken in June 2010, after leaf fall. The trunk samples were collected as wood drillings using a 5-mm drill bit. For each vine, holes were drilled at four positions along the vine trunk, two holes above the graft union, and two holes below the graft union. Samples from the vine were collated to ensure sufficient samples and to capture any variation within the vine. Root samples (5-mm diam) were collected at 10 cm from the trunk of each vine. Cane samples were collected from five dormant canes at pruning. Samples were taken between node positions 1 and 4 from each vine for analysis. All samples were kept on dry ice until storage in a freezer (−80°C). All samples were then freeze-dried (Alpha 2–4 LSC; John Morris Scientific, Adelaide, Australia) and ground in an electrical grinder (model LM1-P; Labtech Essa, Bassendean, Australia).

### Carbohydrate analysis.

Carbohydrate analysis was performed using a published method (Edwards et al. 2011). Briefly, soluble sugars were extracted from a 5 mg subsample of each tissue using an 80% aqueous ethanol wash. Concentrations of starch and fructose were determined with commercial enzyme assays (Megazyme International, Bray, Ireland). For the determination of starch, an α-amylase solution was used with a sodium acetate buffer and GOPOD reagent and measured in a spectrophotometer (Multiskan Spectrum, model 00300011; Thermo Electron Corporation, Vantaa, Finland) at 505 nm. The concentration of total starch was determined using a glucose standard curve.

### Predawn leaf water potentials.

Predawn leaf water potential measurements commenced at the start of the first irrigation in 2010 and were taken at Nuriootpa to coincide with both irrigation schedule and key phenological events during the season: fruit set, veraison, and harvest. However, only harvest predawn leaf water potentials are discussed here. Five vines per replicate were sampled and assessed for leaf water potential. Three leaves from each vine were excised using a single-edge razor blade through the petiole. Water potential was measured using a 3000 series leaf pressure chamber (Soil Moisture Equipment, Santa Barbara, CA).

### Statistical analysis.

Statistical analysis of data was performed using GenStat statistical package (11th ed., VSN, Hemel Hampstead, UK). The Adelaide data set was analyzed using a one-way analysis of variance (ANOVA). To account for rootstock and irrigation treatments, a split-plot analysis was performed on the Nuriootpa data.

## Results

### Treatment effects on fruitfulness and yield.

Potential fruitfulness per node was significantly affected by rootstock at the two sites, where Shiraz OR and 140 Ruggeri had the highest potential fruitfulness while Ramsey had the lowest. Higher potential fruitfulness was observed in the unirrigated treatments than the irrigated treatments. Actual fruitfulness was significantly higher in 140 Ruggeri and Shiraz OR at Nuriootpa than in Schwarzmann and Ramsey. No significant differences in actual fruitfulness were found among the rootstocks at Adelaide or between irrigation treatments (Table 1, Table 2).

View this table:
[Table 1](http://www.ajevonline.org/content/63/2/277/T1)

**Table 1** 
Vegetative components for rootstock and irrigation treatments for the combined 2009–2010 and 2010–2011 growing seasons at Nuriootpa, South Australia.

View this table:
[Table 2](http://www.ajevonline.org/content/63/2/277/T2)

**Table 2** 
Vegetative and reproductive components for rootstock treatments for the 2010–2011 growing season at Adelaide, South Australia.

The incidence of PBN was significantly affected by rootstock at Adelaide: 140 Ruggeri and Ramsey had significantly higher levels of PBN than Shiraz OR and Schwarzmann (Table 2). No treatment effect was observed at Nuriootpa (Table 3).

View this table:
[Table 3](http://www.ajevonline.org/content/63/2/277/T3)

**Table 3** 
Reproductive components for rootstock and irrigation treatments for the 2010–2011 growing season at Nuriootpa, South Australia.

Yield, bunch number, and bunch weight were measured only at Nuriootpa, and significant differences were observed among rootstocks and between irrigation treatments. 140 Ruggeri and Ramsey had significantly higher yield than either Shiraz OR or Schwarzmann. 140 Ruggeri also had significantly higher bunch numbers than Shiraz OR and Schwarzmann. Schwarzmann had significantly lower bunch weights and yield than all other treatments. Higher bunch number and bunch weight per meter of canopy were observed in the irrigated treatments compared to the unirrigated treatments, which corresponded to higher yield (Table 3).

### Treatment effects on carbohydrates.

Starch concentration in the roots and the trunks was significantly affected by rootstock at the two sites. The highest concentrations of starch (% dry weight) were found in the roots, followed by the trunk and the cane. Ramsey had the lowest concentration of starch in the roots and trunks of all treatments and sites analyzed. At Adelaide and Nuriootpa, 140 Ruggeri had the highest starch concentration in the roots. No significant differences in the ability of the vine to store carbohydrates in the roots and trunks were observed as a result of deficit irrigation. No significant changes in cane starch concentration were observed at both sites for all treatments (Figure 1).

![Figure 1](http://www.ajevonline.org/https://www.ajevonline.org/content/ajev/63/2/277/F1.medium.gif)

[Figure 1](http://www.ajevonline.org/content/63/2/277/F1)

**Figure 1** 
Total starch (% DW) of canes, trunk, and roots of Shiraz scions BVRC12 at Adelaide (**A**, **B**, **C**) and BVRC30 at Nuriootpa (**D**, **E**, **F**) on rootstocks Ramsey, Schwarzmann, 140 Ruggeri, and Shiraz OR, 2010. Numbers within a column followed by the same letter are not different at *p* < 0.05. Error bars represent standard error of the mean (n = 12).

### Treatment effects on vegetative growth.

The components of vegetative growth, pruning weight, cane weight, and cane number were significantly affected by rootstock in 2010 (Table 1, Table 2). Pruning weight and cane weight was highest in Shiraz OR and lowest in Ramsey at Nuriootpa. At Adelaide, Shiraz OR had a significantly higher pruning weight than Schwarzmann. Irrigation treatment had no significant effect on pruning weight or cane weight and there was only a small difference in cane number.

### Yield to pruning weight ratio.

Yield to pruning weight ratio differed significantly among the rootstocks in 2010. Ramsey had a significantly higher yield to pruning weight ratio than 140 Ruggeri. Yield to pruning weight ratio was lowest in Shiraz followed by Schwarzmann (Figure 2). A higher ratio was observed in the irrigated treatment compared to the unirrigated.

![Figure 2](http://www.ajevonline.org/https://www.ajevonline.org/content/ajev/63/2/277/F2.medium.gif)

[Figure 2](http://www.ajevonline.org/content/63/2/277/F2)

**Figure 2** 
Yield to pruning weight ratio (kg/m canopy) of treatments at Nuriootpa, 2010–2011 growing season. Numbers within a column followed by the same letter are not different at *p* < 0.05. Statistical significance of the effects of irrigation at Nuriootpa (rootstocks) are given by *p* < 0.05 (*). Error bars represent standard error of the mean.

## Discussion

This study has confirmed that grapevine rootstock cultivar can influence PBN, fruitfulness, and carbohydrate storage in Shiraz. It is one of the few studies where bud fertility components and carbohydrates have been assessed for rootstocks relative to an ungrafted (*Vitis vinifera*) control.

Shiraz has been shown to be susceptible to PBN (Dry and Coombe 1994), supported by findings at both sites with PBN levels >20% for all treatments. At Adelaide the incidence of PBN was further affected by rootstock. For example, the incidence of PBN was 17% higher in Ramsey, 42% higher in 140 Ruggeri, and 34% lower in Schwarzmann relative to Shiraz OR. Increased vigor associated with high shoot growth and shoot weight is known to influence PBN (Lavee et al. 1981, Dry and Coombe 1994). Previous studies have found more necrotic buds on vigorous shoots than on weak shoots (Lavee et al. 1981). Although shoot length was not measured in the present study, an indication of vegetative growth can be deduced at pruning time through the measurement of pruning weight (Smart and Robinson 1991). No relationship between the incidence of PBN and pruning weight was observed at Adelaide, even though there were significant differences among treatments in other parameters measured. At Nuriootpa, no significant differences in the incidence of PBN were observed even though there were pruning and cane weight differences among treatments. High levels of PBN for all treatments were observed at Nuriootpa in the 2010–2011 season, which may be attributed to the climatic conditions during bud development in 2009 when maximum temperatures ranged from 34 to 42°C ([http://www.bom.gov.au/climate/data/](http://www.bom.gov.au/climate/data/)). Temperatures above 32°C have previously been shown to interrupt reproductive development of young floral buds in pea (*Pisium sativium*) followed by abscission several days after the cessation of the temperature stress (Guilione et al. 1997). Dry and Coombe (1994) observed that a higher incidence of PBN was associated with lower bud fertility (i.e., bunches per shoot, bunch weight, and fruit weight per node) due to the loss of the primary bud. At Adelaide, significant differences in PBN among treatments were observed, but as actual fruitfulness (measured as inflorescences per node) was not significantly different among treatments, a significant relationship between PBN and actual fruitfulness was not found at *p* < 0.05. While it was apparent there was an inverse relationship (R2 = 0.442) (Figure 3) between actual fruitfulness and PBN in the treatments at Adelaide, no such relationship among PBN, bunch number, and bunch weight was found at Nuriootpa, as PBN did not significantly differ among treatments. Therefore, to confirm a relationship between PBN and bud fertility, further studies are required.

![Figure 3](http://www.ajevonline.org/https://www.ajevonline.org/content/ajev/63/2/277/F3.medium.gif)

[Figure 3](http://www.ajevonline.org/content/63/2/277/F3)

**Figure 3** 
Inverse relationship for actual fruitfulness and % PBN of treatments at Adelaide, 2010–2011 growing season.

Rootstock cultivar significantly affected fruitfulness at Nuriootpa: rootstocks with a higher potential fruitfulness per node measured in winter had a higher actual fruitfulness per node in the following spring. This suggests potential fruitfulness measured at dormancy is a good indicator of potential inflorescence number in the following spring. Actual fruitfulness was also indicative of yield. Both bunch number and bunch weight contributed to yield differences between treatments. Lower bunch number per cane has previously been observed for Sultana grafted to Ramsey than for Sultana on own roots. However, a high bunch weight for Ramsey resulted in a higher harvestable yield than that for the own roots (Sommer et al. 2001). In this study, Ramsey had a higher yield than own roots due to higher bunch weight. *V. berlandieri* x *V.riparia* crosses (140 Ruggeri) have been shown to increase reproductive growth and yield (Keller et al. 2001). In this study, 140 Ruggeri had higher bunch numbers than Shiraz OR and Schwarzmann, which resulted in a higher harvested yield. Schwarzmann has previously been reported as a rootstock of low to moderate yield under Australian conditions (Dry 2007). In the present study, yield was significantly lower for Schwarzmann than the other treatments due to lower bunch number and bunch weight.

Yield to pruning weight ratio was significantly different between irrigated and unirrigated vines even though there were no differences in vegetative growth. Yield was reduced from water shortage more than vegetative growth due to a reduction in bunch number, bunch weight, and lower berry weights. The majority of vegetative growth occurs from budburst until flowering, also termed the “grand” period of growth (Smart and Robinson 1991). Predawn leaf water potentials measured at berries pea-sized in December 2010 were −0.23 MPa for the irrigated treatments and −0.26 MPa for the unirrigated treatments, suggesting that water was not a limiting factor for initial vegetative growth. Given the high soil water-holding capacity at Nuriootpa (sandy loam A horizon overlying a red brown earth B horizon) along with a winter (June–August) rainfall of 221 mm ([http://www.bom.gov.au/climate/data/](http://www.bom.gov.au/climate/data/)), it may be concluded that water stress in the vines did not occur until after this period. A similar result was found when a 35% reduction in irrigation was applied to Chardonnay grapevines (Stevens et al. 2008). Yield was significantly affected under deficit irrigation, due to lower berry weights, yet pruning weights and cane numbers were not. Furthermore, predawn leaf water potentials measured at harvest in the present study were −0.34 MPa for the irrigated treatments and −0.43 MPa for the unirrigated treatments, suggesting that unirrigated vines were more water stressed than the irrigated vines and may have led to lower berry weights and hence lower yield.

A review article found that mild water deficits may promote potential fruitfulness through improved canopy microclimate (Keller 2010). Given that bud initiation occurred in 2009 when deficit irrigation reduced vegetative growth, as assessed through pruning weights (Table 1), it is likely that this effect may have improved light interception on the developing buds. In the present study, the higher potential fruitfulness was not realized at harvest because of a lower actual fruitfulness and bunch number in the unirrigated vines than in the irrigated vines, suggesting that inflorescence and/or bunch necrosis occurred postbudbreak, thereby reducing final yield. In previous studies it has been proposed that water stress may trigger a vine to sacrifice bunches in a similar manner as basal leaf loss (Hardie and Considine 1976, Keller and Koblet 1994, Keller et al. 2001).

Rootstock type significantly affected the ability to store carbohydrates. In general, highest concentrations of starch (% dry weight) were found in the roots, followed by the trunk and the cane at both sites. Vrsic et al. (2009) also reported a higher concentration of carbohydrates in the roots than in the trunk and the cane. The degree to which a vine is able to store carbohydrates has been directly attributed to a combination of vegetative growth and yield (Candolfi-Vasconcelos and Koblet 1990, Bennett et al. 2005). Rootstocks with the greater vegetative growth (measured by pruning weight, cane number, and cane weight)—such as 140 Ruggeri, Shiraz OR, and Schwarzmann—had highest concentrations of starch in the roots at both Adelaide and Nuriootpa. Ramsey had a reduced capacity to accumulate carbohydrates at both sites. Previous authors have reported a negative effect on the ability to accumulate carbohydrates when yield is high (Holzapfel and Smith 2007). A combination of low vegetative growth (pruning weight, cane number, and cane weight) coupled with high yield (bunch number and bunch weight) may have affected the ability of Ramsey to accumulate carbohydrates.

No significant differences in the ability of the vine to store carbohydrates in the roots, trunks, or canes were observed as a result of deficit irrigation. Total carbohydrates have been found to decrease under deficit irrigation due to a reduction in shoot growth (Edwards et al. 2011). However, in the present study there was no significant effect on both shoot number and pruning weight. Rootstock cultivar rather than irrigation treatment had the greatest impact on carbohydrate concentration.

## Conclusion

Results demonstrate that bud fertility and carbohydrate concentration can be affected as a result of grafting to American *Vitis* rootstocks. This work also highlights the value of bud fertility measurements for yield prediction and pruning decision-making. This work demonstrated an effect of water deficit on bud fertility measures and yield. As a consequence, effective water management strategies are needed to ensure that a deficit does not negatively impact on yield through a reduction in bunch number and bunch weight.

Carbohydrate concentration was affected by rootstock cultivar and correlated with vine growth. Yield to pruning weight ratios should be considered in determining vine balance between vegetative and reproductive growth, as an imbalance in favor of reproductive growth was at the expense of carbohydrate accumulation. Given the lack of significant effect of water deficit on vegetative growth in 2010, the present study failed to find a response in carbohydrate accumulation for the water-deficit treatments. Overall, an effect of rootstock on carbohydrate accumulation was identified at the sites, and it was apparent that some rootstocks may be advantageous for carbohydrate accumulation compared with own-rooted Shiraz.

## Acknowledgments

Acknowledgments: This research was funded by The Phylloxera and Grape Industry Board of South Australia.

The authors thank Coordenação de Aperfeiçoamento de Pessoal de Nível Superior for the scholarship granted to A.C. Favero; the Barossa Viticulture Technical Group, Barossa Grape Growers Vine Selection Society and Elders, for funding through the Barossa Young Viticulturist Fellowship awarded to C. Cox; and Everard Edwards at CSIRO for assistance with carbohydrate methodology and calculations.

*   Received February 2011.
*   Revision received July 2011.
*   Revision received November 2011.
*   Accepted February 2012.


*   ©2012 by the American Society for Enology and Viticulture

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