Impact of rootstock on yield and ion concentrations in petioles,juice and wine of Shiraz and Chardonnay in different viticultural environments with different irrigation water salinity

Background and Aims: Within-site comparisons were made of rootstock effects on yield, and chloride and sodium concentrations in petioles, juice and wine of Shiraz and Chardonnay vines at sites with irrigation water salinities (EC_iw) ranging from low (0.4 dS/m) to moderate-high (1.8 to 3.3 dS/m). It also compared consistency of yield performance of the various rootstocks with both scions over 8 years at one site with an EC_iw of 2.1 dS/m. Methods and Results: Chardonnay and Shiraz on own roots and on Ramsey, 1103 Paulsen, 140 Ruggeri, K51-40, Schwarzmann, 101-14, Rupestris St. George and 1202 Couderc were compared. Ramsey resulted in better yields relative to most of the other rootstocks at three of the four sites for each scion. Exceptions were the low salinity site where Schwarzmann was best with Chardonnay, and Padthaway where 140 Ruggeri was best with Shiraz. Chardonnay wine chloride concentrations were similar to grape juice chloride concentrations, but Shiraz wine chloride concentrations were on average 1.7-fold higher than grape juice chloride. Conclusions: Shiraz on own roots, K51-40 and 1202C rootstocks carry some risk of accumulating unacceptable levels of chloride in grape juice and wine when the salinity of the irrigation water is at moderate to high levels. Rootstocks K51-40 (with Chardonnay and Shiraz) and potentially 101-14 (with Shiraz) should be avoided in situations of long term irrigation with moderate to high salinity water. Significance of the Study: The study identifies rootstocks with acceptable yields and grape juice chloride concentrations for potential use in regions affected by salinity.     

Profiles of free amino acids in grapes of grafted Chardonnay grapevines

Chardonnay grapes from a rootstock trial in the Murray Valley region of South Australia were sampled for two seasons and concentrations of free amino acids in grape extract ('juice') were determined. The lowest concentrations of free assimilable amino-N were measured in Chardonnay grapes from vines on 140 Ruggeri and 101–14 rootstocks, and the highest concentrations were in grapes from vines on their own roots, Schwarzmann and K51–40. Free assimilable amino-N concentrations were sufficient to sustain fermentation through to completion. Arginine concentrations were generally too low to expect significant concentrations of urea in the wine. Amino-S concentrations were much lower and varied less than amino-N concentrations. The effect of any particular rootstock on the concentration of total free amino acids in Chardonnay grape 'juice' did not appear to be related to the known effects of those rootstocks on the NO₃-N status of petioles at flowering. The concentrations of leucine, iso-leucine, valine, threonine, tyrosine and phenylalanine were generally higher in Chardonnay grapes grafted onto K51–40 in comparison to grapes from Chardonnay vines grafted on the other rootstocks. Any of these amino acids may be associated with the presence of specific higher alcohols in wine.     

An assessment of rootstocks for Sunmuscat (Vitis vinifera L.): a new drying variety

Sunmuscat scions, either grafted onto one of seven rootstock, or as own-rooted vines, were grown under irrigation according to the practices of warm-climate viticulture in north-western Victoria. The trial was located within a commercial vineyard on a sandy loam soil, and represented a typical replant situation. Grapevine performance was assessed over five seasons, viz. 1999–2004 inclusive, in terms of yield per vine, berry weight, juice composition and vigour (based on trunk girth). The highest yielding rootstock over the trial period was 1103 Paulsen (28.9 kg /vine) followed by 140 Ruggeri and Ramsey (26.1 and 25.8 kg /vine respectively), S04 (22.5 kg /vine), Schwarzmann, 101-14 and Teleki 5A (19.9, 18.7 and 18.4 kg /vine respectively). Scions on their own roots returned lowest yield (15.5 kg /vine). Berry weights were largest for the three high yielding rootstocks (2.3 g) and smallest with own roots (2.0 g). Total soluble sugars in harvested fruit were largely unaffected by rootstock in most seasons, although taken over all seasons, fruit from scions grafted onto Ramsey rootstock had the lowest levels, while Teleki 5A had the highest levels (viz. 23.4^oBrix and 24.7^oBrix respectively). Comparative vigour for all seven graft combinations was inferred from trunk circumference. There was a 2-fold difference in rootstock girth below the graft union (viz. 265 mm for 1103 Paulsen, compared to 135 mm for S04), whereas differences in the scion girth above the graft union were minor (only 16%). Relative compatibility of scion and stock was inferred from 'girth ratio' of trunk circumference above compared with below the graft union. Girth ratio was highest for Sunmuscat scions grafted onto SO4 rootstock, and lowest for scions on 1103 Paulsen. Scion girth and vine yield were broadly correlated.     

Reproductive growth of grapevines in response to nitrogen supply and rootstock

Nitrogen fertiliser was applied at two rates (0 or 100 kg N/ha) to field-grown Müller-Thurgau grapevines grafted onto six rootstocks (Kober 5BB, Teleki 5C, Teleki 8B, Selection Oppenheim 4, Couderc 3309, Ruggeri 140). Half the nitrogen was applied four weeks pre-flowering and half at the end of flowering. Nitrogen supply reduced symptoms of inflorescence necrosis and improved fruit set, but increased bunch-stem necrosis, Botrytis cinerea bunch rot and yield. This was associated with reduced grape sugar, higher acidity and lower pH. Rootstocks had no significant effect on inflorescence necrosis, bunch-stem necrosis and bunch rot, but vines grafted on C-3309 and Ru-140 had both lowest yields and highest fruit quality. Nitrogen × rootstock interactions were rare and contributed little to total variance, suggesting that rootstock-induced differences in scion performance were, except for SO4, largely independent of soil nitrogen level.     

Reduced irrigation and rootstock effects on vegetative growth,yield and its components,and leaf physiological responses of Shiraz

Background and Aims: The study investigated whether rootstocks can modify grapevine responses to reduced irrigation. Methods and Results: Drip-irrigated Shiraz vines on eight rootstocks were subjected to industry standard and 30% reduced irrigation regimes over four seasons. Reducing irrigation decreased pruning weights and yield, but did not consistently affect irrigation water use index (IWUI). It increased leaf Δ¹³C. Reduced irrigation and elevated vapour pressure deficit (VPD) were associated with decreases in leaf water potential (ψ_l), leaf stomatal conductance and assimilation rate. Reducing irrigation raised leaf transpiration efficiency, whereas elevated VPD lowered it. These effects of reduced irrigation were independent of rootstock. Vines grafted to 101-14 had a higher ψ_l and achieved the highest yield and IWUI. The yields of vines grafted to Ramsey, Schwarzmann and 140 Ruggeri were also high. Vines grafted to 101-14, Ramsey and 1103 Paulsen had the higher rates of leaf assimilation. Rootstock did not affect Δ¹³C. Conclusion: The gain in leaf transpiration efficiency caused by reducing irrigation was not associated with a gain in IWUI. Rootstocks 101-14, Ramsey, Schwarzmann and 140 Ruggeri achieved higher yields and IWUI under both standard and reduced irrigation regimes. Significance of the Study: Among grafted vines growing on saline soil but receiving non-saline irrigation water and subject to a 30% reduction in irrigation, the yield responses of vines grafted on rootstocks rated as having good drought tolerance were the same as those of vines grafted on rootstocks rated as having poor drought tolerance.     

Soil nitrogen utilisation for growth and gas exchange by grapevines in response to nitrogen supply and rootstock

This study investigated the response to nitrogen (0 or 100 kg N/ha) of field-grown Müller-Thurgau grapevines grafted on six rootstocks (Kober 5BB, Teleki 5C, Teleki 8B, Selection Oppenheim 4, Couderc 3309, Ruggeri 140). Half the nitrogen was applied four weeks pre-flowering and half at the end of flowering. Glutamine accounted for over 85% of xylem nitrogen, indicating that most soil nitrogen was assimilated by way of vine root metabolism. Nitrogen supply increased the translocation of glutamine, glutamate, NO₃^-_-, NH₄+, K+, Ca²⁺, Mg²⁺and PO₄^3–in the xylem sap and decreased the ratio of organic to inorganic nitrogen. V. berlandieri × V. riparia crosses generally resulted in higher xylem solute concentrations compared with other rootstocks, but were less effective in total nitrogen assimilation. High soil nitrogen increased vine leaf area by stimulating lateral-shoot growth, increased leaf chlorophyll, photosynthesis, transpiration and stomatal conductance, and delayed leaf senescence. There was no difference among rootstocks in scion leaf area, but rootstocks affected scion response to soil nitrogen level in terms of leaf chlorophyll content and leaf gas exchange; SO4 induced the strongest reaction to soil N, whereas Ru-140 elicited the least reaction. Chlorophyll content was highest for vines grafted on 5BB and lowest for C-3309. Photosynthesis response to both nitrogen and rootstock was regulated at the mesophyll level. There were few interactions between nitrogen and rootstocks, and their contribution to total variance was small relative to main effects. Thus, with the exception of SO4, differences due to rootstocks were mostly unaffected by soil nitrogen level.     

Rootstock response of Shiraz (Vitis vinifera) grapevines to dry and drip-irrigated conditions

The yield and growth of Vitis vinifera cv. Shiraz scions grafted onto seven rootstocks were compared with that of own-rooted vines in a shallow sandy soil that was free of nematodes and phylloxera in the Barossa Valley of South Australia. In the absence of irrigation, own-rooted vines yielded as much fruit as vines grafted on Ramsey, the highest-yielding unirrigated rootstock-scion combination. Scions grafted to the rootstocks 110R, K51–40, 1103P and Freedom yielded poorly without irrigation. The yield and growth of all vines increased significantly when a small volume of irrigation water (40–160 mm/annum) was applied; however, only scions grafted to Ramsey and Freedom rootstock yielded more fruit than own-rooted vines.     

Carbon and nitrogen partitioning in either fruiting or non-fruiting grapevines: effects of nitrogen limitation before and after veraison

Fruit effects on carbon (C) balance between reproductive and vegetative growth, and between shoots and roots, were studied under low versus high nitrogen (N) availability before and after veraison. Fruiting vines were compared with non-fruiting vines, and N was supplied at either a low or high rate, and either continuously or as a split application before and after veraison. In non-fruiting grapevines, leaf growth was greatly affected by N supply, but root growth was little affected. Low N supply before veraison favoured berry development, whereas after veraison enlarging fruits were disadvantaged by low N supply. Fruit growth was highly competitive with root growth, particularly before veraison, when N supply was low. Whole plant C and N accumulation rates were lower in fruiting plants. Berry amino acid content was influenced by all combinations of N treatments. Overall, fruit development was favoured by ensuring a low N supply rate before veraison, but this occurred at the expense of root growth as well as C and N uptake by the grapevines. After veraison, fruit can express a high sink strength if N is made available, probably because photosynthetic activity increases. These results provide new insights into how N may be managed in order to control grapevine C partitioning, to encourage berry development, and to sustain overall C and N uptake by grapevines.     

Effects of the rootstock Ramsey (Vitis champini) on ion and organic acid composition of grapes and wine, and on wine spectral characteristics

The influence of Ramsey, used as rootstock of the scion cvs Muscat Gordo Blanco (syn. Muscat of Alexandria), Shiraz (syn. Syrah), Riesling, Cabernet Sauvignon and Chardonnay, on the characteristics of the grape berries and of wine made from them was investigated, comparing ‘own-rooted’ and ‘grafted’, and comparing wine fermented as juice (without skins) and must (juice and skins). The study involved the partitioning of K+ within berries, changes in juice K+, malic and tartaric acid through fermentation, wine inorganic ion and organic acid composition, and wine spectral characteristics. K+ concentration was higher in berries from grafted than from own-rooted for all varieties except Chardonnay, and highest for grafted Shiraz. It was higher in skin than in pulp and seeds. In the pulp, it was highest for grafted Shiraz. K+ concentrations in all ferments using must (i.e. juice plus skins) increased during the initial two days after crushing, with the increase reflecting extraction from skins, being greatest for Shiraz and Muscat Gordo Blanco. Tartaric acid concentration in must also increased during the initial two days after crushing and then decreased. Malic acid concentration was higher in juice of Ramsey-grafted than own-rooted vines, especially for Shiraz; concentrations did not change markedly during the initial 12 days of fermentation, except where malo-lactic fermentation occurred. Wine made from grapes of grafted contained significantly less tartaric and more malic acid than that made from own-rooted for all varieties and for both fermentation types, with the exception of tartaric acid in wine of Muscat Gordo Blanco fermented as must. Wine made from juice had significantly higher tartaric acid and lower malic acid than that made from must for all varieties except for tartaric acid in wine from grafted Shiraz and malic acid in own-rooted Chardonnay. Wine had a smaller tartaric acid/malic acid ratio when made from must. Wine pH was positively correlated with K+ but negatively with tartaric acid and with the tartaric acid to malic acid ratio. Overall, Shiraz wine contained highest Cl?, Na+ and K+ concentrations. Red wines obtained from grafted had higher colour hue, especially those from Shiraz. Wines made from fruit borne on own-rooted Cabernet Sauvignon had the highest concentration of total anthocyanins, ionised anthocyanins and total phenolics.     

Organic and inorganic anions in Shiraz and Chardonnay grape berries and wine as affected by rootstock under saline conditions

Background and Aims: Rootstocks influence the inorganic ion and organic acid composition of grapes of the scion variety. The aim was to investigate the impact of rootstocks on the inter-relationship of inorganic ions and organic acid anions in the skin and pulp of grapes and in resultant wine. Methods and Results: Vines were irrigated with water having electrical conductivities in the range 1.6–2.1 dS/m. Chloride, sodium, potassium, malic and tartaric acid concentrations were higher in almost all cases in skin than in pulp. Significant positive correlations existed between chloride and sodium concentrations in both pulp and skin. A significant negative linear regression existed between malic acid and both chloride and sodium concentrations in skin of Chardonnay berries. There were positive linear regressions in chloride concentration between berry (pulp and skin) and resultant wine chloride in both Chardonnay and Shiraz. Conclusion: The higher malic acid and lower chloride concentrations in skin of most grafted Chardonnay and Shiraz vines, and vice versa for own rooted vines, may indicate competition for similar transporter proteins involved in loading into skins. Alternatively, higher salt concentrations in skins may be associated with accelerated malic acid catabolism. Significance of the Study: Chloride-excluding rootstocks demonstrated advantages through reduced chloride (but not sodium) in pulp and skin of grape berries and in resultant wines. Where rootstocks reduced chloride concentrations in skin of grape berries, there is potential for higher malic acid in skin and in the resultant red wines.     

Shiraz berry size in relation to seed number and implications for juice and wine composition

This study was conducted over three seasons on irrigated Shiraz grapevines growing in a warm climate. We addressed the question of whether differences in berry size (within a population of berries from minimally pruned, own‐rooted or Ramsey‐grafted vines), would lead to differences in juice composition, wine composition or wine sensory score. Predictably, berry mass was found to increase with seed number, but berries in the smallest mass categories (0.3–0.7 g) still had similar juice soluble solids and pH; and similar concentrations of K+, tartaric acid and malic acid, compared with larger berries (1.4–2.0 g). Only for the very smallest mass category (0.3–0.55 g) was there any indication of better colour density (both for own‐rooted and Ramsey‐grafted vines) or higher anthocyanin concentration (for own‐rooted vines) compared with larger berries (1.4–2.0 g). Concentrations of tartaric acid and K+ in berry skins were highest in the smallest berry mass categories (0.3–0.7 g) and decreased with increasing berry mass (up to 1.4–2.0 g). A strong correlation (R²= 0.85) between skin tartaric acid and K+ concentrations was observed across that range. Small‐scale wine lots based on small berries (0.8–0.9 g) versus large berries (1.2–1.3 g) showed no differences in measures such as soluble solids, total acids or pH of juice; nor any differences in pH, total acids, K+, tartrate, malate, spectral characteristics or sensory score of corresponding wines. Moreover, small berries had a similar skin to fruit ratio, and a similar juice yield, compared to large berries. However, when measured post‐fermentation, the ratio of seed weight to skin weight was higher for small berries. The mass range of berries used here for small‐scale winemaking (i.e. from 0.8–0.9 g up to 1.2–1.3 g), covered the range of Shiraz berry mass typically found in irrigated vineyards (from 0.8 to 1.5 g), and thus confirms the relevance of present outcomes to practical winemaking. Finally, our data for variation in juice and wine composition as a function of berry size, showed consistent trends for all seasons, and thus implies that reported instances of improved wine quality from small berries (often associated with certain pruning treatments or deficit irrigation strategies), are more likely due to treatment effects that lead to small fruit, rather than to intrinsic developmental differences between large and small berries.     

A diminished capacity for chloride exclusion by grapevine rootstocks following long-term saline irrigation in an inland versus a coastal region of Australia

Shiraz and Chardonnay grapevines that had been initially assessed for Cl^‐ exclusion in the 1996 and 1997 harvest seasons at both Merbein (inland region of Victoria) and at Padthaway (sub‐coastal region of South Australia), were re‐evaluated in 2003 and 2004 at those same two locations. Both scion varieties were grown either on their own roots or were grafted to one of the following rootstocks: Ramsey, 1103 Paulsen, 140 Ruggeri, K51‐40, Schwarzmann, 101‐14, Rupestris St George and 1202 Couderc. Both sites had been irrigated with saline water since 1994. The salinity of irrigation water at Merbein was approximately 2.1 dS/m; at Padthaway irrigation salinity varied between approximately 1.6 dS/m and 2.5 dS/m during the survey period. Changes in the Cl^‐‐excluding ability of all rootstock/scion combinations between 1996, 1997 and 2003, 2004 were based upon analysis of Cl^‐ concentrations in grape juice and in laminae at harvest, as well as Electrical Conductivity (EC), pH and Sodium Adsorption Ratio (SAR) of the 1:5 soil:water extract. Taking juice Cl^‐ as indicative of rootstock effectiveness for Cl^‐ exclusion, and considering data from Merbein, our analyses demonstrated that overall means for Shiraz juice Cl^‐ increased from around 190 to 427 mg/L over the survey period (7 years). In Chardonnay grapevines at Merbein, overall mean concentrations of Cl^‐ in juice increased from around 70 to around 225 mg/L over 7 years. Significant differences between rootstocks were evident, with some rootstocks at Merbein showing a diminished capacity for Cl^‐ exclusion in 2003 and 2004. By contrast, in Padthaway there was no consistent deterioration in Cl^‐‐excluding capacity by rootstocks supporting either Shiraz or Chardonnay as scions. In 2004 there were significant differences between grapevines at Merbein and Padthaway in the concentration of Cl^‐ accumulated, even though the mean soil EC_1:5 after harvest for 0–90 cm depth was the same at both sites, namely 0.4 dS/m. Containment of grapevine salinity at Padthaway (relative to Merbein) between 1996/97 and 2003/04 was most likely due to factors such as a lower volume of saline irrigation, double the rainfall and 27% lower pan evaporation.     

Dynamics of grape berry growth and physiology of ripening

Data from two experiments on development of grape berries is re-examined with emphasis on partitioning of berry weight into non-solutes per berry (largely water) and solutes per berry (largely sugar), using weight times juice °Brix. This approach is based on the thought that, since xylem flow is blocked after veraison, time curves of solutes per berry indicate the activity of phloem transport into the berry during ripening growth. Experiment 1: Measurements of Muscat Gordo Blanco berries from inflorescences with a spread of flowering times showed typical double-sigmoid volume/time curves but with divergent rates and amounts of volume increase. Despite this divergence, °Brix curves after veraison were almost coincident because, in each case, the rate of increase in solutes per berry was proportional to that of berry volume. These results indicate that sugar and water increments after veraison are linked and depend on the same source, namely, phloem sap. Experiment 2: An irrigation experiment on cv. Shiraz also showed divergent berry weight curves between treatments and years but with the difference that all berries shrank after a maximum berry weight was attained at 91 days after flowering (at about 20 °Brix). At this point, the curves of solutes per berry slowed then plateaued, indicating that inflow of phloem sap had become impeded. Prior to shrinkage these berries accumulated primary metabolites (mainly phloem sugar) but, during shrinkage, when berries were apparently isolated from vascular transport, non-anthocyanin glycosides accumulated. These results have implications for the study of berry flavour buildup and berry composition, and also for the understanding of sink competition within the vine, fresh and dried yield, and juice °Brix levels.     

Rootstock and salinity effects on rates of berry maturation, ion accumulation and colour development in Shiraz grapes

Shiraz grapevines on either their own roots, or on the rootstocks Ramsey, 1103 Paulsen, 140 Ruggeri or 101–14, were grown at two separate sites within the Murray‐Darling viticultural region with similar irrigation regimes but with an irrigation water salinity of either 0.43 dS/m (low salinity site) or 2.3 dS/m (high salinity site). Rootstock effects on grape berry development, ion concentrations, soluble solids and acidity were followed during one season. Wines were also made and compared using spectral analysis and sensory evaluation. Rootstock effects that were common across both sites were (1) a close relationship between K+and soluble solids accumulation in developing grape berries which commenced at the onset of veraison and was indicative of a link between K+and sucrose transport in the phloem, and (2), higher wine K+, pH and colour hue for all rootstocks with one exception, namely 101–14 at high salinity where 101–14 responded similarly to own roots. Juice K+, pH and loss of K+from juice during winemaking were highest for grapes from the high salinity site. Mean berry weight was smaller and the range in berry size across rootstocks was narrower at the saline site. The narrower range in berry sizes may have contributed to fewer rootstock effects on wine spectral characteristics at high salinity. There was no effect of rootstock on CO₂ assimilation rate or stomatal conductance at either site, although intrinsic leaf‐based water‐use efficiency measured as A/g was 50% higher at the saline site. All treatments exhibited berry shrivel at maturity, but the extent was smaller at high salinity. Slower development of berry colour during veraison was observed on some rootstocks, for example 101–14, and while unrelated to canopy size per se, a higher leaf‐to‐fruit ratio for 101–14 may have been a factor. Slower berry colour development during veraison had no bearing on the colour density of wine made from the harvested grapes.     

Direct measurement of hydraulic properties in developing berries of Vitis vinifera L. cv Shiraz and Chardonnay

Berries of Vitis vinifera L. cv Shiraz can undergo weight loss during later stages of ripening. Existing published views on how weight loss occurs are based on changes in capacity of the vascular system to import water during development (McCarthy and Coombe, Australian Journal of Grape and Wine Research, 5, 17–21, 1999). One important element of these views is the proposed cessation of water flow through the xylem after veraison. We have now measured the water flow into berries of Shiraz and Chardonnay as they develop using the pressure probe and the high pressure flow meter (HPFM). The pressure probe connected to the pedicel of individual berries provided measurements of single berry hydraulic conductance. By systematic excision of tissue segments of the berry and pedicel we determined where in the pathway hydraulic conductance changed during development. The HPFM was used on whole bunches showing that berries (including pedicels) represent parallel high hydraulic resistances and that the hydraulic resistance of the bunch axis was rather small. The hydraulic conductance per berry could be determined from excision experiments. There was close agreement between the pressure probe and HPFM measurements. Both showed a ten‐fold reduction in hydraulic conductance of whole berries from veraison to full ripeness. Shiraz had hydraulic conductances that were 2‐ to 5‐fold higher than those for Chardonnay. Shiraz maintained a higher hydraulic conductance past 90 days after flowering than Chardonnay. The decrease in hydraulic conductance occurred in both the distal and proximal parts of the berry for both varieties. The pressure probe also provided measurements of the xylem pressure that non‐transpiring berries could develop. These pressures were –0.2 to –0.1 MPa until veraison and increased to zero when the juice osmotic potential reached about –3 MPa in Chardonnay and –4 MPa in Shiraz. The results suggest values of the reflection coefficient of the osmotic barrier around the xylem vessels of about 0.1–0.2 at veraison decreasing to 0 at harvest. It is suggested that in addition to changes in xylem anatomy, aquaporins in berry membranes may play a role in regulating hydraulic conductance. Water movement from the berry back to the parent vine via the xylem (backflow) may be an important component of berry weight loss in Shiraz, particularly if the phloem ceases functioning at high osmotic potentials near maximum weight. Backflow could account for a weight loss of 43 mg per day in Shiraz berries for a relatively small gradient of 0.1 MPa.     

Influence of grapevine leafroll associated viruses (GLRaV-2 and -3) on the fruit composition of Oregon Vitis vinifera L. cv. Pinot noir: Free amino acids,sugars, and organic acids

Individual free amino acids, yeast assimilable amino acid (YAN) content, ammonia, organic acids, and simple sugars of berries from vines infected with GLRaV-2 or -3 were compared with paired vines free of these viruses. Samples were taken from two commercial vineyards during two growing seasons (2005 and 2006), with three different rootstock/scion combinations. Vines infected with GLRaV-2 did not differ significantly from their healthy counterparts in individual free amino acids, ammonia, or YAN content. Vines infected with GLRaV-3 were significantly lower in valine and methionine from Vitis riparia rootstock/‘Pinot noir’ clone 114 (VY2a) samples, and lower in glutamic acid from self-rooted/‘Pinot noir’ clone Pommard (VY2b) samples, compared to samples from their healthy counterparts. Samples from VY2b (self-rooted/‘Pinot noir’ clone Pommard) infected vines had significantly lower levels of malic acid and total organic acids compared to samples from their healthy counterparts. There were no significant differences between healthy and infected vines from all three rootstock/scion pairs in ammonia or free amino acids in samples taken during the weeks before ripening and at commercial harvest. This is the first study to report the influence of GLRaV-2 and -3 on ‘Pinot noir’ berries nitrogen (N) compounds significant to fermentation. Individual free amino acids may be inferior to phenolic compounds as indicators of GLRaV infection status.     

Free amino acid profiles from ‘Pinot noir’ grapes are influenced by vine N-status and sample preparation method

This study examined the impact of extraction method on ammonia, free amino acids, and yeast assimilable nitrogen (YAN) concentrations in ‘Pinot noir’ berries obtained from a vine nutrition study (altered supply of N, P, or K). Berries were either juiced or exhaustively extracted as whole berries prior to analysis. Extracts, compared to juice samples, had a significantly higher level of ammonia–N, assimilable amino acid–N, and YAN. For example, juice YAN values were approximately 50% of extract YAN values, when both were expressed in the same units. Free amino acid profiles and relative concentrations of individual amino acids were different in juice versus extracts, depending on how well the skin fraction was extracted prior to analysis. Lowering N supply reduced free amino acids, with arginine being reduced more than the other 20 free amino acids identified in ‘Pinot noir’ berries. This was true in both juice and extracts. Since berry skin contributed to actual YAN, wineries that determine YAN from mainly the pulp fraction (juice) may underestimate YAN and as a result add more (artificial) N supplement than is required for the healthy fermentation of red winemaking (whole berry fermentations). Extraction procedure should be taken into consideration when comparing grape YAN.     

In vitro assessment of grapevine resistance to two populations of phylloxera from Australian vineyards

A perlite-based medium is described for in vitro cocultivation of phylloxera with micropropagated vines. Using this system, as well as cocultivations on excised primary roots, six vine types were screened for resistance to one or two populations of phylloxera (SRU-1 or VWL-1) sourced from different Australian vineyards. When inoculated with VWL-1 phylloxera, V. vinifera cv. Shiraz was rated as susceptible, Ramsey as resistant, Schwarzmann, V. riparia and Börner as highly resistant and V. rotundifolia as immune. When inoculated with SRU-1 phylloxera, both V. vinifera and Schwarzmann were rated as susceptible. The potential use of these in vitro methods for rootstock resistance screening and determination of phylloxera biotypes is discussed. Phylloxera behaviour and root responses observed in vitro are also described.     

Accumulation of potassium and calcium by ripening berries on field vines of Vitis vinifera (L) cv. Shiraz

Ripening berries of Vitis vinifera (L) cv. Shiraz can show pre-harvest weight loss at sub-optimal sugar content (shrinkage). This later-age decline in berry weight implies that water loss from mature berries has begun to exceed water inflow from the parent grapevine. Such decrease in net inflow has been attributed to a cessation of xylem flow subsequent to veraison, followed by a cessation of phloem flow into berries during later stages of ripening. We address this issue in this present paper, and show a continuing increase in berry content of both potassium and calcium throughout ripening. We measured changes in berry fresh weight and berry content of potassium (phloem mobile) and calcium (phloem immobile) in fruit on field vines sampled from set to harvest. Berry fresh weight reached a plateau between 81 and 95 days after flowering, then declined to 75% of maximum fresh weight by 115 days. Dry weight maximum occurred 14 days after the onset of the fresh weight plateau. Potassium accumulation was slow pre-veraison, increased 3.5-fold post-veraison, and continued during berry shrinkage. Calcium content per berry also showed a linear increase throughout fruit enlargement and ripening phases. Assuming both potassium and calcium were entering berries via vascular conduits, our results imply a continuing connection between parent grapevine and ripening berries. Moreover, an abrupt change (increase) in the ratio of potassium/calcium content per berry subsequent to veraison implies that phloem inflow has increased relative to xylem inflow during post-veraison enlargement.     

Potassium concentration and pH inter‐relationships in grape juice and wine of Chardonnay and Shiraz from a range of rootstocks in different environments

Background and Aims: pH adjustment during winemaking is a significant cost to the Australian wine industry. This study addresses potassium (K⁺) concentration and pH inter‐relationships in grape juice and wine of Chardonnay and Shiraz. Methods and Results: Chardonnay and Shiraz on own roots, and on Ramsey, 1103 Paulsen, 140 Ruggeri, K51‐40, Schwarzmann, 101‐14, Rupestris St. George and 1202 Couderc were compared at Koorlong and Merbein (Victoria), and Padthaway, Nuriootpa and Rowland Flat (South Australia). Petiole K⁺ concentrations at flowering were a poor indicator of grape juice and wine K⁺ concentrations. The concentration of H⁺ ions in grape juice and wine decreased as K⁺ concentrations increased resulting in increased pH. The relationship between H⁺ and K⁺ concentrations was linear for Chardonnay but exponential for Shiraz, where K⁺ concentrations were higher. Wine K⁺ and grape juice K⁺ concentrations exhibited a positive linear relationship, with slope for Chardonnay about half that for Shiraz, indicating a net loss of K⁺ between grape juice and wine of 58% for Chardonnay and 13% for Shiraz. Conclusions: The study has linked higher wine pH to both higher juice soluble solids and K⁺, and to poorer wine colour hue. Loss of K⁺ during fermentation and cold stabilisation appeared higher for Chardonnay than for Shiraz. Significance of the Study: Rootstocks that lead to lower K⁺ concentrations and pH in grape juice and wine are identified. Differences in the K⁺ concentration dynamics between grape juice and wine of Chardonnay and Shiraz are described and quantified.