The influence of 110-Ritcher and SO 4 rootstocks on the performance of scions of Vitis vinifera L . cv . Albariño clones

The use of rootstocks is widespread in modern viticulture; non-grafted Vitis vinifera vines are now grown in only a handful of places with very specific conditions. Since the need to graft vine-scions onto American rootstocks, a lot of work has been performed in which different aspects of the relationship between the vine and the rootstock have been studied. Despite this there are still many open questions, which remained unanswered. The present paper reports a study performed on five ‘Albariño’clones (MBG-1, MBG-2, MBG-7, MBG-9 and MBG-10), in which the influence of rootstock type (110R and SO4) on a number of agronomic variables was examined. The results show that these rootstocks have no influence on many of the variables which were studied (phenology, cluster size and weight, fertility, yield, and berry size and weight), although they do influence variables such as the probable alcohol content, the quantity of free-run juice, must total acidity and weight of pruned wood. Therefore it is possible to conclude, that rootstocks influence agronomic parameters. Additional key words: agronomic traits, interclonal variability, Vitis berlandieri × Vitis riparia, Vitis berlandieri × Vitis rupestris.

resistant rootstocks is the only reliable way to ensure the quality of the grapes produced (Hidalgo, 2002).
According to Martínez de Toda (2002), rootstocks seem to exercise their influence fundamentally through plant vigour, and consistently have an effect on leaf exposure and on water and nitrogen availability at maturation.Rootstocks that induce less vigour tend to produce higher quality wine (McCarthy and Cirami, 1990), except in poor soils where leaf surface area is insufficient.However, no generalisations can be made regarding the effect of a single rootstock type across cultivars (Clímaco et al., 1999(Clímaco et al., , 2003)).It is also not clear whether all the effects on fruit quality in grafted vines are due directly to the rootstock or whether they are a product of the microclimate formed around the plant.
The effects of rootstocks on plant vegetative growth, production, and wine composition and quality have been studied for many years in different vine varieties.Studies have also been performed on different clones of Chardonnay (Chambre d'Agriculture de l' Aude, 2004) to determine the influence of rootstock type on their susceptibility to powdery mildew (Uncinula necator Schw.Burril.) and botrytis (Botrytis cinerea Pers.).No influence was seen on the former, but rootstocks that conferred greater vigour led to increased susceptibility to the latter.These results confirm the observations of Cristinzio et al. (2000).
Among the rootstocks most commonly used in the study area are those of V. berlandieri hybrids.These show high adaptability to saline soils and have good affinity with cultivated vines (Hidalgo, 2002).The rootstock 110 Richter is a hybrid between V. berlandieri and V. rupestris, while SO4 is a hybrid between V. berlandieri and V. riparia.Both are commonly used for their ability to adapt to many types of soil and environmental conditions (Reynier, 2002).
The aim of this work was to compare five Albariño clones grafted onto 110 Richter or SO4 and determine how rootstock type influences the agronomic characteristics of the clones.These clones show variability at the agronomic level (Boso et al., 2004a) and in their resistance to downy mildew (Boso et al., 2004b), although the latter is not influenced by rootstock type (Boso et al., 2007).

Plant material
The study was conducted over five years from 2000-2004 on five Vitis vinifera cv.Albariño clones (MBG-1, MBG-2, MBG-7, MBG-9 and MBG-10) grafted on Ritcher 110-R (Vitis berlandieri × V. rupestris) and SO4 rootstocks (V.berlandieri × V. riparia), the most common and best adapted to the study area.Each clone/rootstock (C/R) combination was represented by 10 randomly distributed vines.Every year a different group of these vines was used.All the vines were seven years old at the start of the work.The experiment was located at the Misión Biológica de Galicia Research Station (Consejo Superior de Investigaciones Científicas) in the province of Pontevedra (north-western Spain).All plants were therefore subject to the same soil, climatic and cultivation conditions.The soil had a sandy loam texture (13.88% clay, 16.1% silt, 70.1% sand, 8% organic matter).The soil was ploughed several times a year, but received no irrigation.
Plants were grown en espalier with a distance between rows of 2.5 m and a distance between plants of 2 m.The Sylvoz pruning method was used, leaving one horizontal vine 1.10 m from the ground with twobudded renewal spurs and 4-5-budded fruit canes.The latter curved downwards and were tied to a wire at 70 cm above ground.Two parallel wires were situated 1.30 m and 1.70 m from the ground, and all green shoots were placed between them as they grew.Twenty buds were left on each sample plant.

Stages in grapevine shoot development
The shoot and bud development was recorded weekly for two years, from mid-March 2001, following the methods of Eichhorn and Lorenz (1977) and Baggliolini (1952).

Fertility and characteristics of berries and seeds
Clones were sampled between the end of September and the second week of October (berry ripening stage).
From physiological stage 38 of Eichhorn and Lorenz (1977) (i.e., soft berries, tasty flavour and yellow colour), maturation was monitored to select full maturity berries.Both sugar concentration and total must acidity were measured daily, from this stage, and the evolution of these parameters in each clone was observed.When berries were at optimum ripeness (when they stopped concentrating sugar) they were harvested.The number of grape clusters per vine shoot on each of the 10 specimens per clone was counted.They were then removed, placed in a bag and weighed (yield = kg plant -1 ).
Five representative clusters from each of the 10 specimens planted per clone were then selected according to the norms of the OIV (1983), and their weight (g), length (cm), width (cm) and number of berries were recorded.Stem length (cm) was also measured.
Fifty berries per clone were selected from the central part of the clusters, and each berry was numbered.The length of the pedicel (cm) and the length (cm), width (cm), and weight (g) of each berry were recorded, and the number of seeds per berry was counted.Once seeds were dry, 50, from each clone, were randomly selected and their individual length, width and weight were recorded.

Free-run juice
Berries were selected from each of the 10 specimens per clone, and were placed in a centrifuge tube, gently ground, and centrifuged for 3 min at 3,000 r.p.m.The supernatant volume was measured (mL) and the must yield per berry (%) estimated as follows: (must of berries/ weight of berries) × 100.

Probable alcohol content
A 50 mL sample of the supernatant was taken with a Pasteur pipette and placed in a refractometer to obtain the sugar concentration (Brix).The probable alcohol content of the juice (degrees Baumé) was estimated using conversion charts (OJ, 1990b).

Total must acidity
Sampling was conducted following the same procedures as for determining must yield per berry.Total must acidity was estimated using the colouration pattern volumetric method (OJ, 1990a).

Must pH
Must pH was measured with a pH meter (Crison micro pH 2000).

Fertility
Taking into account the number of buds left at the last pruning, the fertility index was calculated using the equation: number of clusters per plant × 10/number of buds per plant.

Weight of pruned wood
Vines were pruned by the end of February, and the wood obtained from each of the 10 specimen plants per clone was weighed.

Statistical analysis
Each variable was examined separately by analysis of variance (ANOVA) using triple factorial.Year was considered as a random factor whereas clones and rootstocks were considered as fixed factors.Fisher's protected test [least signif icant difference (LSD) method], was used to establish whether there were significant differences among the clones (P ≤ 0.05) and rootstocks.All calculations were performed using the GLM procedure of SAS System software, version 9.1.2.(SAS, 2004).
Using data from the full five years of the study, principal component analysis (PCA) was performed on the results for cluster and must variables, the weight of pruned wood, and berry and seed variables.

Phenolological stages
There were no significant differences among clones with respect to influence of rootstock type.Nor was there a significant influence of the interaction clone × rootstock type (Table 1).Bud-break (stage B) always occurred in March, sometimes at the beginning of the month and sometimes towards the end of the second week.Harvest was generally in September, although  in some years it was in the second week of October.

Clusters, musts and pruned wood
Table 2 shows the results of the ANOVA for these variables.There was no significant difference with respect to rootstock type with the exception of probable alcohol content, quantity of free-run juice, acidity and weight of pruned wood.Clones grafted onto the 110-R rootstock had a higher probable alcohol content, less free-run juice, a lower must total acidity and produced less pruned wood than clones grafted onto SO4 (Fig. 1).There were significant differences in the interaction clone × rootstock type with respect to quantity of freerun juice and must pH.With respect to these two variables, the same clone behaved differently depending on the rootstock used.For some parameters such as cluster weight, cluster width, berries per cluster, quantity of free-run juice, acidity and clusters per vine shoot, each rootstock type gave different results depen-ding of the year (Table 3).The interaction clone × rootstock type × year had no significant effect on any variable except for probable alcohol content (P = 0.01) and weight of pruned wood (P = 0.05).These discrepancies were due to different slopes shown by few clones (MBG-1R, MBG-7R and MBG-2S for probable alcohol content, and MBG-9R and MBG-7S on weight of pruned wood).
The differences observed for the different variables were always attributable to the rootstock type.Therefore, the rootstock with greater or smaller magnitude according to each variable, always showed this behaviour irrespective of year or clone (Table 4).
The PCA of all five years data for cluster and must variables and weight of pruned wood showed the first three axes accounted for 79.35% of the variance (Prin1: 43.52%, Prin2: 23.77%, Prin3: 12.06%).Figure 2 shows the distribution of the different clones with respect to these three axes.With respect to Prin1, the most important variables were: berries per cluster, cluster weight, length and width, total acidity (there was a negative correlation between this variable and all others) and yield (kg grapes plant -1 ).Clone MBG-9 grafted onto either the 110-R or SO4 rootstock had the largest and heaviest clusters and the greatest number of berries.It also produced the most kg grape per plant and its must had one of the lowest acidities.Clone MBG2 on either rootstock showed opposite characteristics.With respect to Prin2 the most important variables were: clusters per vine shoot, fertility and weight of pruning wood (kg).In this component these clones lay towards the back of the graph.MBG-1R (i.e., MBG-1 on 110-R) and MBG-1S (i.e., MBG-1 on S04) showed the highest numbers of clusters per shoot, the highest fertility indices, and produced the greatest amount of pruned wood clones.The clones MBG-9R, MBG-10R and MBG-10S lay in the front part of the graph, with characteristics opposite to those of MBG-1R and MBG-1S.With respect to Prin3 the most important variable was alcohol potential (°Baumé).Clones MBG-1R, MBG-1S, MBG-2R and MBG-9R lay in the upper part of the graph with the highest probable alcohol contents.Clone MBG-7, on either rootstock, occupied the lower part of the graph with the lowest values for these variables.
Generally, the number of clusters per shoot on all clones was 1-2, and sometimes 3. Clusters were generally small.The mean number of berries per cluster varied from 50 for clones MBG-1S and MBG-2S to a maximum of 120 on clone MBG-9R.

Berries and seeds
There was no significant differences in berry and seed variables with respect to rootstock type, with the exception of seed width.Clones on the 110-R rootstock produced wider seeds (0.35 cm) than those grafted onto SO4 (0.33 cm).There was no significant effect of the interaction clone × rootstock type on the measured variables.However, there were signif icant difference in the interaction rootstock × year for all variables (P = 0.05-0.01),except for seeds per berry, seed weight and seed length (Table 3).The interaction clone × rootstock type × year had a signif icant influence on all variables except seed weight.However, as for clusters, must and pruned a WC: weight of cluster (g).WdC: width of cluster (cm).Nb: number of berries per cluster.Juice: free-run juice (%).Ac: total acidity expressed as tartaric acid (g L -1 ).Cs: clusters per vine shoot.Lp: Length of pedicel (cm).Lb: Berry length (cm).Wdb: Berry width (cm).Wb: Berry weight (g).Wds: Seeds width (cm).
wood, this interaction was due to rootstock type independent of year or clone.
In PCA analysis, the first three axes accounted for 90.02% of the variance (Prin1: 49.53%, Prin2: 25.43%, Prin3: 15.05%).Figure 3 shows the distribution of the clones with respect to these axes.With respect to Prin1, the most important variables were: length and width of berry and pedicel length.Clone MBG-9R lay to the right of the graph since it had the largest berries and the longest pedicel.Clone MBG-10S lay to the left with the smallest berries and the shortest pedicels.With respect to Prin2, the most important variables were: seed weight and width and berry weight (There was a negative correlation between this variable and all others).Clones MBG-7R and MBG-7S lay to the back of the graph, with the widest berries and lightest seeds.Finally, with respect to Prin3, the most important variable was the number of seeds.Clone MBG-7, on either rootstock, had the greatest seed number.Clones MBG-2 and MBG-1 on either rootstock were

MBG2R MBG2S
at the bottom of the graph with the smallest number of seeds.

Discussion
With regard to phenological stage, all clones behaved in the same way, irrespective of rootstock.However, clones grafted onto the SO4 rootstock (S) always took longer to reach the same stage of development as their counterparts grafted onto 110-R rootstock (R).Based on the time required to reach the different phenological stages proposed by Baggliolini (1952) and Eichhorn and Lorenz (1977), all clones had a long growth cycle and did not reach optimum ripeness until the f irst weeks of October.
The variables probable alcohol content, quantity of free-run juice, must total acidity and weight of pruned wood were influenced by the rootstock type.Other authors have reported the same results in table grape varieties (Venegas and Martínez-Peniche, 2004) and in grapes destined for winemaking (Main et al., 2002;Clímaco et al., 2003;Van den Heuvel et al., All clones grafted onto the S04 rootstocks produced must with a lower probable alcohol content, produced more free-run juice, had a high total must acidity and produced greater quantities of pruned wood.The result for the last of these variables agrees with the results of Galet (1990), Hidalgo (2002), Reynier (2002) and Santiago (2004) who suggest that the SO4 rootstock confers greater vigour.High must pH values were seen for MBG-9 on rootstock 110-R.However, on SO4 the must pH of these varieties was the lowest.Clone MBG-10 on SO4 rootstock had the lowest value for kg grapes per plant, berry weight and pedicel length.On the 110-R rootstock these values were intermediate.
In some clones the rootstock type influenced some parameters but only in specific years.Considering the climatic conditions in the years that this happened, it does not seem that this would be the reason, because the climatic conditions did not differ much among the years of the study.Therefore we could not identify an explanation for these results.Continued data collection over the coming years, could help clarify this question.
In the Albariño clones studied, rootstock type has no influence on many agronomic variables [e.g., phenology, cluster size and weight, fertility, yield (kg grapes plant -1 ), and berry size and weight] -as seen for resistance to downy and powdery mildew (Chambre d'Agriculture de l'Aude, 2004; Boso et al., 2007)-but did have considerable influence on probable alcohol content, quantity of free-run juice, must total acidity and weight of pruned wood.Therefore it can be concluded, that the rootstocks influence agronomic parameters.

Figure 3 .
Figure 3. Principal component analysis for parameters measured in berry and seeds of Albariño clones.

Table 1 .
Baggliolini (1952)days to reach different stages in grapevine shoot development following the method ofBaggliolini (1952)andEichhorn and Lorenz (1976), counting from C stage (opening the buds) over five years of the study according to rootstock type a Mean separation by Fisher's protected test [least significant difference (LSD) method], at p ≤ 0.05.Means within main effect and column having the same letters are not significantly different at p < 0.05.

Table 3 .
Averages and standard deviations (SD) for the variables that showed significant differences depending on rootstock type used and year of the study for clusters, berries and seed

Table 4 .
Averages and standard deviations (SD) for the parameters probable alcohol content (°AP) and weight of pruned wood (Wp) measured in clones of the Albariño cultivar Figure 2. Principal component analysis for parameters measured in cluster, juice and pruned wood of Albariño clones.