EFFECT OF ROOTSTOCK ON YIELD QUANTITY AND QUALITY OF GRAPEVINE ‘ REGENT ’ IN SOUTH-EASTERN POLAND

Globally, the application of rootstocks for grapevine cultivation has been a standard, while in the northern regions, like in Poland where the viticulture tradition is relatively short, the selection of the most suitable rootstock types requires multi-year observation and research. The objective of the present study was to assess the effect of six following rootstock types: ‘101-14 Mgt’, ‘161-49C’, ‘125AA’, ‘5BB’, ‘SO4’, ‘SORI’, and own-rooted vines on yield quantity and quality of ‘Regent’ grapevine in south-eastern Poland. The three-year research period indicates that the vines on ‘125AA’ tended to produce not only the highest yields but had positive influence on the number and weight of clusters and berry weight as well. Whereas the vines grafted onto ‘161-49C’ gave the lowest yields and had the smallest number of clusters per vine. The fruit extract content in ‘Regent’ grapes on ‘101-14 Mgt’ rootstock was found to be significantly lowest among those under study. The extract content and yield of grapevines evaluated in the own-rooted vines and those grafted to the rootstocks which formed one group, did not differ.


INTRODUCTION
Viticulture has been gaining in popularity in Poland and hence, the increasing number of vineyards, especially those with the processing grape cultivars.Grapevine worldwide is considered to have really great economic importance but in Poland it is hindered by numerous agrotechnical problems arising from limited knowledge of this exothermic species [Myśliwiec 2009].
Currently, commercial vineyards have been planted using the scions grafted to rootstocks imported from Europe.However, lack of local traditional knowledge and thereby no, practical experience makes the best suited rootstock-cultivar match very challenging as it merely requires many-year cultiva-tion and observation.Besides, the selection of most suitable rootstocks is hampered because of a high number of new types that have been marketed lately [Loreti and Massai 2006].
Grafting practice of grapevines dates back to 2nd century BC but this propagation technique became very popular in the 1880s to overcome a serious threat of root louse phylloxera (Phylloxera vitifoliae, Fitch.) that severely devastated most of viticultural areas [Coombe 1999].At present, cultivation of this plant species relies mainly on grafted vines.
According to Reynolds and Wardle [2001], Satisha et al. [2010] appropriate selection of a rootstock can affect vine resistance to phylloxera, nematodes, soil pH, salinity, soil nutrient availability and drought.Numerous reports point out that rootstocks have influence on vine vigour, yield, quality of fruit and wine [Sivilotti et al. 2007, Sabir et al. 2010].However, these effects of rootstocks on growth characteristics and development of grapevines are noticeable to a greater or lesser extent because they are the consequences of interactions between a cultivar and environmental, physiological and agrotechnical factors, which have still remained unclear [Rizk-Alla et al. 2011].A vast body of scientific papers highlighted positive influence of rootstocks on growth, size and quality of grapevine yield as compared to own-rooted vines [Hedberg et al. 1986, Miller et al. 1988a, b, Palliotti et al. 1991, Ferre et al. 1996, Wunderer et al. 1999, Sommer et al. 2001].Interestingly, negative or indifferent impact of vine grafting management on grapevine performance was also noted [Boselli et al. 1992, Ferroni and Scalabrelli 1995, Reynolds and Wardle 1995, 2001].
Globally, there have been many researches related to rootstock effects on cold hardiness and this knowlegde seems to be of primary importance as regards the location of the Polish vineyards.The studies of Miller et al. [1988a] demonstrated considerable responsiveness of cane and bud hardiness to a type of rootstock used; rootstock '3309C' vines were hardier and recovered better after cold damage as against '5BB' and 'SO4'.Miller et al. [1998b] pointed out that grafted 'White Riesling' was hardier than the own-rooted vines.Substantial influence of a rootstock on the studied frost sensitivity was determined for grapevines 'Cabernet Sauvignon' and 'Chardonnay', which when grafted on '5BB' and '1103P' had less cold damage than on 'SO4' and '420A Mgt' [Palliotti et al. 1991].
The objective of the study was to assess the effect of rootstocks on yield quantity and quality of 'Regent' grapevine in south-eastern Poland.
The test aimed to assess the yield size and quality analyzing the parameters: number and weight of clusters, number and weight of berries and finally, total extract content.The fruit harvest date, irrespective of a rootstock type applied, was the same, i.e. 28.09.2012; 30.09.2013; 26.09.2014.The yield and number of clusters per vine from each plot were estimated through counting and weighing of fruits from each vine with an accuracy of 0.001 kg.Average weight of berries was determined by weighing and counting of fruits from five average-sized clusters, from each replication.A fruit extract content was measured using an Abbe refractometer, its percentage was established while squeezing the juice from 20 representative berries from each plant.
The trial was set up in a randomized block design and included 7 treatments with 5 replications.The replicates were the plots in which 3 plants were grown.
The results obtained in this test were analyzed statistically using the one-way analysis of variance and Tukey's confidence intervals.Besides, the results were depicted graphically by means of a box-plot.The inference was based on the significance level p < 0.05.The correlations between the grape qualitative parameters were estimated through the counting of Pearson's correlation coefficients.There were applied the experimental data multidimensional analysis techniques conducting the cluster analysis in order to group the objects (types of rootstocks) in relatively homogeneous groups in such a way that the objects in the same cluster were more similar to each other than to those in other clusters.The results of the cluster analysis are summarized using a dendrogram.All the statistical analyses were performer using SAS Enterprise Guide 5.1.software.

RESULTS AND DISCUSSION
Table 1 presents the average monthly air temperatures and precipitation totals in the years 2012-2014.It was observed that the weather conditions at particular study years were conducive to grape production.The mean annual air temperature in each research year was slightly higher compared to the multi-year average.The average air temperatures in January, February and December 2012 were found lower as against the multi-year average.A similar relationship was noted in January, February and March 2013.The annual precipitation totals in 2013 and 2014 were higher than the multi-year average and the differences were 38.6 mm and 30.5 mm, respectively.In 2012, total precipitation was lower as compared to the muli-year average.The analysis of precipitation distribution at particular vegetation periods showed that in 2012 high precipitation totals were recorded in October, while in 2013 in June and finally, in May 2014.The weather conditions throughout the research time did not affect negatively the grapevine growth or yielding.The three-year observation period highlighted significant effect of a rootstock type on yield size and quality of the grapevine of the 'Regent' variety (tab.2).The statistical analysis showed that a rootstock type affects significantly the cluster numbers on a vine that ranged between 13.53 and 23.23 units.It was found that the vines grafted onto '125AA' and 'SO4' produced significantly more clusters than onto '161-49C' and '5BB'.In 2013, the vines had the significantly highest number of clusters, while significantly the least in 2012.Reynolds and Wardle [2001] investigated eight grapevine cultivars and did not determine any significant differences in the number of clusters per vine between the varieties grafted on 'SO4' and '5BB'.The studies of Satisha et al. [2010] demonstrated the influence of a type of a rootstock on cluster numbers of 'Thompson Seedless' grapevines which when grafted onto the '110R' rootstock produced the highest mean number of clusters over the four-year research period.It was found that the own-rooted vines generated more clusters than those grafted to the '99R', 'Dog Ridge', '1103P' and 'St.George'.Similar dependences were observed in this work: the own-rooted vines produced more clusters than those grafted onto '101-14 Mgt', 'SORI', '161-49C', and '5BB' rootstocks, however these differences were insignificant.Different viticultural results were reported by Ferre et al. [1996] who investigated the 'Cabernet Franc' variety which was shown to produce a lower number of clusters by the own-rooted plants versus those on the rootstocks '3309C', '101-14 Mgt', '5C', '1616E', SO4', '18-815C' and '5BB'.
The cluster weight depended significantly on a rootstock type and ranged from 85.11 up to 127.8 g.Significant differences were seen between the vines grafted to '125AA' and '101-14Mgt', '161-49C', '5BB' and the own-rooted plants.The statistical analysis did not demonstrate any significant effect of the study year on the investigated parameter.The researches of Satisha et al. [2010] indicated that most of the grafted grapevines produced bigger clusters than those grown on their own roots, except for the plants grafted onto the 'St.George'.Reynolds and Wardle [2001] who worked on the vines of 'Chardonnay', 'Gewürztraminer', 'Ortega', 'Riesling', The present studies have shown that the vines grafted on '5BB' produced significantly less berries than the plants on '101-14 Mgt', 'SORI', SO4' and own-rooted.There was found significant effect of the study year on the investigated characteristic as on average significantly more berries were reported in the first study year than in others.Reynolds and Wardle [2001] found significant impact of a rootstock type on berry number per cluster and stated that vines of the 'Gewürztraminer' variety grafted on 'SO4' rootstock generated significantly higher number of berries than the plants on '5BB'.The present research results have confirmed this finding.The opposite effect was reported by Reynolds and Wardle [2001] for 'Marechal Foch' grapevines.The authors observed that the number of berries in clusters in the own-rooted vines and those grafted on 'SO4' did not differ significantly in the case of 'Seyval Blanc', 'Verdelet', 'Ortega'.While in the 'Marechal Foch' and 'Gewürztraminer' the vines grown on their own roots produced clusters with significantly higher berry numbers as against those on 'SO4'.No significant impact of a type of rootstock on the parameter investigated was found for the vines of 'De Chaunac', 'Okanagan Riesling', 'Chardonnay', Riesling' variety.Ferre et al. [1996] worked on 'Cabarnet Franc' grapevines and indicated that the 'SO4', '5C' and '18-815C' rootstocks tend to generate big clusters containing many berries, whereas the own-rooted plants produce smaller clusters and less berries.This finding does not fully agree with this paper.
Average berry weight ranged between 1.16 and 1.96 g and it differed significantly between the combinations under study (tab.2).The vines grafted on '125AA' had significantly heavier fruits than those from other combinations.It was observed that throughout the growing cycle, the plants on their own roots yielded the smallest berries.Significant impact of the study year on the studied characteristic was shown, significantly smaller berries were obtained in the first study year as compared to other years.Satisha et al. [2010] investigated 'Thompson Seedless' grapevine variety and highlighted significant effect of a rootstock type on berry weight as on average in the four-year research period, the berries from the ownrooted vines were found to be significantly smaller than from the plants grafted on 'Dog Ridge ', '1103P', '110R' and'99R'. Reynold andWardle [2001] working on vines of 'De Chaunac', 'Marechal Foch', 'Chardonnay' grafted onto 'SO4' rootstock showed that these plants produced significantly larger berries than those on '5BB' ,which has not been confirmed in the present paper.
On average, during the three-year study period, the vines grafted on '101-14 Mgt' produced fruits of a significantly lower extract content as against others.Main et al. [2002] evaluated the impact of rootstocks on yield quality of 'Chardonel' grapevines and concluded that the plants grown on their own roots displayed significantly higher extract content compared to those grafted on 'Cynthiana' and '5BB'.The present researches have shown that the studied parameter was significantly dependent on the study year; in the first year the extract content in 'Regent' fruits was found significantly lower than in other years.
Fruit yield oscillated from 1.16 up to 2.92 kg• vine -1 , i.e. from 5.78 up to 14.58 t•ha -1 and differed significantly between the combinations assessed.The bestyielding vines throughout the research period were those grafted on '125AA', while the poorest on '161-49C'.It was reported that the plants grafted onto 'SORI' and 'SO4' rootstocks yielded higher than the own-rooted, but the differences were not significant.
As for the vines on the other rootstocks, the opposite relationship was noted.The vines grafted on '161-49C' and '5BB' had significantly lower yield than the ownrooted.In the first study year, the vines of the tested variety yielded significantly lower as compared to the second and third study year.
The rootstock influence on yield size was widely documented in the literature around the world.As early as in 1937, Vaile confirmed that a rootstock can exert definite influence on the behavior of the scion cultivars, predominantly growth vigour and performance.Snyder and Harmon [1958] observed that highly vigorous rootstocks generate much wood, especially in the first growth stage.Inverse relationship was noted in the case of less vigorous rootstocks with lower growth rate but positive impact on fruit quality.According to Wolf and Pool [1988] and Parejo et al. [1995], yield quality is negatively correlated with vine vigour.Loomis [1952] assessing 14 rootstocks and 12 grape varieties found that nearly all the rootstocks have beneficial influence on yield, vigour and longevity of grapevines as compared to the own-rooted, which has not been fully confirmed in the present work.Special attention was paid to 'Dog Ridge' that considerably affected profitability of the crop.Nithya D. Menora et al. [2015] who worked on the impact of '1103P', 'SO4', 'Dog Ridge' and the vines grown on their own roots on the size yield of 'Thompson Seedless', 'Flame Seedless', 'Kishmish Chorni' grape showed that regardless of a variety, the own-rooted vines yielded higher than those grafted on 'SO4'.Among the grafted vines, the plants on 'SO4' had the lowest yield while the highest on 'Dog Ridge'.Hedberg [1980] established that performance of all grafted grape cultivars evaluated in his studies was substantially higher as compared to those grown on their own roots, the attention was focused on 'Ramsey' and 'Dog Ridge'.Similarly, Ferre et al. [1996] confirmed higher performance of the grafted 'Cabernet Franc' and 'White Riesling' than the own-rooted .Wunderer et al. [1999] demonstrated that 'Gruner Veltliner' grape varieties grafted onto 'SO4', '5BB' and '5C' rootstocks were characterized by greater growth vigour and wood production (green matter) than the vines grown on their own roots.
There are numerous reports available in literature that indicate negative or indifferent impact of rootstocks on vigour, productivity and profitability of grapevines.Boselli et al. [1992] reported that application of '5C', '5BB', 'G13', '8B', 'SO4', '1103 P', '41B' rootstocks in 'Chardonnay' grape did not have any considerable impact on performance as compared to the own-rooted plants.Whereas in the Ferroni and Scalabrelli [1995] studies, the 'Chardonnay' grapevines on '5BB' and '1103P' were observed to have poorer growth as against those own-rooted.Reynolds and Wardle [1995] showed no differences in yield size, fruit composition or removed green matter between the 'Gewürztraminer' own-rooted vines and grafted ones.Novello et al. [1996] in their rootstock trials demonstrated that 'Erbaluce' grape grafted on '101-14 Mgt', '420A', 'Rupestris du Lot', '5BB', 'SO4' had lower vigour than the own root.Sommer et al. [2001] found that grafted 'Sultana' vines always produced smaller fruit as compared to own-rooted vines.The calculated Pearson's coefficient (tab.3) manifested a strong correlation between the number of clusters per vine and yield (R = 0.8725, p < 0.05).The correlation results confirmed the inverse relationship between berry weight and their number in cluster (R = 0.5040, p < 0.05).
The presented dendrogram (fig. 1) defined the similarity of the effect of rootstock types on fruit extract content in 'Regent' grape variety.On the basis of the obtained results distinct clusters were defined which allowed for the explicit interpretation of the results.There were specified three distinct clusters displaying some similarities and one separate cluster for '101-14 Mgt' rootstock.It was found that own-rooted vines and the rootstock 'SO4' had very similar influence on fruit extract concentration, similar relationships were established between the rootstocks: '123AA' and '161-49C' as well as '5BB' and 'SORI'.The A, B and C clusters join at some level and thus visualize some similarities of the effect on extract content.The presented results have unequivocally indicated the weakest impact of '101-14 Mgt' rootstock on the tested parameter.
The multidimensional analysis showed marked influence of a rootstock type on yield of 'Regent' grape variety (fig.2).There were found clusters and similarities of the effect on the examined parameters reported between the rootstocks '5BB' and '161-49 C' that form cluster B and the ownrooted vines, 'SORI' and '101-14 Mgt' constituting cluster D. The separate clusters A and C visualize the rootstocks '125AA' and 'SO4' that had the highest yields.
The measurements of fruit extract content that were analyzed statistically and presented in a graphical form as box-plot (fig.3) aimed at the comparison of the level of the tested parameter between the own-rooted vines and those grafted on the rootstocks recognized as one group.They did not show any substantial differences in the content of the investigated quality parameter.It does not agree with the results given by Reynolds and Wardle [2001] who demonstrated that the fruit content in grapes from the vines grown on their own roots was significantly lower compared to those grafted onto rootstocks.Alike, fruit yield of grapevines of 'Regent' presented by means of the box-plot did not differ significantly between the own rooted versus grafted plants (fig.4) and that is consistent with the results obtained by Reynolds and Wardle [2001].
Weight of berries developed in the first clusters on-own rooted 'Regent' vines was slightly smaller than those on grafted ones (figs 4 and 5).

CONCLUSION
The obtained research results show that the application of various types of rootstocks in grapevine cultivation under the conditions of south-eastern Poland can affect yield size and quality of 'Regent' grape.These results may be useful in further improvement of grapevine cultivation.The three-year observation period indicated that the vines grafted on '125AA' produced the highest yield among those evaluated, besides, they displayed very positive effect on cluster numbers and weight and berry weight.The vines on '161-49C' had the lowest yielding crops and produced the smallest cluster number per vine.The fruit extract content of 'Regent' grapevine variety grafted on the rootstock '101-14 Mgt' was the significantly lowest among those investigated.Fruit extract and yield of the own-rooted grapevines versus grafted onto rootstocks recognized as one group did not differ.

Fig. 3 .Fig. 4 .
Fig. 3. Fruit extract between the own-rooted vines and those grafted on the rootstocks recognized as one group

Fig. 5 .
Fig. 5. Berry weight between the own-rooted vines and those grafted on the rootstocks recognized as one group

Fig. 6 .
Fig. 6.Cluster weight between the own-rooted vines and those grafted on the rootstocks recognized as one group

Table 1 .
Mean air temperatures and total precipitation according to weather station inSandomierz, Poland 2012-2014

Table 3 .
Correlation coefficients between measured parameters of grapevine 'Regent'