## 3 Results and Discussion  
### Summary of 5-Year Observation  
Table 1 shows the average monthly air temperatures and precipitation totals for the months of April to October from 2016 to 2020. It was observed that the weather conditions during most of the growing seasons were favorable for grapevine cultivation. The average air temperature in the months from April to October in the consecutive years of the study was higher than the multiyear average. The warmest year was 2018, while the coolest year was 2017. Precipitation totals during the months of April through October in 2017 were greater than multiyear totals. The trend was the opposite in the other years of the study. The average air temperature was higher than the average for many years, the opposite relationship was observed in the case of the sum of precipitation. The five-year observation showed a significant effect of rootstock type on the yield and properties of Regent grapevines. The average number of grapes on a vine of Regent cultivar ranged from 17.76 to 20.86 and differed significantly between the assessed rootstock types (Table 2). The significantly highest number of grapes was on vines grafted on 125 AA rootstock and the least on 161-49 C rootstock. Statistical analysis showed no significant differences in the evaluation of the examined parameter between SO4 rootstocks and own-root shrubs as well as 101-14 Mgt, SORI, and 5 BB. The years of the study significantly modified the level of the evaluated yield parameter. It was found that in 2018, the number of clusters per bush was significantly higher than in the other years of the study, while significantly, the fewest clusters were observed in 2020. Research conducted by [34] did not show significant differences in the number of clusters of the eight grape varieties assessed between bushes grafted on S04 and 5 BB. A study by [30] showed an effect of rootstock on the number of grapes of the Thompson Seedless grape variety; on average, for the four years of the study, shrubs grafted on 110R rootstock produced the most grapes. [27], evaluating Cabernet Franc vines showed that they produced fewer grapes on their own roots than on rootstocks: 3309C, 101-14 Mgt, 5C, 1616E, 18-815C, and 5 BB. The cluster weight ranged from 97.20 to 133.78 g and was significantly modified by the type of rootstock used. It was found that the shrubs grafted on 125 AA rootstock had the largest clusters, significantly, while the smallest ones, significantly, were on 5 BB and 161-49 C rootstocks. No significant differences in the evaluation of the examined trait were found between SO4 rootstocks, own-root shrubs, and SORI or between 5 BB, 161-49 D, and 101-14 Mgt. The years of the study had a significant effect on the cluster size of Regent grapevines. It was shown that the 2018 vines had significantly heavier clusters than the other years of the study, while they had the smallest clusters in 2020, significantly. Ref. [29] found that grafted Sultana bushes always had smaller fruit than from bushes on their own roots. Observations by [30] showed that in most cases shrubs grafted on rootstocks produced larger clusters than own-rooted shrubs, the exception being plants grafted on ST. George. Ref. [34], evaluating Chardonnay, Gewurztaminer, Ortega, Riesling, DeChaunae, Marechal Foch, Okanagan Riesling, Seyval Blanc, and Verdelet vines grafted on 3309C, K5 BB, 5C, and S04 rootstocks, did not find any significant effect of rootstock on yield, number, or weight of grapes and berries. They suggested that the use of rootstocks has no significant advantage over shrubs on their own roots under Pacific North Western U.S. and British Columbia conditions. A study by [48] showed a significant effect of rootstock type on cluster weight and berry quality