الفهرس 
INTRODUCTION
Abscisic acid (ABA):Only 14 pages are availabe for public view
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Abstract
Experiment was carried out throughout two successive seasons of 2016 and 2017 on Flame Seedless, Ruby Seedless and Thompson Seedless grapevines grown at the Experimental Orchard of Assiut University, Faculty of Agriculture. Sixty-five uniform grapevines (13 treatments x 5 replications) of each cultivar were chosen. Abscisic acid (ABA) treatments were applied at the concentration of 200, 400 and 600 ppm on the surface of grape cluster at the beginning of veraison, while, cluster thinning was done by removing 10, 20 and 30% of the total clusters. ABA and cluster thinning were applied individually or in combination with GA3at 10 ppmwhen the cluster length reached about 8-10 cm. The plant growth regulators (PGRs) were applied directly to the clusters with a handheld sprayer until runoff. The following traits were estimated:
1) Yield components and cluster measurements: At harvest date in both seasons, clusters per vine were collected and weighed to determine the yield weight (kg/vine). Samples of 3 clusters were randomly taken from each vine to determine the average cluster weight and then these clusters were used to estimate the other characteristics.•Cluster dimensions:Cluster lenght (cm) and cluster width (cm),cluster length/width (L/W ratio), Cluster rachis weight (g).2- Berry measurements: 100 berries weight (g), berry length (cm) and berry diamete 3-(cm), berry L/D ratio, 100 berries juice weight (g) 3) Chemicalconstituents: • Total Anthocyanin’s content(mg/100 g fresh wt.) of Flame seedless and Ruby seedless.
• Chlorophyll (a,b) and Carotenoids(mg/100 g fresh wt.) in the berry skin of Thompson Seedless were determined.• Total soluble solids percentage (T.S.S. %).•Total acidity (%) was determined by the direct titration method. TSS / acid ratio was then calculated.• The reducing sugars percentage.•Ascorbic acid content (V.C) (mg / 100 ml juice):•Vitamin C was determined by the method described by A.O.A.C. (1995).
The obtained results can be summarized as following:1- Yield components and cluster measurements:1-1. Yield weight (kg/vine):Application of Abscisic acid (ABA) increased yield weight (kg/vine) while cluster thinning decreased it.1-2. Cluster weight (g):Cluster weight increased due to most of tested treatments in comparison with the control treatment. The highest cluster weight was obtained from the vines which subjected to individual cluster thinning treatments or their combinations.1-3. Cluster dimensions:1-3-1. Cluster length (cm):The effect of tested treatments was significant on cluster length during the 1st season (2016) of study. During the second season of study (2017) most of treatments significantly exceeded the control.1-3-2. Cluster width (cm):
The treatments, with an exception of GA3 at 10 ppm + 30% cluster thinning, had not a significant effect on this trait during 2016. In 2017, most of the treatments significantly exceeded the control.1-3-3. Cluster length/width (L/W ratio):In 2016 all the treatments had not any significant effect on this ratio. In 2017 the control significantly surpassed most of the treatments. 1-4. Cluster rachis weight (g):Cluster rachis weight in 2016 increased significantly as a result of the treatments with an exception of ABA at 400 ppm + GA3 at 10 ppm + 20% cluster thinning. In 2017, most of the treatments significantly exceeded the control treatment.2- Berry measurements 2-1. 100 berries weight (g):Data indicated that, all the treatments significantly exceeded the control.The most effective treatments in 2016 were cluster thinning at 30% and 20% followed by ABA at 400 ppm + GA3 at 10 ppm + 20% cluster thinning. In 2017 season the vines which subjected to ABA at 400 ppm + GA3 at 10 ppm + 20% cluster thinning, GA3 at 10 ppm + 30% cluster thinning and ABA at 600 ppm recorded the highest values.The results also showed that Flame Seedless grape cultivar significantly exceeded both Ruby Seedless and Thompson Seedless in 2016. During 2017 season no significant differences could be observed between Flame and Ruby Seedless cultivars while both cultivars significantly surpassed Thompson Seedless. 2-2. berry dimension:2-2-1. Berry length (L) (cm):Data showed that the treatments had not a significant effect on berry length in 2016 season while in 2017 most of the treatments significantly impacted on this trait.2-2-2. Berry diameter (D) (cm):In 2016 season these were no significant differences between the treatments on berry diameter. In 2017, ABA at 400 ppm + GA3 at 10 ppm + 20% cluster thinning or ABA at 200 ppm and ABA at 600 ppm or ABA at 400 ppm + GA3 at 10 ppm recorded the highest values.2-2-3. Berry L/D ratio:There were no significant differences between various treatments on L/D ratio in 2016 season. In 2017 most of the treatments significantly exceeded the control.2-3. 100 berries juice weight (g):
The obtained results revealed that the majority of treatments significantly surpassed the control during the two studies season.3- Chemical constituents:3-1. Total anthocyanins content of Flame Seedless and Ruby Seedless grapes:Data demonstrated that the impact of treatments was more pronounced in the 1st season (2016) than the 2nd one (2017). All the treatments which comprised of ABA significantly exceeded the control in both seasons. Data also revealed that, Flame Seedless grapes significantly surpassed Ruby Seedless concerning anthocyanins content during the two studied seasons.3-2. Chlorophyll a, b and total carotenoids content of Thompson Seedless grapes: Data revealed that, most of treatments significantly decreased chlorophyll a, b and carotenoids content as compared with the control during the two seasons of study.3-3. Total soluble solids percentage (TSS%):Data indicated that ABA at 600 and 400 ppm significantly exceeded the controlin the 1st season (2016); ABA combined with GA3 and/or cluster thinning had also a significant effect,while the rest of treatments had not a significant effect. In 2017, all the treatments did not have a significant impact on this trait.Concerning the cultivars, in 2016, Thompson Seedless grapes significantly exceeded both Flame Seedless and Ruby Seedless cultivars. However in 2017, Thompson Seedless and Ruby Seedless significantly exceeded Flame Seedless cultivar. 3-4. Total acidity (%):During 2016 season the total acidity percentage significantly decreased due to applications of ABA at 600 ppm, ABA at 400 ppm + GA3 at 10 ppm, ABA at 200 ppm, GA3 at 10 ppm + 20% cluster thinning and ABA at 400 ppm + 20% cluster thinning. In 2017 season only cluster thinning at 30% caused a significant decrease on this trait while ABA at 400 ppm significantly increased it.On the other side, Thompson Seedless grapes significantly exceeded the other two cultivars while Ruby Seedless recorded the lowest acidity percentage.3-5. Total soluble solids/acid ratio:The ratio of TSS and acidity was significantly affected by treatments during 2016 season. The highest ratios were obtained from the vines subjected to ABA at 400 ppm + GA3 at 10 ppm, ABA at 600 ppm, ABA at 200 ppm and ABA at 400 ppm + 20% cluster thinning. In 2017 season there were no significant differences between the treatments concerning this ratio.3-6. Reducing sugars percentage:Although there were an increase in reducing sugars due to various treatments comparing with the control, the differences were not significant in most cases.Thompson Seedless cultivar significantly surpassed the other two cultivars in 2016 and significantly exceeded Flame Seedless in 2017.3-7. Ascorbic acid [vitamin C] (mg/100 ml juice):Data revealed that, in 2016season only cluster thinning at 10% significantly exceeded the control,while the rest of treatments and all the treatments in 2017 had no significant differences comparing with the control. Flame Seedless significantly exceeded the other two cultivars in 2016 while Thompson Seedless significantly surpassed the two cultivars in 2017 season.
Conclusion and recommendation:Results of the present study showed that spraying clusters with Abscisic acid (ABA) individually or combined with cluster thinning significantly increased the yield weight, cluster weight, improved coloringand berry quality.Moreover, cluster thinning led to an increase of cluster weight and enhance the berry quality but it decreased especially the severe thinning, the total yield weight.Accordingly, from the majority of present results it can be recommended that to execute the moderate cluster thinning (20%) in combination with ABA spraying (400 ppm) at the beginning of veraison stage in order to obtain a reasonable yield with the best fruit quality.