Effect of cane regulation and GA3 spray on berry thinning in ‘Thompson Seedless’ grape (Vitis vinifera L.) S.D. Shikhamany*, Swapnil V. Borade, Sanjay K. Jeughale and Suryakant Y. Patil Maharashtra State Grape Growers’ Association Manjri Farm Post, Pune 411 032, India *E-mail: sdshikhamany@gmail.com ABSTRACT A field trial was conducted during 2013-14 and 2014-15 fruiting seasons in growers’ vineyards around Nashik, Maharashtra, India to improve efficacy of GA 3 sprays in berry- thinning. As smaller clusters have fewer berries, cluster compactness derived at by number of berries per unit length (cm) of rachis, and, berry-diameter were considered as a measure of berry-thinning. As GA3 effect in berry-thinning is stage-specific, canes uniformly thick in a vine only were retained to achieve uniformity in flowering, by inducing uniform bud-break. Cane regulation did not result in uniformity in bud-break or flowering. Blanket spray of GA 3 thrice @ 20g a.i./ha, each coupled with either removal of non-uniform canes or retention of all the canes could effectively reduce cluster compactness by reducing number of berries per cluster, without increasing total length of the rachis/cluster or berry diameter. Vine yield and quality in terms of total soluble solids and acid content were not affected by the treatments. Considering cluster-compactness, yield and ease of cultural operations, retention of all the canes in a vine, coupled with three blanket sprays each of GA 3 @ 20g a.i/ha, on alternate days commencing from initiation of the bloom, is recommended for ‘Thompson Seedless’. Key words: Cane regulation, GA 3 spray, uniform flowering, cluster compactness, ‘Thompson Seedless’ INTRODUCTION ‘Thompson Seedless’ is the predominant variety of grape grown in India for table and raisin purposes. This variety is grown in over 70% of the total area under grape in the country. Clusters in this variety are very compact, prone to berry cracking and rotting, during ripening, transit and storage. Hence, berry- thinning is necessary. Berry-thinning is achieved with blanket sprays of GA 3 prior to bloom under temperate viticulture. Response to GA3 for berry-thinning is highly stage-spe cific. According to Turne r (1972), the effective stage is three days to one day prior to initiation of bloom. Phenological development stages in the panicle are uneven on any given day under tropical conditions of peninsular India, owing to uneven bud- break after fruit pruning. Hence, growers in this region resort to GA 3 sprays during the bloom, supplementing it with manual thinning. Manual thinning is not only labour-intensive, but also time-consuming. Delayed thinning deprives the berries retained from gaining in size (Winkler et al, 1974; Coombe, 1960). Moreover, manual thinning often leaves unseen bruises on the berries retained, which are then prone to decay in transit and storage (Chadha and Shikhamany, 1999). In view of the importance of chemical thinning, a field trial was undertaken with an aim to improve the efficacy of blanket pre-bloom sprays of GA3 on berry-thinning by induc ing uniform flowering through cane regulation. Uniformity in flowering depends mainly on uniformity in bud-break which, in turn, depends on uniformity in thickness of the canes in a vine. Bud-break was found to be earlier in thin canes compared to the thick ones (Reddy and Shikhamany, 1990; Shikhamany and Manjunath, 1992). Hence, removal of non-uniform canes was attempted, to induce uniform flowering, mediated through uniform bud-break in the vine. MATERIAL AND METHODS This trial was conducted during the cropping season of 2013-14 and 2014-15 on six/seven – year- J. Hortl. Sci. Vol. 11(2): 131-142, 2017 132 old ‘Thompson Seedless’ grapevines in farmers’ vineyards at two locations (Mohadi and Pimpalgaon) around Nashik (Maharashtra). All the experimental vine s were space d at 2.7m X 1.5m gra fted on ‘Dogridge’ rootstock, and trained on extended Y trellis. These were pruned for fruiting in the second week of October, and grapes were harvested on 140th day after pruning. The vines were subjected to uniform viticulture practices, namely, ethrel sprays for pre-pruning defoliation, hydrogen cyanamide application for promoting bud-break, and GA 3 sprays for cluster elongation. Experiments in each vineyard were laid out in Factorial A x B x C Randomized Block Design, with the following treatments replicated thrice: Factor A - Season: S1: 2013-14 and S2: 2014-15 Factor B - Location: L1 (Mohadi) and L2 (Pimpalgaon) Factor C - Treatments (Removal of abnormally thin or abnormally thick canes within a vine, coupled with GA3 sprays): T1 -Cane removal, coupled with three sprays each of GA3 @ 20g a.i./ha T2 -Cane removal, coupled with two sprays each of GA3 @ 30g a.i./ha T3 -Retention of all canes, coupled with three sprays each of GA 3 @ 20g a.i./ha T4 -Retention of all canes, coupled with two sprays each of GA3 @ 30g a.i./ha T5 -Control (growers’ practice of retaining all the canes, and spraying GA 3 @ 80g a.i./ha at 50% bloom) The first spray of GA 3 was applied three days prior to full bloom stage (approximately at initiation of calyptras-opening in a panicle), repeated on alternate days. GA3 at specified dose was sprayed with a blower-assisted-sprayer irrespective of the volume of spray solution. Obs e rvations r ec ord ed : Obse rvations wer e recorded on five canes tagged in each of the five vines selected at random in each replication/ treatment Number of canes/vine: Number of canes left on the vine after forward-pruning in T3, T4 and T5, and, after cane removal in T1 and T2 Cane diameter: Diameter at the middle of each cane was measured, and the average diameter calculated. Uniformity in bud-break: Number and position of buds opening on selected canes was recorded every day from the 5th to 12th day after pruning. The day on which highest number of buds broke was taken as the standard (D-day) and a score of 100 was given for each bud. For deviation in bud-break by a day from the D-day, either early or late, a score of 75 was given for each bud; a score of 50 for each bud deviating by two days, and a score of 25 for each bud deviating by 3 days. The sum of the scores was divided by the total number of broken buds, and expressed as ‘per cent uniformity in bud-break’. Uniformity in flowering: The stage of inflorescence- development specified for applying the first spray of GA3 for thinning wa s use d a s a re fer enc e . Observations we re re corded on the number of inflorescences attaining this stage from the 30th day after pruning, on selected canes. The day on which highest number of panicles attained this stage was taken as the standard (D-day), and was given a score of 100 for each panicle. For deviation by one day from the D-day, either early or late, a score of 75 was given for each panicle; 50 for each deviating by two days, and 25 for each deviating by 3 days. The sum of scores was divided by the total number of panicles and expressed as ‘per cent uniformity in flowering’. Cluster Compactness Index: This was derived by dividing the number of berries per cm of the total length of rachis. Berry-count and total length of rachis was recorded after removal of berries in five clusters selected at random from each plot. Berry-thinning has been found to increase the size of berries retained in a cluster (Coombe, 1960; Winkler et al, 1974). Hence, berry diameter was included in factors determining cluster compactness in these studies. Total length of rachis: Sum of the length of main rachis and all its branches was measured in cm. Number of berries/cluster: Average number of berries was counted in five, selected clusters. Berry diameter: Average diameter of 25 berries was measured (at the middle of the berry, using callipers). Yield/vine: Average yield of 10 vines in a plot was recorded in kg at harvest. Shikhamany et al J. Hortl. Sci. Vol. 11(2): 131-142, 2017 133 Cluster weight: Mean weight of five clusters selected at random from each plot was calculated. Total soluble solids content (TSS): Soluble solids content was determined in °B using a hand-held refractometer in the juice extracted by crushing the 25 berries selected at random. Titratable acids content: This was determined by titrating an aliquot of 10ml juice against 0.1N NaOH using phenolphthalein indicator and expressed as gram equivalent tartaric acid in 100ml juice. Statistical analysis: Data were analyzed in factorial A x B x C (2 x 2 x 5) design, with eight treatment combinations and three replications, where ‘A’ denotes the season, ‘B’ location and ‘C’ treatment. RESULTS AND DISCUSSION Reducing cluster compactness was a major objective in our trial, therefore, greater emphasis is laid on presenting this parameter. Any treatment reducing cluster compactness should not result in reduction of any yield or quality attribute/s. Hence, trea tment e ffe cts on thes e a ttribute s ar e a lso presented. Effect on cluster compactness Number of berries per cm length of the rachis is a recognized measure of cluster compactness (Chadha and Shikhamany, 1999), but berry-size also contributes to cluster compactness. At a given number of berries/cm length of rachis, a cluster with berries of 20mm diameter will be more compact, for example than one with 16mm berry diameter. Cluster compactness differed significantly with season, location and treatment (Table 1) being low less in 2014-15 (S2) compared to that in 2013-14 (S1). This can be attributed to an increased total length of rachis, a nd re duce d numbe r of be rrie s/c luste r. Le s s compactness in S2, despite greater berry-diameter is an indication of greater cluster elongation and/or a Chemical thinning in ‘ Thompson Seedless’ grape Table 1. Effect of Cane Regulation and GA treatment on components of cluster compactness Factor Cluster compactness Rachis length No. of berries/ Berry index (cm) cluster diameter (mm) A. Season 1. 2013-14 34.5b 47.6 a 79.0 b 17.9 a 2. 2014-15 32.0a 64.6 b 66.2 a 18.8 b S.Em ± 0.52 1.21 1.61 0.11 C.D. (P=0.05) 1.5 3.5 4.6 0.3 B. Location 1. L1 32.2 a 63.9 b 66.1 a 18.0 a 2. L2 34.3 b 48.2 a 79.2 b 18.8 b S.Em ± 0.52 1.21 1.61 0.11 C.D. (P=0.05) 1.5 3.5 4.6 0.3 C. Treatment 1. T1 29.9 a 51.4 a 69.0 a 18.3 2. T2 33.2b 59.8b 72.2 a 18.3 3. T3 30.3a 53.8 a 68.4 a 18.5 4. T4 35.9 c 54.8 a 75.0 a 18.4 5. T5 36.8c 60.6b 78.5b 18.3 S.Em ± 0.82 1.91 2.55 0.17 C.D. (P=0.05) 2.3 5.5 7.3 NS Interaction A X B * ** ** ** A X C * NS NS NS B X C ** ** ** NS A X B X C * NS NS NS NS= Non-significant J. Hortl. Sci. Vol. 11(2): 131-142, 2017 134 reduction in berry-number per cluster in this season. When locations were compared, cluster compactness was less in the vineyard at Mohadi (L1) than in the one at Pimpalgaon (L2). Contributory factors for less compactness at L1 were: comparatively longer rachis, reduced number of berries/cluster, and lower berry diameter. These results indicate that the general prac tice of growe rs for cluster elonga tion and treatments imposed to reduce number of berries/cluster were more effective in S2 and in the vineyard at L1. On the other hand, practices for increasing berry diameter were more effective in S2 and in the vineyard at L2. All the treatments were effective in reducing number of berries/cluster, but owing to less elongation of rachis, cluster compactness was not low in T4 (retention of all canes, coupled with two sprays of GA 3 @ 30g a.i/ha). However, the rest of the treatments more effectively reduced compactness, compared to that in the Control. Variation in rachis length cannot be attributed to treatments, because, neither cane removal before initiation of growth nor GA3 sprays applied between three to one day prior to bloom, have any effect on rachis elongation. The ideal stage for GA3 application for cluster elongation has been found to be 25 days prior to full-bloom (Turner, 1972). Berry diameter was not affected by treatments. Reduced berry number in the treatments did not result in increased berry-size. The reason for ineffectiveness of GA3 treatments in increasing berry-diameter is the mode of action of GA 3 and its stage of application. GA3 increases berry length but not berry diameter. The ideal stage for GA 3 application for berry elongation is from five to ten days after full-bloom (Turner, 1972). Hence, application of GA 3 just before bloom was ineffective in increasing berry-diameter. The growers’ practices for increasing berry-diameter appear to have masked treatment effect, if any. Effect of the treatments on cluster compactness varied with season and location. Interaction of season with treatments influenced cluster compactness only, but not rachis length, number of berries/cluster, or berry diameter. In individual effects of treatments, all the treatments, excepting T4 (retention of all canes, coupled with two sprays of GA3 @ 30g/ha) greatly reduced compactness, compared to the Control (T5- growers’ practice). However, all the treatments, including T4, reduced compactness in S1; whereas, in S2, only T3 (retention of all canes, coupled with three sprays of GA3 @ 20g/ha) reduced the compactness, compared to that in Control, consistently, over the years (Table 1a). Location x Treatment interaction also Shikhamany et al Table 1a. Season x Treatment effect on cluster compactness index Season Treatment T1 T2 T3 T4 T5 2013-14 29.2a 35.4de 30.7ab 36.9e 40.2f 2014-15 30.5ab 31.0a 29.9 a 34.9cde 33.5bcd S.Em ± 1.16; CD (P=0.05) = 3.3 influenced cluster compactness. In its major effect, across locations, T2 (cane removal, coupled with two sprays of GA3 @ 30g a.i./ha) reduced compactness greatly, compared to Control; But, at L1 it could not do so. At L2, all the treatments (except T4) reduced compactness greatly compared to the Control. T1 (cane removal, coupled with three sprays of GA 3 @ 20g a.i./ ha) and T3 were consistent in their effect in reducing the compactness, over the Control, at both the locations (Table 1b). Rachis length was also influenced by Location x Treatment interaction. When effects of the trea tme nts ove r the s eas on a nd loc ation were considered, rachis length was greater in Control, but at par with T2. Similar was the trend at L1; but, at L2, all the treatments were at par with Control. Although GA 3 spray at initiation of bloom had little effect on rachis elongation, rachis length was consistently greater in T2 over locations (Table 1c). Interaction effect of Location x Treatment revealed that T1 and T4 were more effective at L1 than at L2, in reducing number of berries/cluster (Table 1d), although all the treatments were effective over locations and seasons (Table 1). Effect of the treatments in reducing number of berries/ cluster seems to have been deviated by comparison with the inherently small clusters obtained in T1 and T4 at L1, and in Control at L2 (Table 1e). In addition to the berry-thinning effect of GA3 sprays, inherent size of the cluster appears to be the reason for reduced number of berries/cluster. Interaction of treatments with season and loca tion als o influe nc ed c luste r c ompa c tnes s significantly. Interactions of S1L1T1, S1L1T3, S2L1T1, S2L1T3, S2L2T2 and S2L2T3 resulted in lower compactness, than that of S1L1T5, S1L2T4 or S1L2T5 (Table 1e). J. Hortl. Sci. Vol. 11(2): 131-142, 2017 135 Table 1b. Location x Treatment effect on cluster compactness index ____________________________________________________________________________________ Location Treatment —————————————————————————————————— T1 T2 T3 T4 T5 —————————————————————————————————————————— L1 27.8a 34.2efg 29.5abcd 32.2de 37.2gh L2 31.9cde 32.2de 31.2bcde 39.5h 36.5fgh —————————————————————————————————————————— S.Em ± 1.16; CD (P=0.05) = 3.3 Table 1c. Location x Treatment effect on rachis length (cm) —————————————————————————————————————————— Location Treatment —————————————————————————————————— T1 T2 T3 T4 T5 —————————————————————————————————————————— L1 53.4b 68.4cd 63.9c 61.5c 72.4d L2 49.4ab 51.2ab 43.7a 48.1ab 48.8ab —————————————————————————————————————————— S.Em ± 2.70 CD (P=0.05) = 7.7 Table 1d. Location x Treatment effect on number of berries/cluster —————————————————————————————————————————— Location Treatment —————————————————————————————————— T1 T2 T3 T4 T5 —————————————————————————————————————————— L1 57.7a 69.1bc 66.8abc 61.4ab 75.3cde L2 80.2def 75.4cde 70.1bcd 88.5f 81.8ef —————————————————————————————————————————— S.Em ± 3.60 CD (P=0.05) = 10.3 Table 1e. Season x Location x Treatment effect on cluster compactness index —————————————————————————————————————————— 2013-14 2014-15 —————————————————————————————————— Treatment L1 L2 L1 L2 —————————————————————————————————————————— T1 25.7a 32.8fghijk 30.0abcdefgh 31.1bcdefgh T2 34.1ghijkl 36.7jkl 34.3hijkl 27.7abcd T3 29.3abcdef 32.2defghij 29.6abcdefg 30.2abcdefgh T4 32.0cdefghi 41.7mn 32.5efghij 37.3klm T5 42.3n 38.0lmn 32.0cdefgi 35.0ij _____________________________________________________________________________________ S.Em ± 1.63 CD (P=0.05) = 4.7 Chemical thinning in ‘ Thompson Seedless’ grape 136 In the overall analysis, considering variation due to season and location in the effects of treatments on rachis length, number of berries/cluster and the berry diameter, it can be concluded that T1 and T3 were equally effective in reducing cluster compactness over the Control. Effect on uniformity in flowering Uniformity in flowering is considered to be the basic requirement for blanket sprays of GA 3 to be effective in reducing number of berries/cluster. A perusal of variation in uniformity in flowering and numbe r of be rries /cluster within se asons a nd locations, would reveal that greater uniformity in flowering was associated with a lower number of ber ries /clus ter. Trea tment e ffec ts on uniform flowering were influenced by season and location, as evidenced by a significant effect of Season x Treatment and Location x Treatment interactions (Table 2). Cons idering the ir main effe cts and inter ac tion e ffe c ts with se a son a nd loca tion, treatments comprising cane removal (T1 and T2), envisaged at increasing the uniformity in bud-break (eventually increasing uniformity in flowering), failed to do so (Tables 2a, 2b and 2c). Uniformity in flowering was concordant with uniformity in bud- break only in the case of season but not location or tre a tme nt (Ta ble 2). Inte ra c tion of Se as on x Treatment also influenced uniformity in bud-break significantly. This could be due to a differential rate of flowe r de velopme nt, influenced by we ather conditions during flower development (Christensen, 1969; Negi and Randhawa, 1974). However, the component of cane removal in T1 and T2 did not result in increased uniformity in bud-break (Table 2d). Ca ne diameter was highe r in T1 and T2 where uneven canes were removed (Table 2). This implies that it was the undersized canes that were r e mov e d in T 3 a n d T 4 . Ca n e di a me te r wa s influenced by Season x Treatment interaction, being higher in T1 and T2 in 2014-15, but not in 2013-14 (Table 2e). Increased cane diameter in T1 and T2 did not result in increased uniformity of bud break (Table 2d) or flowering (Table 2a). In addition to uniformity in cane thickness, uniformity in bud-break depends on pre-pruning defoliation, diurnal variation in tempe rature a fter pruning (Shikhamany and Manjunath, 1992), and use of chemicals that promote bud-break (Shulman et al, 1983; Williams, 1987). Effect of cane removal on inducing uniform bud- break could have been masked by growers’ practice of using Ethrel for pre-pruning defoliation, pruning when temperature is conducive for bud-break, and using hydrogen cyanamide for inducing increased and uniform bud-break. These results point at the futility of cane- regulation in inducing uniform flowering under viticulture practices followed by growers in the course of our experimentation. Effect on yield Yield/vine was higher in 2014-15 compared to that in 2013-14, and higher at L1 than at L2. Yield did not diffe r signific antly among trea tments. However, interaction of Treatment x Location (Table 2 f)and Treatment x Season x Location (Table 2 g) influenced yield significantly. Yield/vine was greater in T3 compared to T1 and T2 at L1, but not at L2 (Table 3 a,b,c). Treatments T3 and Control fared better at L2, than at L1 (Table 3a). Yield /vine is a function of number of canes/vine, number of clusters/ cane and mean weight of the cluster. Increased yield in 2014-15 over that in 2013-14 can be attributed to increased number of canes and higher weight of cluster. In spite of mean bunch-weight being the same (Table 3), and cane number/vine being lower (Table 2), yield at L1 was higher. Similarly, mean weight of cluster and number of canes/vine was lower in T1compared to T3, T4 or T5, but, yield was not lower (Table 3). This could be attributed to a greater number of clusters/cane, which depends on c onditions be ing favoura ble for f ruit-bud formation during the vine growth season. Effect on quality Quality of grapes, as judged by the total soluble solids (TSS) and acids content did not differ significantly among tre atments. However, TSS content varied with season and location, and, acid content with the location only. Interaction of Season x Location also influenced both quality-components (Table 3). T SS content is primarily a varietal character, often modified by diurnal variation in temperature during the ripening period (Coombe, 1992). It is mainly controlled by Genotype x Environment interaction. Similarly, acid content is a ls o de termine d by Ge notype x Environment interaction. Shikhamany et al J. Hortl. Sci. Vol. 11(2): 131-142, 2017 137 Chemical thinning in ‘ Thompson Seedless’ grape Results of this trial indicate that: i) T1 and T3 a r e e qu a l ly e f f e c ti ve in r e d uc i ng c l us t e r compactness; ii) cane regulation did not result in significant improvement in uniformity of bud-break or flowering; iii) None of the treatments influenced yield or quality. In overall analysis, T3 (retention of all the canes in a vine, and spraying GA3 thrice @ 20g a.i./ha on alternate days, commencing from initiation of the bloom) is recommended for reducing cluster compactness, without compromising yield or quality in ‘Thompson Seedless’ grape. ACKNOWLEDGEMENT The authors a re gra teful to Shri Sure sh Ka lamka r (Mohadi) a nd Shri. Arun Mor e (Pimpalgaon) for facilitating these studies in their vineyards. Also, they thank the office bearers and Chairma n, Ce ntra l Re se a rc h Committe e of Maharashtra State Grape Growers’ Association, Pune, for supporting these studies. Support given by Prof. T.S. Mungare and Shri. T.S. Shelke, and guidance provided by Research Advisory Committee of the Association, are gratefully acknowledged. Table 2. Effect of season on vine growth characters Factor Canes/vine Cane diameter Uniformity in Uniformity in (mm) bud break (%) flowering (%) A. Season 1. 2013-14 33.4a 7.13a 83.1b 79.7a 2. 2014-15 35.2b 7.46b 77.2a 91.7b S.Em ± 0.34 0.032 0.52 0.73 C.D. (P=0.05) 1.0 0.09 1.5 2.1 B. Location 1. L1 30.3a 7.33 81.7b 88.4b 2. L2 38.2b 7.26 78.6a 83.1a S.Em ± 0.34 0.032 0.52 0.73 C.D. (P=0.05) 1.0 NS 1.5 2.1 C. Treatment 1. T1 29.5a 7.44b 81.3b 84.4ab 2. T2 30.1a 7.49b 79.3ab 83.2a 3. T3 35.5b 7.16a 80.4ab 86.6bc 4. T4 38.8c 7.18a 80.9ab 89.7c 5. T5 37.4c 7.19a 78.7a 84.7ab S.Em ± 0.54 0.050 0.82 1.16 C.D. (P=0.05) 1.6 0.14 2.3 3.3 Interaction A X B ** ** NS NS A X C NS ** ** * B X C ** NS NS ** A X B X C ** NS NS * NS= Non significant Table 2a. Season x Treatment effect on uniformity in flowering (%) —————————————————————————————————————————— Treatment Season ——————————————————————————————————— T1 T2 T3 T4 T5 —————————————————————————————————————————— 2013-14 78.9ab 76.0a 81.5b 86.2cde 76.0a 2014-15 89.9defg 90.3efg 91.7fg 93.3g 93.4g —————————————————————————————————————————— S. Em ± 1.64 CD (P=0.05) = 4.7 J. Hortl. Sci. Vol. 11(2): 131-142, 2017 138 Table 2b. Location x Treatment effect on uniformity in flowering (%) —————————————————————————————————————————— Location Treatment —————————————————————————————————— T1 T2 T3 T4 T5 —————————————————————————————————————————— L1 84.9a 83.2a 91.4b 96.4c 85.9a L2 83.9a 83.1a 81.8a 83.0a 83.5a —————————————————————————————————————————— S.Em ± 1.64 CD (P=0.05) = 4.7 Table 2c. Season x Location x Treatment effect on uniformity in flowering (%) —————————————————————————————————————————— 2013-14 2014-15 ——————————————————————————————————— Treatment L1 L2 L1 L2 —————————————————————————————————————————— T1 79.8a 78.0 a 90.0 bcd 89.8 bcd T2 74.6 a 77.5 a 91.9 bcde 88.8 b T3 87.3b 75.7 a 95.5cde 87.8 b T4 96.7e 75.7 a 96.2de 90.4 bcde T5 78.5 a 73.5a 93.3 bcde 93.6 bcde —————————————————————————————————————————— S.Em ± 2.31 CD (P=0.05) = 6.6 Table 2d. Season x Treatment effect on uniformity in bud-break (%) —————————————————————————————————————————— Treatment Season —————————————————————————————————— T1 T2 T3 T4 T5 —————————————————————————————————————————— 2013-14 83.4e 84.2e 84.3e 85.7e 77.8bcd 2014-15 79.3cd 74.4a 76.5abcd 76.2abc 79.7d —————————————————————————————————————————— S. Em ± 1.16 CD (P=0.05) = 3.3 Shikhamany et al J. Hortl. Sci. Vol. 11(2): 131-142, 2017 139 Table 2e. Season x Treatment effect on cane diameter (mm) —————————————————————————————————————————— Treatment Season —————————————————————————————-—————- T1 T2 T3 T4 T5 —————————————————————————————————————————— 2013-14 7.18abc 7.08ab 7.04a 7.20abc 7.12abc 2014-15 7.71d 7.90d 7.29c 7.16abc 7.25bc —————————————————————————————————————————— S. Em ± 0.071 CD (P=0.05) = 0.20 Table 2f. Location x Treatment effect on number of canes/vine —————————————————————————————————————————— Location Treatment ———————————————————————————-——————- T1 T2 T3 T4 T5 —————————————————————————————————————————— L1 27.0a 26.2a 32.3cd 34.0d 32.0bcd L2 32.0bcd 34.0d 38.7e 43.6f 42.8f —————————————————————————————————————————— S.Em ± 0.0.77 CD (P=0.05) = 2.2 Table 2g. Season x Location x Treatment effect on number of canes/vine —————————————————————————————————————————— 2013-14 2014-15 ——————————— —————————————————— Treatment L1 L2 L1 L2 —————————————————————————————————————————— T1 26.7a 32.1fghij 27.3abc 31.9efghij T2 26.9ab 30.0bcdef 25.5a 37.9lm T3 33.1ghijk 35.2kl 31.6defghij 42.2n T4 34.5jk 42.7n 33.6hijk 44.6no T5 33.8ijk 38.9m 30.3cdefg 46.7o _____________________________________________________________________________________ S.Em ± 1.08 CD (P=0.05) = 3.1 Chemical thinning in ‘ Thompson Seedless’ grape J. Hortl. Sci. Vol. 11(2): 131-142, 2017 140 Table 3. Effect of cane regulation and GA treatment on yield and quality attributes —————————————————————————————————————————— Factor Yield/vine Weight/cluster T.S.S. content Acid content (kg) (g) (oB) (g/100ml) —————————————————————————————————————————— A. Season 1. 2013-14 9.01a 385.2a 16.9b 0.500 2. 2014-15 19.16b 423.6b 14.9a 0.490 —————————————————————————————————————————— S.Em ± 0.459 9.48 0.15 0.0060 C.D. (P=0.05) 0.31 27.2 0.4 NS —————————————————————————————————————————— B. Location 1. L1 15.35b 404.7 15.5a 0. 535b 2. L2 12.82a 404.1 16.4b 0.455a —————————————————————————————————————————— S.Em ± 0.459 9.48 0.15 0.0060 C.D. (P=0.05) 0.31 NS 0.4 0.017 —————————————————————————————————————————— C. Treatment 1. T1 13.26 372.2a 15.9 0.493 2. T2 14.44 417.1bc 15.9 0.491 3. T3 14.39 404.8abc 15.9 0.497 4. T4 13.93 392.5abc 15.8 0.495 5. T5 14.42 435.2c 16.1 0.501 —————————————————————————————————————————— S.Em ± 0.725 14.99 0.24 0.0095 C.D. (P=0.05) NS 42.9 NS NS —————————————————————————————————————————— Interaction A X B ** ** ** ** A X C NS NS NS NS B X C ** ** NS NS A X B X C * NS NS NS —————————————————————————————————————————— NS= Non significant Shikhamany et al J. Hortl. Sci. Vol. 11(2): 131-142, 2017 141 Table 3a. Location x Treatment effect on yield/ vine (kg) —————————————————————————————————————————— Location Treatment ——————————————————————————————————— T1 T2 T3 T4 T5 —————————————————————————————————————————— L1 12.83ab 14.44bcd 17.60e 15.91cde 15.99de L2 13.70abcd 14.44bcd 11.18a 11.94ab 12.84ab —————————————————————————————————————————— S.Em ± 1.026 CD (P=0.05) = 2.94 Table 3b. Season x Location x Treatment effect on yield/vine (kg) —————————————————————————————————————————— 2013-14 2014-15 ——————————— —————————————————— Treatment L1 L2 L1 L2 —————————————————————————————————————————— T1 11.08cdefg 6.57ab 14.57ghi 20.83mno T2 10.35bcdef 7.27abcd 18.53ijklmn 21.61no T3 12.43efgh 7.09abc 22.77o 15.27hi T4 13.29fgh 4.87a 18.53ijklmn 19.01jklmno T5 11.37defgh 5.77 a 20.62lmno 19.91klmno —————————————————————————————————————————— S.Em ± 1.450 CD (P=0.05) = 4.15 Table 3c. Location x Treatment effect on weight of cluster (g) —————————————————————————————————————————— Location Treatment ———————————————————————————————————— —————-——— T1 T2 T3 T4 T5 —————————————————————————————————————————— L1 321.3a 418.4efgh 428.6gh 376.9abcdefg 478.2h L2 423.2fgh 415.9defg 381.1abcdefg 408.1cdefg 392.2bcdefg —————————————————————————————————————————— S.Em ± 21.20 CD (P=0.05) = 60.7 Chemical thinning in ‘ Thompson Seedless’ grape J. Hortl. Sci. Vol. 11(2): 131-142, 2017 142 (MS Received 13 April 2016, Revised 12 June 2016, Accepted 20 December 2016) REFERENCES Chadha, K.L. and Shikhamany, S.D. 1999. The Grape Improvement, Production and Post Harvest Management (ISBN: 81-85048-40-1). Malhotra Publishing House, New Delhi, India, pp. 129-30 Christensen, P. 1969. Seasonal changes and distribution of nutritional elements in ‘Thompson Seedless’ grapevines. Amer. J. Enol. and Viticulture, 20:176-90 Coombe, B.G. 1960. 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