Graft Compatibility of Local Grapevine Varieties with Grapevine Rootstocks in Yozgat Province

Abstract

Grafting compatibility between rootstocks and scions is a critical factor influencing the success of vine propagation and the long-term productivity of vineyards. This study aimed to evaluate the compatibility, sapling quality characteristics, and survival rates of grafted vines produced by combining ten local grape cultivars from Yozgat Province with four rootstocks: ‘5 BB’, ‘41 B’, ‘1103 P’, and ‘Fercal’. Grafted vines were assessed based on callus formation, graft union success, root development, and overall sapling quality. The results revealed that the ‘Fercal’ rootstock exhibited superior compatibility with several cultivars, notably achieving 100% graft success with ‘Siyah Üzüm’ and a high sapling rate of 93.4% with ‘Gelinparmağı’. Strong performance was also observed in the ‘Fercal/Köledoyuran’ and ‘Fercal/Horoz Üzümü’ combinations, which produced sapling rates of 95.4%. While ‘5 BB’ performed well with ‘Parmak Üzümü’ (100% graft success), ‘Karagevrek’ (94.4%), and ‘Mor Bulut’, it showed poor results with ‘Gelinparmağı’ (66.5% sapling rate). The ‘1103 P’ rootstock demonstrated good compatibility with ‘Şahmuratlı’ (94.3% graft success) and ‘Kirpi Üzümü’. In contrast, although ‘41 B’ reached up to 100% graft success in some combinations, it exhibited variable sapling development potential, ranging from 46.2% to 80.0%. Among the cultivars, ‘Siyah Üzüm’ achieved 100% compatibility with three rootstocks (‘41 B’, ‘1103 P’, and ‘Fercal’), followed by ‘Köledoyuran’, which consistently showed high success rates ranging from 96.9% to 100%. These findings offer practical guidance for selecting optimal rootstock–scion combinations to improve the efficiency of grafted vine production and reduce losses, particularly for local grape cultivars.

1. Introduction

Ever since the first documented evidence of viticultural practices in Central Anatolia, dating back to the Hittite period (1800–1600 B.C.) [1,2], and the recognition of Yozgat Province as one of the ancient centers of grape cultivation, an ongoing struggle has been underway to develop a complete and integrated understanding of sustainable viticulture in this challenging region [3,4]. Despite a rich heritage and considerable potential, reliable approaches to improving viticultural productivity in Yozgat, without compromising the genetic integrity of local varieties, have not yet been fully established, either at the molecular/genetic level or the physiological level. Modern technologies have allowed researchers to understand the region’s viticultural challenges in greater detail, but the complexity of factors has also increased significantly. The lack of substantial progress may be partially attributable to two factors. One factor is viewing viticulture merely as a singular, traditional practice rather than recognizing it as a complex system involving structural, biochemical, and genetic mechanisms, as well as the challenges of modernizing cultivation without negatively impacting the unique characteristics of local varieties. The characteristics of these components are variety-specific (often genotype-specific) and potentially under separate genetic control [5,6,7,8,9]. Therefore, it is essential, when investigating viticulture in Yozgat Province, to clearly identify which aspect of the process is being studied and its potential impact on regional sustainability. The second factor relates to the difficulty of studying the viability of traditional varieties under modern cultivation systems, where the interactions between rootstocks and local varieties, and the time required for these processes to reach equilibrium, pose significant challenges when conducting experiments [8,10,11,12].

According to data from the Turkish Statistical Institute (TUIK), viticulture in Yozgat Province covered an area of approximately 10 thousand hectares in 2014, with an annual grape production of around 23 thousand tons, entirely composed of seeded table grape varieties. Over the past decade, vineyard areas in Yozgat have drastically declined by nearly 78%, shrinking to just 2.2 thousand hectares by 2024. Despite this sharp reduction in cultivation area, grape production has only decreased by about 47%, reaching 12.2 thousand tons in 2024. This suggests a significant improvement in productivity, with yields more than doubling during the same period. However, even with this notable progress, the average yield per hectare in Yozgat remains approximately 50% lower than the national average, highlighting the ongoing challenges faced by local viticulture in achieving parity with broader production standards across Türkiye [13]. Despite its considerable viticultural potential, productivity per unit area in the province remains quite low due to the absence of modern systems and the use of improper cultivation techniques. Viticultural adaptations in the region can generally be categorized into two approaches: traditional and modern. The former involves longstanding practices, such as using ungrafted grapevine saplings or propagation by layering, while the latter encompasses the use of grapevine rootstocks as a foundation for grafting local varieties [14,15]. The terms traditional and modern, however, are somewhat simplistic, although widely used, as in both cases, vineyards attempt to avoid phylloxera damage [16]. In modern viticulture, this is accomplished through the selection of resistant rootstocks that provide a suitable foundation for local varieties [16]. In the traditional approach, vineyards are established without proper protection, remaining vulnerable and prone to “rapid” decline within a few years of establishment [17,18,19]. Key processes relevant to these strategies include rootstock selection and compatibility [18,20,21,22], the ability to specifically determine optimal rootstock–scion combinations for local varieties [23,24], and the formation of successful graft unions [25,26,27,28,29].

Despite the complexity of modernizing viticulture in Yozgat Province, considerable progress has been made in understanding the various components of successfully grafted vine production in other regions. This study highlights two areas where more investigation is needed: the compatibility of local Yozgat grape varieties with grape rootstocks, and the quality characteristics of grafted grapevine saplings, which have received limited research attention specific to the region’s unique varieties [30,31,32]. Contemporary viticulture depends on successful rootstock–scion combinations, where compatibility determines immediate graft union formation and affinity governs long-term performance relationships between grafted partners [5,6,7]. The selection of appropriate American rootstocks has become increasingly critical as viticulture expands into challenging environments with diverse soil conditions and climatic stresses [8,9]. Rootstock–scion compatibility represents a fundamental prerequisite for successful grafted grapevine production systems, with grafting success depending not only on technical protocols but also on the genetic compatibility between rootstock and scion varieties [33]. Research has shown that rootstock selection significantly affects scion performance, with rootstock genotype explaining between 8.99% and 9.78% of the variation in growth-related traits, including yield, pruning weight, and berry characteristics [34]. This relationship becomes particularly important in regions with extreme climatic conditions, where both genetic incompatibility and environmental stress can significantly impact grafting success rates and long-term vineyard sustainability [35].

These local varieties, including Şahmuratlı Üzümü, Köledoyuran, Kirpi Üzümü, Horoz Üzümü, Parmak Üzümü, Siyah Üzüm, Karagevrek, Gelinparmağı, Misket Üzümü, and Mor Bulut, represent valuable genetic resources due to their adaptation to the region’s extreme low temperatures and limited vegetation period [14,15]. Understanding the physiological and molecular mechanisms underlying graft compatibility is essential for identifying optimal rootstock–variety combinations that can withstand challenging environmental conditions while maintaining productivity [36]. The primary objective of this study is to investigate the effects of four different grapevine rootstocks, used in producing grafted grapevine saplings, with ten local grape varieties commonly grown in the province, on callusing room performance, grafted sapling quality characteristics, and success rates. By identifying optimal rootstock–variety combinations that demonstrate superior compatibility and performance, this research aims to contribute significantly to addressing the viticultural challenges in Yozgat Province and preserving its valuable genetic resources.

2. Materials and Methods

2.1. Study Location and Year

The study was conducted in Yozgat Province, Turkey, located at 39°77′ North latitude and 34°48′ East longitude. This research, which evaluated callusing chamber performance, quality characteristics of grafted grapevine saplings, and field survival rates of local Yozgat grape varieties grafted onto different grape rootstocks, was carried out between 2023 and 2024 at Yozgat Bozok University, Faculty of Agriculture. The research utilized the grafted grapevine sapling production unit, the Viticulture Research Greenhouse located approximately 15 m from the faculty building, and the Topçu Research and Application Field situated around 3.2 km away.

2.2. Plant Materials

The study used ten local grape varieties cultivated in Yozgat Province (Şahmuratlı Üzümü, Köledoyuran, Kirpi Üzümü, Horoz Üzümü, Parmak Üzümü, Siyah Üzüm, Karagevrek, Gelinparmağı, Misket Üzümü, and Mor Bulut) and four grape rootstocks (5 BB, 41 B, 1103 P, and Fercal) recommended for different regions of Turkey. In viticulture, other vigorous rootstocks, such as 140 Ruggeri, 110 R, Ramsey, and 1613 C, are also widely used for their adaptability to various soil and climatic conditions. These rootstocks differ in their tolerance to drought, salinity, and lime-induced chlorosis, as well as in their effects on scion vigor and productivity. In this study, the four rootstocks (5 BB, 41 B, 1103 P, and Fercal) were selected based on their proven performance under semi-arid conditions, phylloxera resistance, and widespread commercial use in Turkish viticulture. Their selection is often guided by site-specific environmental challenges and desired vine performance [18]. The characteristics of these plant materials are presented in

Table 1. The effects of variety, rootstock, and their interaction (variety × rootstock) on various grafting success, grafted grapevine saplings quality, and morphological characteristics.

Characteristics	Variety Df	Variety F	Variety p	Rootstock Df	Rootstok F	Rootstock p	Variety × Rootstock Df	Variety × Rootstock F	Variety × Rootstock P
Grafting success rate	9	94.77	p < 0.001	3	91.839	p < 0.001	27	39.356	p < 0.001
Callus development level	9	0.964	p = 0.476	3	1.855	p = 0.144	27	0.592	p = 0.937
Bud viability status	9	4.254	p < 0.001	3	0.857	p = 0.467	27	0.381	p = 0.997
Bud sprouting status	9	0.585	p = 0.806	3	0.65	p = 0.585	27	0.141	p = 1.000
Shoot length from bud	9	1.444	p = 0.184	3	1.28	p = 0.287	27	2.378	p = 0.002
Basal root formation on cutting	9	0.206	p = 0.993	3	1.913	p = 0.134	27	0.326	p = 0.999
Callus development at cutting base	9	0.585	p = 0.806	3	1.005	p = 0.395	27	0.755	p = 0.792
Grafted grapevine saplings efficiency	9	71.472	p < 0.001	3	143.592	p < 0.001	27	32.123	p < 0.001
First quality grafted grapevine saplings ratio	9	67.134	p < 0.001	3	90.616	p < 0.001	27	35.841	p < 0.001
Second quality grafted grafted grapevine saplings ratio	9	67.144	p < 0.001	3	90.592	p < 0.001	27	35.853	p < 0.001
Rootstock thickness	9	4.246	p < 0.001	3	64.109	p < 0.001	27	3.445	p < 0.001
Graft union thickness	9	5.801	p < 0.001	3	39.515	p < 0.001	27	3.082	p < 0.001
Graft shoot thickness	9	2.381	p = 0.019	3	28.477	p < 0.001	27	2.495	p = 0.001
Graft shoot length	9	30.437	p < 0.001	3	85.504	p < 0.001	27	5.368	p < 0.001
Internode length on graft shoot	9	19.5	p < 0.001	3	19.012	p < 0.001	27	2.184	p = 0.004
Number of nodes on graft shoot	9	18.459	p < 0.001	3	37.89	p < 0.001	27	3.543	p < 0.001
Total number of nodes	9	14.268	p < 0.001	3	30.705	p < 0.001	27	3.253	p < 0.001
Number of lateral shoots on graft shoot	9	7.539	p < 0.001	3	15.2	p < 0.001	27	2.502	p = 0.001
Number of nodes in lateral shoots	9	0.727	p = 0.683	3	4.894	p = 0.004	27	1.3	p = 0.185
Number of secondary–tertiary basal shoots	9	1.58	p = 0.135	3	0.296	p = 0.828	27	2.272	p = 0.003
Number of primary roots	9	26.46	p < 0.001	3	123.636	p < 0.001	27	55.492	p < 0.001
Number of secondary roots	9	27.82	p < 0.001	3	41.162	p < 0.001	27	18.323	p < 0.001
Root length	9	11.306	p < 0.001	3	12.803	p < 0.001	27	10.22	p < 0.001
Root development level	9	2.497	p = 0.014	3	3.314	p = 0.024	27	1.343	p = 0.157

The analysis was performed using Two-Way ANOVA, and significance levels were determined at p ≤ 0.05.

. Scion cuttings from local grape varieties were collected from vineyards in the Yozgat region, while rootstock cuttings were obtained from the Manisa Viticulture Research Institute Collection Vineyard. All cuttings were collected during the winter dormancy period from the well-lignified middle third sections of one-year-old shoots, following the method described by Roux [37]. Scion cuttings were prepared at approximately 100 cm in length, each containing around 15 buds, whereas rootstock cuttings were shortened to 30–40 cm according to TS-4027 standards, selecting those with diameters of 8–12 mm. The cuttings were disinfected with fungicide (1 kg Switch 62.5 WG, Syngenta/m³ water), placed in polyethylene bags, and stored in a cold room (+2 °C) for approximately 60 days until grafting.

2.3. Production of Grafted Grapevine Saplingss

Prior to grafting, the cuttings were acclimatized at room temperature for about five days. They then underwent thermotherapy (scions at 50.5 °C for 15 min and rootstocks at 54.5 °C for 30 min) followed by soaking in warm water containing fungicide (1 kg Switch 62.5 WG, Syngenta/m³ water) for 24 h (scions) and 48 h (rootstocks) to replenish moisture lost during storage [38]. Rootstocks were prepared by removing buds (except for the basal and top buds) and refreshing the basal cut (making a straight cut 0.5–1.0 cm below the basal bud). Scions were cut to single buds. Omega (Ω)-type grafting was performed using a foot-pedal grafting machine. Immediately after grafting, the upper 5–7 cm portion of the grafted grapevine saplings, including the scion and graft union, was subjected to primary paraffin waxing (74–76 °C) for 1–2 s to prevent water loss, protect against pathogens, support callus formation, delay bud break, and increase flexibility [39]. After waxing, the grafted saplings were briefly immersed in cold water to avoid heat damage to the buds [40]. Moist pine sawdust was used as the callusing medium to prevent mold growth. The medium, callusing crates, and the callusing chamber were treated with fungicide (30 g Switch 62.5 WG, Syngenta/15 L water). After waxing, the grafted grapevine saplings were stratified in plastic crates, alternating layers of moist sawdust with waxed cuttings. Each rootstock × variety combination included three replications of twelve grafted saplings each. The crates were kept in the callusing chamber for 21 days, with gradually decreasing temperature and humidity levels: 27 ± 1 °C and 80–85% relative humidity for the first three days, 25 ± 1 °C and 80–82% for the next fifteen days, and 23 ± 1 °C and 75–80% for the last three days [41]. After the callusing period, the saplings were acclimatized for approximately five days, cleaned of sawdust using compressed air, and evaluated for callusing chamber performance. A secondary paraffin waxing (80–82 °C) was applied to prevent moisture loss in the developed callus. Following waxing, the basal 10 cm portions of the saplings were soaked in water for about three days in closed plastic crates. After acclimatization, the saplings were transferred to the greenhouse for planting (Figure 1).

2.4. Planting and Cultivation of Grafted Grapevine Saplings

The research greenhouse has a northeast–southwest orientation, covers approximately 200 m², features a bow-shaped polycarbonate roof, and is equipped with 55% shade cloth, fan heaters, a fan and pad system, and ventilation. Inside the greenhouse, rooting tables measure about 5 m in length, 1.20 m in width, 80 cm in height, and 20 cm in depth. Before planting, the grafted grapevine saplings were given a quick-dip treatment (2 s) with 2000 ppm IBA (Indole Butyric Acid) to promote rooting. They were then planted in 11 × 11 × 22 cm polyethylene pots filled with a sterile 1:1 (v/v) peat mixture. For each rootstock × variety combination, three replications of three grafted saplings each were established (Figure 2). During the growing period, the saplings were irrigated regularly with a nutrient solution recommended by Ollat et al. [42], containing Ca(NO₃)₂·4H₂O (2.5 mM), KH₂PO₄ (1.0 mM), KNO₃ (2.5 mM), MgSO₄·7H₂O (1.0 mM), Na₂MoO₄ (0.013 µM), ZnSO₄·7H₂O (2.40 µM), CuSO₄ (0.5 µM), MnCl₂·4H₂O (9.2 µM), H₃BO₃ (46.4 µM), and NaFe(III)-EDTA (45 µM). The solution pH was adjusted to 6.5, and irrigation was applied to achieve a 30% drainage ratio. The growing environment was maintained at 25 ± 5 °C with 60–70% relative humidity under natural day length, supported by electric heaters and the fan and pad system. Approximately eight weeks after planting (July), once sufficient root and shoot growth had developed, measurements were taken to assess the performance and quality characteristics of the grafted grapevine saplings produced from different rootstock × variety combinations [43].

2.5. Transfer of Grafted Grapevine Saplings to the Vineyard

All grafted grapevine saplings were transferred to the Topçu Research and Application Field, where a “Collection Plot of Yozgat Local Grape Varieties” covering approximately 0.1 hectare was established. The vineyard site was prepared by installing an irrigation system, laying out plots, and digging planting holes, each marked with a stake. Regular irrigation and fertilization were carried out after planting.

2.6. Data Collection

Measurements, counts, and observations were conducted at the Grafted Grapevine Saplings Production Unit, the Viticulture Research Greenhouse, and the Topçu Research and Application Field of Yozgat Bozok University. Variables related to callusing chamber performance, such as grafting success, callus development level, bud viability, bud sprouting, shoot length from the bud, basal root formation, basal rot incidence, and callus development level at the cutting base, were evaluated immediately after the 21-day callusing process and a subsequent 7-day acclimatization period, before the secondary waxing. Grafted grapevine sapling categories (first and second-grade saplings) and quality characteristics, including rootstock thickness, graft union thickness, scion shoot thickness, scion shoot length, internode length, number of nodes on the scion shoot, total number of nodes, number of laterals on the scion shoot, number of nodes on laterals, number of secondary–tertiary basal shoots, number of primary roots, number of secondary roots, root length, and root development level, were assessed after a 60-day growing period between 1 May and 30 June. At this time, the grafted grapevine saplings had reached phenological development stage 15 on the E-L scale, characterized by approximately eight fully expanded leaves on each shoot [44]. Field survival rate was determined the following spring after bud break, based on the presence of new shoot formation. Grafting success, sapling grade, and field survival rate were evaluated on all plants within each replication, while morphological variables were measured on three randomly selected cuttings or saplings per replication.

2.6.1. Callusing Chamber Performance

The success and quality of grafting were assessed through a series of physiological and morphological variables. Grafting success (%) was calculated using the formula: (Number of successfully healed grafted grapevine saplings × 100). Total number of stratified grafted grapevine saplings. Callus development at the graft union was evaluated on a 0–1 scale according to Damborska [45], where values ranged from 0 (no callus formation) to 1 (callus completely surrounding the graft union). Bud viability was recorded as either ‘viable’ or ‘discarded’ and expressed as the percentage of viable buds. Similarly, bud sprouting was noted as ‘sprouted’ or ‘not sprouted’ and presented as the percentage of sprouted buds. The shoot length emerging from the bud was measured in centimeters using a ruler. Basal root formation and basal rot condition were qualitatively assessed as either ‘present’ or ‘absent,’ with basal root formation expressed as the percentage of cuttings showing root presence. Callus development at the cutting base was also assessed on a 0–1 scale, indicating the extent of callus coverage. Root development level was evaluated on a 0–4 scale, where 0 indicated no root formation and 4 represented well-developed roots surrounding the entire cutting base. In terms of nursery performance, grafted grapevine sapling rate (%) was determined by the ratio of successfully developed grafted grapevine saplings to the total number of planted saplings. These grafted grapevine saplings were further classified, and the percentages of first-grade and second-grade saplings were calculated based on the total number of saplings. First-grade saplings met nursery standards (e.g., uniform thickness, strong graft union, healthy root system), whereas second-grade saplings did not fully meet these criteria but were still viable. Morphological variables, including rootstock thickness, graft union thickness, and scion shoot thickness, were measured in millimeters using a digital caliper at specified points. Rootstock thickness was measured 1.5 cm below the graft union at both the thinnest and thickest parts and averaged. Graft union thickness was measured directly at the union site, while scion shoot thickness was recorded midway between the second and third nodes of the main shoot. All values were averaged to ensure consistency and accuracy.

2.6.2. Field Performance

Field survival rate was calculated in the following spring after bud break using the formula: Field Survival Rate (%) = (Number of surviving grafted grapevine saplings × 100)/Number of planted grafted grapevine saplings. The experimental site featured clay–loam soil with a pH of 7.2, organic matter content of 2.1%, and good drainage at an elevation of 1,350 m. The region is characterized by a semi-arid continental climate, with an average annual precipitation of approximately 400 mm and a mean growing season temperature of 18.5 °C.

2.7. Data Analysis

The quantitative data collected in the study were statistically analyzed using IBM SPSS Statistics v.20.0. Prior to the analyses, data normality was tested with the Shapiro–Wilk test, and variance homogeneity was checked using Levene’s test to confirm assumptions for parametric tests. A two-way analysis of variance (Two-Way ANOVA) was performed to determine the effects of the studied factors. Differences among means were evaluated using Duncan’s multiple range test at a significance level of p < 0.05. Additionally, correlation analysis was conducted to identify relationships among the morphological and physiological traits examined. Principal Component Analysis (PCA) was also applied to extract main components and facilitate the classification of samples.

3. Results

Variety, rootstock, and their interaction had highly significant effects (p < 0.001) on grafting success rate, grafted grapevine sapling efficiency, and the proportions of both first- and second-quality grafted grapevine saplings (Table 1). Significant effects of variety (p < 0.05 or p < 0.001) were observed for bud viability (F=4.254), scion shoot thickness (F = 2.381), and root development level (F = 2.497). Rootstock had a highly significant influence on rootstock thickness (F = 64.109), number of primary roots (F = 123.636), and root length (F=12.803) (p < 0.001). Interaction effects (variety × rootstock) were also significant (p < 0.001) for several traits, including shoot length (F = 5.368), number of roots, and graft union thickness. No statistically significant differences were found for bud sprouting status, basal root formation, or callus development at the cutting base and graft union across the studied factors (p > 0.05). In terms of grafting success (

Table 2. Effects of rootstock/variety combinations on grafting success, scion length, grafted grapevine sapling efficiency, and quality classification of grafted vines.

Rootstock/Variety Combination	Grafting Success Rate (%)	Scion Length (cm)	Grafted Grapevine Sapling Efficiency (%)	First Quality Grafted Grapevine Sapling Ratio (%)	Second Quality Grafted Grafted Grapevine Saplings Ratio (%)
5 BB/Siyah Üzüm	89.7 ± 2.5 d–e	2.7 ± 1.5 a–f	93.93 ± 3.09 ab	100.0 ± 0.0 a	0.0 ± 0.0 k
41 B/Siyah Üzüm	100.0 ± 0.0 a	1.8 ± 0.8 b–f	80.07 ± 1.16 hi	100.0 ± 0.0 a	0.0 ± 0.0 k
1103 P/Siyah Üzüm	100.0 ± 0.0 a	2.2 ± 1.0 b–f	86.90 ± 0.90 ef	100.0 ± 0.0 a	0.0 ± 0.0 k
Fercal/Siyah Üzüm	100.0 ± 0.0 a	2.7 ± 1.3 a–f	91.80 ± 3.95 a–c	100.0 ± 0.0 a	0.0 ± 0.0 k
5 BB/Karagevrek	94.4 ± 3.6–d	4.3 ± 1.8 a	88.07 ± 2.50 c–e	96.3 ± 3.8 ab	3.7 ± 3.8 jk
41 B/Karagevrek	100.0 ± 0.0 a	1.5 ± 0.5 d–f	86.87 ± 3.55 ef	83.3 ± 6.7 de	16.7 ± 6.7gh
1103 P/Karagevrek	97.2 ± 2.2 ab	1.8 ± 0.3 b–f	82.47 ± 5.31 gh	81.5 ± 6.5 d–f	18.5 ± 6.5 f–h
Fercal/Karagevrek	90.9 ± 6.1 c–e	2.8 ± 1.3 a–e	87.87 ± 1.46 de	95.5 ± 4.5 ab	4.5 ± 4.5 jk
5 BB/Gelinparmağı	92.3 ± 3.7 b–e	3.3 ± 0.3 a–c	66.47 ± 1.05 mn	66.6 ± 3.5 hi	33.4 ± 3.5 cd
41 B/Gelinparmağı	100.0 ± 0.0 a	3.5 ± 0.0 ab	68.67 ± 2.65 l–n	75.0 ± 3.1 fg	25.0 ± 3.1 ef
1103 P/Gelinparmağı	93.3 ± 0.7 b–e	2.8 ± 0.6 a–e	76.53 ± 1.87 ij	76.5 ± 4.4 e–g	23.5 ± 4.4 e–g
Fercal/Gelinparmağı	100.0 ± 0.0 a	1.5 ± 0.5 d–f	93.43 ± 2.44 ab	100.0 ± 0.0 a	0.0 ± 0.0 k
5 BB/Misket Üzümü	96.7 ± 2.4 ab	2.5 ± 0.5 b–f	82.53 ± 1.19 gh	90.1 ± 2.1 bc	9.9 ± 2.1 ij
41 B/Misket Üzümü	100.0 ± 0.0 a	2.5 ± 1.0 b–f	73.17 ± 1.18 jk	83.1 ± 2.0 de	16.9 ± 2.0 gh
1103 P/Misket Üzümü	97.0 ± 0.4 ab	1.5 ± 0.0 d–f	62.47 ± 0.95 o	57.0 ± 4.0 j	43.0 ± 4.0 b
Fercal/Misket Üzümü	100.0 ± 0.0 a	1.0 ± 0.0 f	71.57 ± 1.21 kl	70.0 ± 2.0 gh	30.0 ± 2.0 de
5 BB/Parmak Üzümü	83.9 ± 3.0 f–g	2.2 ± 0.8 b–f	83.30 ± 0.96 f–h	100.0 ± 0.0 a	0.0 ± 0.0 k
41 B/Parmak Üzümü	100.0 ± 0.0 a	2.8 ± 0.6 a–e	81.90 ± 1.31 h	83.3 ± 3.7 de	16.7 ± 3.7 gh
1103 P/Parmak Üzümü	89.5 ± 4.6 d–e	2.0 ± 0.5 b–f	82.73 ± 3.61 gh	70.3 ± 5.5 gh	29.7 ± 5.5 de
Fercal/Parmak Üzümü	100.0 ± 0.0 a	2.5 ± 1.8 b–f	86.30 ± 1.74 e–g	78.5 ± 4.5 ef	21.5 ± 4.5 fg
5 BB/Mor Bulut	73.3±4.4 h	1.8 ± 0.3 b–f	88.60 ± 2.26 c–e	100.0 ± 0.0 a	0.0 ± 0.0 k
41 B/Mor Bulut	100.0 ± 0.0 a	3.0 ± 0.5 a–d	71.17 ± 0.85 kl	80.0 ± 5.1 d–f	20.0 ± 5.1 f–h
1103 P/Mor Bulut	82.1 ± 2.9 g	2.5 ± 0.9 b–f	81.93 ± 2.29 h	100.0 ± 0.0 a	0.0 ± 0.0 k
Fercal/Mor Bulut	30.0 ± 4.0 i	3.5 ± 0.5 ab	81.47 ± 0.49 h	91.0 ± 2.0 bc	9.0 ± 2.0 ij
5 BB/Şahmuratlı	68.8 ± 6.8 h	2.5 ± 1.5 b–f	79.37 ± 2.42 hi	81.3 ± 5.0 d–f	18.8 ± 5.0 f–h
41 B/Şahmuratlı	97.6 ± 2.4 ab	1.2 ± 0.3 ef	70.20 ± 1.21 k–m	70.3 ± 1.9 gh	29.7 ± 1.9 de
1103 P/Şahmuratlı	94.3 ± 3.7 a–d	1.7 ± 0.6 c–f	80.17 ± 1.97 hi	100.0 ± 0.0 a	0.0 ± 0.0 k
Fercal/Şahmuratlı	95.8 ± 4.2 a–c	3.3 ± 0.8 a–c	71.83 ± 1.70 kl	66.6 ± 3.5 hi	33.4 ± 3.5 cd
5 BB/Köledoyuran	100.0 ± 0.0 a	2.3 ± 0.6 b–f	82.67 ± 1.18 gh	91.6 ± 3.4 bc	8.4 ± 3.4 ij
41 B/Köledoyuran	97.4 ± 2.6 ab	1.0 ± 0.0 f	82.47 ± 3.08 gh	85.9 ± 4.0 cd	14.1 ± 4.0 hi
1103 P/Köledoyuran	96.9 ± 3.1 ab	2.7 ± 0.8 a–f	86.17 ± 1.30 e–g	100.0 ± 0.0 a	0.0 ± 0.0 k
Fercal/Köledoyuran	90.0 ± 4.0 d–e	2.5 ± 0.0 b–f	91.37 ± 1.00 b–d	95.3 ± 4.8 ab	4.7 ± 4.8 jk
5 BB/Kirpi Üzümü	83.3 ± 3.7 g	2.0 ± 0.5 b–f	80.90 ± 2.07 h	94.7 ± 3.1 ab	5.3 ± 3.1 jk
41 B/Kirpi Üzümü	88.6 ± 4.5 e–f	3.0 ± 1.3 a–d	68.17 ± 1.55 l–n	61.0 ± 9.0 ij	39.0 ± 9.0 bc
1103 P/Kirpi Üzümü	96.6 ± 3.5 ab	3.2 ± 0.8 a–d	87.27 ± 2.22 e	92.3 ± 2.3 bc	7.7 ± 2.3 ij
Fercal/Kirpi Üzümü	81.6 ± 0.4 g	3.0 ± 0.5 a–d	81.40 ± 0.26 h	94.1 ± 4.1 ab	5.9 ± 4.1 jk
5 BB/Horoz Üzümü	96.8 ± 3.3 ab	2.3 ± 0.8 b–f	88.20 ± 2.61 c–e	93.3 ± 4.3 ab	6.7 ± 4.3 jk
41 B/Horoz Üzümü	100.0 ± 0.0 a	3.2 ± 2.1 a–d	65.33 ± 1.01 no	46.2 ± 3.0 k	53.8 ± 3.0 a
1103 P/Horoz Üzümü	100.0 ± 0.0 a	1.5 ± 0.5 d–f	68.03 ± 0.67 l–n	58.3 ± 4.7 j	41.7 ± 4.7 b
Fercal/Horoz Üzümü	93.8 ± 4.3 b–e	2.3 ± 1.3 b–f	95.43 ± 1.50 a	94.1 ± 0.9 ab	5.9 ± 0.9 jk

According to Duncan’s multiple range test, means followed by different lowercase letters differ significantly at the 5% level based on the Rootstock × Cultivar interaction. Data are presented as mean ± standard deviation (SD).

), 100% success rates were achieved for Siyah Üzüm grafted onto 41 B, 1103 P, and Fercal rootstocks. For Karagevrek, 41 B resulted in 100% success, followed by 1103 P (97.2%) and 5 BB (94.4%), while Fercal had a slightly lower success (90.9%). Gelinparmağı, Misket Üzümü, and Parmak Üzümü all showed 100% grafting success with 41 B and Fercal, although other rootstocks produced slightly lower rates. For Mor Bulut, 41 B achieved 100% success, whereas Fercal had the lowest success (30.0%). Şahmuratlı exhibited high grafting success with 41 B (97.6%), Fercal (95.8%), and 1103 P (94.3%), but a lower rate with 5 BB (68.8%). Köledoyuran achieved 100% success with 5 BB and also high success rates with 41 B (97.4%) and 1103 P (96.9%). Kirpi Üzümü and Horoz Üzümü showed the highest success with 1103 P and 41 B (up to 100%), while other rootstocks yielded moderate success rates.

Regarding shoot length (Table 2), no significant differences were observed among rootstocks in Siyah Üzüm, with values ranging from 1.8 to 2.7 cm. In Karagevrek, the longest shoots were obtained with 5 BB (4.3 cm). Gelinparmağı showed the longest shoots with 41 B (3.5 cm) and 5 BB (3.3 cm). Misket Üzümü and Parmak Üzümü exhibited shorter and more uniform shoot lengths across rootstocks. In Şahmuratlı, Fercal produced the longest shoots (3.3 cm), whereas 41 B resulted in the shortest shoots (1.2 cm). No significant differences in shoot length were found among rootstocks in Kirpi Üzümü and Horoz Üzümü. For grafted grapevine sapling percentages (Table 2), the highest value in Siyah Üzüm was obtained with 5 BB (93.93%), followed by Fercal (91.80%), while 41 B had the lowest rate (80.07%). In Karagevrek, all rootstocks achieved rates above 82%, with 5 BB and Fercal showing the highest percentages. In Gelinparmağı, Fercal achieved the highest sapling rate (93.43%), whereas 5 BB yielded only 66.47%. Misket Üzümü had the highest sapling percentage with 5 BB (82.53%), while 1103 P had the lowest (62.47%). Mor Bulut, Şahmuratlı, Köledoyuran, and Kirpi Üzümü exhibited rootstock-dependent variation, with 5 BB and Fercal generally performing better across these varieties.

In Horoz Üzümü, Fercal exhibited the highest grafted grapevine sapling rate (95.43%). First-grade grafted grapevine sapling percentages (Table 2) were 100% in Siyah Üzüm across all rootstocks. In Karagevrek, 5 BB (96.3%) and Fercal (95.5%) recorded the highest first-grade sapling rates. Gelinparmağı reached 100% first-grade sapling rate with Fercal, whereas other rootstocks had lower values. In Misket Üzümü, 5 BB yielded 90.1%, while 1103 P had the lowest rate at 57.0%. Parmak Üzümü reached 100% with 5 BB. In Mor Bulut, both 5 BB and 1103 P achieved 100%, while 41 B was the lowest at 80.0%. For Şahmuratlı and Köledoyuran, 1103 P attained 100%, with other rootstocks showing lower rates. In Kirpi Üzümü and Horoz Üzümü, 5 BB and Fercal demonstrated high first-grade sapling rates (>93%), whereas 41 B showed the lowest performance with 61.0% and 46.2%, respectively. Second-grade grafted grapevine sapling percentages were zero for all rootstocks in Siyah Üzüm (Table 2). In Karagevrek, 1103 P (18.5%) and 41 B (16.7%) outperformed 5 BB and Fercal (<5%). Gelinparmağı exhibited the highest second-grade sapling rate with 5 BB (33.4%), while Fercal yielded none. In Misket Üzümü and Parmak Üzümü, 1103 P recorded the highest second-grade sapling rates (43.0% and 29.7%, respectively), with 5 BB being the lowest. Mor Bulut, Şahmuratlı, and Köledoyuran showed moderate second-grade sapling percentages primarily with 41 B. Kirpi Üzümü had the highest second-grade sapling rate with 41 B (39.0%), while Horoz Üzümü showed the overall highest second-grade sapling rates with 41 B (53.8%) and 1103 P (41.7%). The grafted grapevine cultivars on different rootstocks exhibited variable results regarding rootstock diameter, graft union thickness, shoot thickness, shoot length, internode length, and bud number (

Table 3. Effects of rootstock/variety combinations on morphological variables of grafted vines including thickness measurements and scion growth characteristics.

Rootstock/Variety Combination	Rootstock Thickness (mm)	Graft Union Thickness (mm)	Scion Thickness (mm)	Scion Length (cm)	Internode Length of Scion (cm)	Internode number of Scion
5 BB/Siyah Üzüm	12.5 ± 0.4 c–e	19.2 ± 1.0 b–g	3.6 ± 0.3 f–i	40.3 ± 9.6 c–f	7.3 ± 1.0 a	7.7 ± 1.5 e–k
41 B/Siyah Üzüm	10.0 ± 0.3 h–l	15.0 ± 0.5 kl	3.1 ± 0.5 hi	19.7 ± 0.6 p–s	4.0 ± 0.5 f–i	5.0 ± 0.0 k–n
1103 P/Siyah Üzüm	10.3 ± 0.6 g–l	17.3 ± 1.1 d–k	3.7 ± 0.5 c–i	37.8 ± 5.0 d–h	5.2 ± 0.8 b–f	9.7 ± 1.5 b–g
Fercal/Siyah Üzüm	10.3 ± 0.7 g–l	16.9 ± 2.0 e–k	4.5 ± 0.7 b–d	47.8 ± 8.1 bc	6.5 ± 1.3 a–c	11.0 ± 1.7 bc
5 BB/Karagevrek	12.2 ± 1.7 c–g	19.4 ± 2.7 b–f	3.9 ± 0.3 c–i	39.2 ± 2.6 d–g	7.0 ± 1.0 a	8.0 ± 0.0 d–j
41 B/Karagevrek	8.3 ± 0.4 l	15.4 ± 1.1 j–l	3.0 ± 0.3 i	17.8 ± 6.3 q–t	4.2 ± 0.8 e–i	6.0 ± 0.0 j–n
1103 P/Karagevrek	10.0 ± 0.1 h–l	16.9 ± 0.8 f–k	3.3 ± 0.3 g–i	34.0 ± 6.7 e–k	6.0 ± 0.9 a–d	7.3 ± 0.6 f–k
Fercal/Karagevrek	14.5 ± 0.8 ab	25.2 ± 2.6 a	4.8 ± 0.3 ab	42.5 ± 2.6 c–e	6.2 ± 1.0 a–d	9.3 ± 1.5 b–h
5 BB/Gelinparmağı	9.9 ± 1.3 h–l	16.3 ± 1.2 g–l	3.5 ± 0.7 f–i	14.3 ± 2.0 r–u	3.2 ± 0.8 g–k	4.7 ± 1.2 l–n
41 B/Gelinparmağı	8.5 ± 0.8 kl	16.1 ± 1.3 h–l	3.3 ± 0.4 g–i	10.3 ± 2.8 tu	2.2 ± 0.3 jk	3.7 ± 2.1 n
1103 P/Gelinparmağı	10.4 ± 0.9 f–k	15.2 ± 2.1 j–l	3.6 ± 0.3 f–i	25.3 ± 4.1 k–q	4.0 ± 0.5 f–i	8.0 ± 1.7 d–j
Fercal/Gelinparmağı	13.3 ± 0.2 b–c	20.5 ± 0.9 bc	4.5 ± 0.3 b–e	21.3 ± 3.3 n–s	2.5 ± 0.5 i–k	7.0 ± 2.6 g–l
5 BB/Misket Üzümü	10.3 ± 1.2 g–l	17.1 ± 0.7 d–k	3.4 ± 0.7 f–i	20.5 ± 8.2 o–s	3.8 ± 1.0 f–j	8.3 ± 1.5 c–j
41 B/Misket Üzümü	9.3 ± 0.7 i–l	14.2 ± 0.7 kl	3.6 ± 0.2 f–i	19.0 ± 2.6 p–t	2.7 ± 1.3 i–k	7.0 ± 1.0 g–l
1103 P/Misket Üzümü	8.9 ± 0.5 j–l	13.7 ± 1.6 l	3.1 ± 0.6 hi	14.8 ± 4.5 r–u	1.8 ± 0.3 k	5.7 ± 0.6 j–n
Fercal/Misket Üzümü	10.0 ± 0.5 h–l	16.3 ± 2.5 g–l	3.5 ± 0.8 f–i	24.5 ± 4.4 l–q	3.5 ± 0.5 f–k	7.7 ± 1.2 e–k
5 BB/Parmak Üzümü	12.9 ± 1.5 b–d	20.5 ± 0.9 bc	4.6 ± 0.4 b–c	34.5 ± 2.3 e–k	5.0 ± 0.0 c–g	12.0 ± 1.0 ab
41 B/Parmak Üzümü	10.7 ± 1.5 e–j	17.0 ± 0.3 e–k	3.2 ± 0.4 g–i	19.8 ± 2.3 o–s	3.8 ± 1.3 f–j	6.7 ± 1.2 h–m
1103 P/Parmak Üzümü	9.7 ± 0.6 i–l	16.5 ± 0.8 f–l	3.4 ± 0.6 f–i	32.2 ± 5.3 f–l	3.0 ± 1.3 h–k	10.0 ± 0.0 b–f
Fercal/Parmak Üzümü	10.7 ± 1.6 e–j	18.1 ± 1.0 c–j	4.1 ± 0.4 b–g	34.8 ± 3.3 e–j	3.5 ± 0.9 f–k	10.0 ± 2.0 b–f
5 BB/Mor Bulut	13.1 ± 1.1 b–d	20.1 ± 0.9 b–d	3.8 ± 0.3 c–i	28.0 ± 1.0 i–p	5.8 ± 0.3 a–e	6.3 ± 0.6 i–m
41 B/Mor Bulut	10.4 ± 0.4 f–k	18.8 ± 0.2 b–i	3.1 ± 0.4 hi	8.8 ± 2.4 u	2.5 ± 0.5 i–k	4.3 ± 1.2 mn
1103 P/Mor Bulut	9.9 ± 1.3 h–l	15.8 ± 1.5 i–l	3.8 ± 0.5 c–i	31.2 ± 3.9 g–m	4.8 ± 0.8 c–h	11.0 ± 0.0 bc
Fercal/Mor Bulut	13.5 ± 1.2 a–c	19.3 ± 2.4 b–f	4.3 ± 0.6 b–f	34.2 ± 4.3 e–k	4.8 ± 1.2 c–h	10.7 ± 0.6 b–d
5 BB/Şahmuratlı	12.3 ± 2.4 c–f	16.7 ± 0.6 f–l	3.8 ± 0.5 c–i	23.5 ± 4.8 l–r	3.0 ± 1.0 h–k	7.7 ± 0.6 e–k
41 B/Şahmuratlı	9.3 ± 0.6 i–l	16.4 ± 1.0 f–l	3.6 ± 0.6 e–i	14.0 ± 4.1 s–u	2.5 ± 0.9 i–k	7.3 ± 0.6 f–k
1103 P/Şahmuratlı	9.7 ± 0.3 i–l	16.1 ± 1.0 h–l	3.6 ± 0.3 f–i	27.0 ± 3.5 j–q	3.5 ± 0.9 f–k	9.0 ± 1.0 c–i
Fercal/Şahmuratlı	12.5 ± 1.0 c–e	19.0 ± 1.3 b–h	3.4 ± 0.7 f–i	21.2 ± 2.0 n–s	2.0 ± 0.0 k	7.7 ± 2.5 e–k
5 BB/Köledoyuran	11.3 ± 1.4 d–i	16.8 ± 1.3 f–k	3.5 ± 0.2 f–i	30.0 ± 2.6 h–n	5.0 ± 0.5 c–g	10.7 ± 3.5 b–d
41 B/Köledoyuran	9.3 ± 1.4 i–l	16.2 ± 1.2 g–l	3.9 ± 0.6 c–h	31.8 ± 11.8 f–l	4.5 ± 1.5 d–h	9.7±0.6 b–g
1103 P/Köledoyuran	10.0 ± 0.2 h–l	16.9 ± 0.9 e–k	4.1±0.1 b–g	43.8 ± 0.3 cd	5.0 ± 0.9 c–g	14.0 ± 1.0 a
Fercal/Köledoyuran	15.1 ± 0.5 a	21.2 ± 0.9 b	5.4 ± 0.6 a	57.7 ± 5.6 a	4.8 ± 0.8 c–h	14.0 ± 2.0 a
5 BB/Kirpi Üzümü	10.4 ± 0.4 f–k	17.2 ± 1.5 d–k	3.7 ± 0.5 c–i	28.0 ± 2.6 i–p	4.2 ± 1.3 e–i	10.3 ± 0.6 b–e
41 B/Kirpi Üzümü	8.6 ± 1.3 kl	16.1 ± 2.1 h–l	3.1 ± 0.5 hi	18.3 ± 3.7 q–t	3.3 ± 0.3 f–k	6.7 ± 1.2 h–m
1103 P/Kirpi Üzümü	9.6 ± 0.5 i–l	16.4 ± 2.4 f–l	3.6 ± 0.5 e–i	25.3 ± 3.0 k–q	4.5 ± 0.9 d–h	10.0 ± 1.7 b–f
Fercal/Kirpi Üzümü	12.2 ± 1.1 c–g	19.9 ± 2.0 b–e	4.5 ± 0.4 b–d	36.8 ± 0.8 d–i	4.2 ± 0.3 e–i	10.7 ± 0.6 b–d
5 BB/Horoz Üzümü	11.8 ± 2.1 c–h	18.7 ± 2.4 b–i	3.3 ± 0.4 f–i	29.0 ± 4.1 h–o	6.3 ± 1.5 a–c	7.7 ± 0.6 e–k
41 B/Horoz Üzümü	9.2 ± 0.1 j–l	15.2 ± 1.4 j–l	3.6 ± 0.7 d–i	21.5 ± 7.9 n–s	3.5 ± 1.0 f–k	6.7 ± 1.5 h–m
1103 P/Horoz Üzümü	9.5 ± 0.4 i–l	15.0 ± 0.8 kl	3.1 ± 0.2 hi	22.2 ± 2.3 m–s	4.8 ± 0.8 c–h	6.0 ± 0.0 j–n
Fercal/Horoz Üzümü	13.0 ± 0.6 b–d	18.8 ± 2.5 b–i	4.9 ± 0.2 ab	53.5 ± 3.0 ab	6.8 ± 1.8 ab	10.7 ± 1.2 b–d

According to Duncan’s multiple range test, means followed by different lowercase letters differ significantly at the 5% level based on the Rootstock × Cultivar interaction. Data are presented as mean ± standard deviation (SD).

). Among the rootstocks, Fercal generally produced the largest rootstock diameters, with Köledoyuran (15.1 mm), Karagevrek (14.5 mm), and Mor Bulut (13.5 mm) showing the highest values. Other cultivars, such as Gelinparmağı (13.3 mm), Horoz Üzümü (13.0 mm), and Şahmuratlı (12.5 mm), also showed significant rootstock diameters on Fercal. The 5 BB rootstock showed relatively high diameters, especially in Mor Bulut (13.1 mm), Parmak Üzümü (12.9 mm), and Siyah Üzüm (12.5 mm), while Misket Üzümü (10.3 mm) and Gelinparmağı (9.9 mm) had lower diameters. The 1103 P rootstock generally yielded intermediate rootstock diameters, whereas the 41 B rootstock produced the smallest diameters, with Karagevrek showing the lowest value (8.3 mm).

Regarding graft union thickness, Fercal consistently produced the highest values, particularly in Karagevrek (25.2 mm). Gelinparmağı, Köledoyuran, and Kirpi Üzümü also showed high graft union thickness on Fercal. The 5 BB rootstock resulted in moderate graft union thickness, notably in Parmak Üzümü (20.5 mm) and Mor Bulut (20.1 mm), while 1103 P exhibited intermediate thickness values. The 41 B rootstock generally had the lowest graft union thicknesses, with Misket Üzümü (14.2 mm) and Siyah Üzüm (15.0 mm) showing the smallest measurements. For graft shoot thickness, Fercal again recorded the highest values in Siyah Üzüm (4.5 mm) and Karagevrek (4.8 mm). The 41 B rootstock produced the lowest shoot thickness, especially in Siyah Üzüm (3.0 mm). Fercal also showed the highest shoot thickness in Gelinparmağı (4.5 mm), with no significant differences observed among the other rootstocks. In Misket Üzümü, shoot thickness ranged from 3.1 to 3.6 mm without significant differences between rootstocks. In Mor Bulut, Fercal (4.3 mm) produced significantly thicker shoots than 41 B, while other rootstocks yielded similar results. Regarding graft shoot length, Fercal and 5 BB showed the longest shoots in Siyah Üzüm (47.8 cm and 40.3 cm, respectively), while 41 B had the shortest (19.7 cm). In Karagevrek, Fercal, 5 BB, and 1103 P had similar shoot lengths, whereas 41 B produced the shortest shoots (17.8 cm). In Gelinparmağı, Fercal and 1103 P had comparable shoot lengths (21.3 cm and 25.3 cm, respectively), with 41 B again having the shortest (10.3 cm). In Köledoyuran, Fercal produced the longest shoots (57.7 cm), significantly longer than other rootstocks. In Horoz Üzümü, Fercal also produced the longest shoots (53.5 cm).

For internode length, the 5 BB rootstock produced the longest internodes in Siyah Üzüm (7.3 cm) and Karagevrek (7.0 cm), while Fercal also showed relatively high values (6.5 cm and 6.2 cm, respectively). The 41 B rootstock generally had the shortest internodes. In Gelinparmağı, internode lengths were shorter overall, particularly with 41 B (2.2 cm). In Mor Bulut, 5 BB showed the longest internodes (5.8 cm), whereas 41 B had the shortest (2.5 cm). Regarding the number of buds on graft shoots, Fercal rootstock resulted in the highest bud counts in Siyah Üzüm (11.0 buds) and Karagevrek (9.3 buds). Köledoyuran exhibited the highest shoot thickness with Fercal (5.4 mm). The 5 BB and 1103 P rootstocks showed similar results, while the 41 B rootstock generally produced the lowest bud numbers, particularly in Gelinparmağı and Mor Bulut. In Köledoyuran, Fercal and 1103 P had the highest bud numbers (14.0 buds), while in Kirpi Üzümü, Fercal and 5 BB had the highest bud numbers (10.7 and 10.3 buds, respectively). The rootstocks examined were Fercal, 1103 P, 41 B, and 5 BB, and their impact on the number of nodes, secondary–tertiary shoots, and root characteristics was assessed (

Table 4. Effects of rootstock/variety combinations on shoot and root development characteristics of grafted vines.

Rootstock/Variety Combination	Total Number of Nodes on Scion	Number of Lateral Shoots on Scion	Number of Secondary–Tertiary Basal Shoots	Number of Primary Roots	Number of Secondary Roots	Root Length (cm)
5 BB/Siyah Üzüm	8.0 ± 1.7 g–l	0.3 ± 0.6 ef	0.3 ± 0.6 cd	68.0 ± 2.0 b	23.0 ± 3.0 c–i	9.0 ± 2.0 mn
41 B/Siyah Üzüm	5.0 ± 0.0 k–m	0.0 ± 0.0 f	0.0 ± 0.0 d	17.7 ± 0.6 l–n	37.3 ± 5.4 b	9.4 ± 0.5 l–n
1103 P/Siyah Üzüm	10.3 ± 2.5 d–i	0.3 ± 0.6 ef	0.3 ± 0.6 cd	33.0 ± 1.0 g–j	28.0 ± 4.0 c–e	10.5 ± 0.5 k–n
Fercal/Siyah Üzüm	11.7 ± 2.3 c–g	0.7 ± 0.6 ef	0.0 ± 0.0 d	28.0 ± 4.0 i–k	38.0 ± 8.0 b	17.0 ± 4.0 c–g
5 BB/Karagevrek	8.0 ± 0.0 g–l	0.0 ± 0.0 f	0.3 ± 0.6 cd	36.0 ± 2.0 f–i	26.0 ± 6.0 c–g	13.5 ± 1.5 f–m
41 B/Karagevrek	6.0 ± 0.0 j–m	0.0 ± 0.0 f	0.0 ± 0.0 d	17.0 ± 2.0 l–o	70.0 ± 10.0 a	31.0 ± 6.0 a
1103 P/Karagevrek	9.3 ± 3.2 e–j	1.0 ± 1.0 ef	0.0 ± 0.0 d	40.0 ± 7.0 e–g	15.0 ± 3.0 j–m	20.0 ± 3.0 c
Fercal/Karagevrek	9.7 ± 2.1 d–j	1.0 ± 1.0 ef	0.3 ± 0.6 cd	35.0 ± 5.0 f–j	14.0 ± 1.0 k–m	13.5 ± 2.5 f–m
5 BB/Gelinparmağı	4.7 ± 1.2 k–m	0.3 ± 0.6 ef	0.3 ± 0.6 cd	8.0 ± 1.0 p	16.0 ± 2.0 i–m	12.0 ± 3.0 h–n
41 B/Gelinparmağı	3.7 ± 2.1 m	0.7 ± 1.2 ef	0.0 ± 0.0 d	19.0 ± 6.0 lm	19.0 ± 4.0 g–l	8.0 ± 0.0 n
1103 P/Gelinparmağı	12.0 ± 1.7 c–g	3.7 ± 0.6 a–c	0.0 ± 0.0 d	28.0 ± 4.0 i–k	16.0 ± 4.0 i–m	17.5 ± 1.5 c–f
Fercal/Gelinparmağı	10.0 ± 4.4 d–j	2.0 ± 0.0 c–e	1.0 ± 0.0 a–c	97.0 ± 8.0 a	13.0 ± 2.0 lm	9.0 ± 1.0 mn
5 BB/Misket Üzümü	9.7 ± 2.1 d–j	1.7 ± 0.6 d–f	0.0 ± 0.0 d	49.0 ± 9.0 cd	20.0 ± 3.0 f–l	11.5 ± 0.5 i–n
41 B/Misket Üzümü	7.0 ± 1.0 h–m	0.7 ± 0.6 ef	0.0 ± 0.0 d	15.0 ± 3.0 l–p	14.0 ± 3.0 k–m	19.5 ± 2.5 c
1103 P/Misket Üzümü	6.3 ± 0.6 i–m	0.7 ± 0.6 ef	0.3 ± 0.6 cd	6.7 ± 0.6 p	14.0 ± 0.0 k–m	9.0 ± 2.0 mn
Fercal/Misket Üzümü	8.7 ± 2.1 f–k	1.0 ± 1.0 ef	0.0 ± 0.0 d	15.0 ± 1.0 l–p	17.0 ± 3.0 h–m	12.5 ± 2.5 g–n
5 BB/Parmak Üzümü	13.7 ± 0.6 b–d	1.7 ± 0.6 d–f	0.3 ± 0.6 cd	14.0 ± 2.0 l–p	20.0 ± 6.0 f–l	14.0 ± 1.0 e–l
41 B/Parmak Üzümü	6.7 ± 1.2 i–m	0.0 ± 0.0 f	0.7 ± 0.6 b–d	42.0 ± 7.0 d–f	26.0 ± 3.0 c–g	18.5 ± 2.5 c–e
1103 P/Parmak Üzümü	11.3 ± 1.5 c–g	1.3 ± 0.6 d–f	0.3 ± 0.6 cd	46.0 ± 5.0 c–e	28.0 ± 4.0 c–e	16.5 ± 3.5 c–h
Fercal/Parmak Üzümü	11.3 ± 3.1 c–g	1.3 ± 0.6 d–f	0.0 ± 0.0 d	54.0 ± 6.0 c	23.0 ± 3.0 c–i	16.5 ± 1.0 c–h
5 BB/Mor Bulut	6.7 ± 0.6 i–m	0.7 ± 0.6 ef	0.3±0.6 cd	41.0±6.0 e–g	30.0±5.0 c	16.0 ± 1.0 c–i
41 B/Mor Bulut	4.3 ± 1.2 lm	0.7 ± 0.6 ef	0.3 ± 0.6 cd	9.7 ± 2.2 n–p	22.7 ± 1.4 d–i	17.0 ± 3.6 c–g
1103 P/Mor Bulut	15.0±0.0 a–c	4.0 ± 0.0 ab	1.7 ± 0.6 a	18.0±4.0 l–n	17.0±1.0 h–m	19.0±4.0 cd
Fercal/Mor Bulut	11.3±0.6 c–g	0.7±0.6 ef	0.3±0.6 cd	19.0±3.0 lm	21.0±1.0 e–k	11.0±4.0 j–n
5 BB/Şahmuratlı	9.7±3.1 d–j	1.0±1.0 ef	0.3±0.6 cd	40.0±7.0 e–g	20.0±1.0 f–l	10.0±3.0 k–n
41 B/Şahmuratlı	8.0±1.0 g–l	0.7±0.6 ef	0.0±0.0 d	10.0±2.0 n–p	25.0±3.0 c–g	14.5±2.5 d–k
1103 P/Şahmuratlı	11.0 ± 1.0 c–h	2.0 ± 0.0 c–e	0.0 ± 0.0 d	21.0 ± 1.0 kl	15.0 ± 4.0 j–m	17.0 ± 0.0 c–g
Fercal/Şahmuratlı	10.0 ± 4.6 d–j	2.0 ± 2.0 c–e	0.7 ± 0.6 b–d	27.0 ± 4.0 j–k	10.0 ± 1.0 m	12.0 ± 2.0 h–n
5 BB/Köledoyuran	12.3 ± 5.0 c–f	2.0 ± 2.0 c–e	0.3 ± 0.6 cd	28.7 ± 1.2 h–k	17.0 ± 2.0 h–m	20.0 ± 1.0 c
41 B/Köledoyuran	13.7 ± 0.6 b–d	1.7 ± 1.2 d–f	0.0 ± 0.0 d	30.0 ± 3.0 h–j	27.0 ± 4.0 c–f	15.5 ± 1.0 c–j
1103 P/Köledoyuran	18.3 ± 1.5 a	5.0 ± 1.7 a	0.3 ± 0.6 cd	30.0 ± 1.0 h–j	16.0 ± 2.0 i–m	12.0 ± 2.0 h–n
Fercal/Köledoyuran	17.0 ± 3.6 ab	3.0 ± 1.7 b–d	0.0 ± 0.0 d	37.0 ± 4.0 f–h	11.0 ± 0.0 m	16.5 ± 3.0 c–h
5 BB/Kirpi Üzümü	12.0 ± 0.0 c–g	1.7 ± 0.6 d–f	0.0 ± 0.0 d	31.0 ± 3.0 h–j	15.0 ± 1.0 j–m	11.0 ± 0.0 j–n
41 B/Kirpi Üzümü	6.7 ± 1.2 i–m	0.0 ± 0.0 f	1.3 ± 1.2 ab	12.0 ± 2.0 m–p	22.0 ± 4.0 d–j	12.0 ± 2.0 h–n
1103 P/Kirpi Üzümü	12.0 ± 2.6 c–g	2.0 ± 1.0 c–e	0.0 ± 0.0 d	50.0 ± 8.0 c	21.0 ± 2.0 e–k	25.0 ± 4.0 b
Fercal/Kirpi Üzümü	13.0 ± 1.0 c–e	3.0 ± 1.0 b–d	0.3 ± 0.6 cd	9.0 ± 0.0 op	26.0 ± 4.0 c–g	11.0 ± 1.0 j–n
5 BB/Horoz Üzümü	8.3 ± 1.5 f–l	0.7 ± 1.2 ef	1.0 ± 1.0 a–c	52.0 ± 7.0 c	29.0 ± 1.0 cd	11.0 ± 2.0 j–n
41 B/Horoz Üzümü	8.3 ± 1.5 f–l	0.7 ± 1.2 ef	0.0 ± 0.0 d	8.0 ± 1.0 p	19.0 ± 3.0 g–l	16.5 ± 1.5 c–h
1103 P/Horoz Üzümü	6.0 ± 0.0 j–m	0.0 ± 0.0 f	0.3 ± 0.6 cd	18.0 ± 5.0 l–n	13.0 ± 4.0 lm	12.5 ± 2.5 g–n
Fercal/Horoz Üzümü	12.3 ± 1.5 c–f	1.7 ± 2.1 d–f	0.3 ± 0.6 cd	53.0 ± 7.0 c	24.0 ± 4.0 c–h	19.5 ± 3.5 c

According to Duncan’s multiple range test, means followed by different lowercase letters differ significantly at the 5% level based on the Rootstock × Cultivar interaction. Data are presented as mean ± standard deviation (SD).

). In the Siyah Üzüm variety, rootstock significantly influenced the number of nodes. The highest number of nodes (11.7 nodes) was observed with Fercal, followed by 1103 P (10.3 nodes). The 41 B rootstock produced a notably lower number of nodes (5.0 nodes). Similarly, in Karagevrek, although rootstock selection did not result in significant differences in node number, 41 B exhibited a slightly lower count (5.0 nodes) compared to other rootstocks. In Gelinparmağı, the highest number of nodes was observed with 1103 P (12.0 nodes), while Fercal (10.0 nodes) also showed good results. In contrast, 41 B and 5 BB rootstocks produced the lowest number of nodes (3.7 and 4.7 nodes, respectively). For Misket, no significant differences in node number were observed among the rootstocks, with values ranging from 6.3 to 9.7 nodes. However, in Parmak, 5 BB showed the highest number of nodes (13.7 nodes), followed by 1103 P and Fercal. The 41 B rootstock produced the lowest number of nodes (6.7 nodes). The Mor Bulut variety showed the highest number of nodes with 1103 P (15.0 nodes), while Fercal (11.3 nodes) also performed well. The lowest number of nodes in Mor Bulut was observed with 41 B (4.3 nodes).

In terms of secondary–tertiary shoots, the 1103 P rootstock produced the highest number of shoots in Mor Bulut (1.7 shoots), while other rootstocks generally had fewer or no secondary–tertiary shoots. In Kirpi Üzümü, the 41 B rootstock showed the highest number of secondary–tertiary shoots (1.3 shoots), while other rootstocks did not significantly contribute. For Gelinparmağı, Fercal produced the highest number of secondary–tertiary shoots (1.0 shoot), whereas 41 B and 1103 P showed no secondary–tertiary shoots. Root characteristics also varied among the rootstocks. In Siyah Üzüm, 5 BB had the highest root number (68.0 roots), followed by 1103 P (33.0 roots) and Fercal (28.0 roots). The 41 B rootstock produced the lowest root number (17.7 roots). In Karagevrek, the 1103 P rootstock exhibited the highest root number (40.0 roots), while Fercal and 5 BB showed similar values (35.0 and 36.0 roots, respectively). Secondary root number was highest in Karagevrek with the 41 B rootstock (70.0 roots). In Gelinparmağı and Misket, the differences in secondary root number between rootstocks were not significant. Regarding root length, Fercal showed the highest value in Siyah Üzüm (17.0 cm), whereas other rootstocks such as 1103 P, 41 B, and 5 BB had shorter roots, ranging from 9.0 to 10.5 cm. These findings demonstrate that rootstock selection has a significant influence on various morphological traits, including node number, shoot development, and root characteristics. Fercal and 1103 P rootstocks generally performed better across most variables, suggesting their potential for enhancing grapevine growth and development. For bud viability, Gelinparmağı, Şahmuratlı, Misket Üzümü, and Kirpi Üzümü demonstrated the highest performance, with a 100% viability rate (Figure 3). Parmak Üzümü, Mor Bulut, and Köledoyuran followed closely, showing a bud viability rate of 91.7%. Horoz Üzümü exhibited a viability rate of 75.0%, while Siyah Üzüm and Karagevrek had the lowest bud viability, at 58.3% and 41.7%, respectively.

For root development, Siyah Üzüm showed the highest score of 4.0, followed by Mor Bulut and Köledoyuran, each with a score of 3.8. Karagevrek recorded 3.6, while Kirpi Üzümü and Parmak Üzümü showed a score of 3.5. Şahmuratlı and Gelinparmağı were ranked at 3.4 and 3.3, respectively. Misket Üzümü and Horoz Üzümü displayed the lowest root development score of 3.2. Regarding node count on the shoots, the 1103 P rootstock showed the highest performance with 1.0 node (Figure 4), followed by Fercal with a value of 0.9. The 5 BB rootstock recorded 0.5 nodes, while 41 B had the lowest node count with 0.3. In terms of root development, the rootstock with the highest root development score was 5 BB (3.8), followed by Fercal with 3.6. 1103 P scored 3.5 points, while 41 B showed the lowest performance with 3.3 points. No statistically significant differences were found between the different rootstock/cultivar combinations in terms of callus development, bud viability, bud sprouting, and root formation at the base of the cutting. However, callus development at the base of the cutting was found to be 0 for all rootstock/cultivar combinations, while the grafted grapevine sapling survival rate was recorded as 100% for all combinations.

General Evaluation

A correlation analysis was performed to assess the relationships among grafting root performance, grafted grapevine sapling development, and quality variables across different rootstock/cultivar combinations (Figure 5). The strongest positive correlations were identified between root development and first-order grafted saplings (r = 0.99), as well as between total bud number and bud number on the grafted shoot (r = 0.95). Conversely, the most significant negative correlations were observed between first- and second-order grafted vines (r = −1.00) and between root development and second-order grafted vines (r = −0.99).

Notable positive correlations included graft union thickness and rootstock thickness (r = 0.87), grafted sapling and first-order grafted sapling (r = 0.83), and bud number on the grafted shoot and total bud number (r = 0.82). A strong negative correlation was observed between grafted sapling and second-order grafted sapling (r = −0.82). Moderate positive correlations were detected between grafted shoot thickness and graft union thickness (r = 0.68), bud number on the grafted shoot and total bud number (r = 0.66), and total bud number and grafted shoot thickness (r = 0.65). Moderate negative correlations were found between internode length on the grafted shoot and bud viability (r = −0.65), internode length on the grafted shoot and second-order grafted sapling (r = −0.57), and grafted shoot length and second-order grafted sapling (r = −0.55). Weak positive correlations were observed between rootstock thickness and first-order grafted sapling (r = 0.49), grafted shoot thickness and first-order grafted sapling (r = 0.49), and root development and graft union thickness (r = 0.49). Weak negative correlations were detected between rootstock thickness and second-order grafted sapling (r = −0.49), grafted shoot thickness and second-order grafted sapling (r = −0.49), and graft union thickness and second-order grafted sapling (r = −0.48). Very weak positive correlations were noted between graft union thickness and shoot length from the bud (r = 0.25), grafted shoot thickness and callus development at the base of the cutting (r = 0.25), and main root number and bud number on the cutting (r = 0.25).

Very weak negative correlations were observed between internode length on the grafted shoot and callus development (-0.25), as well as between bud number on the grafted shoot and grafting success (-0.25). Principal Component Analysis (PCA) was conducted to better elucidate the relationships between rootstock/cultivar combinations and the studied traits (Figure 6).

The first two principal components explained 46.29% of the total variance. The first principal component (PC1), accounting for 33.89% of the variance, showed positive loadings for grafting success, callus development level, and second-order grafted saplings. Rootstock/cultivar combinations best representing these traits included 5BB/Gelinparmağı, 41B/Gelinparmağı, and 1103P/Misket Üzümü, among others. The negative axis of PC1 was associated with bud sprouting status, root formation at the base of the cutting, and root development level, with 5BB/Siyah Üzüm, Fercal/Siyah Üzüm, and others as notable representatives. The second principal component (PC2), explaining 12.40% of the variance, had positive loadings for shoot length from the bud and secondary root number. Combinations, such as 41B/Siyah Üzüm, 5BB/Karagevrek, and 1103P/Siyah Üzüm were the best representatives on this axis. The negative axis of PC2 was associated with bud viability, bud number on the grafted shoot, and total bud number on the cutting, with 1103P/Gelinparmağı, 5BB/Misket Üzümü, and others representing these traits.

Regarding the hierarchical clustering heatmap, the results classified the examined traits into two main clusters (Figure 7). The first main cluster comprised secondary root count, root length, grafting success, callus development level, second-year grafted saplings, and bud viability, while the second main cluster consisted of the remaining traits. The second main cluster was further divided into two sub-clusters. The first sub-cluster included grafted saplings, first-year grafted saplings, rootstock thickness, graft union thickness, graft shoot thickness, graft shoot length, internode length on graft shoots, primary root count, and root development level. The second sub-cluster consisted of bud sprouting status, shoot length emerging from buds, root formation at the base of the cutting, callus development level at the cutting base, number of buds on graft shoots, total bud count, number of axillary buds on graft shoots, number of buds on axillary shoots, and secondary–tertiary root sprout count. The heatmap also clustered the rootstock/cultivar combinations into two main groups. The first main cluster comprised 41 B combinations (except 41 B/Siyah Üzüm), 5 BB/Gelinparmağı, 1103 P/Misket Üzümü, Fercal/Misket Üzümü, 1103 P/Horoz Üzümü, Fercal/Şahmuratlı, 1103 P/Parmak Üzümü, and Fercal/Parmak Üzümü. These combinations exhibited significantly higher mean values for second-year grafted saplings. The second main cluster was further divided into two sub-clusters. The first sub-cluster included Fercal/Gelinparmağı, 5 BB/Misket Üzümü, 1103 P/Kirpi Üzümü, and 1103 P/Karagevrek, characterized by higher average values for first-year grafted saplings and root development level. The second sub-cluster consisted of 5 BB/Siyah Üzüm, 5 BB/Karagevrek, Fercal/Kirpi Üzümü, and 5 BB/Şahmuratlı, which showed higher mean values for first-year grafted saplings, root development level, rootstock thickness, graft union thickness, and graft shoot thickness. The environmental conditions during the grafting period showed temperature fluctuations between 15 and 25 °C, which particularly favored Fercal and 5 BB rootstocks in terms of cambial activity and callus formation. Soil pH levels ranged from 6.8 to 7.2 at the experimental site, where 1103 P demonstrated superior performance in lime-tolerant combinations, especially in Gelinparmağı and Mor Bulut cultivars. Correlation analysis revealed a perfect negative correlation (-1.00) between first- and second-grade saplings. Fercal exhibited consistent performance across morphological traits, including diameter, union thickness, and shoot characteristics, while 5 BB recorded the highest root development score of 3.8. The 41 B rootstock showed variable performance, with grafting success ranging from 30% to 100% depending on cultivar compatibility. Hierarchical clustering analysis identified two main clusters: one characterized by high first-grade sapling performance combinations (predominantly Fercal-based), and the other by high second-grade sapling performance combinations (predominantly 41 B-based).

4. Discussion

This study provided a comprehensive assessment of the compatibility between various grape rootstocks and traditional grape cultivars in Yozgat province (Table 1). The findings demonstrated considerable variation in graft success among different scion–rootstock combinations, reinforcing the critical need for genotype-specific selection in vine propagation programs. This result is consistent with previous observations indicating that scion–rootstock interactions directly affect not only initial graft union success but also subsequent vegetative and anatomical development [46,47,48,49,50,51]. Traditional cultivars like Misket Üzümü showed significant grafting success differences among rootstocks, with 41 B and 1103 P demonstrating superior compatibility, consistent with Bekişli et al. [52]. In contrast, rootstocks like Fercal and 5 BB demonstrated lower compatibility with some varieties. For instance, Fercal yielded only 30% success with Mor Bulut, and 5 BB showed 68.8% success with Şahmuratlı. These outcomes reaffirm the significance of genetic affinity between Vitis vinifera scions and grape rootstocks, which is critical for grafting success and overall grafted grapevine sapling production efficiency [53,54]. Beyond anatomical compatibility, recent research highlights that rootstock–scion interactions can modulate not only physiological performance but also rhizospheric and endophytic microbiome composition, which further influences plant development [5,55,56]. These multi-level interactions reinforce the need for genotype-specific rootstock selection in sustainable viticulture systems. The varying levels of statistical significance observed across different traits reflect distinct biological control mechanisms. Highly significant effects for grafting success indicate genetic compatibility as the primary determinant, while moderate significance (p < 0.05) for morphological traits suggests combined genetic and environmental influences. Non-significant results for callus development reflect standardized experimental conditions minimizing variability in fundamental healing processes. Rootstock compatibility may influence not only grafting success but also the accumulation of secondary metabolites, as highlighted by Blank et al. [57]. Therefore, the superior compatibility observed in our study between certain local cultivars and specific rootstocks may be attributed to physiological as well as anatomical compatibility. The outstanding performance of 41 B rootstock may be linked to its V. vinifera origin, facilitating better physiological compatibility [58].

Evaluations of grafted grapevine saplings revealed that Fercal produced the highest 1st-grade grafted grapevine saplings in most varieties, with 95.43% in Horoz Üzümü and 93.43% in Gelinparmağı. Similarly, 5 BB rootstock achieved a grafted grapevine sapling yield of 93.93% with Siyah Üzüm. The 1103 P rootstock also performed well with Kirpi Üzümü and Siyah Üzüm, but yielded only 62.47% in Misket Üzümü. Conversely, 41 B provided lower and less consistent results, particularly in 1st-grade grafted grapevine saplings. These findings align with Köse et al. [59,60], who reported the positive influence of 5 BB on grafted grapevine sapling development, and with Gündeşli et al. [61], who emphasized 1103 P’s role in enhancing saplings. Analysis of shoot development from the grafted bud revealed that Gelinparmağı and Kirpi Üzümü produced the longest shoots, particularly with 41 B and Fercal. While 5 BB led to shorter shoots in some combinations, it also facilitated significant shoot elongation in others, demonstrating a variety-dependent effect. Although 1103 P yielded favorable results with some cultivars, it was not consistently superior across all. These outcomes support findings by Dardeniz and Şahin [62] and Baydar and Ece [63], who reported that 41 B and 5 BB rootstocks enhance vegetative development and grafted grapevine saplings. Similarly, the study by Blank et al. [64] reported that different rootstocks had varying effects on shoot biomass and nitrogen balance in the Pinot noir cultivar, which in turn, influenced overall plant development. This supports the variation observed in our study among different rootstock–scion combinations with respect to variables, such as shoot length, number of lateral shoots, and node count (Table 2). Regarding grafted grapevine sapling quality, Siyah Üzüm was the only variety that consistently achieved the highest 1st-grade sapling across all rootstocks. Fercal and 5 BB provided high-quality grafted grapevine saplings across multiple cultivars. However, 1103 P’s results were more variable, and 41 B generally underperformed. The findings reaffirm the priority of maximizing 1st-grade grafted grapevine sapling proportions in grafted vine production, as highlighted by Köse et al. [60] and Baydar and Ece [63]. In terms of 2nd-grade grafted grapevine saplings, 41 B rootstock produced higher proportions in several cultivars, most notably 53.8% in Horoz Üzümü. However, in varieties, such as Siyah Üzüm, 2nd-grade grafted grapevine sapling rates were negligible or zero, especially with 1103 P. This inverse relationship between 1st- and 2nd-grade grafted grapevine saplings illustrates the qualitative trade-offs between rootstock performance and grafted grapevine sapling classification.

Fercal demonstrated the greatest rootstock thickness, particularly in combinations with Köledoyuran, Karagevrek, and Mor Bulut, indicating robust root development potential. 5 BB followed closely, whereas 41 B produced the thinnest rootstocks, suggesting weaker growth and potentially limited nutrient transport (Table 4). These results are consistent with Bekişli et al. [52], who associated rootstock thickness with vine vigor and cutting origin. Similarly, graft point thickness was highest in Karagevrek grafted onto Fercal (25.2 mm), further indicating Fercal’s contribution to strong structural development. 5 BB also showed relatively high values, while 1103 P and particularly 41 B produced thinner graft unions. A direct relationship between graft and rootstock thickness was evident, reinforcing the importance of vigor in grafted grapevine sapling quality [52]. Fercal also excelled in graft shoot thickness and shoot length, providing 4.8–5.4 mm in Köledoyuran and Horoz Üzümü and reaching 53.5–57.7 cm in graft shoot length. These values exceeded those obtained with 1103 P and 5 BB, while 41 B lagged significantly. These patterns support earlier observations by Köse et al. [59] and Çelik and Kısmalı [47], who emphasized the variety-dependent nature of rootstock effects. As reported by Blank et al. [64], high-vigor rootstocks enhance shoot development and leaf nitrogen content, which in turn, indirectly influence quality variables. The superior performance of Fercal and 5 BB in our study suggests that similar physiological mechanisms may also operate in local cultivars.

In terms of internode length, 5 BB and Fercal yielded the longest measurements in Siyah Üzüm, Karagevrek, and Horoz Üzümü. Similarly, 1103 P performed well in selected cultivars, while 41 B consistently gave shorter internodes (Table 3). These results align with studies by Çoban and Kara [65], highlighting internode length as a sensitive indicator of rootstock compatibility and vigor. The relationship between nitrogen balance and vegetative growth has previously been demonstrated by Blank et al. [64] based on chlorophyll index measurements. This finding is consistent with the superior performance of certain rootstocks in specific cultivars in our study, as reflected by shoot length and internode number. Fercal and 1103 P also provided the highest number of nodes on graft shoots, particularly in Siyah Üzüm, Parmak Üzümü, and Kirpi Üzümü. 5 BB showed intermediate values, while 41 B generally exhibited fewer nodes. These differences in nodal development are consistent with findings by Aslan et al. [41], who linked grafted grapevine sapling quality to rootstock–scion interactions. 1103 P and Fercal rootstocks significantly increased the number of axillary shoots in cultivars such as Gelinparmağı, Şahmuratlı, and Kirpi Üzümü. This supports the results of Gündeşli et al. [61], reinforcing the importance of rootstock choice for maximizing shoot development and overall grafted grapevine sapling quality. Hormonal cross-talk between the scion and rootstock—particularly involving auxin and related growth regulators—has been implicated in modifying root system architecture and vigor [66,67]. This may help explain the superior vegetative responses observed in combinations involving high-vigor rootstocks like Fercal and 1103 P. Additionally, 1103 P with Mor Bulut, 41 B with Kirpi Üzümü, 5 BB with Horoz Üzümü, and Fercal with Gelinparmağı yielded the highest secondary and tertiary basal shoot numbers. These results emphasize that basal shoot development is strongly influenced by rootstock–scion compatibility, contributing to vegetative robustness [60].

Fercal and 5 BB rootstocks provided the highest main root numbers in combinations such as Gelinparmağı, Parmak Üzümü, and Horoz Üzümü. 1103 P also performed well with Kirpi Üzümü and Parmak Üzümü, while 41 B yielded lower values. These outcomes support Köse et al. [60], who documented the superior rooting potential of 5 BB under nursery conditions. As also demonstrated by Herms et al. [68], modifications in root morphology, such as diameter and branching, can directly impact the recruitment of beneficial microorganisms. Therefore, the superior root morphology observed in combinations involving Fercal and 5 BB may also contribute to more favorable microbiome assemblages, indirectly supporting grafted grapevine sapling health and vigor. These multi-level biological interactions explain the observed statistical patterns, where fundamental physiological processes show higher significance levels compared to environmentally modulated developmental traits. Our findings indicating that high-vigor rootstocks have a positive influence on vegetative development and grafted grapevine sapling quality align with the results reported by Blank et al. [64] for Pinot noir. In their study, high-vigor rootstocks such as 125AA and SO4 were associated with higher nitrogen balance and shoot biomass. Interestingly, 41 B produced the highest secondary root numbers in Karagevrek and Köledoyuran, suggesting that although it underperforms in other aspects, it can still be advantageous in promoting finer root systems [69]. Fercal and 5 BB also showed favorable performance in this category in selected combinations. Root length analyses demonstrated that 41 B and 1103 P provided the greatest root lengths, especially in Karagevrek and Kirpi Üzümü. Fercal produced the longest roots in Siyah Üzüm, while 5 BB generally lagged. These outcomes suggest that different rootstocks may promote distinct rooting traits, each potentially beneficial depending on environmental and varietal requirements.

General Evaluation

The correlation analysis provides a comprehensive understanding of the relationships between rootstock/scion combinations, graft room performance, grafted grapevine sapling development, and quality variables (Figure 5). A highly positive correlation between root development and first-grade grafted vine grafted grapevine sapling indicates the significant impact of root development on grafted grapevine sapling. This finding is consistent with the work of Çelik [18], who emphasized that a robust root system enables grafted grapevine saplings to absorb more nutrients from the soil, fostering better growth. Consequently, grafted grapevine saplings with well-developed root systems are more likely to be classified as first-grade grafted grapevine saplings. A strong positive correlation between the total bud count and the number of buds on the graft shoot further supports this, as a single shoot typically develops from the grafting point. A higher number of buds indicates strong shoot development and a higher growth potential of the grafted grapevine saplings. The very strong negative correlation observed between first- and second-grade grafted grapevine sapling can be explained by the classification of grafted grapevine sapling quality. If a grafted grapevine sapling is classified as first-grade, it naturally will not be part of the second-grade category, explaining the negative relationship between these two quality variables. The strong negative correlation between root development and second-grade grafted grapevine sapling is also logical, as grafted grapevine saplings with weaker root systems are often classified as second-grade. Thus, grafted grapevine saplings with stronger root systems are more likely to be classified as first-grade. A robust positive correlation between grafted grapevine sapling and first-grade grafted vine grafted grapevine sapling suggests that successful grafting results in a higher proportion of grafted grapevine saplings meeting first-grade quality standards. Similarly, the strong negative correlation between grafted vine grafted grapevine sapling and second-grade grafted grapevine sapling shows that as grafting success improves, the proportion of weaker, lower-quality grafted grapevine saplings decrease.

Furthermore, the positive correlation between the number of axillary buds on the graft shoot and total bud count indicates that more axillary buds facilitate the formation of a greater number of buds. The positive relationship between rootstock thickness and grafted grapevine sapling suggests that stronger rootstocks promote better grafted grapevine sapling development. In addition to their structural contribution, robust root systems may also support a more diverse and beneficial microbial network [70], potentially enhancing grafted grapevine sapling quality beyond what is solely explained by nutrient transport efficiency. However, this relationship, while significant, is not as strong as that of other factors, such as root development [52]. These findings demonstrate how the selection of the correct rootstock–scion combination can have a lasting effect on grafted grapevine sapling development and quality. The importance of identifying the right rootstock–scion combinations, as emphasized by Çelik and Kısmalı [47], is crucial in optimizing these relationships. Recent studies suggest that the scion–rootstock combination, rather than either genotype alone, plays a decisive role in shaping rhizosphere and endophyte microbial communities, with direct consequences on nutrient uptake, growth performance, and stress tolerance [71,72]. This may provide a complementary explanation for the differences observed in grafted grapevine sapling quality across combinations in our study.

Principal Component Analysis (PCA) further elucidates the cause-and-effect relationships between rootstock/scion combinations and grafted grapevine sapling development traits. The positive axis of PC1, including traits like grafting success, callus development, and second-grade grafted grapevine sapling, indicates a connection between these factors and lower-quality (second-grade) grafted grapevine saplings. Combinations, such as 5BB/Gelinparmağı, 41B/Gelinparmağı, and 41B/Misket Üzümü, are positioned along this axis, suggesting that while these combinations may exhibit high grafting success, they tend to produce a higher proportion of second-grade grafted grapevine saplings. In contrast, the negative axis of PC1, which includes features like root formation in cuttings, grafted grapevine sapling, first-grade grafted grapevine sapling, rootstock thickness, and shoot thickness, is associated with stronger root development and the production of higher-quality (first-grade) grafted grapevine saplings. Rootstock/scion combinations, such as 5BB/Siyah Üzüm and Fercal/Siyah Üzüm, are represented, exhibiting superior results in terms of root development and grafted grapevine sapling performance. PCA also highlights the relationships between grafting success, callus development, root development, and grafted grapevine sapling quality across different rootstock/scion combinations (Figure 6). These results are consistent with the findings of Çelik and Kısmalı [47], reinforcing the importance of selecting the optimal rootstock–scion combinations for long-term vineyard success. Optimal combinations balance grafting success and grafted grapevine sapling quality, which is a key strategy for achieving the best results in modern viticulture.

Hierarchical clustering heatmap analysis provides additional clarity by categorizing the relationships between rootstock/scion combinations and the studied traits. The heatmap reveals that grafting success, grafted grapevine sapling, and root development are key variables influencing these relationships. The first main cluster includes traits like secondary root count, root length, grafting success, callus development, and second-grade grafted grapevine sapling, all of which are associated with combinations such as 41B, 5BB/Gelinparmağı, and 1103P/Misket Üzümü. These combinations tend to exhibit high callus development and grafting success but produce more second-grade grafted grapevine saplings. The second main cluster is divided into two sub-clusters. The first sub-cluster includes traits such as grafted grapevine sapling, first-grade grafted grapevine sapling, rootstock thickness, shoot thickness, and grafting point thickness, which are linked to the production of higher-quality (first-grade) grafted grapevine saplings. Combinations like Fercal/Gelinparmağı, 5BB/Misket Üzümü, and 1103P/Kirpi Üzümü fall into this sub-cluster (Figure 7). These combinations exhibit superior results in producing high-quality grafted grapevine saplings and robust root development, aligning with the findings of Çelik and Kısmalı [47]. The second sub-cluster, associated with traits like bud viability, shoot length, and root formation in cuttings, highlights combinations that excel in shoot development and root structure, such as 1103P/Gelinparmağı and Fercal/Parmak Üzümü. This heatmap analysis provided valuable insights into the relationships between rootstock/scion combinations and grafted grapevine sapling traits, underscoring the critical role of selecting optimal combinations for successful grafted grapevine sapling production. As demonstrated by Çelik and Kısmalı [47] and Bekişli et al. [52], the right rootstock–scion combinations are essential for improving grafted grapevine sapling quality and development in viticulture.

The observed variation in rootstock performance can be attributed to specific environmental adaptation patterns under Mediterranean climatic conditions. Temperature fluctuations during the grafting period (15–25 °C) particularly favored Fercal and 5 BB rootstocks, which demonstrated enhanced cambial activity and faster callus formation. Soil pH levels (6.8–7.2) in the experimental site may have influenced the superior performance of 1103 P in lime-tolerant combinations, particularly evident in cultivars like Gelinparmağı and Mor Bulut. The correlation analysis revealed that rootstock selection should prioritize first-grade sapling production over total sapling performance, as evidenced by the perfect negative correlation (−1.00) between first- and second-grade sapling performance. Fercal’s consistent performance across morphological traits (diameter, union thickness, shoot characteristics) suggests its broad adaptability, while 5 BB’s superior root development (3.8 score) indicates its potential for long-term vineyard establishment. The 41 B rootstock’s variable performance (ranging from 30% to 100% success) indicates its sensitivity to cultivar compatibility, requiring careful selection based on specific variety requirements. The hierarchical clustering results provide a practical framework for rootstock selection, where combinations can be grouped into high first-grade sapling performance clusters (Fercal-dominated) versus high second-grade sapling performance clusters (41 B-dominated), enabling targeted nursery production strategies.

5. Conclusions

This study demonstrates the significant impact of rootstock–scion combinations on grafting success, grafted grapevine sapling, and root development in viticulture. Among the various rootstocks evaluated, Fercal emerged as the most compatible rootstock, showing superior performance in key variables such as grafting success, first-grade grafted vine grafted grapevine sapling, and root development. The best-performing rootstock–scion combinations included Fercal/Siyah Üzüm and Fercal/Gelinparmağı, which exhibited high grafted grapevine sapling and root growth, while combinations, such as Fercal/Köledoyuran and Fercal/Horoz Üzümü, followed closely behind. Conversely, rootstocks, such as 41B and 1103P, showed variable performance, with 41B performing well in grafting-related traits but underperforming in grafted grapevine sapling development. Additionally, the study found that certain local grape varieties, such as Siyah Üzüm, demonstrated high compatibility with multiple rootstocks, while Misket Üzümü performed best with 5BB. Considering the environmental conditions of Yozgat province, the combinations of Fercal/Gelinparmağı and 5 BB/Misket Üzümü emerged as the most suitable due to their high first-grade sapling and robust vegetative development. The results of this research provide valuable insights for optimizing rootstock–scion combinations for high-quality grafted grapevine sapling production and the establishment of sustainable vineyards, particularly for producers seeking to establish resilient vineyards with diverse climatic conditions.