Rootstock Scion Research Articles

Soil–Plant Interaction Mediated by Indigenous AMF in Grafted and Own-Rooted Grapevines under Field Conditions

Plant–soil biota represent a unique living system crucial for improving crops’ adaptation to climate change. In vineyards, plant–soil relations are mediated by rootstock–scion interaction, with grafted vines being the main plant material employed in vineyard planting. The interaction between two deeply different biological systems such as Vitis vinifera sativa and the American Vitis species may modify vines’ adaptation to abiotic stress. The aim of this study was to investigate the physiological response (chlorophyll content—CHL; stomatal conductance—gs) of grafted and ungrafted vines and assess the involvement of Arbuscular Mycorrhizal Fungi (AMF) in this response. In two vineyards located in Central Italy, the presence of AMF was assessed in the roots of grafted and ungrafted cv ‘Aleatico’ vines. The morphological traits of AMF and root mycorrhizal colonization differed in the grafted and ungrafted vines. Under limited climate conditions, ungrafted vines showed better leaf resilience traits (high CHL and gs values) and larger AMF storage organs (vesicles). On the other hand, the grafted ones—which are more sensitive to climate conditions (lower gs and CHL)—involved AMF colonization strategies (greater abundance of arbuscoles and mycorrhizal colonization potential) linked to the improved uptake and transport of water from the bulk soil to the vine. Taken together, these findings highlight different mycorrhizal colonization strategies and storage behaviors in grafted and ungrafted vineyards and with respect to different physical and chemical soil traits.

Rootstock–scion interaction mediated impact on fruit quality attributes of thick-skinned melon during storage under different temperature regimes

Grafting is a technique widely utilized to enhance the tolerance of melon against various abiotic and biotic stresses and improve fruit quality and crop production. Melon is a popular Cucurbitaceae crop around the world due to its unique taste and aroma. Improved postharvest fruit quality with prolonged shelf-life is important to ensure the supply of melon in the market. In this study, we evaluated the postharvest fruit quality of melons grafted on ten pumpkin rootstocks during storage at room temperature (25°C ± 2°C) and cold conditions (10°C ± 1°C). We investigated several physiological, biochemical, and anti-oxidative parameters related to postharvest fruit quality. These quality parameters were evidently affected by the use of different rootstocks, storage temperature, and storage duration. The melon fruits obtained from Tianzhen No. 2 rootstock had no weight loss and relatively lower titratable acidity (0.21%), malic acid (0.84 mg/g), and total phenolic (15.96 mg/g) contents compared with other grafting combinations after 7 days of room storage. Moreover, Yinguang rootstock-grafted melon fruits showed relatively higher total soluble solids (15.40°) and sucrose (169.30 mg/g) but lower malic acid (0.97 mg/g) and total phenolic (15.31 mg/g) contents after 28 days of cold storage. The melon fruits grafted on Tianzhen No. 2 with membership function value (0.67) and Yinguang rootstock (0.66) ranked 1st regarding overall fruit quality attributes after short-term room-temperature and long-term cold storage, respectively. Considering the results of our study, the use of rootstock helped maintain the post-harvest fruit quality during storage and extended the shelf life of melons. Thus, the use of rootstocks along with other post-harvest storage techniques can be a potential research area to improve the storage life of melon fruits.

Scion/Rootstock Interaction Studies for Quality Traits in Mango (Mangifera indica L.) Varieties

To explore the quality rootstocks which impart better quality fruits in mango varieties, we studied the interactive effect of the scion and rootstock using five mango varieties (Mallika, Amrapali, Dashehari, Pusa Arunima, and Pusa Surya) grafted on three rootstocks (Olour, Kurukkan, and K-5). A total of 25 physico-chemical parameters were studied in the five grafted varieties viz., fruit weight, yield efficiency, fruit per plant, pulp percent, total soluble solids (TSS), acidity, physiological loss in weight (PLW), peel thickness, respiration rate, etc., and were found to be altered through scion–rootstock interaction. Among the five mango varieties, Olour rootstock proved best to improve the fruit quality and shelf life using the grafting approach. Physico-chemical-traits-based clustering was unable to precisely group scion varieties according to their grafting rootstock. A total of 35 shelf-life specific markers were designed from ripening genes, such as expansin, polygalactouranase, ethylene insensitive, ethylene sensitive, etc. Of these specific primers, 24 showed polymorphism among the studied genotypes. The gene diversity (GD), allele per locus (An), polymorphism information content (PIC), and major allele frequency (MAF) observed were 0.43, 2.00, 0.34, and 0.63, respectively. Cluster analysis clearly showed that scion grafted on Kurukkan and Olour rootstock, and scion varieties grafted on K-5 rootstock grouped together have more similarity. A total of eight simple sequence repeats loci (SSRs) markers were associated with eight physiological traits. Strong association of SSR loci NMSLC-12 and NMSLC-14 with yield efficiency and fruit weight were observed with a phenotypic variance of 85% and 70%, respectively.

Application of the Impedance Measurement Method to Evaluate the Results of Winter Grafting of Pear Cuttings Using Cold Plasma

Electroimpedance spectroscopy technology can be used to accelerate the healing of complete trees and estimate the plant condition after grafting. This approach will allow sorting out low-vigor plants at the early stages of their development to save time and resources. Still, in some cases, the use of electrical impedance spectroscopy can be difficult due to the complexity of the equipment and special measurement conditions. In this paper, we attempt to overcome this limitation by suggesting a compact device developed in-house that is usable even in the field. Pear (Pyrus communis L.) Otradnenskaya was used as the object of this study. We assessed the treatment effect of the scion–rootstock interface with cold atmospheric plasma (CAP) and plasma-treated solution (PTS) on the survival of the grafts. The dependence of the impedance of the complete grafted tree on the signal frequency and the length of the measuring section was analyzed. It is shown that the treatment of the scion and rootstock with CAP and PTS promotes the fusion of scion and rootstock. The impedance value in the control was on average 24–35% higher than in plants treated with CAP and PTS, which indicates a better healing process of the grafting site. This can be an indication of better quality of the planting material which can be obtained much earlier than with the conventional approach (monitoring the plants in a nursery).

Response of grafts of different scion varieties on the different rootstock of mango (Mangifera indica L.) under nursery conditions

The investigation was carried out at the College of Horticulture, Bidar to study the “Performance of grafts of different scion varieties on the different rootstock of mango (Mangifera indica L.) under nursery conditions” with thirty-six treatments comprising of twelve rootstocks (Kurukkan, Kitchner, Olour, EC-95862, Kensington, Peach, Nekkare, Muvandan, Bappakai, Mylepelian, Starch and Local) and three scions (Baneshan, Dashehari and Kesar). Among different rootstocks, Nekkare registered minimum days for sprouting, maximum sprout length, graft success, the height of grafted plant and number of leaves per graft (12.47 days, 6.08 cm, 89.17%, 29.4 cm and 18.33 respectively) whereas the maximum scion girth and root-collar diameter was registered with Bappakai (5.67 and 6.57mm respectively). In scion varieties Kesar recorded minimum days for the emergence of sprouts (15.92 days), maximum sprout length (5.39 cm), graft success (85.83 %), the height of grafted plant (26.74 cm), scion girth (5.55 mm) and root-collar diameter (6.51mm). In the case of different rootstock scion combinations, Nekkare grafted with Kesar recorded a minimum number of days taken for sprouting (11.4 days), maximum sprout length (7.15 cm), graft success (95 %), the height of grafted plant (33.55 cm) and several leaves per graft (19.7) whereas, scion girth and root-collar diameter were found non-significant.

Scion–Rootstock Relationship: Molecular Mechanism and Quality Fruit Production

Most tree fruits are commercially grown on different root systems, hence called composite plants. The section provides the root system as the rootstock, and the atop ground portion is called the scion. The combination is selected based on different traits of scion varieties, rootstock, and prevailing edaphic situations. The dated back plant propagation technique of joining two plants (grafting/budding) that directly communicates new physiological traits to the desirable scion variety from the rootstock remains unclear. In spite of this, this propagation technique continues widely applied in the multiplication of several fruit plant species. In a grafted plant, rootstocks impacted the scion variety’s growth, yield and quality attributes, physiology, nutrient accumulation as well as biotic and abiotic stress tolerance in many ways. Modern research in plant science for next-generation sequencing providing new vital information about the molecular interactions in composite plants multiplied using grafting. Now it was confirmed that genetic exchange is occurring between rootstock and scion variety through grafting joints. In this aspect, we discuss the process and the molecular mechanism of rootstock scion interactions. This review finally explains the dynamics of rootstock–scion interactions as well as their effect on physiology in terms of production, environmental stresses, and fruit quality. The morphological, physiochemical, and molecular mechanisms have been reviewed to develop an integrated understanding of this unknowable process that questions existing genetic paradigms. The present review summarizes the reported molecular mechanism between scion and rootstock and the impact of rootstocks on the production biology of scion varieties of economically important fruit crops and identifies numerous key points to consider when conducting rootstock scion interaction experiments. Rootstocks may offer a non-transgenic approach to rapidly respond to the changing environment and expand agricultural production of perennial fruit crops where grafting is possible in order to meet the global demand for fruit, food, and demands of the future.

Comparative Transcriptomic Analysis of Inarching Invigorating Rootstock onto Incompatible Grafts in Citrus

Grafting is a technique that is widely used in citrus production. Graft incompatibility often occurs in the orchard. Inarching can effectively improve the vigor of incompatible grafts, but its mechanism remains poorly understood. Our previous studies investigated the scion-rootstock interaction of citrus and highlighted the role of hormonal balance and genes in abscisic acid biosynthesis regulation. To further elucidate the mechanism of inarched grafts rejuvenation, Hm/Pt combination (Citrus maxima (Burm.) Merrill cv. 'Hongmian miyou' grafted onto Poncirus trifoliata) were inarched with 'Pujiang Xiangcheng' (a novel citrus rootstock cultivar recently selected from wild Citrus junos populations), and comprehensive analysis was performed to compare the inarched grafts and controls. Compared with incompatible grafts, the results revealed that inarching could recover the leaf metabolism balance, including reducing starch content, increasing chlorophyll content and restoring the cell structure. Additionally, our results corroborated that hormonal balance and hormone-related genes played a central role in inarching compatibility. Furthermore, the roles of Hsf4, ERF1, NCED3 and PYL were highlighted, and a model for explaining inarched grafts recovery invigoration was proposed. This study shed light on the mechanism of inarching regulation tree vigor and offered deep insights into the scion-rootstock interaction in citrus.

Study on the Resistance of ‘Cabernet Sauvignon’ Grapevine with Different Rootstocks to Colomerus vitis

In recent years, Colomerus vitis has caused serious economic losses due to reduced grape production in Xinjiang (northwest China). Several rootstock varieties have been reported to improve the resistance of Cabernet Sauvignon to Colomerus vitis. This study explored the influence of Cabernet Sauvignon with different rootstocks on the resistance to Colomerus vitis. In particular, Cabernet Sauvignon/Cabernet Sauvignon (CS/CS) was selected as the control, and Cabernet Sauvignon grafted with five resistant rootstocks (3309C, 1103P, 140R, SO4, and 5C) was employed as the treatment. The infestation rate and injury index of Colomerus vitis to grapevines was investigated, and insect-resistant types of grapevines with different rootstocks were determined. The resveratrol (Res) content, the gene expression of resveratrol synthase (RS), and the activities of peroxidase (POD), polyphenol oxidase (PPO), catalase (CAT), and superoxide dismutase (SOD) in the leaves of each rootstock grapevine were measured. The activity of the four enzymes and the content of Res were negatively correlated with the injury index. The results revealed the ability of the rootstock to improve the resistance of grapevines to Colomerus vitis by increasing the enzyme activity or Res content. In particular, 140R, SO4, and 5C rootstocks can be employed as rootstocks of the ‘Cabernet Sauvignon’ grapevine with resistance to Colomerus vitis. The contents of Res and the four resistance enzymes studied here can be used as indexes to evaluate the insect resistance of rootstock–scion combinations.

A Mini Review of Citrus Rootstocks and Their Role in High-Density Orchards.

Dwarfing is an important agricultural trait for intensive cultivation and effective orchard management in modern fruit orchards. Commercial citrus production relies on grafting with rootstocks that reduce tree vigor to control plant height. Citrus growers all over the world have been attracted to dwarfing trees because of their potential for higher planting density, increased productivity, easy harvest, pruning, and efficient spraying. Dwarfing rootstocks can be used to achieve high density. As a result, the use and development of dwarfing rootstocks are important. Breeding programs in several countries have led to the production of citrus dwarf rootstocks. For example, the dwarfing rootstocks 'Flying Dragon', 'FA 517', 'HTR-051', 'US-897', and 'Red tangerine' cultivated in various regions allow the design of dense orchards. Additionally, dwarf or short-stature trees were obtained using interstocks, citrus dwarfing viroid (CDVd) and various chemical applications. This review summarizes what is known about dwarf citrus rootstocks and the mechanisms underlying rootstock-scion interactions. Despite advances in recent decades, many questions regarding rootstock-induced scion development remain unanswered. Citrus rootstocks with dwarfing potential have been investigated regarding physiological aspects, hormonal communication, mineral uptake capacity, and horticultural performance. This study lays the foundation for future research into the genetic and molecular mechanisms underlying citrus dwarfing.

Trifoliate Orange-Related Rootstocks Enhance the Horticultural Performance of ‘Shamouti’ Sweet Orange under Humid Subtropical Condition

The narrow genetic pool for both scions and rootstocks used in the Brazilian orchards makes the citrus industry vulnerable to biotic and abiotic threats. Orchard diversification by using different scion–rootstock combinations is an efficient measure to promote citrus protection, through increasing the level of genetic diversity. In this paper, we report the horticultural performance of the mid-season ‘Shamouti’ sweet orange grafted on five different rootstocks (‘Rangpur’ lime, ‘Swingle’ citrumelo, ‘C-13′ citrange, and ‘Cleopatra’ and ‘Sunki’ mandarins) in a long-term experiment (2007–2017) under the Brazilian humid subtropical condition. ‘Shamouti’ trees were assessed for vegetative growth, yield, and fruit quality. Additionally, a study was performed to estimate tree density and yield for new plantings. Trees grafted on ‘Swingle’ and ‘C-13′ rootstocks were less vigorous and more productive, with cumulative yields of >480 kg per tree, allowing high-density plantings (363–337 trees·ha−1). Trees on ‘Cleopatra’, ‘Sunki’, and ‘Rangpur’ were the most vigorous among the tested rootstocks, with tree heights > 4.20 m. However, they took longer to establish in the field, evidenced by their growth progress. These combinations also displayed the lowest tree density estimation (≤311 trees·ha−1). Trees on ‘Cleopatra’ exhibited the lowest cumulative yield (255 kg per tree). Although some significant differences were found for fruit quality, all rootstock combinations produced fruit of suitable quality, attending the commercial grading. Our findings evidence the potential of the trifoliate orange-related rootstocks ‘C-13′ and ‘Swingle’ to be used as promising rootstocks for ‘Shamouti’ cultivation in the humid subtropics, promoting genetic diversification and enhancing yield and tree density in new orchards.

Fruit Yield in Sweet Orange Trees under Huanglongbing (HLB) Conditions Is Influenced by Reproductive Phenological Characteristics of the Scion-Rootstock Combination

Since greening (aka HLB), the most economically devastating disease of citrus worldwide was detected in Florida in 2005, citrus acreage and fruit production has reduced by more than 70%. Transmitted by the insect vector Asian citrus psyllid, the disease results in exacerbated preharvest drop, smaller fruit, and a rapid decline of trees leading to a significant reduction of yield. Currently, there is no cure for the disease. A strategy to cope with the disease relies on identifying tolerant or more productive varieties, and understanding factors that make them more productive. Under these circumstances, a combination of rootstock and scion that results in better fruit yield is highly desirable. In this paper we investigated phenological attributes of the main sweet orange varieties planted in Florida, Hamlin and Valencia, grafted on Swingle and US-942 rootstocks, two of the most used rootstocks by Florida citrus growers. Our goal was to better understand the phenology associated with the consistently higher yields of trees grafted on US-942. We assessed fruiting characteristics and abscission dynamics of fruit and leaves. We found that trees on US-942 rootstock, especially from Valencia scion, significantly set more terminals than cluster fruit; terminal fruit is larger and experiences less drop resulting in better yields. In general, rootstock did not have a significant influence on the fruit-bearing characteristics in Hamlin. Similarly, we found that fruit detachment force was not significantly influenced by rootstock. Our results show that in an HLB endemic situation, fruiting characteristics should be considered when selecting rootstocks and rootstock–scion combinations, so genetics resulting in larger, single fruits per fruiting branch should be favored.

Phytochemical profile of Brazilian grapes (Vitis labrusca and hybrids) grown on different rootstocks.

Important factors may influence the bioactive compounds in grapes, including scion–rootstock interaction. Therefore, the bioactive compounds and antioxidant activity in grape skin and pulp fractions of ‘Isabel Precoce’, ‘BRS Carmem’, ‘BRS Cora’, ‘BRS Violeta’ and ‘IAC 138–22 Máximo’ were assessed. These cultivars, from genetic improvement programs in Brazil, have good adaptation to subtropical and tropical climate conditions, and can be widely used by winegrowers aiming at adding value to the grape. All grapevines were grafted onto ‘IAC 766’ and ‘IAC 572’ rootstocks under tropical conditions in Brazil. The highest concentration of bioactive compounds was found in skins of ‘BRS Violeta’, followed by ‘IAC 138–22 Máximo’, both grafted onto ‘IAC 766’. There was a strong correlation between phenolic content and antioxidant properties, since antioxidant activity also decreased in the sequence: ‘BRS Violeta’ > ‘IAC 138–22 Máximo’ > ‘BRS Cora’ > ‘BRS Carmem’ > ‘Isabel Precoce’. Skin from hybrid grapes (‘BRS Violeta’, ‘IAC 138–22 Máximo’, ‘BRS Cora’ and ‘BRS Carmem’) grafted in both rootstocks contains higher levels of (poly)phenolic compounds and antioxidant activity than ‘Isabel Precoce’ (V. labrusca). Skin from ‘BRS Violeta’ grafted onto ’IAC 766’ stand out from the others due to their high content of bioactive compounds.

Plant Hormone and Inorganic Ion Concentrations in the Xylem Exudate of Grafted Plants Depend on the Scion-Rootstock Combination.

In grafted plants, inorganic ions and plant hormones in the xylem exudate transported from the rootstock to the scion directly or indirectly affect the scion, thereby improving the traits. Therefore, the concentration of these components in the xylem exudate of grafted plants may be an indicator for rootstock selection. On the other hand, few reports have presented a comprehensive analysis of substances transferred from the rootstock to the scion in plants grafted onto different rootstocks, primarily commercial cultivars. In this study, we measured inorganic ions and plant hormones in the xylem exudate from the rootstock to the scion in various grafted plants of tomato and eggplant. The results revealed that the concentrations of inorganic ions and plant hormones in the xylem exudate significantly differed depending on the type of rootstock. In addition, we confirmed the concentration of the inorganic ions and plant hormones in the xylem exudate of plants grafted onto the same tomato rootstock cultivars as rootstock with tomato or eggplant as the scions. As a result, the concentrations of inorganic ions and plant hormones in the xylem exudate were significantly different in the grafted plants with eggplant compared with tomato as the scion. These results suggest that signals from the scion (shoot) control the inorganic ions and plant hormones transported from the rootstock (root).

Scions impact biomass allocation and root enzymatic activity of rootstocks in grafted melon and watermelon plants.

Vegetable grafting is increasingly recognized as an effective and sustainable plant production alternative. Grafted plants usually show increased uptake of water and minerals compared with self-rooted plants, mostly thought a consequence of the vigorous rootstocks selected. However, while studies frequently addressed the effects of rootstocks on the performance of scions, knowledge on the influences of scions on biomass allocation, morphology, and metabolic activity of roots is rare. In particular, the plasticity of root traits affecting resource acquisition and its efficiency remains poorly understood. Two different rootstock species, Cucurbita maxima × Cucurbita moschata and Lagenaria siceraria, were grafted in combination with melon (Cucumis melo) and watermelon (Citrullus lanatus). Self-grafted rootstocks were used as control. Plant biomass and root traits were determined after destructive harvesting 30 and/or 60 days after grafting. Traits included biomass allocation, leaf and root morphology, potential activities of four extracellular enzymes on root tips and basal root segments, and root respiration. Successfully grafted scions increase the ratio of root to whole plant dry matter (RMF), and increased ratios of root length to whole plant dry matter (RLR) and to plant leaf area (RL : LA). In contrast, morphological root traits such as diameter, tissue density, and specific root length remain surprisingly stable, and thus scion-induced changes of those traits may only play a minor role for the beneficial effects of grafting in Cucurbitaceae. Incompatibility in melon/L. siceraria grafts, however, was likely responsible for the reduced root growth in combination with clear changes in root morphological traits. Reduced root respiration rates seem to be the effects of a non-compatible rootstock–scion combination rather than an active, C-efficiency increasing acclimation. In contrast, heterografts with melon and watermelon frequently resulted in root-stock-specific, often enhanced potential enzymatic activities of acid phosphatase, β-glucosidase, leucine-amino-peptidase, and N-acetyl-glucosaminidase both at root tips and basal parts of lateral roots—presenting a potential and complementary mechanism of grafted plants to enhance nutrient foraging. The studied melon and watermelon scions may thus increase the nutrient foraging capacity of grafted plants by fostering the relative allocation of C to the root system, and enhancing the extracellular enzymatic activities governed by roots or their rhizobiome.

The Expression of Aroma Components and Related Genes in Merlot and Marselan Scion-Rootstock Grape and Wine.

Rootstocks were bred and selected from several species in order to enhance the resistance against biotic or abiotic stresses. There are few studies on the effect of rootstocks on aroma and related gene expression. This study focused on the effects of three rootstocks, Kober 5BB (5BB), 1103 Paulsen (1103P), and Selection Oppenheim (SO4), on the aroma and volatile-related gene expression levels of Merlot and Marselan berries and wines. These three rootstocks reduced the total aroma content of Merlot wine. 5BB upregulated VvLoXA and showed increased C6 alcohols. 1103P enhanced the linalool from Merlot berry, with marked upregulation of VvLinNer1. Conversely, rootstocks increased the total aroma content of Marselan berry, verified by the related expression levels of volatile-related genes. For Marselan berry, 5BB and 1103P upregulated five VvGTs and nine genes from the LOX and MEP pathway. 1103P increased the contents of C6 alcohols, C6 aldehydes, and citronellol from Marselan berry. Compared to 5BB and SO4, rootstock 1103P provided berries of better quality and richer aroma volatiles to Merlot and Marselan, while all three of the rootstocks had a significant effect on scion–rootstocks.

Improving Bell Pepper Crop Performance and Fruit Quality under Suboptimal Calcium Conditions by Grafting onto Tolerant Rootstocks

Calcium deficiency or its inefficient translocation to pepper fruits leads to considerable economic loss by reducing the number of marketable fruits. The present study proposes grafting as an environmentally friendly technique to effectively reduce such loss. A commercial variety (Al-cudia F1; V) was grafted onto two pepper (Capsicum annum L.) accessions (V/A6 and V/A8), a hybrid rootstock (V/N) and was also self-grafted (V/V). All rootstock–scion combinations were cultivated under greenhouse conditions with optimal and suboptimal Ca supply and assessed for fruit yield and biomass production, gas exchange and chlorophyll fluorescence, mineral concentration in leaves and fruits as well as several fruit quality parameters. The V/N plants demonstrated an enhanced capacity for increased biomass, higher yield and number of commercial fruits and greater mean fruit weight compared with the other rootstock–scion combinations. These improvements are attributed primarily to increased intrinsic water efficiency. Additionally, a significantly higher Ca concentration in leaves was found under suboptimal Ca conditions in the V/N combination than that found in the other rootstock–scion combinations indicating a higher capacity for Ca uptake and translocation. Under the same conditions, the concentration of organic acids in fruits, such as citric and tartaric, which impact the organoleptic quality, was also higher in V/N plants. Consequently, we can conclude that grafting pepper onto tolerant rootstocks is a successful tool for ameliorating the negative impact of suboptimal Ca conditions on pepper crop performance and fruit quality.

Application of Phenomics to Elucidate the Influence of Rootstocks on Drought Response of Tomato

The cultivation of nutritionally and economically important crops like tomato are often threatened by dry spells due to drought as these crops largely depend on an assured water supply. The magnitude and intensity of drought is predicted to intensify under climate change scenarios, particularly in semi-arid regions, where water is already a scarce resource. Hence, it is imperative to devise strategies to mitigate the adverse effects of drought on tomato through improvement in the plant’s efficiency to utilise the moisture in the growth medium. Since the root is the entry point for water, its intrinsic structure and functions play a crucial role in maintaining the soil–water–plant continuum during moisture deficit at the rhizosphere. Grafting offers a great opportunity to replace the root system of the cultivated tomato plants with that of wild species and hence provide a rapid solution to modulate root system architecture in contrast to the time-consuming conventional breeding approach. However, the success in developing the best graft combination of cultivated tomato and rootstock depends on the source of rootstock and selection methods. In this study, we used a high throughput phenomics facility to assess the efficiency of tomato, grafted on the rootstocks of different genetic backgrounds, at different levels of moisture in the soil. Rootstocks included tomato cultivars and the hybrids, derived from the crosses involving wild relatives, as donor parents. Among the rootstocks, an interspecific (Solanum lycopersicum × S. pennellii) derivative RF4A was highly efficient in terms of productive use of water. The RF4A rootstock-grafted plants were more conservative in water use with higher plant water status through relatively better stomatal regulation and hence were more efficient in generating greater biomass under water stress conditions. These plants could maintain a higher level of PSII efficiency, signifying better photosynthetic efficiency even under water stress. The distinct response of interspecific rootstock, RF4A, to water stress can be ascribed to the effective root system acquired from a wild parent (S. pennellii), and hence efficient water uptake. Overall, we demonstrated the efficient use of a phenomics platform and developed a protocol to identify promising rootstock–scion combinations of tomato for optimization of water use.

Effects of Rhizobacteria Application on Leaf and Fruit Nutrient Content of Different Apple Scion–Rootstock Combinations

The plant pomological characteristics and physiological behaviors of genotypes in modern apple cultivation could be different depending on the use of rootstock, changing growth ecology and application of biological control agents. The aim of this research was to determine the effects of rhizobacteria application on leaf and fruit nutrient contents in different apple scion–rootstock combinations. This study was carried out with seven standard cultivars (Scarlet Spur, Red Chief, Fuji, Jeromine, Galaxy Gala, Granny Smith, and Golden Reinders) budded on M.9 and MM.106 rootstocks. In the experiment, trees were sprayed by a nitrogen + phosphorus solvent rhizobacteria three times, with an interval of 15 days in the spring period. The effect of rhizobacteria application on leaf and fruit nutrient contents was statistically significant and provided generally significant positive contributions, except for leaf Mg content. Comparing both rootstocks, the positive effect of bacterial application was higher on the M.9 rootstock for leaf N and B content and fruit N and Fe content, and on the MM.106 rootstock for other nutrient content. While the effects of bacterial application on the basis of cultivars were generally positive, the highest positive contribution was made in leaf P content (10.7%) and fruit Mn content (32.1%) of the Fuji cultivar. Considering the total increase in nutrients in scion–rootstocks combination, rhizobacteria application had a positive effect on the leaf nutrient contents in Golden Reinders/MM.106, but not leaf K content. The highest increases in leaves of scion-rootstock combinations were determined as 4.0% in N content in Granny Smith/M.9, 14.1% in P content in Scarlet Spur/MM.106, 7.1% in K content in Fuji/MM.106, 4.4% in Ca content in Jeromine/M.9, and 14.0% in Mg content in Granny Smith/MM.106. The highest increase in fruit nutrient contents was between 4.9% (N content) and 13.5% (Ca content) for macro elements, and between 9.5% (Cu content) and 41.8% (Mn content) for microelements. The results of the present study may provide significant leads for further studies on this subject.

Deficit irrigation differently affects aroma composition in berries of Vitis vinifera L. (cvs Sangiovese and Merlot) grafted on two rootstocks

Background and Aims Water deficit modifies the concentration of the aroma compounds of grape berries, but little information is available on the effect of deficits applied at different phenological stages. We evaluated the effect of deficit irrigation on glycosylated volatile organic compounds (VOCs) responsible for the aroma of berries of Sangiovese and Merlot cultivars grafted on 1103P or SO4 rootstocks. Methods and Results Vines were subjected to either pre- or post-veraison water stress, and berry composition compared against that of fruit of fully irrigated vines. At harvest, a higher concentration of glycosylated VOCs was measured in berries from vines stressed pre-veraison, but while it increased as water deficit increased in Sangiovese, this occurred only at a low or moderate level of stress in Merlot. Post-veraison water stress had a negative or negligible effect on the concentration of glycosylated VOCs in berries at harvest. The rootstock affected the concentration of glycosylated VOCs, particularly in vines stressed pre-veraison, with higher glycosylated VOCs observed for SO4 grafted vines than for 1103P grafted vines. Conclusions Pre-veraison water deficit enhanced the concentration of berry glycosylated VOCs, while post-veraison deficit did not. The rootstock–scion interaction might amplify the irrigation effect on berry glycosylated VOCs. Significance of the Study Modifying the timing and volume of irrigation might allow management of berry flavour for improved fruit and wine composition. Irrigation protocols should be tailored for specific cultivar–rootstock combinations.

Enhancement of the Plant Grafting Technique with Dielectric Barrier Discharge Cold Atmospheric Plasma and Plasma-Treated Solution

A garden plant grafting technique enhanced by cold plasma (CAP) and plasma-treated solutions (PTS) is described for the first time. It has been shown that CAP created by a dielectric barrier discharge (DBD) and PTS makes it possible to increase the growth of Pyrus communis L. by 35–44%, and the diameter of the root collar by 10–28%. In this case, the electrical resistivity of the graft decreased by 20–48%, which indicated the formation of a more developed vascular system at the rootstock–scion interface. The characteristics of DBD CAP and PTS are described in detail.