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Vegetable grafting has been applied to fruiting crops, yet only to a limited extent in leafy greens and herbs which may also benefit from grafting. In this study, we examined the effect of reciprocal grafting two sweet basil (Ocimum basilicum L.) cultivars of differing vigor on plant growth and leaf mineral nutrient concentration to test whether differences in growth exist due to grafting and whether such differences are due to altered plant nutrient status in two trials. Two cultivars 'Nufar' (NU), a high vigor cultivar, and 'Dolce Fresca' (DF), a cultivar developed for compact growth, were selected. Four grafted treatments (scion/rootstock) were created by self-grafting (NU/NU and DF/DF) and reciprocal inter-cultivar grafting (DF/NU and NU/DF). Un-grafted plants (ug-NU and ug-DF) served as controls. Following grafting, plants were grown for 26 or 21 days in a greenhouse. DF rootstocks decreased NU shoot dry mass (19-29%) and stem length (12%) compared to ug-NU in both trials, while dry root mass was reduced (28%) in the second trial. In contrast, NU rootstocks did not affect DF growth in the first trial but significantly decreased dry shoot (18%) and root (31%) mass, compared to ug-DF in the second. Concentration of most inorganic nutrients examined was affected by both rootstock and scion genotype. For NU scions, DF rootstocks resulted in significantly higher (5-29%) levels of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, copper, and zinc in leaf tissue than ug-NU. For DF scions, NU rootstocks resulted in significantly higher (7-9%) levels of potassium and phosphorus but significantly lower (11-23%) levels of magnesium, sulfur, boron, copper, and zinc when compared to ug-DF. Results of this study show that intercultivar grafting sweet basil using a more vigorous cultivar as a rootstock did not enhance the growth of a less vigorous scion and reduced concentrations of certain nutrients. However, grafting a vigorous scion to a less vigorous rootstock reduced shoot growth but generally increased nutrient concentrations. This suggests that changes in growth in grafted basil are not due to altered nutrient status. Further research is needed to determine specific physiological processes influencing grafted basil growth. [ABSTRACT FROM AUTHOR]

Grafting in species of Pinus is used to establish asexual seed orchards. Generally, grafting success is low, therefore, it is required to study the influencing factors. Such as the technique and the contact surface of the cambium that depends on the length of the cut on the scion and the rootstock. The objective of this study was to evaluate graft success, growth, and needle development on Pinus patula grafts as functions of the grafting technique and cutting length. It was expected that a specific combination of technique and cutting length would allow predicting the graft success. The techniques of top cleft, side-veneer and splice grafting were used with three cutting lengths (1.5, 2.0, and 2.5 cm) in a completely randomized design with factorial array. The data were analysed with an analysis of variance and treatment means were compared with the Tukey test (p = 0.05). Sixty days after grafting, technique influenced success; top cleft grafting had the highest value (80%) but was not statistically different from side veneer grafting (73.3%). There was, however, statistical difference between top cleft and splice grafting (56.7%, p = 0.05). There were no differences among the three cutting lengths in terms of the three variables evaluated. The effect of the interaction showed that top cleft and side veneer grafts with the cutting length of 1.5 cm expressed the greatest growth (32.4 and 32.2 mm, respectively); followed by side veneer grafting with the cutting length of 2.0 cm (30.4). The study demonstrated that the most viable techniques to increase grafting success in P. patula are the top cleft and side veneer techniques. Cutting length of the scion and the rootstock can be set within the range 1.5 to 2.5 cm. [ABSTRACT FROM AUTHOR]

Cut roses are grown throughout the four distinct seasons of spring, summer, autumn, and winter in Korea. Especially in the very hot or cold seasons of summer or winter, the temperature and light environments inside a greenhouse cause abiotic stress on the growth of horticultural crops. In a greenhouse where shade cultivation is performed in summer, the temperature is high and the light intensity is low, whereas in winter when shade cultivation is not performed, both temperature and light intensity are low. This experiment investigated the year-round growth and yield changes of cut roses grafted onto three rootstocks. The root activity of rootstocks was generally higher than that of the scion. The stomata of the grafted cut roses showed morphological changes according to the seasons. Compared with the scion, the stomata of grafted cut roses became smaller and their number increased in summer, whereas only the stomata size increased in winter. The grafted cut roses had characteristics of high photosynthetic efficiency such as photosynthesis rate, stomatal conductance, transpiration rate from rootstocks under harsh environmental conditions including temperature and light intensity, and thus the photosynthetic efficiency was higher than that of the scion. There was no significant change in the yield of grafted cut roses, but flower quality parameters such as the stem height, stem thickness, and weight of grafted cut roses were improved according to the rootstocks compared with those of the scion. In particular, in cut roses grafted with R. multiflora cv. Natal Briar and Rosa indica 'Major' rootstocks, the weight increased as the stem lengthened and thickened in spring, autumn, and winter. Therefore, grafting is effective in improving the quality of cut roses grown under abiotic stress caused by harsh temperature and light intensity conditions during winter. [ABSTRACT FROM AUTHOR]

Tomato, which is mainly established with grafted seedlings, is one of the most popular vegetables worldwide with a high nutritional value,. Market demand for grafted seedlings is high in specific seasons; thus, commercial nurseries face a problem of limited space availability during the healing stage. Light quality is an essential parameter during healing that can adjust seedling development towards desirable traits and lead to time and space saving during seedling production. Moreover, transplant shock constitutes another challenge that could limit crop yield. The objective of this study was to evaluate the overall quality of grafted tomato seedlings and their potential adjustment to transplant shock as affected by different light spectra during healing in a chamber. Evaluations were conducted immediately after exiting the healing chamber and after transplantation into pots. Light wavelengths were used from fluorescent lamps (FL) or light-emitting diodes with red (R), blue (B), red–blue combinations with 12 and 24% blue (12B and 24B), and white (W) emitting 11% blue. W enhanced the dry shoot biomass and the root architecture before and after transplantation. 24B led to an increased stem diameter, root development, and phenolic and antioxidant accumulation at both phases of the experiment. 12B enhanced the leaf area before transplantation and root development after transplantation. FL, R and B induced inferior seedling growth compared to the red–blue-containing LEDs, with B performing poorly in almost all tested parameters. Overall, red, including 11–24% blue, provides the optimum light conditions during the healing stage for the production of high-quality grafted tomato seedlings, with advanced capabilities of abiotic stress adaptation to transplant shock. [ABSTRACT FROM AUTHOR]

Citrus holds the key position in horticulture sector of Pakistan in terms of area and production. Kinnow is considered as the trademark of Pakistan's citriculture industry. Cultivation experiment was conducted to evaluate the endogenous plant hormones, leaf gas exchange, photosynthetic pigments, vegetative performance, and yield of Kinnow mandarin grafted on nine rootstocks (Rough lemon, cox mandarin, Fraser hybrid, Troyer citrange, Cleopatra mandarin, Poncirus trifoliata, Benton, C-35, and Carrizo citrange). Maximum indole acetic acid (IAA), gibberellic acid (GA3), and zeatin (ZT) levels were recorded in scion and rootstock of Poncirus trifoliata followed by Fraser hybrid. Troyer citrange rootstock depicted maximum amount of abscisic acid in scion and rootstock. Maximum leaf gas exchange in Kinnow mandarin was recorded on Fraser hybrid rootstock. Kinnow grafted on Troyer citrange rootstock had minimum stomatal conductance and photosynthetic activity because of high ABA level. Photosynthetic pigments of Kinnow mandarin were maximum on Poncirus trifoliata and minimum on Troyer citrange. A positive correlation was observed among the levels of IAA, GA, ZT, and vegetative growth of Kinnow mandarin. It is concluded that endogenous hormones modulated the growth of Kinnow mandarin. Poncirus trifoliata and Fraser hybrid rootstocks could be an alternate rootstocks of traditional Rough lemon for Kinnow mandarin. [ABSTRACT FROM AUTHOR]

Cucumber (Cucumis sativus) is one of the most important vegetables produced and consumed in the United States. In the midwestern United States, a major obstacle to spring cucumber production is low soil temperatures during plant establishment. High tunnel is a popular tool for season extension of vegetable production. Low soil temperature is a challenge for cucumber production even inside high tunnels. Grafting is a cultural practice known to help control soilborne diseases and improve plants’ tolerance to abiotic stresses. Recent studies found that using grafted cucumber plants with cold-tolerant rootstocks greatly benefited early-season seedless cucumber production in high tunnels. The objective of this study was to analyze the economic feasibility of growing grafted cucumber in high tunnels. A comparison of partial costs and returns between growing grafted and nongrafted cucumbers in a high tunnel in Vincennes, IN, was conducted. Data were used to develop a partial budget analysis and sensitivity tests. Data included production costs, marketable yield, and price of cucumber through different market channels. This study provided a baseline reference for growers interested in grafting seedless cucumber and for high tunnel production. Although costs of grafted transplants were higher, their yield and potential revenue helped to offset the higher costs. Results indicated that grafting can help farmers increase net returns through the increasing yield of grafted plants. Results from the sensitivity analysis illustrated how the increased yield of grafted cucumbers offsets the extra cost incurred in the technique while providing a higher revenue. While actual production costs for individual farmers may vary, our findings suggested that grafting can be an economically feasible tool for high tunnel seedless cucumber production.

Vegetable grafting has been applied to fruiting crops, yet only to a limited extent in leafy greens and herbs which may also benefit from grafting. In this study, we examined the effect of reciprocal grafting two sweet basil (Ocimum basilicum L.) cultivars of differing vigor on plant growth and leaf mineral nutrient concentration to test whether differences in growth exist due to grafting and whether such differences are due to altered plant nutrient status in two trials. Two cultivars ‘Nufar’ (NU), a high vigor cultivar, and ‘Dolce Fresca’ (DF), a cultivar developed for compact growth, were selected. Four grafted treatments (scion/rootstock) were created by self-grafting (NU/NU and DF/DF) and reciprocal inter-cultivar grafting (DF/NU and NU/DF). Un-grafted plants (ug-NU and ug-DF) served as controls. Following grafting, plants were grown for 26 or 21 days in a greenhouse. DF rootstocks decreased NU shoot dry mass (19–29%) and stem length (12%) compared to ug-NU in both trials, while dry root mass was reduced (28%) in the second trial. In contrast, NU rootstocks did not affect DF growth in the first trial but significantly decreased dry shoot (18%) and root (31%) mass, compared to ug-DF in the second. Concentration of most inorganic nutrients examined was affected by both rootstock and scion genotype. For NU scions, DF rootstocks resulted in significantly higher (5–29%) levels of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, copper, and zinc in leaf tissue than ug-NU. For DF scions, NU rootstocks resulted in significantly higher (7–9%) levels of potassium and phosphorus but significantly lower (11–23%) levels of magnesium, sulfur, boron, copper, and zinc when compared to ug-DF. Results of this study show that inter-cultivar grafting sweet basil using a more vigorous cultivar as a rootstock did not enhance the growth of a less vigorous scion and reduced concentrations of certain nutrients. However, grafting a vigorous scion to a less vigorous rootstock reduced shoot growth but generally increased nutrient concentrations. This suggests that changes in growth in grafted basil are not due to altered nutrient status. Further research is needed to determine specific physiological processes influencing grafted basil growth.

The purpose of this study was to evaluate the effect of mandarin scions on total flavonoids and individual flavanones as well as antioxidant capacity in peel and pulp of fruits. Total flavonoids and total phenols content was measured using aluminum chloride colorimetric and Folin-Ciocalteau colorimetric method respectively. Assay of DPPH radical scavenging was used to evaluate antioxidant activities. Individual flavanones (narirutin, naringin and hesperidin) detected and analyzed using HPLC-PDA. Among the flavonones, hesperidin was determined in the highest concentration in all investigated samples. Level of flavanones (25.05 mg/g DW) and total flavonoids (10 mg/g DW) in peel of Satsuma mandarin and the amount of phenolic acids (1.17 mg/g DW) in peel of Younesi tangerine was higher than other scions. The results of correlation showed that there was a high positive correlation between the amount of total flavonoids and hesperidin. The results of this study showed useful information on functional and phytochemical compounds in mandarin cultivars that can be used in pharmaceutical industry and provide valuable genetic resources for breeding programs. [ABSTRACT FROM AUTHOR]

Interest is growing among small-scale growers in grafting tomato (Solanum lycopersicum) for improved crop productivity. Healing of newly grafted plants is often considered to be a critical process requiring a highly controlled environment. Setting up healing chambers and managing healing conditions can be major challenges for small-scale producers that limit graft survival and discourage further attempts at using grafting technology. Here, we demonstrate a simple “chamberless healing” strategy for grafted tomato plants using regular indoor conditions without the need to install and manage a sophisticated healing chamber. We hypothesize that tomato can form a high-quality graft in a healing environment with relative humidity below 70% and ambient temperatures between 22 and 25 °C. ‘Tribute’ beefsteak tomato as the scion was grafted onto ‘Estamino’ rootstock in the 2018 experiment, whereas ‘Multifort’ and ‘Shield RZ F1 (61-802)’ were used as the rootstocks in the 2019 experiment. After grafting, the seedlings for the chamberless healing treatment were kept in uncovered seedling trays and misted with water two or three times per day. Seedlings in other treatments were placed in a humidity dome or wrapped chamber to maintain high humidity during the first few days after grafting. In the 2018 experiment, chamberless healing was compared with covered treatments with different ventilation times during the first few days after grafting. In the 2019 experiment, chamberless healing was compared with a standard graft healing chamber treatment to further validate its feasibility. In both 2018 and 2019, all treatments showed high graft survival rates (>85%) at 21 days after grafting (DAG), and plants from the chamberless healing treatment had a lower incidence of adventitious root growth than plants from other healing treatments (0% to 7% vs. 33% to 78%). In the 2019 experiment, no differences in graft union strength, photosynthetic rate, biomass accumulation, or flowering time were observed between the chamberless and standard healing treatments. Plants with chamberless healing were slightly (8%) shorter than the standard treatment at 21 DAG, but no difference was observed at 27 DAG. Although some additional management is required during healing to prevent water loss, the alternative chamberless system assessed in this study exhibited great potential to facilitate small-scale graft healing for producing grafted tomato transplants under standard indoor conditions without any sophisticated healing environment and management.

The use of tomato (Solanum lycopersicum) grafting is gaining traction across the United States, but small-scale growers face the challenge of creating optimum postgrafting healing conditions. The practice of blocking light for a period of 2 to 4 days while maintaining high humidity is commonly recommended for healing grafted tomato transplants; however, research is exploring alternatives to this practice. The present study investigated a low-input healing method for grafted tomato transplants with a specific focus on light and the use of propagation heat mats to regulate substrate and healing chamber air temperatures during the 7-day healing process. We hypothesized that 4 days of light exclusion and the use of propagation heat mats would improve grafted tomato transplant survival and growth. ‘Cherokee Purple’ was used as the scion and ‘RST-04-106-T’ was used as the rootstock. The whole plot factor was heat [propagation mats set at 80 °F (heat) or no propagation mat (no heat)] and the subplot factor was light exclusion (0, 4, or 6 days of dark). The highest survival rate among treatments was 97% in 0 days of dark with no heat treatment; survival decreased to 84% in 4 and 6 days of dark with no heat treatments. The plant survival rate was 96% with 0 days of dark and heat treatment; however, the survival rates were 63% and 45% for the 4- and 6-day dark treatments, respectively. The scion stem diameter was largest for transplants grown in 0 days of dark, but there was no difference in stem diameter due to heat treatments. There were no differences among scion or rootstock biomasses due to heat or light treatments. These results demonstrate that propagation mats set at 80 °F to regulate the substrate temperature were detrimental to grafted transplant survival under extended periods of light exclusion. However, this finding creates the basis to explore lower levels of substrate temperature modification. Our work also indicates that light exclusion may not be necessary for healing grafted tomato plants regardless of root-zone temperature treatments. Future work should examine the interactions of various substrate and air temperatures under full light conditions and their effects on grafted tomato transplant survival and growth. This work contributes to the ongoing research of how to optimize low-input healing methods that may be readily adopted by small-scale tomato growers.

Micrografting can be used to produce healthy seedlings, assess scion-rootstock compatibility and promote precocity. The first objective of this project was to study the impacts of in vitro micropropagation of four major Iranian pistachio cultivars, namely ‘Ahmad Aghaei’, ‘Akbari’, ‘Badami Sefid’ and ‘Kalle Ghochi’ in two different medium Murashige and Skoog (MS) and Driver and Kuniyuki Walnut (DKW) at different concentrations of benzyl adenine (0, 0.5, 1 and 2 mg L-1). The second objective of this project was to examine the effects of ‘Badami-Riz-Zarand’ and ‘Akbari’ rootstocks and micro-scion size (less than 5 and between 5-10 mm) on micrografting of the pistachio cultivars. The results showed that explants of the Akbari cultivar had the highest survival rate of meristems establishment in the DKW medium with 1 mg L-1 benzyl adenine. In the proliferation stage, ‘Akbari’ showed the highest values ​​for proliferation rate, shoot number, shoot length and leaf number whereas, ‘Kalle Ghochi’ had the lowest values ​​for these traits. Moreover, no significant differences were observed between ‘Ahmad Aghaei’, ‘Akbari’ and ‘Badami Sefid’ plantlets in terms of quality during the growing season. The micrografting results on seedlings showed that the scion of the Badami Sefid cultivar with a 5-10 mm size on the ‘Badami-Riz-Zarand’ rootstock had the highest grafting success rate and the lowest cultivar; in contrast, was ‘Kalle Ghochi’ with a scion less than 5 mm on ‘Akbari’.

Abstract Rootstocks are widely used in viticulture worldwide and can affect the yield components and quality of grapes and their juices and wines. The aim of the present study was to determine the effect of the rootstock on the yield performance and physical and physical-chemical traits of ‘BRS Magna’ juice grapes grown in the Submédio do Vale do São Francisco. The study was performed over six production cycles in the period from 2015 to 2019 in the Bebedouro experimental field of Embrapa Semiárido in Petrolina, PE, Brazil. The treatments consisted of seven grapevine rootstocks: IAC 572, IAC 766, IAC 313, Paulsen 1103, SO4, Harmony, and Freedom. The following variables were evaluated: estimated yield, number of grape bunches per plant, branch and leaf fresh matter, bunch weight, bunch length and width, berry weight, total soluble solids content (SS), titratable acidity (TA), and SS to TA ratio (SS:TA). Significant effects of the rootstock were observed in all the variables except for SS. The rootstock ‘IAC 572’ led to increases of up to 61% in the yield of ‘BRS Magna’ grapevines, or 32.78 ton.ha-1, with significant responses in the other yield components. Results of the scatterplot in relation to the first three principal components allowed separation of the rootstocks in accordance with production cycles. The mean values for SS and TA characterize this cultivar in the Vale do Submédio São Francisco, with high soluble solids content and low acidity resulting in high SS:TA, as having potential for preparation of high quality juices, regardless of the rootstock used.

The Miocene period saw substantially warmer Earth surface temperatures than today, particularly during a period of global warming called the Mid Miocene Climatic Optimum (MMCO; ∼17–15 Ma). However, the long‐term drivers of Miocene climate remain poorly understood. By using a new continuous climate‐biogeochemical model (SCION), we can investigate the interaction between volcanism, climate and biogeochemical cycles through the Miocene. We identify high tectonic CO2 degassing rates and further emissions associated with the emplacement of the Columbia River Basalt Group as the primary driver of the background warmth and the MMCO respectively. We also find that enhanced weathering of the basaltic terrane and input of explosive volcanic ash to the oceans are not sufficient to drive the immediate cooling following the MMCO and suggest that another mechanism, perhaps the change in ocean chemistry due to massive evaporite deposition, was responsible. Plain Language Summary: The Miocene period was much warmer than today, with the Mid Miocene Climatic Optimum (MMCO, roughly 17–15 million years ago) especially warm. Due to the high surface temperatures, comparisons to projected climatic conditions as a result of anthropogenic climate change have been drawn. However, the drivers of climate during the Miocene are not well understood. By using a new type of climate model, we investigate the impact volcanic eruptions had on the period, and link the extreme warmth of the MMCO with greenhouse gas release from the eruption of the Columbia River Basalts Group (CRBG). We find weathering of the CRBG does not explain the cooling at the end of the MMCO, and so discuss other potential explanations such as evaporite deposition. Key Points: A new climate‐biogeochemical model allows investigation of drivers of climate change in the MioceneColumbia River Basalt Group (CRBG) degassing is sufficient to have caused the Mid Miocene Climatic Optimum (MMCO)Weathering of CRBG insufficient to drive cooling after the MMCO. This may be linked to evaporite deposition and changes to marine chemistry [ABSTRACT FROM AUTHOR]

The aim of this study was to find out whether causal agents of bacterial canker and the premature death of apricot trees are present in the internal tissues of propagating material of various origins. In total, 33 samples of apricot (Prunus armeniaca L.) scion materials from eight and six samples of rootstocks from four European localities were analysed for the presence of the pathogenic Pseudomonas species. Significant differences were found in the diversity of the culturable bacterial population and the incidence of Pseudomonas bacteria in internal tissues of scion and rootstock buds. In most of the rootstocks, no Pseudomonas bacteria were detected. A total of 148 Pseudomonas-like strains isolated from scion samples were collected mainly from localities F1-F5 (in France) and G1-G2 (in Germany). These strains were clustered into 11 groups by means of fatty acid methyl ester (FAME) analysis; 91.9% of them were able to induce a hypersensitive reaction on tobacco leaves and 37.8% were positive in ice nucleation activity. A set of 89 Pseudomonas strains was characterised by means of Psy-PCR targeting of the Pseudomonas syringae (Ps) complex, complex phylogroup (PG), syrB-PCR targeting of the syringomycin synthesis, pathogenicity on detached apricot twigs, and the ability to survive within epiphytic microflora. Pseudomonas strains attributed to PG01, PG04, and PG07-08 were slightly pathogenic to detached apricot twigs. Altogether, 5% of Pseudomonas strains highly pathogenic to detached apricot twigs were isolated from apricot scion samples originated in localities F2, F5, and G1. These strains were attributed to PG02 and PG03, and rpoD sequencing confirmed a similarity to strains of P. syringae pv. syringae and P. amygdali pv. morsprunorum known to be pathogenic to apricot, respectively. The occurrence of these pathogens in buds of scion materials increases the risk of bacterial canker and the premature death of young apricot trees. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work was to evaluate the air-layering and grafting techniques in the production of cambuci (Campomanesia phaea) plants. Two experiments were conducted in randomized complete blocks for air-layering, using adult cambuci plants, and two completely randomized for the grafting, using seedlings. Air layering was evaluated with different rates of indolebutyric acid; the splice, side-veneer, and chip-budding techniques were used for grafting. Air-layering rooting was not favored by the application of indolebutyric acid rates, whereas side-veneer grafts ensured the fixation of 6% of the grafts. Histological analyses of the air layers revealed the action of parenchyma cells from the xylem in the formation of structures similar to calluses. In the grafted plants, these cells ensured tissue union and regeneration. The air-layering technique was unfeasible, but grafting is recommended to establish cambuci tree genotypes.

Abstract The objective of this work was to evaluate the viability of the micrografting of yellow dragon fruit (Selenicereus megalanthus) on different rootstocks, based on DNA content and anatomical analyses. The used rootstocks were: yellow dragon fruit, white dragon fruit (Hylocereus undatus), Saborosa (Selenicereus setaceus) dragon fruit, and the Cebra and Orejona red dragon fruit (Hylocereus polyrhizus) varieties. The experimental design was completely randomized with five treatments and four replicates of five plants. After 30 days of cultivation, the following traits were evaluated: length and diameter of the micrografts and microrootstocks; and root length, percentage of setting, and fresh mass of the micrografts. Flow cytometry analyzes were performed before and after micrografting to verify genetic stability and the occurrence of endoreduplication. In addition, histological sections were made in the micrografting region to verify the connections of vessels and tissues between the graft and the rootstock. Endoreduplication was observed in all treatments. The amount of DNA in the yellow dragon fruit micrograft increased on the red Orejona variety. The presence of vessel connections was verified between the micrografts and microrootstocks. The yellow dragon fruit was also more vigorous when grafted on Orejona. Based on DNA content and anatomical analyses, in vitro yellow dragon fruit micrografting is feasible in all used rootstocks.

Watermelon (Citrullus lanatus) is a valuable horticultural crop with nutritional benefits grown worldwide. It is almost exclusively cultivated as grafted scions onto interspecific squash rootstock (Cucurbita maxima × Cucurbita moschata) to improve the growth and yield and to address the problems of soilborne diseases and abiotic stress factors. This study aimed to examine the effect of grafting (homo- and hetero-grafting) on the transcriptome level of the seedlings. Therefore, we compared homo-grafted watermelon (WW) with non-grafted watermelon control (W), homo-grafted squash (SS) with non-grafted squash control (S), hetero-grafted watermelon onto squash (WS) with SS, and WS with WW. Different numbers of differentially expressed genes (DEGs) were identified in each comparison. In total, 318 significant DEGs were detected between the transcriptomes of hetero-grafts and homo-grafts at 16 h after grafting. Overall, a significantly higher number of downregulated transcripts was detected among the DEGs. Only one gene showing increased expression related to the cytokinin synthesis was common in three out of four comparisons involving WS, SS, and S. The highest number of differentially expressed (DE) transcripts (433) was detected in the comparison between SS and S, followed by the 127 transcripts between WW and W. The study provides a description of the transcriptomic nature of homo- and hetero-grafted early responses, while the results provide a start point for the elucidation of the molecular mechanisms and candidate genes for the functional analyses of hetero-graft and homo-graft systems in Cucurbitaceae and generally in the plants.

Watermelon (Citrullus lanatus) is a valuable horticultural crop with nutritional benefits grown worldwide. It is almost exclusively cultivated as grafted scions onto interspecific squash rootstock (Cucurbita maxima × Cucurbita moschata) to improve the growth and yield and to address the problems of soilborne diseases and abiotic stress factors. This study aimed to examine the effect of grafting (homo- and hetero-grafting) on the transcriptome level of the seedlings. Therefore, we compared homo-grafted watermelon (WW) with non-grafted watermelon control (W), homo-grafted squash (SS) with non-grafted squash control (S), hetero-grafted watermelon onto squash (WS) with SS, and WS with WW. Different numbers of differentially expressed genes (DEGs) were identified in each comparison. In total, 318 significant DEGs were detected between the transcriptomes of hetero-grafts and homo-grafts at 16 h after grafting. Overall, a significantly higher number of downregulated transcripts was detected among the DEGs. Only one gene showing increased expression related to the cytokinin synthesis was common in three out of four comparisons involving WS, SS, and S. The highest number of differentially expressed (DE) transcripts (433) was detected in the comparison between SS and S, followed by the 127 transcripts between WW and W. The study provides a description of the transcriptomic nature of homo- and hetero-grafted early responses, while the results provide a start point for the elucidation of the molecular mechanisms and candidate genes for the functional analyses of hetero-graft and homo-graft systems in Cucurbitaceae and generally in the plants. [ABSTRACT FROM AUTHOR]

Grafting is an important practice in mango (Mangifera indica L.) orchard management for propagating elite germplasm but there is limited information on the effect of rootstock-scion interactions on the mineral nutrition of mango. Here, we analyzed the variations in leaf nutrients of commercial ('B74' and 'Kensington Pride' [KP]) and newly developed cultivars from the National Mango Breeding Program (NMBP) ('NMBP1243', 'NMBP1201', and 'NMBP4069') grafted onto six different rootstocks ('B', 'KP', 'Mallapunyah', 'SabahBRF', 'Vellaikulamban', and 'Watertank') to determine the influence of the rootstock on the scion leaf nutrient content. Deviation from the optimum percentage (DOP and ΣDOP indexes) was calculated to compare nutrition status/balance among the different rootstocks. Leaf nutrient concentrations and their DOP index were affected by the rootstocks and scions. None of the rootstocks or scions had consistently higher or lower nutrient levels, and interaction effects between rootstock and scion factors were insignificant. The DOP index indicated an imbalance of nutrients in the leaves, but scions grafted onto rootstocks 'Vellaikulamban' and 'SabahBRF' were more nutritionally balanced, indicating that they are preferred rootstocks for propagation. Principal component analysis showed a clear separation among rootstocks according to their differences in nutrient concentrations, such that 'Vellaikulamban' and 'SabahBRF' (Group 1) were different from 'Watertank' and 'B' (Group 2) as well as from 'KP' and 'Mallapunyah' (Group 3). Scions were clustered based on their similarities with 'B74' and 'NMBP1201' in Cluster 1, 'NMBP 4069' in Cluster 2, 'NMBP 1243' in Cluster 3, and 'KP' in Cluster 4. This study provides valuable information to understand the potential impact of the rootstock on the nutritional status of scions as well as for the selection of rootstock-scion combinations for variety improvement. [ABSTRACT FROM AUTHOR]

Single-leaf pinyon pine (Pinus monophylla Torr. & Frém. [Pinaceae]) is a resilient native of the Great Basin and a source of wild-collected, edible pine nuts. It has potential for greater use in sustainable landscaping and as an agroforestry crop on marginal lands. We initiated steps toward identifying superior nut-producing accessions by selecting 6 trees, subjectively based on visible cones on and around the trees, from each of 4 pinyon stands historically used for pine nut collection. Cone production in selected trees was quantified by counting cone abscission scars on 6 branches collected from the top of each tree. Propagation of 3 trees from each stand was undertaken by grafting to seedling double-leaf pinyon pine (Pinus edulis Engelm. [Pinaceae]) rootstocks. Side-wedge and side-veneer grafting techniques were compared by completing 12 replications of each graft for each scion selection. Grafting success was high, and 11 mo after grafting, no significant difference between techniques was seen (91% of the side-wedge and 81% of the side-veneer grafts were successful). Grafted plants were successfully transplanted to an orchard environment as shown by 99% survival after the first field-growing season. Future long-term evaluation of this common garden will provide information toward selecting superior nut-producing trees for northern Utah. [ABSTRACT FROM AUTHOR]

Tree tomato (Solanum betaceum Cav.) is an economically important tree from the Andes. This species was grafted onto cucubo (Solanum stellatiglandulosum Bitter). Cucubo was the rootstock and 3 tree tomato cultivars were used as scions. Trees were cleft grafted by introducing a 15 cm long tree tomato scion onto cucubo. Grafted trees had a survival rate above 94%. Fruits derived from grafted trees were longer, wider, and heavier than ungrafted ones. Best fruit weight results occurred in the grafted común cultivar (193.7 g). Best fruit length results were obtained in the grafted mango cultivar (7.9 cm). Best fruit width occurred in the mora cultivar (6.7 cm). Grafted trees were more productive (about 30–40 fruits/tree) than ungrafted ones (about 10–15 fruits/tree). Fruit features were not modified in grafted trees i.e. color, shape, and taste. Large and small-scale growers worldwide could benefit from bigger-sized tree tomato fruits as a result of grafting. Grafting is key to improve tree tomato quality in global markets. [ABSTRACT FROM AUTHOR]

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Drought-tolerant tomato wild relatives Solanum pennellii and S. peruvianum show heat-tolerant responses, but their use as rootstocks to enhance thermotolerance has not been examined. This study investigated the effects of heat stress on tomato plants grafted onto commercial 'Maxifort' and wild relatives S. pennellii and S. peruvianum rootstocks in high tunnel, open-field and growth chamber experiments. Heat-tolerant 'Celebrity' and heat-sensitive 'Arkansas Traveler' cultivars were used as scions, and non-grafted (high tunnel, open-field) or self-grafted plants (growth chamber) were used as controls. The high tunnel and open-field experiments were conducted in the spring (March – June) and summer (June – September) for control and heat treatment, respectively, with daily high/low average temperatures of 27.5/19.0 °C and 33.2/22.5 °C in the high tunnel and 28.2/17.5 °C and 33.8/23.1 °C in the open-field. The growth chamber experiment was conducted at 38/30 °C (day/night) and 26/19 °C for the heat and control treatments, respectively, for 21 days. The shoot and root growth of S. peruvianum and S. pennellii -grafted tomato plants were adversely affected by potential low graft compatibility resulting from interspecific grafting and their limited adaptability to the open-field soil environment, regardless of stress conditions. S. pennellii -grafted plants showed heat-sensitive responses in root biomass and architecture, leaf chlorophyll fluorescence, electrolyte leakage and relative water content depending on the environment, indicating its unsuitability as a rootstock under heat stress. On the other hand, plants grafted onto S. peruvianum exhibited heat-tolerant responses in physiological aspects, including the gas exchange, leaf chlorophyll, carotenoid and amino acid in the growth chamber, fruit yield in the high tunnel, and chlorophyll fluorescence in both experiments. We suggest that S. peruvianum could be utilized as effective breeding material for developing interspecific hybrid rootstocks with thermotolerance and increased graft compatibility between scion and rootstock to improve shoot and root growth of grafted plants. • Low graft compatibility inhibited shoot and root growth of tomato plants grafted onto wild relatives. • S. peruvianum showed thermotolerance in physiological parameters in growth chamber. • S. pennelliii was heat susceptible as a rootstock in morpho-physiological parameters. • S. peruvianum and S. pennelliii showed low adaptability to open field soil environment. [ABSTRACT FROM AUTHOR]

Pecan (Carya illinoinensis) trees were pruned using varying intensities at planting to determine the effect of pruning on trunk development and shoot growth. Data on trunk diameter, number and length of shoots, as well as the total shoot growth were recorded annually from a completely randomized design experiment that assigned 0%, 50%, and 75% pruning of above-ground height to single-trunk transplants. The results suggest that pruning intensity has little effect on trunk diameter. The pruned trees had fewer shoots initially and more growth per shoot, leading to a difference of 7 cm/shoot higher for the 50% pruning group than the control group and to a difference of 11 cm/shoot higher for the 75% pruning group compared with the control group. The total length of all shoots was not significantly different across treatments. Because previous research has sometimes shown that pruning increases tree survival and this research shows that trees can recover from pruning, there is no need to change the current recommendation of pruning seedlings at planting.

Abstract Background Grafting with rootstocks is essential for the culture of many perennial fruit crops and is increasing being used in the production of annual fruits and vegetables. Our previous work based on microarrays showed that transcripts encoding enzymes of both primary and secondary metabolism were differentially expressed during graft union formation in both homo-grafts (a genotype grafted with itself) and hetero-grafts (two different genotypes grafted together). The aim of this study was to profile primary and secondary metabolites, and quantify the activity of phenylalanine ammonia lyase (PAL) and neutral invertase (NI) in the scion and rootstock tissues and the graft interface of homo and hetero-grafts of grapevine 1 month after grafting. Table-top grafting was done on over-wintering stems (canes) of grapevine and the graft interface tissues (containing some woody stem tissues and callus) were compared to the surrounding rootstock and scion tissues. The objective was to identify compounds involved in graft union formation and hetero-grafting responses. Results A total of 54 compounds from primary and secondary metabolism (19 amino acids, five primary and 30 secondary compounds metabolites) and the activity of two enzymes were measured. The graft interface was associated with an increase in the accumulation of the branched-chain amino acids, basic amino acids, certain stilbene compounds and higher PAL and NI activity in comparison to the surrounding woody stem tissues. Some amino acids and stilbenes were identified as being accumulated differently between the graft interfaces of the scion/rootstock combinations in a manner which was unrelated to their concentrations in the surrounding woody stem tissues. Conclusions This study revealed the modification of primary metabolism to support callus cell formation and the stimulation of stilbene synthesis at the graft interface, and how these processes are modified by hetero-grafting. Knowledge of the metabolites and/or enzymes required for successful graft union formation offer us the potential to identify markers that could be used by nurseries and researchers for selection and breeding purposes.

Abstract Background Grafting is the common propagation method for avocado and primarily benefits orchard production by reducing the time to tree productivity. It also allows use of scions and rootstocks specifically selected for improved productivity and commercial acceptance. Rootstocks in avocado may be propagated from mature tree cuttings (‘mature’), or from seed (‘juvenile’). While the use of mature scion material hastens early bearing/maturity and economic return, the molecular factors involved in the role of the scion and/or rootstock in early bearing/reduced juvenility of the grafted tree are still unknown. Results Here, we utilized juvenility and flowering associated miRNAs; miR156 and miR172 and their putative target genes to screen pre-graft and post-graft material in different combinations from avocado. The abundance of mature miR156, miR172 and the miR156 target gene SPL4, showed a strong correlation to the maturity of the scion and rootstock material in avocado. Graft transmissibility of miR156 and miR172 has been explored in annual plants. Here, we show that the scion may be responsible for grafted tree maturity involving these factors, while the rootstock maturity does not significantly influence miRNA abundance in the scion. We also demonstrate that the presence of leaves on cutting rootstocks supports graft success and contributes towards intergraft signalling involving the carbohydrate-marker TPS1. Conclusion Here, we suggest that the scion largely controls the molecular ‘maturity’ of grafted avocado trees, however, leaves on the rootstock not only promote graft success, but can influence miRNA and mRNA abundance in the scion. This constitutes the first study on scion and rootstock contribution towards grafted tree maturity using the miR156-SPL4-miR172 regulatory module as a marker for juvenility and reproductive competence.

Crop rotation is rarely practiced in greenhouse production, which allows soil borne pathogens and pests to accumulate, progressively reducing crop yields and fruit quality. Grafting cultivars with high quality and productivity on rootstocks that are resistant to the soil pests and diseases is a method known from years ago, which was improved and quickly spread in the last years. The aim of this research was to evaluate the performance of the grafted peppers on some rootstocks, in greenhouse conditions. Marketable yield, fruit quality and nutritional qualities (total soluble solid contents, titratable acidity, soluble carbohydrates, Vitamin C content) have been determined. The marketable yield and fruit number were positively influenced by rootstock as compared with ungrafted peppers. The obtained results showed that grafting has improved the commercial quality of pepper fruits. There were no significant differences in the nutritional qualities of pepper fruits obtained from the grafted or ungrafted plants.

Breadfruit (Artocarpus altilis) is a traditional fruit tree of 15–30 m tall in Oceania. The species is a staple crop for food security in the tropics. Tree loss from tropical windstorms, together with transition toward high-density planting has driven an interest in the dwarf phenotype of the species. Information on dwarfing rootstocks for breadfruit is currently limited. The aim of this study was to assess the performance of breadfruit growth with lakoocha (Artocarpus lakoocha) as rootstocks. We compared the phenotype of breadfruit trees on lakoocha rootstocks with those on self-graft and non-graft within 21 months after grafting. These led to the discovery of a rootstock-induced dwarf trait in breadfruit species. Breadfruit scions on lakoocha rootstocks displayed a reduction in tree height, stem thickness, and internode length, with fewer branches and leaves, resulting in about 32% of the standard height at the end of 21 months after grafting. These suggest lakoocha rootstocks have the potential to control breadfruit tree vigor. Non-structural carbohydrate analysis showed the composite trees exhibited lower hexose concentration in both scion stems and roots, but higher sucrose level in scion stems, and higher starch level in roots. The significance of these parameters in rootstock dwarfing is discussed.

Grafting breadfruit (Artocarpus altilis) on chataigne (Artocarpus camansi) rootstock can potentially benefit commercial establishment of breadfruit, but a suitable protocol needs to be developed. The objective of this study was to evaluate the effect of the grafting technique (whip and tongue, spliced side and top wedge), rootstock age (6, 9 and 18 week old), scion cultivar (two breadfruit cultivars from Trinidad-'Yellow' and 'White', a Jamaican accession-'JA1', and chataigne as the control) and season on grafting success. There were significant (p < 0.05) differences in length of survival neither among grafting technique nor rootstocks of different ages. Among scion cultivar, 'White' and chataigne scions generally survived longer (p < 0.05) than those of other cultivars. Grafting done in the wet season had significantly (p < 0.05) higher survival rate compared to those done in the dry season. Although not directly evaluated, scion quality and post-grafting environment were two factors that emerged as important to grafting these two species. The data suggest that season of grafting, scion quality and post-grafting environment were important determinants of grafting success. Scion harvested from juvenile mother plants during the wet season, matched with rootstock of similar diameter and grafted plants maintained in an environment which minimize water loss for both scion and rootstock for at least 4 weeks after grafting were essential for successful grafting of these selected breadfruit cultivars. When all these requirements were met, survival percentages of 97%, 83%, 80% and 80% for 'White', 'JA1', 'Yellow' and chataigne, respectively, were achieved. [ABSTRACT FROM AUTHOR]

Copyright of COMU Journal of Agriculture Faculty / ÇOMÜ Ziraat Fakültesi Dergisi is the property of Canakkale Onsekiz Mart University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to investigate the compatibility of the melon (khatooni) scions on different cucurbit rootstocks, a field experiment was conducted based on a complete blocks design with three replications in Horticultural Science Research Station of University of Tehran during 2017. Seven different rootstocks named as Rout Power, ES 900, RZ12, Nongwoo 01, RZ6, PS580, Shintozwa and additionally control rootstock (Khatooni) and Khatooni as scion were used in the current research. Compatibility these rootstocks evaluated based on plant growth pattern, performance and fruit quality of Khatooni melon. The highest fruit yield obtained on RZ6 and ES rootstocks, respectively. Large number of fruit per plant was observed on Shintozwa and Rout Power rootstocks, respectively and the highest total soluble solids was found on Shintozwa rootstock. Electrical conductivity of raw sap was higher in the grafted plants compared to non-grafted plants. Maximum amount of raw sap per day was collected from Nongwoo 01 rootstock. Maximum percentage of root dry weight was found on the Nongwoo 01 as compatible rootstock which was significantly higher than other grafted rootstocks and control. The first morphological signs of incompatibility were detected by increasing the diameter difference between grafting union and rootstock or scion. This diameter difference was significantly higher for PS580 as incompatible rootstock compared to Nongwoo 01 as compatible rootstock. Based on the results, Shintozwa and Rout Power rootstocks could be recommended as appropriate and compatible rootstocks for the khatooni melon. [ABSTRACT FROM AUTHOR]

Climate change and enormous increase in population are causing food insecurity situation in developing countries like Pakistan. Major food crops are seemed failing to fulfill food requirements hence, it is imperative to search for alternate food sources. Ber could be very handy alternate food crop if its yield and quality is enhanced. Grafting is a widely used technique to improve yield, disease resistance and fruit quality. This work aims to assess the effect of grafting on production, fruit ripening, physical and chemical properties, and nutritional quality of the fruit. Rootstock has a great influence on plant growth and development, including fruit ripening. However, the presence of a cross-interaction between grafting and rootstock is often neglected. To explore cross-interaction between grafting and rootstock on different fruit yield and quality traits, we examined the scion-root interaction of four scion cultivars viz. Delhi White, Suffen, Karela and Mahmud Wali during March-April 2013-14. After the establishment of plant, data were recorded for yield and fruit quality traits during three consecutive years (2016-19). Results showed that Dehli White grafted plants produced maximum yield kg/plant (60.33, 71.43, 78.00) followed by Mehmud Wali, Karela and Suffen scion grafts. Suffen grafted plants produced better quality fruits in terms of total soluble solids (TSS) (14.67, 15.45, 16.56 Brix0), pH and Ascorbate content followed by Karela, Mehmud Wali and Dehli White scion graft. Based on findings of the experiment, it could be recommended that Mahmud Wali and Suffen scions should be used to be propagated on local rootstocks to enhance yield as well as fruit quality that will contribute in ensuring food security. [ABSTRACT FROM AUTHOR]

Though grafting in plants is in practice since ages only limited information is available on the graft-induced morphological, biochemical and molecular variations. The mechanism(s) by which rootstocks influence scion vegetative growth and development, and vice versa, are not fully understood. Therefore, in the present investigation, we studied graftinduced variations in different apple stionic combinations using scion (Scarlet Gala and Red Fuji) and rootstocks (MM111, MM106, M7, M9 and M26). Under morphological variations, significant difference was found in all the parameters viz. leaf area, shoot length, internodal length and fruit characters except petiole length and fruit firmness. Likewise, significant difference was also observed in the subjected stionic combinations based on total phenolic contents, total free amino acids and peroxidase enzyme activity. These results were further validated using DNA based molecular markers SSR. However, no polymorphism was observed in both the stionic combinations at DNA level. These results imply that rootstocks may influence morphological and biochemical parameter of the scion during graft-union but it does not influence genetic constitution of scion at DNA level. Further studies at RNA or protein level are required to unravel the reasons behind these variations. [ABSTRACT FROM AUTHOR]

Cut roses are grown throughout the four distinct seasons of spring, summer, autumn, and winter in Korea. Especially in the very hot or cold seasons of summer or winter, the temperature and light environments inside a greenhouse cause abiotic stress on the growth of horticultural crops. In a greenhouse where shade cultivation is performed in summer, the temperature is high and the light intensity is low, whereas in winter when shade cultivation is not performed, both temperature and light intensity are low. This experiment investigated the year-round growth and yield changes of cut roses grafted onto three rootstocks. The root activity of rootstocks was generally higher than that of the scion. The stomata of the grafted cut roses showed morphological changes according to the seasons. Compared with the scion, the stomata of grafted cut roses became smaller and their number increased in summer, whereas only the stomata size increased in winter. The grafted cut roses had characteristics of high photosynthetic efficiency such as photosynthesis rate, stomatal conductance, transpiration rate from rootstocks under harsh environmental conditions including temperature and light intensity, and thus the photosynthetic efficiency was higher than that of the scion. There was no significant change in the yield of grafted cut roses, but flower quality parameters such as the stem height, stem thickness, and weight of grafted cut roses were improved according to the rootstocks compared with those of the scion. In particular, in cut roses grafted with R. multiflora cv. Natal Briar and Rosa indica ‘Major’ rootstocks, the weight increased as the stem lengthened and thickened in spring, autumn, and winter. Therefore, grafting is effective in improving the quality of cut roses grown under abiotic stress caused by harsh temperature and light intensity conditions during winter.

Tomato, which is mainly established with grafted seedlings, is one of the most popular vegetables worldwide with a high nutritional value,. Market demand for grafted seedlings is high in specific seasons; thus, commercial nurseries face a problem of limited space availability during the healing stage. Light quality is an essential parameter during healing that can adjust seedling development towards desirable traits and lead to time and space saving during seedling production. Moreover, transplant shock constitutes another challenge that could limit crop yield. The objective of this study was to evaluate the overall quality of grafted tomato seedlings and their potential adjustment to transplant shock as affected by different light spectra during healing in a chamber. Evaluations were conducted immediately after exiting the healing chamber and after transplantation into pots. Light wavelengths were used from fluorescent lamps (FL) or light-emitting diodes with red (R), blue (B), red–blue combinations with 12 and 24% blue (12B and 24B), and white (W) emitting 11% blue. W enhanced the dry shoot biomass and the root architecture before and after transplantation. 24B led to an increased stem diameter, root development, and phenolic and antioxidant accumulation at both phases of the experiment. 12B enhanced the leaf area before transplantation and root development after transplantation. FL, R and B induced inferior seedling growth compared to the red–blue-containing LEDs, with B performing poorly in almost all tested parameters. Overall, red, including 11–24% blue, provides the optimum light conditions during the healing stage for the production of high-quality grafted tomato seedlings, with advanced capabilities of abiotic stress adaptation to transplant shock.

Key message: Exogenous ABA increased the flowering rate and advanced the flower formation of "Fuji" apple cv. "Nagafu No.2" by promoting the accumulation of soluble sugar, glucose and sucrose, and also increased the activities of α-AMY and SPS. "Fuji" apple (Malus domestica Borkh) has a long vegetative growth phase and difficulty in flower induction, which seriously affects apple production. ABA plays important roles in the flower bud induction of fruit trees. However, the effect of exogenous ABA on flower bud induction of apple trees has rarely been reported. In this experiment, 2-year-old "Fuji" apple cv. "Nagafu No. 2" scion material was grafted on dwarf self-rooted rootstock M.26 (DSR), vigorous rootstock M. sieversii (VR) and interstock M.26/M. sieversii (IR). The control trees were sprayed with water solution, while 100 µmol·L−1 ABA and 5 mmol·L−1 sodium tungstate (ST) were applied as treatments. The results showed that exogenous ABA promoted flower formation and increased the flowering rate, but the impact on the VR was not obvious. Furthermore, the accumulation of soluble sugar, glucose and sucrose, as well as the activities of α-amylase (α-AMY) and sucrose phosphate synthase (SPS) in the leaves and buds were also significantly promoted. However, the starch concentrations and sucrose synthase (SS) activities decreased. The increase of leaf specific weight and decrease of the growth of single leaf area were supportive to the growth of flower buds. Linear relationships were discovered between starch concentration and α-AMY activity (R2 = 0.998, p < 0.05), sucrose concentration and the activities of SS and SPS (R2 = 0.854–0.999, p < 0.05). Besides, exogenous ST had negative effects compared with ABA. Exogenous ABA increased sugar metabolism, and enzyme activities of DSR, and also enhanced the absorption and utilization of sugar substances, resulting in easier flowering in the DSR, followed by the IR, except for the difficult-flowering rootstock VR. Finally, the expression levels of TPS7, PPC1 and ABR1 were up-regulated in leaves and buds after ABA application, while the floral inhibiting gene TFL1 was down-regulated, indicating that exogenous ABA may promote flower bud differentiation by inhibiting TFL1 expression in apple. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Grafting has been used in agriculture for over 2000 years. Disease resistance and environmental tolerance are highly beneficial traits that can be provided through use of grafting, although the mechanisms, in particular for resistance, have frequently been unknown. As information emerges that describes plant disease resistance mechanisms, the proteins, and nucleic acids that play a critical role in disease management can be expressed in genetically engineered (GE) plant lines. Utilizing transgrafting, the combination of a GE rootstock with a wild-type (WT) scion, or the reverse, has the potential to provide pest and pathogen resistance, impart biotic and abiotic stress tolerance, or increase plant vigor and productivity. Of central importance to these potential benefits is the question of to what extent nucleic acids and proteins are transmitted across a graft junction and whether the movement of these molecules will affect the efficacy of the transgrafting approach. Using a variety of specific examples, this review will report on the movement of organellar DNA, RNAs, and proteins across graft unions. Attention will be specifically drawn to the use of small RNAs and gene silencing within transgrafted plants, with a particular focus on pathogen resistance. The use of GE rootstocks or scions has the potential to extend the horticultural utility of grafting by combining this ancient technique with the molecular strategies of the modern era.

Plant grafting is an ancient agricultural practice widely employed in crops such as woody fruit trees, grapes, and vegetables, in order to improve plant performance. Successful grafting requires the interaction of compatible scion and rootstock genotypes. This involves an intricate network of molecular mechanisms operating at the graft junction and associated with the development and the physiology of the scion, ultimately leading to improved agricultural characteristics such as fruit quality and increased tolerance/resistance to abiotic and biotic factors. Bidirectional transfer of molecular signals such as hormones, nutrients, proteins, and nucleic acids from the rootstock to the scion and vice versa have been well documented. In recent years, studies on rootstock-scion interactions have proposed the existence of an epigenetic component in grafting reactions. Epigenetic changes such as DNA methylation, histone modification, and the action of small RNA molecules are known to modulate chromatin architecture, leading to gene expression changes and impacting cellular function. Mobile small RNAs (siRNAs) migrating across the graft union from the rootstock to the scion and vice versa mediate modifications in the DNA methylation pattern of the recipient partner, leading to altered chromatin structure and transcriptional reprogramming. Moreover, graft-induced DNA methylation changes and gene expression shifts in the scion have been associated with variations in graft performance. If these changes are heritable they can lead to stably altered phenotypes and affect important agricultural traits, making grafting an alternative to breeding for the production of superior plants with improved traits. However, most reviews on the molecular mechanisms underlying this process comprise studies related to vegetable grafting. In this review we will provide a comprehensive presentation of the current knowledge on the epigenetic changes and transcriptional reprogramming associated with the rootstock–scion interaction focusing on woody plant species, including the recent findings arising from the employment of advanced—omics technologies as well as transgrafting methodologies and their potential exploitation for generating superior quality grafts in woody species. Furthermore, will discuss graft—induced heritable epigenetic changes leading to novel plant phenotypes and their implication to woody crop improvement for yield, quality, and stress resilience, within the context of climate change.

Grafting is typically utilized to merge adapted seedling rootstocks with highly productive clonal scions. This process implies the interaction of multiple genomes to produce a unique tree phenotype. However, the interconnection of both genotypes obscures individual contributions to phenotypic variation (rootstock-mediated heritability), hampering tree breeding. Therefore, our goal was to quantify the inheritance of seedling rootstock effects on scion traits using avocado (Persea americana Mill.) cv. Hass as a model fruit tree. We characterized 240 diverse rootstocks from 8 avocado cv. Hass orchards with similar management in three regions of the province of Antioquia, northwest Andes of Colombia, using 13 microsatellite markers simple sequence repeats (SSRs). Parallel to this, we recorded 20 phenotypic traits (including morphological, biomass/reproductive, and fruit yield and quality traits) in the scions for 3 years (2015–2017). Relatedness among rootstocks was inferred through the genetic markers and inputted in a “genetic prediction” model to calculate narrow-sense heritabilities (h2) on scion traits. We used three different randomization tests to highlight traits with consistently significant heritability estimates. This strategy allowed us to capture five traits with significant heritability values that ranged from 0.33 to 0.45 and model fits (r) that oscillated between 0.58 and 0.73 across orchards. The results showed significance in the rootstock effects for four complex harvest and quality traits (i.e., total number of fruits, number of fruits with exportation quality, and number of fruits discarded because of low weight or thrips damage), whereas the only morphological trait that had a significant heritability value was overall trunk height (an emergent property of the rootstock–scion interaction). These findings suggest the inheritance of rootstock effects, beyond root phenotype, on a surprisingly wide spectrum of scion traits in “Hass” avocado. They also reinforce the utility of polymorphic SSRs for relatedness reconstruction and genetic prediction of complex traits. This research is, up to date, the most cohesive evidence of narrow-sense inheritance of rootstock effects in a tropical fruit tree crop. Ultimately, our work highlights the importance of considering the rootstock–scion interaction to broaden the genetic basis of fruit tree breeding programs while enhancing our understanding of the consequences of grafting.

Synthetic polyploids have been extensively studied for breeding in the last decade. However, the use of such genotypes at the agronomical level is still limited. Polyploidization is known to modify certain plant phenotypes, while leaving most of the fundamental characteristics apparently untouched. For this reason, polyploid breeding can be very useful for improving specific traits of crop varieties, such as quality, yield, or environmental adaptation. Nevertheless, the mechanisms that underlie polyploidy-induced novelty remain poorly understood. Ploidy-induced phenotypes might also include some undesired effects that need to be considered. In the case of grafted or composite crops, benefits can be provided both by the rootstock’s adaptation to the soil conditions and by the scion’s excellent yield and quality. Thus, grafted crops provide an extraordinary opportunity to exploit artificial polyploidy, as the effects can be independently applied and explored at the root and/or scion level, increasing the chances of finding successful combinations. The use of synthetic tetraploid (4x) rootstocks may enhance adaptation to biotic and abiotic stresses in perennial crops such as apple or citrus. However, their use in commercial production is still very limited. Here, we will review the current and prospective use of artificial polyploidy for rootstock and scion improvement and the implications of their combination. The aim is to provide insight into the methods used to generate and select artificial polyploids and their limitations, the effects of polyploidy on crop phenotype (anatomy, function, quality, yield, and adaptation to stresses) and their potential agronomic relevance as scions or rootstocks in the context of climate change.

To understand the roles of Malus rootstock, scion, and their interaction in Cd accumulation and tolerance, four scion/rootstock combinations consisting of the apple cultivars “Hanfu” (HF) and “Fuji” (FJ) grafted onto M. baccata (Mb) or M. micromalus “qingzhoulinqin” (Mm) rootstocks differing in relative Cd tolerance were exposed either to 0 µM or 50 µM CdCl2 for 18 d. Cd accumulation and tolerance in grafted Malus plants varied within rootstock, scion, and rootstock–scion interaction. Cd-induced decreases in photosynthesis, photosynthetic pigment level, and biomass were lower for HF grafted onto Mb than those for HF grafted onto Mm. Reductions in growth and photosynthetic rate were always the lowest for HF/Mb. Cd concentration, bioconcentration factor (BCF), and translocation factor (Tf) were always comparatively higher in HF and FJ grafted onto rootstock Mm than in HF and FJ grafted on Mb, respectively. When HF and FJ were grafted onto the same rootstock, the root Cd concentrations were always higher in HF than FJ, whereas the shoot Cd concentrations displayed the opposite trend. The shoot Cd concentrations and Tf were lower for HF/Mb than the other scion/rootstock combinations. Rootstock, scion, and rootstock–scion interaction also affected subcellular Cd distribution. Immobilization of Cd in the root cell walls may be a primary Cd mobility and toxicity reduction strategy in Malus. The rootstock and scion also had statistically significant influences on ROS level and antioxidant activity. Cd induced more severe oxidative stress in HF and FJ grafted onto Mm than it did in HF and FJ grafted onto Mb. Compared with FJ, HF had lower foliar O2-, root H2O2, and root and leaf MDA levels, but higher ROS-scavenging capacity. The rootstock, scion, and rootstock–scion interaction affected the mRNA transcript levels of several genes involved in Cd uptake, transport, and detoxification including HA7, FRO2-like, NRAMP1, NRAMP3, HMA4, MT2, NAS1, and ABCC1. Hence, the responses of grafted Malus plants to Cd toxicity vary with rootstock, scion, and rootstock–scion interaction.

Neem is an indigenous tree species with medicinal and pesticidal properties. It is generally raised through seed which ripens in August in northern India. The seed viability is only for few weeks and the nursery men are bound to sow the seed in nursery immediately after seed ripening i.e. in August. The initial growth in nursery is very slow and the seedlings are very tender and lanky in first growing season which lasts hardly for about three months in northern India. Moreover, the species is highly susceptible to frost and hence, it becomes very difficult to protect such tender seedlings during winter. To increase the period of growing season and produce vigorous nursery stock of Neem, it was thought to grow it on a potential root stock by way of budding/grafting. Darek (Melia azedarach) with wider adaptability in varied agroecological conditions was selected as a root stock. The experiment conducted in the month of February revealed excellent bud take, survival and growth. The budded plants attained a height of 8 ft in first growing season (February to November) as against just 4 inches of seedling origin plants. The technique has proved useful to enhance initial growth and to increase the growing period of Neem which resulted in production of tall and vigorous plants. The budding technique will also be very useful for cloning Neem. Further, experiments are required to be carried out for screening better genotypes of root stock (Darek) and scion (Neem) for improving growth and desirable traits of Neem.

Plant grafting is an ancient agricultural practice widely employed in crops such as woody fruit trees, grapes, and vegetables, in order to improve plant performance. Successful grafting requires the interaction of compatible scion and rootstock genotypes. This involves an intricate network of molecular mechanisms operating at the graft junction and associated with the development and the physiology of the scion, ultimately leading to improved agricultural characteristics such as fruit quality and increased tolerance/resistance to abiotic and biotic factors. Bidirectional transfer of molecular signals such as hormones, nutrients, proteins, and nucleic acids from the rootstock to the scion and vice versa have been well documented. In recent years, studies on rootstock-scion interactions have proposed the existence of an epigenetic component in grafting reactions. Epigenetic changes such as DNA methylation, histone modification, and the action of small RNA molecules are known to modulate chromatin architecture, leading to gene expression changes and impacting cellular function. Mobile small RNAs (siRNAs) migrating across the graft union from the rootstock to the scion and vice versa mediate modifications in the DNA methylation pattern of the recipient partner, leading to altered chromatin structure and transcriptional reprogramming. Moreover, graft-induced DNA methylation changes and gene expression shifts in the scion have been associated with variations in graft performance. If these changes are heritable they can lead to stably altered phenotypes and affect important agricultural traits, making grafting an alternative to breeding for the production of superior plants with improved traits. However, most reviews on the molecular mechanisms underlying this process comprise studies related to vegetable grafting. In this review we will provide a comprehensive presentation of the current knowledge on the epigenetic changes and transcriptional reprogramming associated with the rootstock–scion interaction focusing on woody plant species, including the recent findings arising from the employment of advanced—omics technologies as well as transgrafting methodologies and their potential exploitation for generating superior quality grafts in woody species. Furthermore, will discuss graft—induced heritable epigenetic changes leading to novel plant phenotypes and their implication to woody crop improvement for yield, quality, and stress resilience, within the context of climate change. [ABSTRACT FROM AUTHOR]