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Plants are able to naturally graft or inosculate their trunks, branches and roots together, this mechanism is used by humans to graft together different genotypes for a range of purposes. Grafts are considered successful if functional vascular connections between the two genotypes occur. Various techniques can evaluate xylem connections across the graft interface. However, these methods are generally unable to assess the heterogeneity and three‐dimensional (3D) structure of xylem vessel connections. Here we present the use of X‐ray micro‐computed tomography to characterize the 3D morphology of grafts of grapevine. We show that xylem vessels form between the two plants of natural root and human‐made stem grafts. The main novelty of this methodology is that we were able to visualize the 3D network of functional xylem vessels connecting the scion and rootstock in human‐made stem grafts thanks to the addition of a contrast agent to the roots and improved image analysis pipelines. In addition, we reveal the presence of extensive diagonal xylem connections between the main axial xylem vessels in 2‐year old grapevine stems. In conclusion, we present a method that has the potential to provide new insights into the structure and function of xylem vessels in large tissue samples. Summary statement: Successful grafting requires the formation of functional vascular connections between two different plants. We describe using X‐ray micro‐computed tomography to characterize the network of xylem vessels formed across the graft interface of natural root and human‐made stem grafts of grapevine. [ABSTRACT FROM AUTHOR]

The global cannabis market is continuously expanding and as a result, the cannabis industry demands new and improved agronomic cultivation practices to increase production efficiency of cannabidiol (CBD), which is valued for its therapeutic benefits. This study investigates the influence of three rootstock types on the survival rate, morphological parameters, and biochemical composition of cannabis: potentially dwarfing rootstocks (PDR), potentially vigorous rootstocks (PVR), and seedlings-as-rootstocks (SAR). Rootstocks were used for grafting two scion genotypes: 'ScionII' = chemotype II of industrial hemp, and 'ScionIII' = chemotype III of high CBD accumulating variety. Contrary to expectations, PVR and SAR did not outperform PDR on most of the measured variables. SAR showed the highest survival rate of the grafted cannabis plants (40–70%). The rootstock type had a statistically significant influence only on the bud compactness index in 'ScionII', with PDR being particularly noticeable. A comparative analysis of the 'rootstock/scion' combinations with their controls (non-grafted scions) revealed grafting's substantial improvement in most traits. Specifically, PDR increased CBD content by 27% in 'ScionIII', inflorescence yield and CBD yield per plant increased by 71% and 84%, respectively, when SAR was used in 'ScionII'. SAR showed to be the most effective rootstock type for CBD production. Our findings suggest grafting as a promising technique for optimizing cannabis's agronomic and medicinal potential, highlighting the necessity for further research on its underlying mechanisms to refine production efficiency and quality. [ABSTRACT FROM AUTHOR]

Grafting serves as a pervasive methodology in the propagation of jujube plants, yet the nuanced molecular mechanisms that dictate rootstock-scion interactions remain inadequately understood. We examined the transcriptomic landscapes of jujube heterograft combinations. Contrary to self-grafting conditions, early-stage heterografting yielded no discernible advantageous effects on scion biomass accretion. Interestingly, the rootstock's biomass was significantly impacted by the scion, varying by species. The differentially expressed genes (DEGs) across graft combinations were mainly enriched for the vegetative growth of rootstocks, secondary metabolism, and resistance improvement of scions. Weighted gene co-expression network analysis (WGCNA) identified 27 hub genes which were negatively correlated with plant growth and biomass enlargement, serving as negative regulators, while the genes, L484_001734, ATHB-15, and BPC1, were involved in positive regulation. With biomass measurements, the transcriptomic data supported that an incomplete vascular recovery during early grafting led to nutrient accumulation at the graft junction, temporarily limiting plant growth while providing development resources for callus. In summary, our work has demonstrated that the intricate biological connections between the rootstock and scion guarantee the effective jujube grafting process by elucidating the molecular processes involved in the process. [ABSTRACT FROM AUTHOR]

Gleditsia sinensis Lam. (Fam. Leguminosae; Gen.: Gleditsia) has various uses, including for medicinal, edible, chemical, and material purposes, and is widely distributed in China. However, the extent of graft compatibility and its impact on growth when using different Gleditsia species as rootstocks for grafting G. sinensis scions is not yet clear. This study examined homologous and heterologous grafting between different Gleditsia species, measuring the survival rate, morphology, photosynthesis, physiology, and hormones of the grafted plants. The results showed that G. sinensis and other Gleditsia seedlings have survival rates of over 86%. The more distant the genetic relationship between species, the lower the grafting survival rate. The grafting of fast-growing G. fera as a rootstock increased the accumulation of photosynthetic products in the grafted plants, while the grafting of slow-growing G. microphylla as a rootstock slowed down the growth rate of the longitudinal extension of the leaves of the grafted plants. Heterografted rootstocks increased the contents of IPA, PP333, ACC, and DZ but decreased the levels of GA4, iP, and SA hormones. Some hormone levels that can be highly expressed in seedlings were used as rootstocks, and the corresponding hormone levels in the grafted seedlings were still highly expressed. This study lays a material and theoretical basis for the development of new resources for the breeding and rootstock selection of G. sinensis. [ABSTRACT FROM AUTHOR]

BACKGROUND: Grafting is widely used in horticulture and rootstocks are known to modify scion growth and adaptation to soil conditions. However, the role of scion genotype in regulating rootstock development and functioning has remained largely unexplored. In this study, reciprocal grafts of two grapevine genotypes were produced as well as the corresponding homo-graft controls. These plants were subjected to a low phosphate (LP) treatment and transcriptome profiling by RNA sequencing was done on root samples collected 27 h after the onset of the LP treatment. RESULTS: A set of transcripts responsive to the LP treatment in all scion/rootstock combinations was identified. Gene expression patterns associated with genetic variation in response to LP were identified by comparing the response of the two homo-grafts. In addition, the scion was shown to modify root transcriptome responses to LP in a rootstock dependent manner. A weighted gene co-expression network analysis identified modules of correlated genes; the analysis of the association of these modules with the phosphate treatment, and the scion and rootstock genotype identified potential hub genes. CONCLUSIONS: This study provides insights into the response of grafted grapevine to phosphate supply and identifies potential shoot-to-root signals that could vary between different grapevine genotypes.

Copyright of Lucrari Stiintifice, Universitatea de Stiinte Agricole Si Medicina Veterinara Ion Ionescu de la Brad Iasi, Seria Horticultura is the property of University of Agricultural Sciences and Veterinary Medicine (Editura Ion Ionescu de la Brad) 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.)

Copyright of Journal of Erciyes Agriculture & Animal Science is the property of Erciyes Tarim ve Hayvan Bilimleri Dergisi 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.)

The global cannabis market is continuously expanding and as a result, the cannabis industry demands new and improved agronomic cultivation practices to increase production efficiency of cannabidiol (CBD), which is valued for its therapeutic benefits. This study investigates the influence of three rootstock types on the survival rate, morphological parameters, and biochemical composition of cannabis: potentially dwarfing rootstocks (PDR), potentially vigorous rootstocks (PVR), and seedlings-as-rootstocks (SAR). Rootstocks were used for grafting two scion genotypes: ‘ScionII’ = chemotype II of industrial hemp, and ‘ScionIII’ = chemotype III of high CBD accumulating variety. Contrary to expectations, PVR and SAR did not outperform PDR on most of the measured variables. SAR showed the highest survival rate of the grafted cannabis plants (40–70%). The rootstock type had a statistically significant influence only on the bud compactness index in ‘ScionII’, with PDR being particularly noticeable. A comparative analysis of the ‘rootstock/scion’ combinations with their controls (non-grafted scions) revealed grafting’s substantial improvement in most traits. Specifically, PDR increased CBD content by 27% in ‘ScionIII’, inflorescence yield and CBD yield per plant increased by 71% and 84%, respectively, when SAR was used in ‘ScionII’. SAR showed to be the most effective rootstock type for CBD production. Our findings suggest grafting as a promising technique for optimizing cannabis’s agronomic and medicinal potential, highlighting the necessity for further research on its underlying mechanisms to refine production efficiency and quality.

Simple Summary: Microorganisms are tightly associated with crops and can be pathogens or beneficials. Rose is the main ornamental crop worldwide. During production, rose varieties (over 100 in a single farm) are permanently grafted in a unique genotype as rootstock to improve plant performance. This work aimed to study the effect of grafting on root-associated microorganisms using next-generation DNA sequencing analysis. To this end, we have demonstrated that root-associated microorganisms of the rootstock (bacteria and fungi) will depend on the grafted genotype. In other words, a change in the variety will drive unique changes in the assembly of microorganisms at the root. This manuscript discusses differences in the bacterial and fungal communities when grafted and non-grafted and their potential impact on plant performance and agriculture. The root microbiome is vital in plant development and health and is highly influenced by crop cultural practices. Rose (Rosa sp.) is the most popular cut flower worldwide. Grafting in rose production is a standard practice to increase yield, improve flower quality, or reduce root-associated pests and diseases. 'Natal Brier' is a standard rootstock used in most commercial operations in Ecuador and Colombia, leading countries in producing and exporting ornamentals. It is known that the rose scion genotype affects root biomass and the root exudate profile of grafted plants. However, little is known about the influence of the rose scion genotype on the rhizosphere microbiome. We examined the influence of grafting and scion genotype on the rhizosphere microbiome of the rootstock 'Natal Brier'. The microbiomes of the non-grafted rootstock and the rootstock grafted with two red rose cultivars were assessed using 16S rRNA and ITS sequencing. Grafting changed microbial community structure and function. Further, analysis of grafted plant samples revealed that the scion genotype highly influences the rootstock microbiome. Under the presented experimental conditions, the rootstock 'Natal Brier' core microbiome consisted of 16 bacterial and 40 fungal taxa. Our results highlight that the scion genotype influences root microbe's recruitment, which might also influence the functionality of assembled microbiomes. [ABSTRACT FROM AUTHOR]

Grafting is a traditional horticultural technique that makes use of plant wound healing mechanisms to join two different genotypes together to form one plant. In many agricultural systems, grafting with rootstocks controls the vigour of the scion and/or provides tolerance to deleterious soil conditions such as the presence of soil pests or pathogens or limited or excessive water or mineral nutrient supply. Much of our knowledge about the limits to grafting different genotypes together comes from empirical knowledge of horticulturalists. Until recently, researchers believed that grafting monocotyledonous plants was impossible, because they lack a vascular cambium, and that graft compatibility between different scion/rootstock combinations was restricted to closely related genotypes. Recent studies have overturned these ideas and open up the possibility of new research directions and applications for grafting in agriculture. The objective of this review is to describe and assess these recent advances in the field of grafting and, in particular, the molecular mechanisms underlining graft union formation and graft compatibility between different genotypes. The challenges of characterizing the different stages of graft union formation and phenotyping graft compatibility are examined. [ABSTRACT FROM AUTHOR]

Plant grafting is a maneuver humans learned from nature and has been practiced since ancient times. The technique has long been applied for efficient propagation as well as for the modification of the traits of interest, such as stress tolerance, tree size, and fruit quality. Since grafting can enhance the environmental tolerance and disease resistance of a plant, its techniques are now used not only in tree species but also among vegetables. Despite such wide advantages of grafting, however, the potential cause behind a compatible graft establishment (scion-rootstock connection) is yet to be fully understood. As compared to succulent herbaceous plants, woody plants often take a longer time for the graft-take and the plants may exhibit incompatible/unsuccessful graft-establishment symptoms within a period ranging from months to years. In this review, we discuss factors involved in a successful/compatible graft establishment along with bottlenecks of our understanding and future perspectives in a simplified manner- particularly focusing on incompatible graft formation on fruit trees based on earlier studies in the field. [ABSTRACT FROM AUTHOR]

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]

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.

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.

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.

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.

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences 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.)

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.

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]

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 (h 2) 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Separately, grafting and the use of plastic mulch can increase yield, quality, and early harvest of watermelon (Citrullus lanatus), especially when plants are under biotic and/ or abiotic stress. A 2-year field study was conducted to evaluate the combination of four different rootstocks and two types of plastic mulch (black and clear) on date of watermelon first flowering, fruit ripening, yield, and fruit quality when plants were exposed to Verticillium dahliae. Seedless watermelon cv. Secretariat was grafted onto rootstocks Lagenaria siceraria cv. Pelop, Benincasa hispida cv. Round, and two interspecific hybrid squash rootstocks Cucurbita maxima X C. moschata cvs. Super Shintosa and Tetsukabuto, with nongrafted 'Secretariat' as the control. Fruit were harvested 0, 7, and 14 days after both the leaflet and tendril attached to the fruit pedicel were completely dry (fruit considered to be physiologically mature). The area under the disease progress curve (AUDPC) values for verticillium wilt were not different for mulch type in either year, although the overall AUDPC value was greatly reduced in the four grafted treatments (227) compared with nongrafted (743). There was no difference in days to male or female flowering due to mulch type or year, and rootstock did not affect first flowering of male flowers. Female flowering was 14 and 11 days later in 2018 and 2019, respectively, for 'Secretariat' grafted onto bottle gourd 'Round' compared with 'Secretariat' grafted onto 'Tetsukabuto'. Female flowering of 'Secretariat' on 'Round' was also 7 days later compared with nongrafted 'Secretariat' both years. However, days to first harvest was not different with mulch or rootstock and was 92 days after transplanting (DAT) in 2018 and 114 DAT in 2019. There was no difference in yield (fruit number and weight) due to year, harvest date, or mulch, but there was a difference due to grafting. 'Secretariat' grafted onto 'Super Shintosa' had the greatest total number and weight of fruit per plant (3.7 and 14.8 kg, respectively), and nongrafted 'Secretariat' had the lowest (0.7 and 3.2 kg, respectively). Fruit quality attributes hollow heart formation (rating 3.2/5 on average), hard seed count (6 on average), total soluble solids (11% on average), and lycopene content were not different among mulch type, rootstock treatment, or harvest date; however, lycopene content did differ due to year (52.44 and 32.51 µg·g-1 in 2018 and 2019, respectively). Flesh firmness was highest for watermelon grafted onto 'Super Shintosa' rootstock (6.7 N) and lowest for nongrafted watermelon (4.3 N). Overall, rootstocks reduced verticillium wilt severity and increased fruit yield whereas mulch had no effects, and 5 V. dahliae colony forming units (cfu)/g of soilmay be theminimum level for impact on watermelon fruit yield. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the stenting (grafted cutting) propagation of commercial pomegranate cultivars as scions on drought tolerant genotypes as rootstocks. The effect of drought stress on nine pomegranate rootstocks was analyzed. Cultivars including 'Daneshgah 13', 'Daneshgah 32' and 'Daneshgah 8' that were used as rootstocks showed the maximum drought tolerance among the studied cultivars; therefore, these three rootstocks were used to investigate the stenting propagation. Furthermore, three pomegranate cultivars including 'Malas Saveh', 'Robab' and 'Bihasteh' were used as scions. The highest percentage of graft success (58.88%) was obtained from grafting on 'Daneshgah 13'. In addition, the highest percentage of graft success (84.22) was found in 'Robab'. 'Robab' and 'Malas Saveh' had the longest shoot (11.50-11.93 cm) and highest shoot fresh weight (33.66-35.00 g) when grafted on 'Daneshgah 13'. 'Daneshgah 13' had higher shoot dry weight (5.47 g) compared to the other rootstocks. Regarding the scion cultivars, 'Robab' and 'Malas Saveh' showed higher shoot dry weight (6.76-6.96 g) in comparison with 'Bihasteh'. Using 'Daneshgah 13' as rootstock resulted in the highest content of chlorophyll a (18.11 mg/g), chlorophyll b (8.02 mg/g) and total chlorophyll (26.13 mg/g) in the scion leaves. 'Robab' and 'Malas Saveh' had highest content of chlorophyll a (18.11-18.33 mg/g), chlorophyll b (8.58-8.62 mg/g) and total chlorophyll (26.73-26.92 mg/g) among the scion cultivars. In all three rootstocks, a negative correlation was observed between the total phenolic content and the percentage of graft success. In addition, there was a negative correlation between the total phenolic content and the percentage of graft success in 'Bihasteh' scion. [ABSTRACT FROM AUTHOR]

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]

This review characterizes, identifies and presents remarks of breeding rootstocks in Palestine. It’s based upon a survey of the rootstocks that have been used along decades of breeding and grafting of local and introduced cultivars. All for acclimatization for hard conditions that confront fruit trees. It also proposes some expected promising rootstocks that might suit the climate change and whatever affected by it of biotic and abiotic stresses in the area. Obviously, this review discusses the advantages of the current confirmed rootstocks that are compatible with most of the species of the popular trees. It also pointed out to inadequate rootstocks that have been used before. In fact, many of these rootstocks still exist, however the elimination of the other rootstocks refers to different reasons either to the environmental conditions or the incompatibility with the preferred cultivars. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

Growth and yield typically increase when tomato plants are grafted to selected interspecific hybrid rootstocks from which distinctive root system morphologies are envisioned to aid nutrient uptake. We assessed these relationships using a range of exogenous nitrogen (N) supplies under field production conditions. This study analyzed the impact of N on growth, root distribution, N uptake, and N use of determinate 'Florida 47' tomato plants grafted onto vigorous, interspecific, hybrid tomato rootstocks 'Multifort' and 'Beaufort'. Six N rates, 56, 112, 168, 224, 280, and 336 kg·ha-1, were applied to sandy soil in Live Oak, FL, during Spring 2010 and 2011. During both years, the leaf area index, aboveground biomass, and N accumulation (leaf blade, petiole, stem, and fruit) responded quadratically to the increase in N fertilizer rates. Averaged over the two seasons, the aboveground biomass, N accumulation, N use efficiency (NUE), andN uptake efficiency (NUpE) were ≈29%, 31%, 30%, and 33% greater in grafted plants than in nongrafted controls, respectively. More prominent increases occurred in the root length density (RLD) in the uppermost 15 cm of soil; for grafted plants, RLD values in this upper 15-cm layer were significantly greater than those of nongrafted plants during both years with an average increase of 69% over the two seasons. Across all the grafted and nongrafted plants, the RLD decreased along the soil profile, with ≈60% of the total RLD concentrated in the uppermost 0 to 15 cm of the soil layer. These results demonstrated a clear association between enhanced RLD, especially in the upper 15 cm of soil, and improvements in tomato plant growth, N uptake, and N accumulation with grafting onto vigorous rootstocks. [ABSTRACT FROM AUTHOR]

High tunnels allow vegetable growers to extend the growing season, increase crop production, and improve produce quality. Tomatoes (Solanum lycopersicum L.) are the most widely grown crops in high tunnels; however, tomato production in high tunnels can be challenging. Continuous cropping in high tunnels can increase soil-borne disease pressure and can lead to soil salinity or nutrient depletion issues. Based on preliminary research, we hypothesized that use of the rootstock 'RST-04-106-T' would increase yield and quality of heirloom and hybrid tomato scions compared with nongrafted plants. To test this hypothesis, our research objectives were to assess marketable yields, fruit quality and nutritional value, and plant growth of grafted and nongrafted hybrid and heirloom tomatoes in a high tunnel production system. Grafted and nongrafted 'Cherokee Purple' (heirloom) and 'Mountain Fresh Plus' (hybrid) tomatoes were grown in the same high tunnel for two seasons (7 May-20 Oct. 2015 and 29 April-7 Oct. 2016) at the Horticulture Research Station in Ames, IA. Grafted plants produced significantly more marketable fruit, although marketable and total fruit weight did not increase significantly. Individual fruit size was unaffected by grafting. Across cultivars, mean soluble solids content (SSC) in fruit was 0.3 8Brix lower in grafted plants as compared with the nongrafted control. Grafting did not affect lycopene content of fruit. Grafting increased stem diameter by an average of 0.8 mm, but overall plant biomass was unaffected. The effect of grafting on leaf chlorophyll concentration (SPAD readings) was mixed. In addition, grafting increased leaf chlorophyll concentration in 'Cherokee Purple' but decreased it in 'Mountain Fresh Plus' plants. Grafting is a valuable tool in tomato production, but the impact of 'RST-04-106-T' rootstock use appears to be specific to certain soil types with high incidence of bacterial wilt. [ABSTRACT FROM AUTHOR]

Despite the importance of grafting in horticultural crops such as tomato (Solanum lycopersicum L.), the structural changes that occur during the graft establishment are little understood. Using histological techniques, the present work examines the time course of changes on the anatomical structure of the graft junction in functional tomato homografts and compares it to that of heterografts and non-functional grafts. No apparent differences were detected between homo- and heterografts, showing similar tissue development. At 10 days after grafting, the cell walls of the scion and rootstock in the area of the graft junction were thicker than usual. Undifferentiated cells and new vascular tissue emerged from the pre-existing vasculature. Adventitious roots appeared mainly on the scion, arising from the pre-existing vasculature. At 20 days, more pronounced vascular tissue was visible, along with large areas showing vascular connection. At 210 days, vestiges of the changes undergone in graft development were still visible. Generally, non-functional grafts presented layers of necrotic remains and deposition of cell wall material in the cut edges, impeding the suitable scion-rootstock connection. Our results show that accurate changes in pre-existing vasculature and the cell walls of the adhesion line are crucial to the development of functional grafts.

Grafting has been utilised for at least the past 7000 years. Historically, grafting has been developed by growers without particular interest beyond the agronomical and ornamental effects, and thus knowledge about grafting has remained largely empirical. Much of the commercial production of fruit, and increasingly vegetables, relies upon grafting with rootstocks to provide resistance to soil-borne pathogens and abiotic stresses as well as to influence scion growth and performance. Although there is considerable agronomic knowledge about the use and selection of rootstocks for many species, we know little of the molecular mechanisms underlying rootstock adaptation to different soil environments and rootstock-conferred modifications of scion phenotypes. Furthermore, the processes involved in the formation of the graft union and graft compatibility are poorly understood despite over a hundred years of scientific study. In this paper, we provide an overview of what is known about grafting and the mechanisms underlying rootstock–scion interactions. We highlight recent studies that have advanced our understanding of graft union formation and outline subjects that require further development. [ABSTRACT FROM AUTHOR]

Root-associated microbes are critical to plant health and performance, although understanding of the factors that structure these microbial communities and theory to predict microbial assemblages are still limited. Here we use a grafted tomato system to study the effects of rootstock genotypes and grafting in endosphere and rhizosphere microbiomes that were evaluated by sequencing 16S rRNA. We compared the microbiomes of nongrafted tomato cultivar BHN589, selfgrafted BHN589, and BHN589 grafted to Maxifort or RST-04-106 hybrid rootstocks. OTU-based bacterial diversity was greater in Maxifort compared to nongraft controls, whereas bacterial diversity in the controls (selfgraft and nongraft) and the other rootstock (RST-04-106) was similar. Grafting itself did not affect bacterial diversity; diversity in the selfgraft was similar to the nongraft. Bacterial diversity was higher in the rhizosphere than in the endosphere for all treatments. However, despite the lower overall diversity, there was a greater number of differentially abundant OTUs (DAOTUs) in the endosphere, with the greatest number of DAOTUs associated with Maxifort. In a PERMANOVA analysis, there was evidence for an effect of rootstock genotype on bacterial communities. The endosphere-rhizosphere compartment and study site explained a high percentage of the differences among bacterial communities. Further analyses identified OTUs responsive to rootstock genotypes in both the endosphere and the rhizosphere. Our findings highlight the effects of rootstocks on bacterial diversity and composition. The influence of rootstock and plant compartment on microbial communities indicates opportunities for the development of designer communities and microbiome-based breeding to improve future crop production. [ABSTRACT FROM AUTHOR]

Breadfruit (Artocarpus altilis) is primarily grown as a staple tree crop for food security in Oceania. Significant wind damage has driven interest in developing its dwarfing rootstocks. Due to the predominantly vegetative propagation of the species, grafting onto interspecific seedlings is an approach to identifying dwarfing rootstocks. However, grafting of breadfruit onto unrelated Artocarpus species has not been investigated.Here we first report the success of breadfruit grafting onto interspecific rootstocks, marang (A. odoratissimus) and pedalai (A. sericicarpus). To address the low graft survival, we investigated the relationship of plasma membrane (PM) H+‐ATPase activity to graft success.We provide the first evidence for a positive correlation between PM H+‐ATPase activity and graft survival. The graft unions of successful grafts had higher PM H+‐ATPase activity compared to those of failed grafts. Rootstocks with low PM H+‐ATPase activity in leaf microsomes before grafting had lower graft survival than those with high enzyme activity, with graft success of 10% versus 60% and 0% versus 30% for marang and pedalai rootstocks, respectively. There was a positive correlation between graft success and the PM H+‐ATPase activity measured from the rootstock stem microsomes 2 months after grafting [marang, r(7) = 0.9203, P = 0.0004; pedalai (r(7) = 0. 8820, P = 0.0017]. Removal of scion's own roots decreased the leaf PM H+‐ATPase activity of grafted plants regardless of the final graft outcome. Recovery of the enzyme activity was only found in the successful grafts.The function of PM H+‐ATPase in graft union development and graft success improvement is discussed. [ABSTRACT FROM AUTHOR]

To study the impact of the top working method of grafting on flowering behavior in tea clones and its applicability in tea breeding two field experiments were carried out. Field established plants of the clone UPASI-9 was used as the rootstock in both the experiments. Recently released clones TRF-1, TRF-3 and TRF-4 were used as scions to study the influence of top working on flowering. One-year-old rooted plants of the clones used as scions field planted in the same year served as standards for comparison. Precocious flowering was noticed in all the top worked clones by eight months from grafting. In self- rooted plants of the scion clones only sparse flowering was noticed after eighteen/nineteen months. Similarly, the duration of flowering and total number of flowers were significantly higher in top worked plants compared to self-rooted plants. The top worked scions were significantly more vigorous than the corresponding self-rooted plants, except TRF-3. In the second experiment by top working the scions of two different clones on the same rootstock; four sets of combinations were tried. The clone TRF-4 was used as one scion in all the four sets and the clones TRF-1, SA-6, Yabukita and SMP-1 served as the other scions in each set. Early flowering as well as synchronization of flowering was observed in both the scion clones in three of the tested pairs. However, the growth and flowering of the common scion clone TRF-4 varied significantly in each set depending on the other clone used as a scion. [ABSTRACT FROM AUTHOR]

This publication explains the different methods of citrus propagation and includes detailed descriptions and photographs of the grafting process and other principles of propagation.

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In vitro micrografting is a propagation technique, involving the grafting of relatively miniature cuttings under axenic culture conditions and it is one of the recent developed propagation techniques compared to other conventional vegetative propagation techniques. This method overcomes some of the limitations of shoot tip culture and grafting, while it also keeps together the advantages of both methods. Micrografting was applied for the eradication viruses and pathogens from some fruit species and cultivars during the first application period, but later, the technique was further developed on various woody plant species in different research areas of plant physiology and development. These includes physiological rejuvenation and incompatibility grafting as a prerequisite for the clonally propagation of mature genotypes of many woody species. Consequently, in vitro micrografting is used in large scale propagation and an original technique which needs experience by overcoming the disadvantages of other propagation technique. It also enables to examine in detail the genetic similarities and differences between the tissues and cells. The aims of this study were (1) to review how micrografting studies passed a process from 1970s until today, first started to obtain virus-free plants from citrus; (2) to reveal what kind of work has been presented particularly on the plant breeding and propagation of the woody plant species, including the type of fruit breeding and reproduction and (3) and to present those studies in a specific order. [ABSTRACT FROM AUTHOR]

A study on grafting bitter gourd on various cucurbitaceous rootstocks was carried out to identify the best rootstocks for grafting bitter gourd and to compare two grafting methods namely, wedge grafting (WG) and tongue approach grafting (TAG). In the study bitter gourd scion (var. Preethi) was grafted on six rootstocks, viz., ash gourd, bottle gourd, smooth gourd, pumpkin, oriental pickling melon and self rootstocks by wedge grafting and tongue approach grafting. There was significant difference in graft success among the rootstocks in WG. In WG, best rootstock in terms of graft success was smooth gourd (80%) followed by pumpkin, bottle gourd, ash gourd, OP melon and self rootstock. There was no significant difference among the rootstocks on graft success in TAG. WG (67%) was superior to TAG (15.17%) in terms of final graft success. Graft success had significant positive correlation with relative humidity and significant negative correlation with maximum and minimum temperature. Anatomical studies of the graft union revealed cell proliferation which is the stage prior to callus formation. [ABSTRACT FROM AUTHOR]

Grafting is a centuries-old technique used in plants to obtain economic benefits. Grafting increases nutrient uptake and utilization efficiency in a number of plant species, including fruits, vegetables, and ornamentals. Selected rootstocks of the same species or close relatives are utilized in grafting. Rootstocks absorb more water and ions than self-rooted plants and transport these water and ions to the aboveground scion. Ion uptake is regulated by a complex communication mechanism between the scion and rootstock. Sugars, hormones, and miRNAs function as long-distance signaling molecules and regulate ion uptake and ion homeostasis by affecting the activity of ion transporters. This review summarizes available information on the effect of rootstock on nutrient uptake and utilization and the mechanisms involved. Information on specific nutrient-efficient rootstocks for different crops of commercial importance is also provided. Several other important approaches, such as interstocking (during double grafting), inarching, use of plant-growth-promoting rhizobacteria, use of arbuscular mycorrhizal fungi, use of plant growth substances (e.g., auxin and melatonin), and use of genetically engineered rootstocks and scions (transgrafting), are highlighted; these approaches can be combined with grafting to enhance nutrient uptake and utilization in commercially important plant species. Whether the rootstock and scion affect each other’s soil microbiota and their effect on the nutrient absorption of rootstocks remain largely unknown. Similarly, the physiological and molecular bases of grafting, crease formation, and incompatibility are not fully identified and require investigation. Grafting in horticultural crops can help reveal the basic biology of grafting, the reasons for incompatibility, sensing, and signaling of nutrients, ion uptake and transport, and the mechanism of heavy metal accumulation and restriction in rootstocks. Ion transporter and miRNA-regulated nutrient studies have focused on model and non-grafted plants, and information on grafted plants is limited. Such information will improve the development of nutrient-efficient rootstocks.