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To further clarify the impact of different rootstocks in grafted blueberry, fruit quality, mineral contents, and leaf gas exchange were investigated in 'O'Neal' blueberry (Vaccinium corymbosum) grafted onto 'Anna' (V. corymbosum) (AO), 'Sharpblue' (V. corymbosum) (SO), 'Baldwin' (V. virgatum) (BO), 'Plolific' (V. virgatum) (PO), and 'Tifblue' (V. virgatum) (TO) rootstocks and own-rooted 'O'Neal' (NO), and differences in anatomic structures and drought resistance were determined in AO, TO, and NO. The findings revealed that fruit quality in TO and PO was excellent, that of BO and SO was good, and that of AO and NO was medium. 'Tifblue' and 'Plolific' rootstocks significantly increased the levels of leaf phosphorus and net photosynthetic rate of 'O'Neal', accompanied by a synchronous increase in their transpiration rates, stomatal conductance, and intercellular CO2. Additionally, the comprehensive evaluation scores from a principal component analysis based on anatomic structure traits from high to low were in the order TO > AO > NO. The P50 (xylem water potential at 50% loss of hydraulic conductivity) values of these grafted plants descended in the order NO > AO > TO, and the branch hydraulic conductivity of TO and sapwood hydraulic conductivity of TO and AO were significantly lower than those of NO. Thus, TO plants exhibited the strongest drought resistance, followed by AO, and NO, and this trait was related to the effects of different rootstocks on the fruit quality of 'O'Neal' blueberry. These results provided a basis for a deeper understanding of the interaction between rootstocks and scions, as well mechanisms to improve blueberry fruit quality. [ABSTRACT FROM AUTHOR]

Key message: Our results from transcriptomics and metabolomics extend the understanding of the consequences of interspecific grafting to improve blueberry fruit quality. Grafting plays an important role in improving fruit quality and plant stress resistance. The effect of interspecific grafting on fruit quality in 'O'Neal' blueberry (Vaccinium corymbosum L.) was investigated with transcriptomics and non-targeted metabolomics. Fruits were collected from own-rooted 'O'Neal' (NO), 'O'Neal' grafted on 'Tifblue' (V. virgatum Ait.) (TO), and 'Anna' (V. corymbosum L.) (AO) bushes. The total soluble solids and anthocyanin concentrations, and solid:acid ratio in TO fruits were higher, while the vitamin C level was lower than AO and NO. The metabolic profiling showed that interspecific grafted blueberry had higher levels of sugars such as glucose, maltose, raffinose, myo-inositol, and galactinol, as well as glucose-6-phosphate and trehalose-6-phosphate as compared to intraspecific grafted blueberry. The fruits of TO also showed higher concentrations of secondary metabolites such as catechin, 5,7-dihydroxy-4'-methoxyisoflavone, glycyl tyrosine, and tocopherol, and lower concentrations of tryptophan and phenylalanine as compared to AO. Transcriptomic data showed that not only sugar metabolism-related enzymes such as trehalose-phosphate synthase and galactol synthase but also shikimate-derived metabolism-related enzymes such as flavonoid 3'-monooxygenase, anthocyanidin glucosyltransferase, isoflavone reductase, alcohol dehydrogenase, and aspartate aminotransferase were up-regulated in a comparison of TO/AO. Moreover, sugar signaling-related genes such as 6-phosphofructokinase, bHLHs, MYBs, 1-aminocyclopropane-1-carboxylate oxidase, 1-aminocyclopropane-1-carboxylate synthase, ABC transporter, and malate transporter were also up-regulated in a comparison of TO/AO. Finally, we proposed the hypothesis that sugar signals regulate the accumulation of sugars and organic acids and fruit ripening. These results will provide interesting insights into the interaction of scions on rootstocks and the promotion of blueberry genetic improvement. [ABSTRACT FROM AUTHOR]

To further clarify the impact of different rootstocks in grafted blueberry, fruit quality, mineral contents, and leaf gas exchange were investigated in ‘O’Neal’ blueberry (Vaccinium corymbosum) grafted onto ‘Anna’ (V. corymbosum) (AO), ‘Sharpblue’ (V. corymbosum) (SO), ‘Baldwin’ (V. virgatum) (BO), ‘Plolific’ (V. virgatum) (PO), and ‘Tifblue’ (V. virgatum) (TO) rootstocks and own-rooted ‘O’Neal’ (NO), and differences in anatomic structures and drought resistance were determined in AO, TO, and NO. The findings revealed that fruit quality in TO and PO was excellent, that of BO and SO was good, and that of AO and NO was medium. ‘Tifblue’ and ‘Plolific’ rootstocks significantly increased the levels of leaf phosphorus and net photosynthetic rate of ‘O’Neal’, accompanied by a synchronous increase in their transpiration rates, stomatal conductance, and intercellular CO2. Additionally, the comprehensive evaluation scores from a principal component analysis based on anatomic structure traits from high to low were in the order TO > AO > NO. The P50 (xylem water potential at 50% loss of hydraulic conductivity) values of these grafted plants descended in the order NO > AO > TO, and the branch hydraulic conductivity of TO and sapwood hydraulic conductivity of TO and AO were significantly lower than those of NO. Thus, TO plants exhibited the strongest drought resistance, followed by AO, and NO, and this trait was related to the effects of different rootstocks on the fruit quality of ‘O’Neal’ blueberry. These results provided a basis for a deeper understanding of the interaction between rootstocks and scions, as well mechanisms to improve blueberry fruit quality.

Abstract: The objective of this work was to evaluate the graft growth and the anatomical characterization of pear (Pyrus communis x P. pyrifolia) and quince (Cydonia oblonga) cultivars grafted on Pyrus calleryana and Chaenomeles sinensis rootstocks. Sprouted graft percentages at 60 days and the length and diameter of the graft sproutings at 120 days were evaluated. Stem cuttings from the grafting region were performed in transversal and longitudinal sections, and the secondary xylem was separated for tissue comparison. The pear trees showed good development on P.calleryana rootstock, and the anatomical sections showed that the vascular tissues were connected, which did not occur when the trees were grafted on C.sinensis, in which the grafts sprouted, but did not develop, and the vascular tissues did not connect. The quince trees showed good development on both rootstocks due to the good connection of the vascular tissues. The connection of vascular tissues is essential for the success of grafting. The evaluated species did not differ significantly as to their secondary xylem tissues. The incompatibility found between the pear trees and the C.sinensis rootstocks is not anatomical.

• The genotype of the coffee scions largely determined agronomic traits, bean qualities and the rootstock phenotype (incl. dry weight of taproot, secondary root mass and overall root system). • Interspecific grafting of coffea arabica scions 'H3' and 'Villa Sarchi' onto C. canephora rootstock 'Nemaya' negatively affected coffee yields and root traits for both varieties compared to the non-grafted plants. However, there were no detected impacts of interspecific on the final bean attributes nor cup quality. • Increasing elevation significantly reduced the trunk, branches and shoot system, chlorophyll fluorescence parameters and other agronomic traits. • The negative impacts on coffee growth associated with Nemaya' rootstock may be a trade-off for nematode-resistance in C. arabica. Interspecific grafting of Coffea arabica scions on C. canephora rootstock has been proposed as a strategy against nematode infestation, but also for cultivation of coffee under environmental stressors (such as temperature extremes). An agroforestry-like microclimate was established using artificial shade nets (30% light interception) across a multi-site elevation trial (from 1000 to 1450 m above sea level) in Costa Rica (Alajuela region). The effects of interspecific grafting of scions from modern C. arabica varieties ('Villa Sarchi' and an F1 hybrid called 'H3') onto C. canephora ('Nemaya') rootstock were tested under these conditions. The interactions between grafting, genotype and elevation were determined on the above- and below ground growth, agronomic traits, photosynthesis as well as bean and cup qualities. Variation in the protuberance of the graft union (trunk vs. below graft union collar diameters) were detected. However, no physical vascular blockages were observed in any of the interspecific grafted plants. Generally, interspecific grafting negatively affected most aerial and root traits as well bean yields for both 'H3' and 'Villa Sarchi' varieties compared to the non-grafted plants. A significant reduction in the photosynthesis of grafted 'H3' (in terms of V cmax and ΦCO 2max) was also observed. However, there were no impacts of grafting on the final bean attributes nor cup quality. Genetics of the scions largely determined coffee yields, with higher yields produced by 'H3' compared to 'Villa Sarchi'. The scion also controlled agronomic traits, bean qualities and belowground biomass (dry weight of taproot, secondary root mass and overall root system). This was observed when either C. arabica or C. canephora scion material was used. Increasing elevation significantly reduced the trunk, branches and shoot system, chlorophyll fluorescence parameters and other agronomic traits. However no significant interactions were found between grafting and elevation (within the range tested). Our results show how interspecific grafting of C. arabica onto C. canephora can reduce plant biomass and productivity under shade and across an elevational gradient, especially when the composite plant involves a vigorous and high yielding F1 hybrid. [Display omitted] [ABSTRACT FROM AUTHOR]

Plant grafting has a long history and it is extensively employed to improve plant performance. In our previous research, reciprocal grafts of Populus cathayana Rehder (C) and Populus deltoides Bart. Ex Marsh (D) were generated. The results showed that interspecific grafting combinations (scion/rootstock: C/D and D/C) grew better than intraspecific grafting combinations (C/C and D/D). To further understand differences in molecular mechanisms between interspecific and intraspecific grafting, we performed an integrated analysis, including bisulfite sequencing, RNA sequencing and measurements of physiological indicators, to investigate leaves of different grafting combinations. We found that the difference at the genome-wide methylation level was greater in D/C vs D/D than in C/D vs C/C, but no difference was detected at the transcription level in D/C vs D/D. Furthermore, the grafting superiority of D/C vs D/D was not as strong as that of C/D vs C/C. These results may be associated with the different methylation forms, mCHH (71.76%) and mCG (57.16%), that accounted for the highest percentages in C/D vs C/C and D/C vs D/D, respectively. In addition, the interspecific grafting superiority was found mainly related to the process of photosynthesis, phytohormone signal transduction, biosynthesis of secondary metabolites, cell wall and transcriptional regulation based on both physiological and molecular results. Overall, the results indicated that the physiological and molecular phenotypes of grafted plants are affected by the interaction between scion and rootstock. Thus, our study provides a theoretical basis for developing suitable scion-rootstock combinations for grafted plants., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

• Combined Cu and Zn lead to greater plant toxicity than each element individually added. • High Cu and Zn contents affected plants biochemical parameters. • Young peach trees accumulated Cu and Zn mainly in root system. • The Zn translocation to plant aerial part is higher when compared to Cu translocation. The frequent application of fungicides containing copper (Cu) and zinc (Zn) in orchards can lead to accumulation of these metals in soil at toxic levels. The aim of this study was to evaluate Cu and Zn distribution and toxicity in young peach trees grown in Cu and Zn supplemented soil. For this purpose, a pot experiment was carried out in a greenhouse using a Typic Hapludalf soil under natural conditions. The two-factor experiment investigated the combination of Cu (0, 30 and 60 mg kg−1) and Zn (0, 15, 30, 60, 120, and 180 mg kg−1) rates in four replicates per treatment. ‛Jade' young peach trees [ Prunus persica (L.) Batsch] grafted on ‛Genovesa' (P. salicina) propagated by herbaceous cuttings were then cultivated for 78 days with one plant per pot. Height increase, dry matter production, Cu and Zn concentration in plant organs, photosynthetic pigments and antioxidant activity were evaluated. Soil available Cu and Zn content increased with the rate. Consequently, plants presented Zn, and mainly Cu, accumulation mechanisms in root system, reduced transport of both elements to leaves, where toxic effects of heavy metals was observed. However, combining high content of soil available Cu and Zn, especially at higher doses, resulted in decreased production of dry matter production. Biochemical parameters were also affected. The SOD activity was smaller in peach leaves grown in the soil supplemented with Cu, while the chlorophyll a and b content decreased according to the increase of Zn rate, compromising the antioxidant response and the photosynthetic activity. Thus, increasing soil available Cu and Zn contents in sandy soil with low organic matter soils may maximize toxic effects to young peach trees. [ABSTRACT FROM AUTHOR]