Figure 2 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Midday stem water potential (MPa) of 'Honeycrisp' apple trees on B.9, M.9, G.969, CG.4292, G.210, G.87, CG.5257, G.814, G.890 rootstocks measured in 2018 (dark grey bars) and 2019 (light grey bars). Error bars denote standard error (N = 3). Lowercase letters account for significant differences between rootstocks measured in 2018. Capital letters account for significant differences between rootstocks measured in 2019. Means determined using a Tukey's mean separation test (α = 0.05).
Source publication
Composite trees combine optimal traits from both the rootstock and the scion. Dwarfing rootstocks are commonly used to reduce shoot vigour and improve fruit quality and productivity. Although growth habits of different rootstocks have been clearly described, the underlying physiological traits affecting scion vigour are not well understood. Plant w...
Context in source publication
Context 1
... affected midday stem water potential in both years (Fig. 2). In this irrigated orchard, mean midday stem water potential (Ψ m ) did not range beyond −0.8 to −1.0 MPa. B.9 had the lowest stem water potential of all rootstock genotypes. However, in 2018, Ψ m for B.9 was only significantly different from CG.5257. In 2019, differences among rootstocks were greater but trends were similar to 2018. Ψ ...
Similar publications
Assai (Euterpe oleracea Mart.) cultivars BRS-Pará (BRS-PA) and BRS-Pai d’Égua (BRS-PDE) were selected for cultivation in upland regions of the Amazon. Given these cultivars were developed from different progenitors, we postulated that they differ regarding water-deficit tolerance. To test this hypothesis, plants of both cultivars were evaluated und...
Citations
... This is especially true for apple trees and other grafted production systems with two genotypes (rootstock and scion) grafted together. In recent years, our understanding of what drives the resilience, productivity, and fruit quality of apple scions has been attributed to specific rootstock qualities Lordan et al., 2019;de Macedo et al., 2021;Biasuz and Kalcsits, 2022;Fazio and Robinson, 2022). The genetic properties of apple rootstocks are associated with differential leaf and fruit mineral nutrient concentrations Fazio et al., 2020), hormone concentrations (Lordan et al., 2017), gene expression (Jensen et al., 2012), tree growth, and productivity (Autio et al., 2020). ...
... The development of lateral roots and associated fine roots is the main component of the root system by which plants explore the soil profile and absorb water and nutrients. The significance of root size and morphology for nutrient uptake has been demonstrated in a number of mathematical models and experiments (Boot, 1990). Relatively thin fine roots, with a specific root length to dry weight ratio, form the smallest parts of the root system. ...
The pH of the solution in the rhizosphere is an important factor that determines the availability and mobility of nutrients for plant uptake. Solution pH may also affect the root distribution and architecture of apple rootstocks. In this study, we evaluated the effect of solution pH on root system development of apple rootstocks using an aeroponics system designed and developed at Cornell AgriTech Geneva, USA. Four Geneva® apple rootstocks (G.210, G.214, G.41, and G.890) were grown in an aeroponic system under nutrient solution misting featuring continuously adjusted pH levels to three pH treatments (5.5, 6.5, and 8.0). Root development was monitored for 30 days and evaluated regularly for distribution and root mass. Images of the developed roots grown in the aeroponic system were collected at the end of the experiment using a high-resolution camera and analyzed using GiA Roots® software, which generates root architecture parameter values in a semi-automated fashion. The resulting root architecture analysis showed that the Geneva® rootstocks were significantly different for two architecture parameters. The length-to-width ratio analysis represented by two GiA Roots parameters (minor-to-major ellipse ratio and network width-to-depth ratio) showed that G.210 was flatter than G.890, which had a greater tendency to grow downward. Rootstocks G.214 and G.41 displayed similar growth values. The solution pH affected most root architecture parameter measurements where overall root growth was higher at pH 8 than at pH 5.5 and 6.5, which showed similar growth. In general, the average root width tended to decrease at higher pH values. While there were no significant differences in the leaf nutrient concentrations of P, K, Ca, Mg, S, B, Zn, Cu, and Fe within the four rootstocks, the pH level of the solution had a significant effect on P, Ca, and Mn. This study is the first of its kind to investigate the effect of pH on root architecture in a soil-free (aeroponic) environment and may have implications for apple root behavior under field conditions where pH levels are different.
... Rootstocks may also contribute to biennial bearing and these interactions may need to be more carefully considered in interpretations of past studies and design of future studies. Differences among rootstocks in carbon assimilation, precocity, water-use efficiency, root-shoot biomass allocation, and shoot vigor all affect the competition for existing carbon pools produced by the tree canopy, potentially influencing biennial bearing (Baldassi et al., 2023;Casagrande-Biasuz and Kalcsits, 2022;Foster et al., 2017;Jupa et al., 2022;Kviklys et al., 2016;Valverdi and Kalcsits, 2021). Water relations also contribute to carbon assimilation efficiency and partitioning. ...
... Water relations also contribute to carbon assimilation efficiency and partitioning. Net-leaf carbon assimilation has been observed to be lower in low-vigor rootstocks (Casagrande-Biasuz and Kalcsits, 2022). When investigating water relations and water-use efficiency, net gas exchange and shoot growth were greater under well-watered conditions (Valverdi and Kalcsits, 2021), with dwarfed apple trees maintaining lower gas exchange rates than vigorous ones during drought (Jupa et al., 2022). ...
Biennial bearing has long been a challenge for perennial tree fruit production. Some cultivars are more susceptible and can have excessive bloom and fruit set in one year followed by insufficient bloom and fruit set in the next year. Although crop load management can be used to reduce biennial bearing, optimum crop loads in one year can still sometimes be followed by high variability in return bloom the next. Moreover, the fundamental mechanisms that drive this behavior are poorly understood. The two primary hypotheses of biennial bearing consider hormonal control and resource competition for carbohydrates and nutrients. Through reviewing the current literature and gaining a better understanding of carbohydrate and hormone cycling/signaling within trees, a framework for biennial bearing control can be developed. With an understanding of the physiological responses contributing to biennial bearing patterns, manipulation of carbohydrate and nutrient cycling within trees through management practices may influence flowering and fruit bud formation. Improved management practices of biennial bearing can be evaluated and adjusted to suit different planting systems and species.
... It may be the grafted plants had a greater ability to operate stomata more efficiently under stress conditions. A vital challenge for water stress mitigation is modulating transpiration through stomata (Casagrande Biasuz and Kalcsits, 2022). Marguerit et al. (2012) reported that rootstock controlled the transpiration rate under water deficit conditions through independent genetic controls because no specific QTLs to these effects were recognized on the grapevine. ...
Hot and humid climatic conditions offer challenges for tomato production under protected environments. The lack of stress tolerance cultivars and their pollen and plant ability to increase fruit set and yield are linked with lower tomato yield under abiotic stress conditions. Therefore, three management approaches, cultivar selection, grafting, and plant density of organically grown hydroponic tomatoes, were evaluated on growth, yield, and quality in a controlled environments greenhouse in Qatar. The experiment was carried out in a split-split plot design with ‘Velocity F1’ and ‘Sigma F1’ as main plot treatments; and a factorial arrangement of grafting combination and planting densities (3.5 and 5.5 plants m‑2) was randomly assigned to the subplots. Tomato cultivar ‘Velocity F1’ grafted on ‘Maxifort F1’ resulted in greater vegetative growth and enhanced phenological traits than non-grafted ‘Velocity F1’ Grafted ‘Velocity F1’ plants grown at 3.5 plants m‑2 had an increase in leaf photosynthetic rates (18%), and less transpiration loss (16%), while maintaining stomatal conductance and intercellular CO2 concentrations. Also, canopy growth was higher (24%), and flowering occurred 3 days earlier with grafted ‘Velocity F1’ than with non-grafted transplants. Higher fruit set (20%) and less flower drop (17%) were also observed in grafted ‘Velocity F1’ transplants than in non-grafted transplants. Therefore, under this protected environment and hydroponic system, grafted tomato ‘Velocity F1’ grown at 3.5 plants m‑2 was the best management strategy to improve growth and mitigate abiotic stresses.
... G.890 was the most vigorous of the four rootstocks used in this study which is consistent with previous rootstock research Kviklys et al., 2014;Valverdi and Kalcsits, 2021). B.9 was expected to have the lowest vigor (Czynczyk et al., 2000;Casagrande Biasuz and Kalcsits, 2022). However, M.9 was significantly smaller than the other rootstocks. ...
... Like what was observed previously (Biasuz and Kalcsits, 2022), d 13 C was related to shoot vigor. Carbon isotope composition can indicate differences in intrinsic water-use efficiency (Goncalves et al, 2007;Seibt et al, 2008;Martıńez-Alcańtara et al, 2013;Foster et al, 2017;. ...
... Under greenhouse conditions in this study, there were no consistent trends in the association between rootstock-induced vigor and stomatal conductance or stem water potential. The controlled conditions of this study may have dulled previously reported rootstock responses (Casagrande Biasuz and Kalcsits, 2022). Other studies had compared water potential among dwarfing and vigorous rootstocks under different soil conditions. ...
Rootstocks are used in modern apple production to increase productivity, abiotic and biotic stress tolerance, and fruit quality. While dwarfing for apple rootstocks has been well characterized, the physiological mechanisms controlling dwarfing have not. Previous research has reported rootstock effects on scion water relations. Root architecture and variability in soil moisture across rooting depths can also contribute to these differences among rootstocks in the field. To exclude these effects on rootstock behavior, scions were grafted onto four different rootstocks with varying effects on scion vigor (B.9, M.9, G.41 and G.890). Non-grafted rootstocks were also grown to examine whether the effects of rootstock occurred independently from scion grafting. Plants were grown in a greenhouse under near steady-state hydroponic conditions. Carbon (δ¹³C), oxygen (δ¹⁸O) and nitrogen (δ¹⁵N) isotope composition were evaluated and relationships with carbon assimilation, water relations, and shoot growth were tested. Rootstocks affected scion shoot growth, aligning with known levels of vigor for these four rootstocks, and were consistent between the two scion cultivars. Furthermore, changes in water relations influenced by rootstock genotype significantly affected leaf, stem, and root δ¹³C, δ¹⁸O, and δ¹⁵N. Lower δ¹³C and δ¹⁸O were inconsistently associated with rootstock genotypes with higher vigor in leaves, stems, and roots. G.41 had lower δ¹⁵N in roots, stems, and leaves in both grafted and ungrafted trees. The effects of rootstock on aboveground water relations were also similar for leaves of ungrafted rootstocks. This study provides further evidence that dwarfing for apple rootstocks is linked with physiological limitations to water delivery to the developing scion.
... Other functional effects of apple rootstocks on the scion include water potential, leaf gas exchange and carbon isotope signatures. Casagrande Biasuz and Kalcsits (2022) studied 9 apple rootstocks grafted with a cultivar Honeycrisp scion. Rootstocks with a high dwarfing capacity had lower stem water potential, lower net CO 2 assimilation, and lower stomatal conductance than the more vigorous rootstocks. ...
The grafting of apple rootstocks on to scions confers benefits including reduced tree size/dwarfing for trellis based growing systems, increased tolerance to physiological stress, and pest and disease management. The current study investigated the effect of rootstock selection on canker and tree death using eight common rootstocks M9 337, M9 337 with Golden Delicious (GD) interstock, M9 EMLA, MM106, M116, M26, Geneva ® G11 and G41, in addition to six advanced selections from the NIAB East Malling apple breeding programme EMR-001—EMR-006, all grafted with Gala scions. One of the rootstocks, M9 377 was also grafted with a GD interstock. Two locations in England were selected, the first at East Malling, Kent, the second, at Newent, Gloucestershire. Several variables were analysed including cumulative numbers of dead trees per rootstock from 2017 to 2020, number of rootstock ‘A type’ cankers, number of scion mainstem ‘B type’ cankers, and number of peripheral ‘C + D + E’ branch cankers at the Kent and Gloucestershire locations in the fourth and final assessment year of 2020. Kendall’s rank correlation was used to test if trunk circumference (a measure of tree vigour) and canker were statistically dependant. Results showed that in Kent, there were significant differences between rootstocks for scion B cankers and peripheral C + D + E cankers. There were no significant differences found between rootstocks for rootstock A cankers at Kent, or any of the three canker types in Gloucestershire. There were up to 31.25% dead trees in Kent (EMR-004), and 30% in Gloucestershire (M9 337 with GD interstock, M26), but there were no significant differences in number of dead trees due to rootstock type in either Kent or Gloucestershire. The Kendall’s rank correlation analysis indicated there was almost no dependence of trunk circumference on canker. The three rootstocks with the overall lowest susceptibility to canker were M116, EMR-006, and EMR-004. The industry standard rootstocks M9 EMLA and M9 337 were ranked 12 and 14, and with EMR-001 were the three worst performing rootstocks. The Geneva ® rootstocks G11 was ranked 6, and G41 was ranked 11. An interplay of factors are likely involved in the development of canker including location and environmental effects—rainfall, relative humidity, temperature, wind, soil type, topography, aspect, and other seasonal infection processes including pathogen inoculum load, and rainsplash of inoculum between trees and within individual trees, the genetics and physiology of each scion/rootstock combination, water and nutritional status of trees, hormonal and molecular signalling, and orchard management including pruning and removal of cankers.
... The vegetative propagation of rootstock and scion allows to choose tolerant genotypes to pests, diseases, drought, and waterlogging, in addition to stimulate the vigor of trees and peach yield (Paula et al., 2011;Klumb et al., 2017;Yordanov et al., 2018;Beckman et al., 2019;Hayat et al., 2020;Mayer et al., 2021a). In the Rosaceae family, the effects of rootstock on tree vigor are more notable on apple (Biasuz & Kalcsits, 2022), plum (Wolf et al., 2019), and apricot (Yordanov et al., 2018) than on peach (Zhivondov et al., 2017;Szymajda et al., 2020). This way, identifying peach rootstock genotypes with different levels of vigor can be useful for different tree densities and training systems. ...
... Nursery trees grafted on EF-SAU-10-78 had their aerial part smaller than those on 'Okinawa', a vigorous rootstock (Table 1). The influence of the rootstock on the trees is well documented for several fruit trees specie, as follows: apple (Zhang et al., 2015;Biasuz & Kalcsits, 2022); plum (Wolf et al., 2019); and for peach trees, in which Zhivondov et al. (2017) also observed a lower vigor of the scion cultivar Baby Gold 9, grafted on n.° 9-205 (clonal rootstock) than on 'Elberta' (seedlings). Differences in vigor (also expressed by collar stem diameter) among rootstocks are related to water and nutrient use efficiency, which results in differences for the synthesis of carbohydrates (Klumb et al., 2017). ...
The objective of this work was to evaluate the effect of the use of rootstocks from clonal and seed production systems on the morphology of nursery peach trees of cultivar Granada. The experiment was carried out in a completely randomized design with five treatments ('Granada' scion grafted onto five rootstocks) and five replicates. The rootstocks from clonal production were the 'Okinawa' peach plant and the GKM-ELD-10-70, EF-SAU-10-78, and EF-SAU-10-87 peach genotypes kept in pots. The rootstocks from the seed production system came from peach seed of some scion varieties (mixed pits) used for canning production and propagated in a nursery field system. Shoot and root morphological variables were evaluated. The rootstock production system did not affect root volume. However, the nursery trees of the clonal rootstocks system kept in pots showed a higher percentage of water in the roots. The clonal rootstocks in the potted system do not affect most of the morphological traits of 'Granada' peach nursery trees; however, they induce a homogeneous root system and delay leaf abscission, besides not requiring root pruning.
... It may be possible that grafted plants had a greater ability to operate stomata more efficiently under stress conditions. A vital challenge for water stress mitigation is modulating transpiration through stomata (Biasuz and Kalcsits 2022). Marguerit et al. (2012) reported that rootstock controlled the transpiration rate under water deficit conditions through independent genetic controls because no specific quantitative trait loci for these Fig. 5. Effects of grafting and cultivar on the transpiration rate (A), assimilation rate (B), intercellular CO 2 (C), and stomatal conductance (D) of tomato. ...
Hot and humid conditions create challenges for tomato production under a controlled environment. Low tomato productivity is related to the lack of stress tolerance of existing cultivars and their ability to maximize fruit set and yield. The aim of this study was to evaluate the effectiveness of three management strategies, cultivar selection, grafting, and plant density, for the growth and production efficiency of organically grown hydroponic tomatoes under adverse environmental conditions in Qatar. The experiment used a split-split plot design with ‘Velocity F1’ and ‘Sigma F1’ as the main plot treatments and a factorial arrangement of grafting combinations and planting densities (3.5 and 5.5 plants/m2) as subplots. Tomato cultivar Velocity F1 grafted on Maxifort F1 resulted in greater vegetative growth and improved phenological attributes than nongrafted Velocity F1. Grafted ‘Velocity F1’ plants grown at 3.5 plants/m2 had an increase in leaf photosynthetic rates (18%), less transpiration loss (16%), and less electrolyte leakage (15%) while maintaining stomatal conductance and intercellular CO2 concentrations. At 9 weeks after transplanting, canopy growth was higher (24%) and flowering occurred earlier (3 days) with grafted ‘Velocity F1’ transplants than with nongrafted transplants. Higher fruit sets (20%), pollen viability (22%), and fewer flower drops (17%) were also observed for grafted ‘Velocity F1’ transplants than for nongrafted transplants. Marketable fruit yields were higher (26%) with grafted ‘Velocity F1’ grown at 3.5 plants/m2 than with nongrafted ‘Velocity F1’. Both grafted ‘Velocity F1’ and ‘Sigma F1’ fruits retained acceptable fruit color (L*, a*, b*, C*, °h), firmness, °Brix, titratable acidity, weight, and prolonged shelf life by 4 additional days than nongrafted ones. We conclude that grafted tomato ‘Velocity F1’ grown at a plant density of 3.5 plants/m2 was the best management strategy for enhancing seedlings quality, plant growth, and postharvest quality and alleviating abiotic stresses under this protected environment and hydroponic system.
... The enrichment of the leaf tissue with 13 C indicates moisture deficits. The ∆ 13 C value has been used in recent decades as an indicator of water stress and as a possible selection trait for selecting tolerant or adaptable crop genotypes, including fruit trees [6,[12][13][14]. The natural discrimination of 13 C integrates water availability effects on a plant in the long term, which has its advantages and disadvantages in comparison with the methods that determine the actual status of plants. ...
... The author did not observe a clear effect of irrigation (70% of pan evaporation) on leaf and shoot ∆ 13 C values in studies conducted on 'Empire' apples [6,15]. Biasuz et al. [14] reported a rather low range of ∆ 13 C values, 17-19‰, for 'Honeycrisp' apple leaves under irrigation replacing 110% of the estimated evapotranspiration levels during the growing season. In our experiment, the ∆ 13 C fell under 20.5‰ ...
... Plant reactions to different water availability levels often differ among cultivars due to numerous interacting factors and morphological and physiological traits. As a result, cultivar differences may be expected in the effect of irrigation on ∆ 13 C [14,52,53]. The presented results for the four-year experiment were obtained from one apple cultivar, 'Red Jonaprince'; thus, more or less different results, compared to other cultivars and/or rootstocks, are also probable. ...
13C discrimination (Δ13C) has been used in research as an indicator of water availability in crops; however, few data are available concerning fruit trees. The aim of this study was to examine the effect of irrigation on the Δ13C values of apple leaves. We assumed that Δ13C would increase with irrigation intensity. The Δ13C of apple trees (Malus domestica) cv. ‘Red Jonaprince’ was determined in the years 2019–2022. Leaf samples were collected in spring, in June, at the beginning of the irrigation campaign, and in autumn, in September, following the harvest. The irrigation doses were applied to replenish the water consumption, 0% (ET0), 50% (ET50), 75% (ET75), and 100% (ET100), of the calculated evapotranspiration (ET) levels. In November, the leaves collected from different positions on the shoots were sampled, assuming the Δ13C signature would reflect the changes occurring in the water supply during their growth. The irrigation rates had a significant effect on the Δ13C of the leaves when the data for the spring and summer months were pooled. On average, Δ13C increased from 20.77‰ and 20.73‰ for ET0 and ET50, respectively, to 20.80‰ and 20.95‰ for ET75 and ET100, respectively. When the data obtained for the spring and summer months were analysed separately, the effect of irrigation was weak (p < 0.043). The Δ13C value was always higher for treatment ET100 than treatment ET0, for individual experimental years and terms; however, the differences were minor and mostly insignificant. The leaf position had a strong significant effect on Δ13C; the values gradually decreased from the leaves growing from two-years-old branches (22.50‰) to the youngest leaves growing at the top of the current year’s shoots (21.07‰). This order was similar for all the experimental years. The results of the experiment suggest that 13C discrimination in apples is affected not only by water availability during growth, but also by the use of C absorbed in previous years.
... Tree water status is an interaction between environmental conditions (primarily vapor pressure deficit), soil water content, light interception, crop and plant development management, irrigation and weeds, and the physiological characteristics of a species [11][12][13]. Currently, soil moisture monitoring, estimates of evapotranspiration from weather data, fruit growth rates, and sap flow measurements are used to estimate plant water needs and schedule irrigation. ...
The weather variations around the world are already having a profound impact on agricultural production. This impacts apple production and the quality of the product. Through agricultural precision, growers attempt to optimize both yield and fruit size and quality. Two experiments were conducted using field-grown “Gala” apple trees in Geneva, NY, USA, in 2021 and 2022. Mature apple trees (Malus × domestica Borkh. cv. Ultima “Gala”) grafted onto G.11 rootstock planted in 2015 were used for the experiment. Our goal was to establish a relationship between stem water potential (Ψtrunk), which was continuously measured using microtensiometers, and the growth rate of apple fruits, measured continuously using dendrometers throughout the growing season. The second objective was to develop thresholds for Ψtrunk to determine when to irrigate apple trees. The economic impacts of different irrigation regimes were evaluated. Three different water regimes were compared (full irrigation, rainfed and rain exclusion to induce water stress). Trees subjected the rain-exclusion treatment were not irrigated during the whole season, except in the spring (April and May; 126 mm in 2021 and 100 mm in 2022); that is, these trees did not receive water during June, July, August and half of September. Trees subjected to the rainfed treatment received only rainwater (515 mm in 2021 and 382 mm in 2022). The fully irrigated trees received rain but were also irrigated by drip irrigation (515 mm in 2021 and 565 mm in 2022). Moreover, all trees received the same amount of water out of season in autumn and winter (245 mm in 2021 and 283 mm in 2022). The microtensiometer sensors detected differences in Ψtrunk among our treatments over the entire growing season. In both years, experimental trees with the same trunk cross-section area (TCSA) were selected (23–25 cm−2 TCSA), and crop load was adjusted to 7 fruits·cm−2 TCSA in 2021 and 8.5 fruits·cm−2 TCSA in 2022. However, the irrigated trees showed the highest fruit growth rates and final fruit weight (157 g and 70 mm), followed by the rainfed only treatment (132 g and 66 mm), while the rain-exclusion treatment had the lowest fruit growth rate and final fruit size (107 g and 61 mm). The hourly fruit shrinking and swelling rate (mm·h−1) measured with dendrometers and the hourly Ψtrunk (bar) measured with microtensiometers were correlated. We developed a logistic model to correlate Ψtrunk and fruit growth rate (g·h−1), which suggested a critical value of −9.7 bars for Ψtrunk, above which there were no negative effects on fruit growth rate due to water stress in the relatively humid conditions of New York State. A support vector machine model and a multiple regression model were developed to predict daytime hourly Ψtrunk with radiation and VPD as input variables. Yield and fruit size were converted to crop value, which showed that managing water stress with irrigation during dry periods improved crop value in the humid climate of New York State.
... When the internal concentration of CO 2 within the leaf tissue decreases due to reduced stomatal conductance, more 13 CO 2 is incorporated into photosynthate and the 13 C of leaf tissue increases [28]. Previous studies have demonstrated the relationship between lower Ψ stem (more negative) or drought stress and higher leaf δ 13 C‰ (less negative) [27,[29][30][31]. Leaf δ 13 C‰ in both asymptomatic and declining trees was particularly high at Site A (Figure 3), suggesting water was less available to the trees at this site, as 13 C-enriched leaf tissue is consistent with a reduction in available intracellular CO 2 due to partial stomatal closure caused by water deficit [28]. ...
In the last decade, a sporadic tree health syndrome affecting high-density apple plantings in North America has become known as Rapid Apple Decline (RAD) or Sudden Apple Decline (SAD). The affected apple trees were typically grafted on small dwarfing rootstocks, often displayed necrosis at the graft union, and suffered from sudden mortality that occurred over 2-3 weeks amid the growing season or a gradual decline. In 2019 and 2020, we conducted a multi-site investigation in the south Okanagan, British Columbia, Canada, to assess the stem hydraulic characteristics, stomatal conductance, leaf δ 13 C‰, and fruit dry matter accumulation of the declining trees during disease progression. In trees that died, mortality appeared to be associated with severe disruption in xylem water transport at the damaged graft union, followed by abrupt hydraulic failure. In contrast, symptomatic trees that did not die exhibited the moderately declined plant water relations and a reduction in fruit dry matter accumulation followed by either further deterioration or eventual recovery. This pattern indicates the risk of carbohydrate depletion over gradual hydraulic decline and the importance of timely horticultural remedies. In the present study, we discuss potential horticultural practices to mitigate hydraulic dysfunctions and enhance crop tolerance.
