Influence of Scion/Rootstock reciprocal effects on post-harvest and metabolomics regulation in stored peaches

Peach is an important stone fruit crop cultivated at commercial scale in Pakistan. While, appropriate selection of rootstock has significant impact on the quality of peach fruit. Therefore, in the current study the influence of three rootstocks viz. ‘GF-677′, ‘Peshawar Local’ and ‘Swat Local’ were evaluated on the quality of ‘Flordaking’ peaches following cold storage during two consecutive years. The fruit from these rootstocks were kept at 0 °C for five weeks were studied for various fruit physical (weight loss, colour, firmness) and biochemical (pH, soluble solids content (SSC), titratable acidity (TA), SSC:TA ratio, fruit juice pH, sugars (total, reducing and non-reducing sugars), ascorbic acid (vitamin C) and free radicals scavenging activities) were evaluated. During both years, fruit harvested form trees grafted on ‘GF-677′ exhibited reduced fruit weight loss, changes in Chroma (C*) and highest fruit firmness, Lightness (L*), ascorbic acid contents and radical scavenging activities as compared to fruit harvested from tree grafted on other rootstocks. In conclusion, the post-harvest quality of scion ‘Flordaking’ peach fruit was significantly influenced and best quality can be obtained when it is grafted on ‘GF-677′ rootstock.     

Differences in Strain Virulence of the European Stone Fruit Yellows Phytoplasma and Susceptibility of Stone Fruit Trees on Various Rootstocks to this Pathogen

Twenty strains of the European stone fruit yellows (ESFY) phytoplasma showed great differences in virulence when examined by graft inoculation of trees on peach, peach hybrid GF 677 and P. 'Marianna' GF 8/1 rootstocks. The most virulent strains killed all trees on peach rootstocks whereas the mild strains did not cause mortality but induced only mild foliar symptoms and slightly reduced vigour. Virulence often depended on the pathogen–scion combination and was in several cases most severe when the scion consisted of the original host of the pathogen. To examine resistance in stone fruits, trees on a total of 23 rootstocks were inoculated with the ESFY strains. Trees on the Prunus domestica stocks Ackermann's, Brompton and P 1275 and on Prunus cerasifera stock Myrabi were little affected. Slightly more damage occurred in trees on rootstocks GF 677, GF 8–1, and the P. insititia stocks St Julien A and St Julien GF 655/2. Ishtara, P. cerasifera stock Myrobalan, and peach rootstocks Higama and GF 305 were shown to be moderately susceptible and a high susceptibility was found in trees on peach rootstocks Montclar, peach seedling, Rutgers Red Leaf, and Rubira, on apricot seedlings and St Julien 2. Of flowering cherry trees on various rootstocks, the least susceptible were those on Gisela 3 and F 12/1 whereas Gisela 1, Weihroot 158 and Gisela 5 were more affected. Phytoplasmas were detected by either DAPI (4'-6-diamidino-2-phenylindole) staining or polymerase chain reaction in all rootstocks and scions tested. However, detection frequency and phytoplasma concentrations were usually lower in the more tolerant hosts than in susceptible genotypes.     

Relative Resistance of Four Peach Rootstocks to Phytophthora cactorum and Phytophthora megasperma

Shoot samples of four peach rootstocks that are important to the peach industry in Greece: KID I, GF305, GF677, and PR204, were inoculated with Phytophthora cactorum and Phytophthora megasperma in the field and in the glasshouse and were then evaluated with regard to susceptibility. The pathogenicity of P. cactorum and P. megasperma to peach rootstocks was confirmed with an excised twig assay. The peach rootstocks showed differential susceptibility to P. cactorum . GF305 was the least susceptible and KID I was the most susceptible, which suggests that the latter rootstock is unsuitable for orchards in which the conditions are favourable for Phytophthora diseases. GF677 and PR204 were moderately susceptible. The plants that were inoculated with P. megasperma in the field and in the glasshouse showed no sign of infection whereas twigs inoculated in vitro with P. megasperma developed necrosis. GF305 was the most resistant, KID I was the most susceptible and PR204 and GF677 were moderately resistant. The present results demonstrate that none of the four peach rootstocks used in this study was completely resistant to P. cactorum , particularly when rootstocks were flooded periodically to enhance disease development. Therefore an integrated approach including host and resistance cultural practices is recommended to manage diseases caused by P. cactorum in peach orchards in Greece.     

The relationship of hydraulic conductance to root system characteristics of peach (Prunus persica) rootstocks

Specific rootstocks can differentially influence the vegetative growth and development of fruit trees. However, the physiological mechanism involved in this phenomenon has been elusive. Recent research comparing different peach ( Prunus persica L. Batsch) rootstocks suggests that the rootstock effect on vegetative growth in peach trees is associated to water relations and more specifically to differences in rootstock hydraulic conductance. This study was intended to confirm differences in hydraulic characteristics of similar size peach trees grafted on different rootstocks and to examine root system characteristics that could be associated with rootstock hydraulic limitations. Trees on rootstocks that were known to have a size-controlling effect when grown under field conditions had lower rootstock conductance than trees on the vigorous (control) rootstock when rootstock hydraulic conductance was measured with both the high-pressure and evaporative flow methods. Rootstocks with the lowest hydraulic conductance had less fine root surface area and length per unit root dry weight than the more vigorous (control) rootstock. However, contrary to previous field studies, in this study there were no significant differences in dry matter production and distribution among trees on the different rootstocks suggesting that whatever the normal growth control mechanism was, it did not differentially influence growth under the specific conditions of this study. This research confirmed that peach rootstocks exhibiting size-controlling behavior under field conditions differed in their hydraulic and morphological characteristics under controlled growth conditions even when those growth conditions negated the expression of the size-controlling behavior.     

Susceptibility of Prunus rootstocks against Marcus and Dideron isolates of Plum pox virus by graft‐inoculation

Sharka (Plum pox virus, PPV) is one of the most important diseases affecting stone fruits. While there is much information on the reaction of cultivars to PPV infection, details about rootstocks are scarce. In this study, we evaluated 28 stone fruit rootstocks belonging to different Prunus species against the Marcus and Dideron strains of PPV. Rootstocks were evaluated under controlled conditions during two growing seasons using two inoculation methods: direct inoculation of own‐rooted rootstocks and grafting onto PPV‐infected GF305 peach seedlings. Our results showed a generalised susceptibility of the rootstocks evaluated. Evaluating own‐rooted rootstocks was more efficient than the traditional method of grafting onto infected GF305 seedlings. As expected, PPV‐M was found to be more aggressive than PPV‐D, producing symptoms and occurring in a higher number of plants, as shown by ELISA. The most susceptible rootstocks were Myran, Viking, Myro pg Pecher, Julior, Myrobolan 29C, Rubira, Myrobolan B, MrS 2/5, Jaspi and MP8. The least susceptible were GF677, Myrotop, Citation and ZH6. These results highlight the necessity to breed PPV‐resistant rootstocks for the different stone fruit species.     

Possible involvement of polyphenols and polyamines in salt tolerance of almond rootstocks

Leaf physiological and biochemical adaptive strategies and more particularly the possible involvement of polyamines and polyphenols in salt stress tolerance were investigated. Three almond rootstocks (GN15, GF677 and bitter almond) were subjected to 0, 25, 50 and 75 mM NaCl for 30 days. The dry mass of leaves, stems and roots decreased with increasing salt concentration in the irrigation solution regardless of genotype. Photosynthetic assimilation rate decreased in the three almond rootstocks, but more so in GF677 and bitter almond. The accumulation of toxic ions was greater in the leaves than in the roots in all genotypes. GN15 accumulated less Na⁺ and Cl⁻ than GF677 and bitter almond. GF677 accumulated polyphenols, but had less anthocyanin and antioxidant activity in its leaves compared to bitter almond. It seems that GN15 was more able to tolerate the excess of toxic ions using anthocyanins which are abundant in its red leaves and free polyamines for a more efficient response to stress. However, most of the antioxidant activity was found in the leaves and was lower in the roots. Given that the upper part of the tree will be of a different cultivar after grafting, this advantage may not be relevant for the tree’s survival. GF677 showed a different antioxidant strategy; it maintained a stable carotenoids content and accumulated polyphenols in its leaves. The three rootstocks used different strategies to deal with the excess of salt in the growth medium.     

Characterization of the tolerance to iron chlorosis in different peach rootstocks grown in nutrient solution

Iron chlorosis is an important problem in peach trees, but differences exist between peach rootstocks in their tolerance to Fe chlorosis in calcareous soils. The purpose of this investigation was to characterize the tolerance of different rootstocks to Fe chlorosis induced by bicarbonate in nutrient solution. The rootstocks studied included peach (Nemaguard), plums (Brompton, San Julian A and Puebla de Soto 101) and almond × peach hybrids (Adafuel and GF677). Young plants obtained from rooted cuttings or from in vitro culture techniques were grown individually, under controlled conditions, in flasks with 700 mL of aerated nutrient solution low in iron and with or without 10 mM bicarbonate or 10 mM phosphate. Susceptiblity to bicarbonate-induced chlorosis was inversely correlated with both the Fe content in young leaves and the reducing capacity of roots, but not with the phosphorus content in young leaves. The plum Puebla de Soto 101 and the hybrid GF677 showed the lowest degree of chlorosis and the highest reducing capacity. Phosphate did not induce chlorosis.     

Responses of two Prunus rootstocks to KCl induced salinity in vitro

The in vitro response of two Prunus rootstocks: GF 677 (Prunus persica × Prunus amygdalus), and Nemared (Prunus persica) to increasing concentrations of KCl of the culture medium was studied. Shoots were grown in vitro for 8 weeks on an Murashige and Skoog medium supplemented with 0, 5, 10, 15, 20, 40 or 80 mM KCl. By increasing KCl concentration from 0 to 40 mM, the number of shoots per explant was not significantly affected for both rootstocks. However, Nemared rootstock formed more shoots per explant than GF 677 under respective KCl concentrations of the medium. Inclusion of 80 mM KCl in the medium resulted in a reduction of growth of both rootstocks. Sodium, Fe, Mn, and Zn concentration in tissues of Nemared rootstock were significantly higher than the respective values of GF 677.     

Growth characteristics and phenylalanine ammonia-lyase activity in peach grafted on different Prunus spp.

Phenylalanine ammonia lyase (PAL) is a key enzyme in the phenylpropanoid pathway responsible for biosynthesis of many secondary metabolites, such as anthocyanins, flavanols, and lignins. The objective of this work was to determine the effect of different rootstock/scion combinations on Prunus tree growth, PAL gene expression, and PAL activity in order to identify compatibility of different graft combinations. The study was performed with peach (P. persica cv. Chimarrita) grafted on two peach rootstocks (Capdeboscq and Tsukuba1) and one Japanese apricot (P. mume cv. Umezeiro). Two or three years after grafting, the growth of peach scion on Umezeiro was weak and finally the death of some trees occurred. The peach rootstocks induced vigorous growth without any tree loss through the three years of evaluation. However, PAL activity and expression of PAL encoding genes were higher in Umezeiro as compared to the other rootstocks. These results show that the differential gene expression together with the PAL activity is a promising strategy to predict graft incompatibility.     

Gas exchange,water relations and osmotic adjustment in two scion/rootstock combinations of Prunus under various salinity concentrations

Plant and Soil - Growth, gas exchange and water relations have been studied on hydroponically grown peach (cv. Armking) plants, grafted on GF677 (Arm/GF) and Mr.S.2/5 (Arm/MrS), exposed to 0, 40,...     

L'epoca Della Differenziazione Delle Gemme Fiorali Nell'olivo

Abstract

Calcium, as in general for all plants, is very important for fruit trees and a tight correlation between leaf content and cropping efficiency has been found.

The annual removal of calcium oxide of an orchard has been estimated in kg per hectare: pear 200, apple 180, peach 150, grape 60–130, olive 35–70, kiwi 55–60.

The rootstock affects the calcium uptake from the soil and content of the scion; frequently a higher calcium content is found in trees grafted an dwarfing rootstocks as pear on quince, apple on M9 and M26, peach on Damas.

By the horticultural point of view, calcium is responsible of two main problems: chlorosis due to high active Ca content in the soil and bitter pit, on the apposite, due to a low Ca level in the fruits.

From soil and leaf studies it seems clear that lime-induced Fe chlorosis results from two conditions: a) slow availability of Fe in the soil, and b) immobilization of Fe in the tree in forms that are not available for chlorophyll formation.

Breeding tolerant rootstocks has been the practical solution of chlorosis for most of the susceptible species.

Bitter pit is a physiological disorder of apple fruits, sometime already evident before picking, more frequently after harvesting, during the storage.

The prevention of the disorder is, essentially, a good horticultural practice (pruning, fertilization, irrigation, fruit thinning). Very effective are also Ca sprays as chloride or nitrate, or citrate, or phosphate, starting after setting, 4–5 times every 10–12 days.     

Variation in the content of bioflavonoids of orange as affected by scion,rootstock, and fruit part

Fruits of citrus cultivars contain bioflavonoids and some other important secondary metabolites in pharmaceutical and nutritional industries. The present experiment was designed to investigate the correlation between the content of flavonoid components like naringin, hesperidin, and neohesperidin of the scions fruits and the same parameters in rootstocks fruits. Six-year-old trees including four citrus cultivars of ‘Moro’, ‘Mars’, ‘Salustiana’, and ‘Italian’ which were previously grafted on the four different rootstocks including ‘Yuzu’, ‘Shelmahalleh’, ‘Citromelo’, and ‘Sour orange’ were selected as experimental trees. The content of the mentioned flavonoids was investigated in the peel and pulp of the fruits of both scions and rootstocks. The results showed that the measured parameters were significantly influenced by scions, rootstocks, and tissues. Based on the obtained results, it can be suggested that the accumulation of chemicals in citrus fruit depends on genetic and inherent abilities of the scion, more than what was previously believed, while the rootstock can also play an important role in the accumulation of these substances.     

Evaluation of Resistance of Stone Fruit Rootstocks to Phytophthora Crown Rot*

The pathogenicity of Phytophthora citrophthora, Phy‐tophthora cactorum and Phytophthora megasperma strains was confirmed on 2‐year‐old stone fruit rootstocks artificially inoculated in the field. Phytophthora mega‐sperma was not virulent or less virulent than P. cactorum or P. citrophthora. The rootstocks Damas and AN 1/7 were resistant whereas the rootstocks Jl, Titan x Nemaguard 5/1, GF 677, Myrandier 613, Italian x Nemaguard 1 and Myrandier 617 were susceptible to P. citrophthora. The rootstocks Tsukuba 9, Tit‐an x Nemaguard 4/7, AN 1/2, AN 1/3, St. Mien 655/2 and Bl showed medium susceptibility to this species. The isolates of P. cactorum induced more extensive necrosis in Myrandier 617 and Italian x Nemaguard than in Myr‐andier 613, GF 677, Jl (ADAFUEL), Tsukuba 9 and St. Julien 655/2. Among seven rootstocks, Tsukuba 5 and St. Julien 655/2 were more resistant than Myrandier 613, Myrandier 617, Jl (ADAFUEL), Tsukuba 9 and St. Julien 655/2.     

Grafting improves cucumber water stress tolerance in Saudi Arabia

Water scarcity is a major limiting factor for crop productivity in arid and semi-arid areas. Grafting elite commercial cultivars onto selected vigorous rootstocks is considered as a useful strategy to alleviate the impact of environmental stresses. This study aims to investigate the feasibility of using grafting to improve fruit yield and quality of cucumber under water stress conditions. Alosama F₁ cucumber cultivar (Cucumis sativus L.) was grafted onto Affyne (Cucumis sativus L.) and Shintoza A90 (Cucurbitamaxima × C. moschata) rootstocks. Non-grafted plants were used as control. All genotypes were grown under three surface drip irrigation regimes: 50%, 75% and 100% of the crop evapotranspiration (ETc), which represent high-water stress, moderate-water stress and non-water stress conditions, respectively. Yield and fruit quality traits were analyzed and assessed. In comparison to the non-grafted plants, the best grafting treatment under water stress was Alosama F₁ grafted onto Shintoza A90 rootstock. It had an overall improved yield and fruit quality under water stress owing to an increase in the total fruit yield by 27%, from 4.815 kg plant^?1 in non-grafted treatment to 6.149 kg plant^?1 in grafted treatment under moderate -water stress, total soluble solid contents (13%), titratable acidity (39%) and vitamin C (33%). The soil water contents were low in soil surface and increase gradually with soil depth, while salt distribution showed an adverse trend. The positive effects of grafting on plant growth, productivity, and water use efficiency support this strategy as an useful tool for improving water stress tolerance in greenhouse grown cucumber in Saudi Arabia.     

Grafting raises the salt tolerance of tomato through limiting the transport of sodium and chloride to the shoot

With the aim of determining whether grafting could improve salinity tolerance of tomato (Lycopersicon esculentum Mill.), and what characteristics of the rootstock were required to increase the salt tolerance of the shoot, a commercial tomato hybrid (cv. Jaguar) was grafted onto the roots of several tomato genotypes with different potentials to exclude saline ions. The rootstock effect was assessed by growing plants at different NaCl concentrations (0, 25, 50, and 75 mM NaCl) under greenhouse conditions, and by determining the fruit yield and the leaf physiological changes induced by the rootstock after 60 d and 90 d of salt treatment. The grafting process itself did not affect the fruit yield, as non-grafted plants of cv. Jaguar and those grafted onto their own root showed the same yield over time under non-saline conditions. However, grafting raised fruit yield in Jaguar on most rootstocks, although the positive effect induced by the rootstock was lower at 25 mM NaCl than at 50 and 75 mM NaCl. At these higher levels, the plants grafted onto Radja, Pera and the hybrid VolgogradskijxPera increased their yields by approximately 80%, with respect to the Jaguar plants. The tolerance induced by the rootstock in the shoot was related to ionic rather than osmotic stress caused by salinity, as the differential fruit yield responses among graft combinations were mainly related to the different abilities of rootstocks to regulate the transport of saline ions. This was corroborated by the high negative correlation found between fruit yield and the leaf Na(+) or Cl(-) concentrations in salt-treated plants after 90 d of salt treatment. In conclusion, grafting provides an alternative way to enhance salt tolerance, determined as fruit yield, in the tomato, and evidence is reported that the rootstock is able to reduce ionic stress.     

Scion and Rootstock Effects on ABA-mediated Plant Growth Regulation and Salt Tolerance of Acclimated and Unacclimated Potato Genotypes

Tolerance of salt stress in potato (Solanum tuberosum L.) increased when the plants were pre-exposed to low concentrations of salt (salt acclimation). This acclimation was accompanied by increased levels of abscisic acid (ABA) in the shoot. To further study the role of roots and shoots in this acclimation process, reciprocal grafts were made between a salt-tolerant (9506) and salt-sensitive ABA(−) mutant and its ABA(+) normal sibling potato genotype. The grafted plants were acclimated with 75 or 100 mM NaCl for 3 weeks and then exposed to 150–180 mM NaCl, depending on the salt tolerance of the rootstock. After 2 weeks of exposure to the salt stress, the acclimated and unacclimated plants were compared for physiologic and morphologic parameters. The response to the salt stress was strongly influenced by the rootstock. The salt-tolerant 9506 rootstock increased the salt tolerance of scions of both the ABA-deficient mutant and its ABA(+) sibling. This salt tolerance induced by the rootstock was primarily modulated by salt acclimation and manifested in the scion via increased plant water content, stem diameter, dry matter accumulation, stomatal conductivity, and osmotic potential, and is associated with a reduction in leaf necrosis. There was also a pronounced scion effect on the rootstock. Using 9506 as a scion significantly increased root fresh and dry weights, stem diameter, and root water content of ABA(−) mutant rootstocks. Specific evidence was found of the role of exogenous ABA in the enhancement of water status in grafted plants under salt stress beyond that of grafting alone. This was verified by more positive stomatal conductivity and upward water flow in ABA-treated grafted and nongrafted plants and the absence of upward water flow in nontreated grafted plants through NMR imaging. Grafting using either salt-tolerant scions or rootstocks with inherently high ABA levels may positively modify subsequent responses of the plant under salt stress.     

Grafting influence on the weight and quality of tomato fruit under salt stress

Two commercial tomato cultivars were used to determine whether grafting could prevent decrease of fruit weight and quality under salt stress conditions. The cultivars Buran F1 and Berberana F1 were grafted onto rootstock ‘Maxifort’ and grown under three levels of elevated soil salinity (EC 3.80 dS m^?1, 6.95 dS m^?1 and 9.12 dS m^?1). Fruit weight reduction of grafted plants was lower (about 20–30%) in comparison with non‐grafted ones. Salt stress at the second salinity level (EC 6.95 dS m^?1) induced the highest alteration of examined growth and quality parameters. The total increase of phenols, flavonoids, ascorbate and lycopene content in the fruits of both grafted and non‐grafted plants for both cultivars had a similar trend and intensity, though some inter‐cultivar variation was observed. The possibility of grafting tomato plants to improve salt tolerance without fruit quality loss is discussed.     

Investigation of tissue structure and xylem anatomy of eight rootstocks of sweet cherry (Prunus avium L.)

Reduction of crop yield from high water stress is a serious agricultural problem worldwide, which is expected to intensify under future global change scenarios. Efforts are underway worldwide to improve crops resistance to drought. One possible way is the careful choice of rootstock-scion combination. It is well known that water stress symptoms of grafted cherry trees to a large extent depend on the rootstock variety. Scions grafted on dwarf rootstocks show more serious stress symptoms, so it is reasonable to hypothesize that these symptoms and the tissue structure of the rootstock stem are connected. This paper examines this connection for 1-year-old seedlings of eight cherry rootstocks with different degree of vigor. Tissue structure was observed via scanning electron microscope images. Investigations were focused on number, size, and distribution of vessels, because they are principally responsible for water transport. Stem porosity (i.e., the total vessel area relative to the stem area, in cross-sectional view) of the dwarfing rootstocks was found to be significantly smaller than that of the others, supporting the notion that stem anatomical characteristics might contribute to water stress sensitivity.     

猕猴桃品种‘金桃’采收指标与果实软熟品质相关性研究

分别对河南省27个果园的中华猕猴桃（Actinidia chinensis Planch.）品种‘金桃’果实的5项采收生理指标及果实软熟时的8项品质性状进行测定,采用主成分分析法对果实软熟时的品质指标进行综合评分,并对果实的采收生理指标、果实软熟品质指标及综合分值间进行相关性分析。结果显示,采收时的生理指标（干物质、色度角、硬度和可溶性固形物）均与果实软熟品质综合分值间呈极显著相关,其中干物质相关系数最高,为0.437。干物质与体现果实软熟品质的关键指标（可溶性固形物、总糖和糖酸比）均呈极显著性相关。研究结果表明‘金桃’果实采收时,干物质含量是果实软熟时品质的重要评价指标,而可溶性固形物和色度角是评判采收期的辅助指标。     

Grafting under water stress in tomato cherry: improving the fruit yield and quality

As the concentrations of essential vitamins and minerals and a number of other health‐promoting compounds are often low in stable crops, research is under way to understand and increase synthesis of phytochemicals in order to improve crop nutritional quality. The question addressed in this study is whether shoot genotypes or root genotypes with tolerant drought character are able to increase the fruit quality and production under moderate water stress. Zarina (drought tolerant) and Josefina (drought sensitive) were grafted self and reciprocally. The results showed that the use of cv. Zarina (drought tolerant) as rootstock (Zar × Jos) results in a greater number of fruits under water‐stress conditions, a moderate increase in some antioxidant compounds, such as ascorbic acid, phenols and flavonoids and lycopene and β‐carotene, and Zar × Jos showed high levels of sugars and organic acids, sweetness index and sugars : acids ratio, as well as important minerals, such as K and Mg, which could increase its nutritional quality under stress conditions. Overall, the use of drought‐tolerant rootstock could provide a useful tool to improve fruit yield and quality of cherry tomato fruit under moderate water stress, which in turn could mean lower costs in the use of irrigation water.