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The experiment was carried out at a Research Station B / Department of Horticulture and Landscape Gardening/ College of Agricultural Engineering Sciences / University of Baghdad during the growth season 2022-2021 on the seedlings of citrus rootstock Rangpur, seedlings were chosen homogeneous in size as much as possible to study the effect of three factors, The first factor is fertilization with balanced NPK in three concentrations, without addition (F0), 2 gm. seedlings-1 (F1) and 4gm seedlings¹ ( F2) The second factor is the root stimulator with three concentrations, which is without addition ( R0)5 ml L-¹ (R1), and 10 ml L-¹ (R2). The third factor is spraying with two concentrations of Nano-micronutrients without spraying, ( N0), with spraying 1 gm L-¹ (N1). A factorial experiment in a randomized complete block design (RCBD) was carried out, (3 concentrations of NPK x 3 concentrations of Root stimulator x 2 concentrations of Nano-micronutrients) with 3 replicates, and 3 plants in an experimental unit, So that the number of seedlings included in the experiment was 162 seedlings. NPK fertilization showed that there were significant differences in increasing the rates for studied traits, where the concentration (4gm seedlings-1) shows that there were significant differences in plant height, the main stem diameter, Leaves number, leaf area, dry matter percentage of the shoot and chlorophyll concentration values were (46.33 cm, 3.283 mm, 107.06 leaf plant -1, 32.57 cm², 53.22 gm, 2.37 mg gm-1) respectively. As for the root stimulator, the concentration (10 ml L-¹) showed that there were significant differences in plant height, Leaves number, leaf area, the main stem diameter, dry matter percentage of the shoot, and chlorophyll concentration, values were (49.50 cm, 30.28 leaf plant -1, 31.99 cm², 3.433mm, 54.67g, 2.33 mg gm-1) respectively. The Spraying with Nano-micronutrients with concentration 1g L-1 showed the highest rates in plant height, leaf area, main stem diameter, dry matter percentage of shoot, and chlorophyll concentration, values were (44.37 cm, 31.31 cm², 3.037 mm, 50.96 g, 2.29 mg gm-1) respectively compared to other treatments. [ABSTRACT FROM AUTHOR]

Grafting is a technique greatly used in fruit trees and vegetable crops by joining the rootstock of one plant with the scion of another plant. The rootstock is chosen for its ability to provide the scion with a healthy root system that provides not only higher tolerance to abiotic stress conditions but also a stronger resistance against pests and pathogens. Therefore, this study aimed to evaluate the effects of two commonly used rootstocks, sour orange and volkamer lemon, in lemon grafting on population densities and life table parameters of Eutetranychus orientalis (Klein). The results were then related to the chemical identification of polyphenol compounds using HPLC. Significant changes in population density and life table parameters of E. orientalis were observed between the two rootstocks used in lemon grafting. The rootstock sour orange had a high influence on population growth of E. orientalis. Balady limes and adalia lemons grafted onto sour orange showed lower density of E. orientalis movable stages than balady limes grafted onto volkamer lemon. Balady limes and adalia lemons grafted onto sour orange significantly increased the total developmental periods of E. orientalis and decreased the adult longevity period, oviposition period, and the total fecundity of females. The total developmental period was 9.64 and 10.14 days, the adult longevity period was 3.58 and 3.59 days, and the total fecundity of females was 4.59 and 5.50 eggs/female, respectively. Additionally, the use of sour orange in grafting lemon resulted in a decrease in the net (R0) and gross (GRR) reproductive rates, which in turn reduced the intrinsic (r) and finite (λ) rates of increase. The rootstock's high performance may be attributed to the presence of high concentrations of polyphenol compounds that deter feeding and reproduction by E. orientalis. The study suggests that this rootstock can be utilized as a tool in integrated pest management strategies against the citrus brown mite, E. orientalis. When incorporated into an integrated pest control program for E. orientalis in citrus orchards, this technique enhances plant tolerance to infestation, while also ensuring that the output is effective and sustainable. [ABSTRACT FROM AUTHOR]

Somatic hybridization has emerged as a valuable tool for developing novel genetic combinations in citrus breeding programs, including the creation of salt-tolerant rootstocks. In this study, the performance of a tetraploid somatic hybrid, obtained by fusing protoplasts derived from salt-tolerant Cleopatra mandarin (Citrus reshni hort. ex Tanaka) and salt-sensitive Carrizo citrange (Citrus sinensis L. Osbeck × Poncirus trifoliata L. Raf), was assessed under in vitro salt stress. Hybrid plants were characterized by leaf morphology, and ploidy level by flow cytometry and molecular markers. In vitro shoots were generated from the micropropagation of mature stem pieces of the somatic hybrid and its parents, and these were challenged by exposure to NaCl (0, 50, or 100 mM) supplemented to the media for three weeks to induce salt stress. The leaves of the somatic hybrid display intermediate morphology compared to the parental Cleopatra mandarin and Carrizo citrange rootstocks. All molecular markers successfully amplified DNA from the three cultivars; however, only 11 of 14 unequivocally confirmed somatic hybridity. The physiological and biochemical parameters, including chlorophyll content, lipid peroxidation, total phenolic compounds, antioxidants activity and proline content, were measured in the leaves. The somatic hybrid exhibited superior salt stress tolerance compared to the parent varieties, as evidenced by the reduced cellular membrane damage indicated by the lower levels of malondialdehyde and electrolyte leakage, particularly under 100 mM NaCl treatment. The somatic tetraploid hybrid also displayed higher total phenolic content than either parent, while Cleopatra mandarin exhibited the highest proline levels under 50 mm NaCl. These results demonstrate the enhanced salinity stress tolerance of the somatic hybrid compared to its parent lines, highlighting its potential as a valuable candidate for developing salt-tolerant citrus rootstocks. [ABSTRACT FROM AUTHOR]

Nanoparticle foliar spray is a new approach and effective for improving seedling growth and survival with adverse conditions such as salt stress. The current study was conducted to investigate the impact of commercial silicon dioxide (SiO2), SiO2 nanoparticles (SiO2 NPs), commercial chitosan (CS), CS nanoparticles (CS NPs) on growth, proline, antioxidant defense enzyme, and ions content in one-year-old for sour orange (Citrus aurantium, L.) and Volkamer lemon (Citrus volkameriana) rootstocks grown under salinity stress. In the current study, a foliar spray of bulk SiO2, SiO2 NPs, Chitosan, and Chitosan NPs with a concentration of 50 ppm was applied at 0 and 50 mM of NaCl concentrations. Vegetative growth was determined, including plant height, stem diameter, leaf area, roots, and total fresh and dry weights. The findings demonstrated that salinity adversely affected plant growth. Salt-stressed plant leaves exhibited greater peroxidase (POD) activity and proline content than the control treatment, and Na+ and Cl- ions accumulated in the leaves of salinized plants. Nano-Silicon dioxide and Nano-chitosan significantly increased full vegetative growth parameters and antioxidant defense enzymes. Nano treatments decreased Na+ and Cl- ions content in the leaf tissue. Finally, as a result SiO2 NPs and CS NPs are employed as part of a combined approach to increase the growth indices of citrus plants, especially achieving a significant impact in alleviating salinity stress.

Somatic hybridization has emerged as a valuable tool for developing novel genetic combinations in citrus breeding programs, including the creation of salt-tolerant rootstocks. In this study, the performance of a tetraploid somatic hybrid, obtained by fusing protoplasts derived from salt-tolerant Cleopatra mandarin (Citrus reshni hort. ex Tanaka) and salt-sensitive Carrizo citrange (Citrus sinensis L. Osbeck × Poncirus trifoliata L. Raf), was assessed under in vitro salt stress. Hybrid plants were characterized by leaf morphology, and ploidy level by flow cytometry and molecular markers. In vitro shoots were generated from the micropropagation of mature stem pieces of the somatic hybrid and its parents, and these were challenged by exposure to NaCl (0, 50, or 100 mM) supplemented to the media for three weeks to induce salt stress. The leaves of the somatic hybrid display intermediate morphology compared to the parental Cleopatra mandarin and Carrizo citrange rootstocks. All molecular markers successfully amplified DNA from the three cultivars; however, only 11 of 14 unequivocally confirmed somatic hybridity. The physiological and biochemical parameters, including chlorophyll content, lipid peroxidation, total phenolic compounds, antioxidants activity and proline content, were measured in the leaves. The somatic hybrid exhibited superior salt stress tolerance compared to the parent varieties, as evidenced by the reduced cellular membrane damage indicated by the lower levels of malondialdehyde and electrolyte leakage, particularly under 100 mM NaCl treatment. The somatic tetraploid hybrid also displayed higher total phenolic content than either parent, while Cleopatra mandarin exhibited the highest proline levels under 50 mm NaCl. These results demonstrate the enhanced salinity stress tolerance of the somatic hybrid compared to its parent lines, highlighting its potential as a valuable candidate for developing salt-tolerant citrus rootstocks.

Soil salinity is one of the most significant stressors limiting plant productivity in the world's irrigated and cultivated agricultural lands. Plants have a wide range of adaptations and mitigation strategies to overcome salinity effects. It is possible to mitigate the effects of salt stress by the development of resistant cultivars and more efficient use of available resources. However, these methods are time-consuming and costly. Solutions to salinity issues need to be developed that are both straightforward and inexpensive, as they will likely only be implemented temporarily. In this study, the effects of the different salinity levels (Control, 20mM, 40mM, 60mM, 80mM, and 100mM) on citrus rootstocks were determined. In the citrus growing regions, the sour orange, trifoliate orange, and Carrizo citrange were the three most popular rootstocks. As a result of the present study, the sour orange was found to have the lowest decline in plant height (13.36%), leaf area (31.19%), and root length (8.13%), while the trifoliate orange had the lowest decrease in fresh weight of the plant (6.82%) and root (4.42%). Trifoliate orange was shown to have the highest levels of catalase activity, whereas superoxide dismutase and peroxidase activities were found to be highest in Carrizo citrange and sour orange, respectively. The highest concentration of plant nutrients was found in the Carrizo citrange. Therefore, sour orange was discovered to be more salinity tolerant in terms of morphological traits, physiological qualities, biochemical composition, and plant nutrition than trifoliate orange and Carrizo citrange. For areas with high salt levels, growing citrus on sour orange rootstock may be a viable alternative. [ABSTRACT FROM AUTHOR]

Copyright of Jornal of Al-Muthanna for Agricultural Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) 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.)

• Industrial digestate fruitfully employed as fertilizer in citrus nurseries. • Nutrient levels of anaerobic digestate are compliant to Italian law. • Volkamer lemon increased chlorophyll level when fertilized with anaerobic digestate. Previous researches have demonstrated the bioenergetic potential of agri-food Mediterranean wastes showing that anaerobic co-digestion is a valuable solution for Mediterranean areas. This implies a great interest for anaerobic digestates use in agriculture to replace fertilizers. The present study aimed at: i) producing knowledge on continuous anaerobic co-digestion of feedstock mixture composed by different Mediterranean agri-food wastes in terms of multielemental characterization and ii) assessing the agronomic value of industrial anaerobic digestate (AD) based on the potential as fertiliser in nursery condition for the citrus seedlings. Results have demonstrated that agro-industrial biomasses have great potentiality to be converted by anaerobic digestion in biofertilizer to be used in citrus nurseries as sustainable alternative to mineral fertilisers. Multielemental traits of the tested AD were valuable in terms of nutritional supply for the growth and development of the plant. AD was useful to replace the mineral fertilizers in terms of total N content (10.81 ± 0.32 %TS) and organic matter (43.32 ± 0.80 %TS). The seedlings nutritive status showed that no need for supplemental of nutrients was requested. Volkamer lemon highly benefited from the administration of liquid digestate, increasing the total chlorophyll level (2.97 ± 0.31 mg g−1 FW) presumably due to the higher ammonium content of the AD (59 ± 0.08 %TKN). Besides providing useful tools for citrus nurseries for conceiving new sustainable fertilization strategies, this study is a starting point for further in-depth works on physiological status and traits of citrus plants fertilized by using agro-industrial anaerobic digestate. [ABSTRACT FROM AUTHOR]

Investigations have demonstrated that ratio of sugars to organic acids affects the particular taste of citrus fruit and carotenoids are essential for prevent of the disease. It seems that some rootstocks enhance the ripening of fruits and stimulatethe biosynthesis of sugars and carotenoids. The aim of this study was to evaluate the effect of rootstocks on sugars, organic acids andcarotenoids of fruit. The content of individual sugars and organic acids in fruits were determined by HPLC. Total acidity (TA), total soluble solids (TSS) and pH value of juice was also evaluated. Total carotenoid and chlorophylls content was measured using a spectrophotometer. The content of ethylene in fruits was determined by Gas chromatograph. HPLC analysis of juice allowed to detection of 3 sugars and 2 acids. Sucrose was the dominant sugar for all rootstocks. The amount of total sugars ranged from 102.27 (mg/ml) (Flying dragon) to 118.07 (mg/ml) (Orlando tangelo). The amount of total acids changed from 6.62 (mg/ml) (Trifoliate orange) to 8.48 (mg/ml) (Flying dragon). The amount of ascorbic acid varied from 0.44 (mg/ml) (Trifoliate orange) to 0.68(mg/ml) (Orlando tangelo).The pH value ranged from 3.65 (Flying dragon) to 3.95 (Orlando tangelo), TSS content changed from11.2 (%) (Flying dragon) to11.9 (%) (Orlando tangelo), TSS/TA varied from15.13 (Flying dragon) to 20.88(Orlando tangelo). Juice content ranged from 49.29 (%) (Trifoliate orange) to 54.47 (%) (Orlando tangelo). The amount of fruit production changed from 12 (Kg /tree) (Flying dragon) to 83(Kg /tree) (Orlando tangelo). The amount of total carotenoid varied from 0.12 (Murcott) to 0.15(Orlando tangelo, Sour orange, Flying dragon) (mg/gr DW). Among the six rootstocks evaluated, Orlando tangelo demonstrated the maximum rate of sugars, pH, TSS, TSS/TA, juice, ascorbic acid and carotenoids. As an outcome of our investigation, we can express that the rootstocks can affect the amount of sugars, acids andcarotenoids of fruit.

Micrografting of lime were evaluated on four different citrus rootstocks; small-fruited sour orange, big-fruited sour orange, lime and lemon in four culture medium supporting systems including paper bridge, perlite and vermiculite supplemented with half MS and paper bridge supplemented with full MS each one with 60 or 75 g L-1 sucrose. Also, micrografted plantlets were evaluated in three beds including perlite, vermiculite, and perlite-vermiculite for acclimatization and growth. Statistical analysis of micrografting and acclimatization was done as factorial in a completely randomized design with 5 replications. According to independent treatments results, the most rate of successful micrografting of lime shoot tip was achieved on seedling rootstocks of lemon. Also, the best micrografting were observed at the highest concentration of sucrose at 75 gL-1media culture. In general, the most rate of successful micrografting of lime shoot tip was obtained on seedling rootstocks of lemon and big fruit sour orange in culture medium supporting systems of perlite and paper bridge with half MS containing 75 gL-1sucrose. After micrografting, the plantlets were transplanted from the in vitro to the culture medium. The highest survival rate and adaptation of micrografted lime based on the number of leaves and length of scion after 5 weeks was obtained with lemon and big-fruited sour orange rootstocks micrografted in paper bridge culture medium and transferred to the perlite- vermiculite bed.

The aim of this study was to determine total flavonoids and individually flavanone glycosides as well as antioxidant capacity in peel of Satsuma mandarin(Citrus unshiu) on different rootstocks. On other hand, the purpose of this study was to identify the rootstock that could produce the highest amount of flavonoids.Total flavonoids content was measured using aluminum chloride colorimetric method, whereas Folin-Ciocalteau colorimetric method was used to determine the total phenols content. The antioxidant activities were evaluated using reducing scavenging assays of DPPH radicals. HPLC-PDA detection was used for the analysis of individual flavanone glycosides (narirutin, naringin and hesperidin).The results showed that, the highest individually flavanone glycosides (27.73 mg/g DW), total flavonoids (10.74 mg/g DW), total phenol (3.91 mg/g DW) and DPPH scavenging activity (60.00 mg/g DW) were in the peel of Satsuma mandarin grafting on the flying dragon rootstock. According to results, the amount of phenolic acids (0.36 mg/g DW) of Satsuma mandarin grafted on trifoliate orange was higher than those of other rootstocks. Among the flavonone glycosides, hesperidin was determined in the highest concentration in all investigated peels. The results of correlation showed that there were a high positive correlation between the amount of total flavonoids and total phenols. Results showed that rootstock had an important role in increasing of concentration flavonoids, as well as antioxidant capacity. Finally based on the obtained results it can be concluded that although the concentration of flavonoid compounds is strongly related to the genotype of fruit, it seems that rootstocks affect the amount of flavonoids in the fruit.

A shade house experiment was conducted in a certified citrus nursery belongs to the Directorate of Agriculture and Forests in Al-Hindiya district, province of Karbalaa, during the period from 1-3-2018 to 1-4-2019 to study the effect of foliar spray with Nano IQ-Combi or seaweed extract (SWE) and their interactions on vegetative growth parameters of citrus rootstock C-35 saplings. Beside the control treatment (plants sprayed with distilled water only), both fertilizers were used at three concentrations which were 0.5, 1 or 1.5 g/L for the IQ-Combi and 3, 6 or 9 ml/L for the SWE. Results showed that both types of fertilizers were effective in increasing all the studied plant growth parameters compared to untreated control plants. The 1 g/L of IQ-Combi and 9 ml/L of SWE were the most effective concentrations among all the treatments. IQ-Cobi at 1 g/L resulted in higher values of all studied growth parameters, but did not differ from those resulted from SWE at 9 ml/L. Best results were obtained from the interaction treatment of 1 g/L of IQ-Combi and 9 ml/L of SWE resulting in the highest values of plant height (58.63 cm), stem diameter (1.62 cm), number of branches per plant (2.97 branch plant -1), number of leaves per plant (65.10 leaf plant-1 ), leaf area (11.80 cm²), leaf content of total chlorophyll (7.86 mg.100g-1 FW) and carbohydrates (36.66 mg.g-1 DW) with significant difference from the control which resulted in 23.74 cm, 1.25 cm, 1.11 branch plant -1, 20.16 leaf plant -1, 5.71 cm², 5.60 mg.100g-1 FW and 24.96 mg.g-1 DW, respectively. [ABSTRACT FROM AUTHOR]

The study was conducted in the Department of Horticulture and Landscaping, Faculty of Agriculture, University of Kufa, during the 2018 growing season to evaluate the effect of spraying four concentrations (0, 1, 2, or 3 ml/L) of liquid organic fertilizer (LIQHUMUS * 18)on some growth parameters of four root stocks of citrus (strange, Cleopatra mandarin, Troyer Strange and Volga Marina). The results showed that the four root stocks significantly differed in their growth parameters and responses to LIQHUMUS * 18 foliar spray. Troyer Strang was the highest in plant height and stalk diameter. Mandarin Cleopatra had the highest values of number of branches, branches length and number of leaves/plant, while the highest average of leaf length was recorded in the Strange root socks. Foliar spray with LIQHUMUS*18 had substantial positive effects on all studied traits compared to the control plants. Spraying with LIQHUMUS*18 at concentration of 2 ml/L resulted in the highest values of all plant parameters studied in all the root stacks. At this concentration, the root stacks performed differently on different plant parts. [ABSTRACT FROM AUTHOR]

Sufficient application of nutrients is one of the most important factors in the development of seedlings from quality citrus root stocks. Some of the key guides for preparing citrus fertilizer programs is by tracking the nutrient content of plants directly. This includes, however, an examination of a large number of leaf samples using costly and time-chemical techniques. It has been shown over the last 10 years that it is possible to quantitatively estimate such nutrient elements in citrus leaves using the spectral reflectance values obtained using hyperspectral spectroscopy. This technique is quick, non-destructive, cost-effective and eco- friendly. Therefore, estimating nitrogen, potassium, and magnesium in seedling leaves of citrus rootstocks by this approach would be useful in determining the seedlings ' mineral status. In this research, 168 leaf samples from four citrus rootstocks seedlings (Volkamer lemon, Sour orange, Trifoliate orange and Balady Lime) were used to conduct three vegetation indices; normalized difference vegetation index (NDVI), normalized difference nitrogen index (NDNI) and modified chlorophyll absorption ratio index (MCARI) and subsequent nutrient estimates for N, K, and Mg concentration. Simple regression models and chemical analysis were used to produce the best model of estimation to predict the values of the three components. A high correlation coefficient (R2) was verified in the estimate of N (R2=0.982) with the lowest root mean square error (RMSE=0.0472) and k (R2=0.983) with the lowest root mean square error (RMSE=0.0491) and the lowest root mean square error (RMSE=0.0062) was also verified. [ABSTRACT FROM AUTHOR]

Huanglongbing (HLB), caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus (CaLas), is the primary biotic stress causing significant economic damage to the global citrus industry. Among the abiotic stresses, salinity affects citrus production worldwide, especially in arid and coastal regions. In this study, we evaluated open-pollinated seedlings of the S10 (a diploid rootstock produced from a cross between two siblings of the Hirado Buntan Pink pummelo (Citrus maxima (Burm.) Merr.) with the Shekwasha mandarin (Citrus reticulata Blanco)) for their ability to tolerate HLB and salinity stresses. In a greenhouse study, ‘Valencia’ sweet orange (either HLB-positive or negative) was grafted onto six clonally propagated lines generated from the screened seedlings in the greenhouse and the trees were irrigated with 150 mM NaCl after eight months of successful grafting and detection of CaLas in the leaf petioles. Cleopatra mandarin was used as a salt-tolerant and HLB-sensitive rootstock control. CaLas infection was monitored using a quantitative polymerase chain reaction before and after NaCl treatments. Following three months of NaCl treatment, ‘Valencia’ leaves on the S10 rootstock seedlings recorded lower levels of chlorophyll content compared to Cleopatra under similar conditions. Malondialdehyde content was higher in HLB-infected ‘Valencia’ grafted onto Cleopatra than in the S10 lines. Several plant defense-related genes were significantly upregulated in the S10 lines. Antioxidant and Na+ co-transporter genes were differentially regulated in these lines. Based on our results, selected S10 lines have potential as salt-tolerant rootstocks of ‘Valencia’ sweet orange under endemic HLB conditions. However, it is necessary to propagate selected lines through tissue culture or cuttings because of the high percentage of zygotic seedlings derived from S10.

Studies have shown that phenolic compounds are important in human health.The purpose of this research was to examine the influence of rootstocks on phenolic compounds. The content of individual phenolic compounds in fruits was determined by HPLC. Total flavonoids content was measured using colorimetric method. Free radical scavenging activity on stable DPPH radicals was also evaluated. HPLC analysis of the peel compounds extracted from Clementine mandarin allowed identification of 7 phenolic components. Hesperidin was the main component for all rootstocks. Among the six rootstocks examined, Flying dragon showed thehighest content of phenolic compounds.As a result of our study, we can conclude that the rootstock can influence the quantity of phenolic compounds present in fruit.

The aim of this study was to determine organic acids and individual sugars as well as carotenoids in fruit of Kumquat [Fortunella margarita (Lour.) Swingle] on different rootstocks. On other hand, the purpose of this study was to identify the rootstock that could produce the highest amount of sugars. The content of individual sugars and organic acids in fruits were determined by HPLC, whereas spectrophotometer was used to determine the total carotenoids and chlorophylls. Total acidity (TA), total soluble solids (TSS) and pH value of juice was also evaluated. The content of ethylene in fruits was determined by Gas chromatograph. The results showed that, the highest of total sugars (51.63 mg/mL), pH (2.43), TSS (11.06%) and TSS/TA (3.71) were in fruit of Kumquat (Fortunella Margarita) grafting on the Troyer citrange rootstock. According to results, the amount of citric acid (45.07 mg/mL), ascorbic acid (0.41 mg/mL), juice (26.78 (%) and carotenoids (0.10 mg/gr DW) of Kumquat grafted on Sour orange was higher than those of other rootstocks. Among the sugars, Sucrose was determined in the highest concentration in all investigated fruits. The results of correlation showed that there were a high positive correlation between the amount of sucrose and glucose. Results showed that Troyer citrange rootstock had an important role in increasing of sugars, pH, TSS, as well as TSS/TA. Finally based on the obtained results it can be concluded that although the concentration of sugars and organic acids is strongly related to the genotype of fruit, it seems that rootstocks affect the amount of sugars and organic acids. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Kirkuk University for Agricultural Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) 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.)

This work compared the expression of the main B transport-related genes (some members of the aquaporin family -NIP5, TIP5 and PIP1- and some efflux-B transporters -BOR1 and BOR4-), and the response of some physiological parameters in two citrus species [Citrus macrophylla W. (CM) and Citrus aurantium L. (CA)] under moderate and low boron (B) conditions. Seedlings were cultured "in vitro" in media supplemented with 50 or 0 μM H3BO3. NIP5, BOR1 and PIP1 expressions were enhanced by low B levels in both genotypes. TIP5 was down-regulated in the roots and leaves of the CA0 seedlings, and in the roots of CM0. BOR4 also lowered in the roots of both species at 0 μM H3BO3. Consequently, citrus species showed a common tolerance mechanism to low B conditions based on the synergism among transport channel NIP5, non-selective aquaporin PIP1 and transporter BOR1, and the impairment of genes TIP5 and BOR4 related with tolerance responses to B-toxic conditions. However, the CA genotype displayed low B symptoms earlier than CM (reduced plant biomass, length, relative growth rate and chlorophyll content). Proline concentration was higher in CM0 than in CA0 leaves, while the latter also enhanced malonaldehyde content. Although both plants had similar B concentrations, they differed in B content and B partitioning fractions. Whereas the CA genotype was more affected by lack of B treatment as more B was needed inside the cell, the more minimal need of cell B in CM favoured its allocation in the insoluble fraction and allowed growth in this genotype. In conclusion, B compartmentalisation seems critical in tolerance to low B level in citrus. [ABSTRACT FROM AUTHOR]

Highlights • Evidence that negative influence of treated waste water (TWW) is mainly salinity. • Secondarily treated waste water's organic load has a marginal influence. • Root zone aeration facilitates ion selectivity and improves plant performance. • X639 was less sensitive to TWW than Volkameriana in these conditions. • Aeration enhanced K transport from the roots to leaves. Abstract The effects of root zone aeration and irrigation water quality (WQ) were studied in two rootstocks with contrasting tolerances to abiotic stress. We hypothesized that the main influence of TWW is that of its salinity (especially Na and K and their ratios), that the organic load and its BOD have a marginal influence and that aeration facilitates selectivity of roots and/or leaves and therefore improves plant performance. The factorial experiment included root zone aeration, fresh water (FW), TWW, and fresh water with a salt concentration similar to TWW (FW + NaCl). One year old unworked rootstocks of sensitive Citrus volkameriana (Volka) and tolerant X639 (Cleopatra mandarin X Poncirus trifoliata) were treated for 4 months, followed by 2 months of recovery. Measurements included ionic and water relations, photosynthetic parameters, growth, morphology, tissue specific membrane properties, and sugar and starch contents. Volka was highly sensitive to WQ and aeration while X639 was influenced much less. During the first two months aeration increased Volka leaf photosynthesis and gas exchange by 15%, water and potassium (K) uptake by 20%, carbon storage by 15% and biomass by 20%; which compensated for the negative effects of poor WQ. Changes in distribution of K and Na ions hint at the mechanisms for the aeration influence on tolerance to poor WQ. Results indicate that aeration enhanced K transport from the roots to leaves and reduced Na concentrations in the roots of the sensitive rootstock. These, as well as changes in the wide range of leaf and root parameters measured, are discussed with relation to their implications for our understanding of plant response and tolerance to low WQ in poorly drained soils. [ABSTRACT FROM AUTHOR]

The accumulation of salt deposits in the soil is becoming a major problem in agriculture. The problem can affect citrus production, which is already seriously hindered in Florida by the disease known as Huanglongbing (HLB, or citrus greening). With the citrus industry declining, it is imperative to study all potential environmental stresses affecting the citrus cultivation and to conduct screening tests to evaluate which rootstocks perform best under these challenging new conditions. This study aims to determine how the 'US-942' rootstock reacts to salinity. Thirty-six 3-month-old 'US-942' citrus rootstock seedlings were grown in a greenhouse. After 15 d of acclimation, plants were assigned to one of six groups and treated for 30 d with solutions of 25% Hoagland solution amended with 0 (control), 30, 60, 90, 120, or 150 mM NaCl. Higher NaCl concentrations significantly hindered plant growth and negatively affected some physiological processes [i.e., stomatal conductance (gS)] and chlorophyll contents. Conversely, plants treated with mild concentrations (30 mM NaCl) had higher plant biomass and exhibited higher photosynthetic efficiency. Free hand sections of fresh roots were taken at the end of the experiment, and the suberin lamellae development was examined under a fluorescence microscope. In conclusion, results reported that 'US-942' rootstock is tolerant to mild salt stress and confirmed the hypothesis that the formation of root apoplastic barriers and the increase in the root biomass could be two possible mechanisms that give the 'US-942' a mild NaCl stress tolerance. [ABSTRACT FROM AUTHOR]

Phytophthora spp. are the most serious threat to citrus industry worldwide. Being a soil borne problem, use of tolerant rootstocks is the most ecofriendly approach to manage the deadly diseases caused by this fungus. Here, we assessed the reaction of eight citrus rootstock genotypes including sour orange, Troyer citrange and six variants of C. jambhiri Lush. viz., RLC-5, RLC-6, RLC-7, Grambiri, rough lemon and Italian rough lemon against the inoculation of Phytophthora nicotianae. Inoculation of P. nicotianae infected the feeder roots of tested rootstocks to varying degree, expressing higher disease incidence (81.25%) and number of infected feeder roots (54.25-60.62%) depending on the rootstock. Troyer citrange and sour orange proved most tolerant rootstocks against the inoculated fungus. Phytophthora inoculation tended to increase the levels of reactive oxygen species (H2O2 and O2 -), antioxidant enzymes (catalase, peroxidase, glutathione reductase, superoxide dismutase and β-1,3-glucanase) and protein content. However, it significantly reduced the levels of macro- (N, P, K Ca and Mg) and micro- (Cu and Zn) nutrients, although the extent of variation was rootstock specific. Overall, Troyer citrange and sour orange expressed the lowest variation in the levels of ROS, peroxidase (POX), superoxide dismutase (SOD) and β-1,3-glucanase, protein and nutrient contents, while rough lemon proved most strongly affected. Of the various variants of Citrus jambhiri, RLC-5 and Italian rough lemon proved more tolerant for Phytophthora nicotianae than rest of the clones tested. [ABSTRACT FROM AUTHOR]

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Studies have shown that oxygenated compounds and TSS/TA are important for beverage and food industries. It seems that Citrus rootstocks have a profound influence on oxygenated compounds and TSS/TA. The aim of this research is to identify rootstock that can synthesize the maximum level of oxygenated compounds and TSS/TA. Peel oil was extracted using mechanical presses and eluted using n-hexane. Finally compounds were analyzed using GC-FID and GC-MS. Total soluble solids were determined using a refractometer. Twenty-seven, twenty-five and twenty-three compounds were identified in Sour orange, Swingle citromelo and Troyer citrang rootstocks, respectively. Limonene (92.87% to 93.16) and myrcene (1.57% to 1.79%) were the main compounds. Among the three rootstocks studied, Swingle citromelo demonstrated the maximum level of oxygenated compounds and TSS/TA. As a result of our research, we can express that the rootstocks can affect the amount of oxygenated compounds and TSS/TA.

The aim of this study was to determine total flavonoids and individually flavanone glycosides as well as antioxidant capacity in peel of Satsuma mandarin (Citrus unshiu) on different rootstocks. On other hand, the purpose of this study was to identify the rootstock that could produce the highest amount of flavonoids. Total flavonoids content was measured using aluminum chloride colorimetric method, whereas Folin-Ciocalteau colorimetric method was used to determine the total phenols content. The antioxidant activities were evaluated using reducing scavenging assays of DPPH radicals. HPLC-PDA detection was used for the analysis of individual flavanone glycosides (narirutin, naringin and hesperidin). The results showed that, the highest individually flavanone glycosides (27.73 mg/g DW), total flavonoids (10.74 mg/g DW), total phenol (3.91 mg/g DW) and DPPH scavenging activity (60.00 mg/g DW) were in the peel of Satsuma mandarin grafting on the flying dragon rootstock. According to results, the amount of phenolic acids (0.36 mg/g DW) of Satsuma mandarin grafted on trifoliate orange was higher than those of other rootstocks. Among the flavonone glycosides, hesperidin was determined in the highest concentration in all investigated peels. The results of correlation showed that there were a high positive correlation between the amount of total flavonoids and total phenols. Results showed that rootstock had an important role in increasing of concentration flavonoids, as well as antioxidant capacity. Finally based on the obtained results it can be concluded that although the concentration of flavonoid compounds is strongly related to the genotype of fruit, it seems that rootstocks affect the amount of flavonoids in the fruit. [ABSTRACT FROM AUTHOR]

Investigations have demonstrated that ratio of sugars to organic acids affects the particular taste of citrus fruit and carotenoids are essential for prevent of the disease. It seems that some rootstocks enhance the ripening of fruits and stimulate the biosynthesis of sugars and carotenoids. The aim of this study was to evaluate the effect of rootstocks on sugars, organic acids and carotenoids of fruit. The content of individual sugars and organic acids in fruits were determined by HPLC. Total acidity (TA), total soluble solids (TSS) and pH value of juice was also evaluated. Total carotenoid and chlorophylls content was measured using a spectrophotometer. The content of ethylene in fruits was determined by Gas chromatograph. HPLC analysis of juice allowed to detection of 3 sugars and 2 acids. Sucrose was the dominant sugar for all rootstocks. The amount of total sugars ranged from 102.27 (mg/ml) (Flying dragon) to 118.07 (mg/ml) (Orlando tangelo). The amount of total acids changed from 6.62 (mg/ml) (Trifoliate orange) to 8.48 (mg/ml) (Flying dragon). The amount of ascorbic acid varied from 0.44 (mg/ml) (Trifoliate orange) to 0.68(mg/ml) (Orlando tangelo).The pH value ranged from 3.65 (Flying dragon) to 3.95 (Orlando tangelo), TSS content changed from11.2 (%) (Flying dragon) to11.9 (%) (Orlando tangelo), TSS/TA varied from15.13 (Flying dragon) to 20.88(Orlando tangelo). Juice content ranged from 49.29 (%) (Trifoliate orange) to 54.47 (%) (Orlando tangelo). The amount of fruit production changed from 12 (Kg /tree) (Flying dragon) to 83(Kg /tree) (Orlando tangelo). The amount of total carotenoid varied from 0.12 (Murcott) to 0.15(Orlando tangelo, Sour orange, Flying dragon) (mg/gr DW). Among the six rootstocks evaluated, Orlando tangelo demonstrated the maximum rate of sugars, pH, TSS, TSS/TA, juice, ascorbic acid and carotenoids. As an outcome of our investigation, we can express that the rootstocks can affect the amount of sugars, acids and carotenoids of fruit. [ABSTRACT FROM AUTHOR]

Usually several environmental stresses occur in nature simultaneously causing a unique plant response. However, most of the studies until now have focused in individually-applied abiotic stress conditions. Carrizo citrange ( Poncirus trifoliata L. Raf . X Citrus sinensis L. Osb.) and Cleopatra mandarin ( Citrus reshni Hort. ex Tan.) are two citrus rootstocks with contrasting tolerance to drought and heat stress and have been used in this work as a model for the study of plant tolerance to the combination of drought and high temperatures. According to our results, leaf integrity and photosynthetic machinery are less affected in Carrizo than in Cleopatra under combined conditions of drought and heat stress. The pattern of accumulation of three proteins (APX, HSP101 and HSP17.6) involved in abiotic stress tolerance shows that they do not accumulate under water stress conditions individually applied. However, contents of APX and HSP101 are higher in Carrizo than in Cleopatra under stress combination whereas HSP17.6 has a similar behavior in both types of plants. This, together with a better stomatal control and a higher APX activity of Carrizo, contributes to the higher tolerance of Carrizo plants to the combination of stresses and point to it as a better rootstock than Cleopatra (traditionally used in areas with scare water supplies) under the predictable future climatic conditions with frequent periods of drought combined with high temperatures. This work also provides the basis for testing the tolerance of different citrus varieties grafted on these rootstocks and growing under different field conditions. [ABSTRACT FROM AUTHOR]

This study compared the effects of chromium toxicity on the carbon and nitrogen metabolism in Kinnow mandarin ( Citrus nobilis Lour x Citrus deliciosa Ten) plants grafted on the diploid (2x) and tetraploid (4x) of Poncirus trifoliata [L.], Citrus reshni , and Citrus limonia Osbeck. Plants were grown under controlled conditions and fertigated with complete nutrient solution supplemented with chromium (0.75 mM). After 120-d of growth under chromium (Cr) stress, carbon (C) and nitrogen (N) metabolism in leaves were studied. In the C metabolism study sucrose, glucose, fructose, starch contents, and the enzymatic activities of acid invertase (AI), neutral invertase (NI), sucrose synthetase (SS), sucrose phosphatesynthetase (SPS), fructokinase (FK), hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK) were investigated. Nitrogen metabolism study was comprised of determination of nitrate, nitrite and ammonium content and the nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthetase (GOGAT), and glutamate dehydrogenase (GDH) activities. Basically, in the C metabolism study the Cr enhanced the enzymatic activities and sugar contents, and decreased starch. Chromium stress caused a decrease in nitrate and nitrite, and an increase in ammonia; it also inhibited all measured enzymatic activities except GDH which was increased. The responses of Kinnow mandarin plants grafted on 2x or 4x for any rootstock followed a similar pattern, although the effects of Cr toxicity were more drastic in 2x grafted plants. Glycolysis was the only metabolic process which had a different behavior between 2x and 4x grafted plants under Cr stress: FK and HK activities under Cr stress were significantly increased in 4x grafted plants than in 2x grafted plants. These data suggest that in Kinnow mandarin plants grafted on 4x rootstocks the C metabolism is modified thereby strengthening the plants to adapt Cr stress, but N metabolism was inhibited by Cr toxicity. [ABSTRACT FROM AUTHOR]

Phosphorus is an essential nutrient for the growth of citrus plants. A pot experiment was conducted in greenhouse to investigate the citrus cultivars grafted on 10 rootstocks (Cuningmeng, Suanju, Suancheng, Honglimeng, Zhike, Goutoucheng, Xiangyuan, Hongju, Xiangcheng, and Zhicheng) in response to the different phosphorus treatments viz, low P (LP) = 0.01 mmol L-1, moderate P (MP) = 0.5 mmol L-1, high P (HP) = 1 mmol L-1) concentrations. All P concentrations were employed in pots containing Hoagland solution. The leaves, branch, root and total dry weight, and nitrogen, phosphorus, potassium and magnesium concentrations in the different plant parts were determined. Results showed that P application increased N, P, K and Mg content in different plant parts. With increasing P application, the root dry weight, branch dry weight, leaves dry weight, and total dry weight increased whilst low P treatment affected the P, K and Mg accumulation in root and ultimately plant growth. Moreover, low P concentrations also affected Mg content in leaves, that can lead to low plant photosynthesis and finally decreased the plant dry biomass [ABSTRACT FROM AUTHOR]

When preparing for replanting, an important factor to consider is the choice of rootstock. Choosing the right rootstock and scion combination can result in higher economic returns without any additional cost. Rootstocks affect scion vigor, yield, fruit size, juice quality, and pest tolerance. However, tree growth, yield, and fruit quality interact strongly with climate, soil type, tree spacing, and other factors, often producing contradictory reports on rootstock performance in different areas. This 3-page fact sheet discusses soil characteristics, rootstock effects on pests and diseases, tree spacing and size, and rootstock/scion combination. Written by Ute Albrecht, Fernando Alferez, and Mongi Zekri, and published by the UF/IFAS Department of Horticultural Sciences, September 2017.

Iron is an essential micronutrient for plants, and plants have evolved adaptive mechanisms to improve iron acquisition from soils. Grafting on iron deficiency-tolerant rootstock is an effective strategy to prevent iron deficiency-chlorosis in fruit-tree crops. To determine the mechanisms underlying iron uptake in iron deficiency, two iron deficiency-tolerant citrus rootstocks, Zhique (ZQ) and Xiangcheng (XC), as well as iron deficiency-sensitive rootstock trifoliate orange (TO) seedlings were studied. Plants were grown in hydroponics system for 100 days, having 50 μM iron (control) and 0 μM iron (iron deficiency) nutrient solution. Under iron deficiency, more obvious visual symptoms of iron chlorosis were observed in the leaves of TO, whereas slight symptoms were observed in ZQ and XC. This was further supported by the lower chlorophyll concentration in the leaves of TO than in leaves of ZQ and XC. Ferrous iron showed no differences among the three citrus rootstock roots, whereas ferrous iron was significantly higher in leaves of ZQ and XC than TO. The specific iron absorption rate and leaf iron proportion were significantly higher in ZQ and XC than in TO, suggesting the iron deficiency tolerance can be explained by increased iron uptake in roots of ZQ and XC, allowed by subsequent translocation to shoots. In transcriptome analysis, 29, 298, and 500 differentially expressed genes (DEGs) in response to iron deficiency were identified in ZQ, XC, and TO, respectively (Fold change ≥ 2 and Probability ≥ 0.8 were used as thresholds to identify DEGs). A Gene Ontology analysis suggested that several genotype-specific biological processes are involved in response to iron deficiency. Genes associated with cell wall biosynthesis, ethylene and abscisic acid signal transduction pathways were involved in iron deficiency responses in citrus rootstocks. The results of this study provide a basis for future analyses of the physiological and molecular mechanisms of the tolerance of different citrus rootstocks to iron deficiency.

A simple multicomponent system is described that is effective for rapid propagation of a diversity of citrus rootstock genotypes by single node cuttings, including new hybrids and cultivars that are most commonly used as rootstocks. Efficiency of this system for rooting shoot explants of six important rootstock cultivars, Swingle, Cleopatra, US-802, US-812, US-897, and US-942 is compared in a repeated study. Many of the cuttings began to grow within 2 weeks after planting into potting mix. Growth for the resultant plants of different genotypes was compared through 20 weeks, and significant differences were observed. US-802 had the highest success in establishing growing plants at 8 weeks, with 82–91% of single node cuttings successfully rooted and growing, while Cleopatra was the least efficient with a 42–45% recovery of growing plants. Comparison of plant weight for cuttings and seedlings indicated that 12 week old nucellar and true-to-type seedlings are similar in size to 12–16 week old cuttings of the same cultivars. Plants of all rootstocks, whether cuttings or seedling-propagated, were observed to approach a dry weight ratio of 80% shoot and 20% root. Pronounced differences in the number and length of roots were identified among the rootstocks, indicating large differences in root structure that might be important in relation to eventual field plant health and growth. The commercial utility of the described methods is discussed. [ABSTRACT FROM AUTHOR]

There are generally inadequate supplies of seed for the newest rootstocks to satisfy the growing demand for the propagation material to be used in commercial citrus nurseries. Consequently, rootstock propagation, which is traditionally by seed, now often makes use of alternative methods such as cuttings and tissue culture (TC). Propagation through cuttings and TC will generate a root system that is largely composed of adventitious or lateral roots, compared with seed propagation, which will generally promote the formation of a well-defined taproot. In this study, we compared root architecture and growth of seven different rootstock plants, generated from seed, stem cuttings, or TC, during the early weeks of growth in the greenhouse. Based on total dry biomass, root mass fraction of plants generated from cuttings ranged from 11% to 16%, and from 16% to 29% and 21% to 30% for micropropagated plants and seedlings, respectively. Plants propagated through cuttings had the most primary roots (7-10), followed by tissue culture-propagated plants which developed an average of 2-6 primary roots. As expected, plants grown from seeds mostly developed a single and well-defined taproot during the first weeks. The total number of first order lateral roots was highest in the plants propagated as cuttings (108-185) compared with 53-103 and 43-78 for tissue culture-propagated plants and seedlings, respectively. Similarly, specific root length (SRL) was highest in plants derived from cuttings (21-43 m·gL1) and lowest in plants grown from seed (7-20 m·gL1). It is suggested that the larger number and length of roots on rootstock plants propagated through vegetative methods may be better suited for resource acquisition as compared with seed propagated plants. [ABSTRACT FROM AUTHOR]

Ebb-and-flow subirrigation is a closed system that applies water to the bottom of the containers, reducing water and nutrient losses due to recirculation of fertilizer solution (FS). The technology can improve plant growth and eliminate the improper disposal of salts into the environment. Subirrigation is widely used in the ornamental industry, and sensor-based ebb-and-flow benches can be used by the citrus nursery industry. There is a need for establishing water and fertilizer guidelines to produce citrus rootstocks. The objectives of this study were: 1) design and build an ebb-and-flow subirrigation equipment, 2) automate the system operation using soil moisture sensors, 3) evaluate the system performance on plant growth, and 4) determine the water and fertilizer guidelines to produce Rangpur lime ( Citrus × limonia ) liners in 56-cm 3 cone-shaped containers. The treatments were four volumetric water content (VWC) to trigger subirrigation (0.12, 0.24, 0.36 and 0.48 m 3 m −3 ), three FS concentrations (25%, 50% and 75% of the fertilizer recommendation) and a control (nursery manual overhead irrigation using breaker nozzles), arranged in a completely randomized 4 × 3 + 1 factorial plus design, with three replications. The system was automated by 39 capacitance sensors connected to a data logger, multiplexer and relay drivers, which controlled independent submersible pumps. Subirrigation was turned on when VWC dropped below the set thresholds. Sensors effectively monitored the substrate moisture and controlled subirrigation. Treatments with highest VWC had higher substrate moisture and number of irrigations over time ( p < 0.0001). The volume of water applied doubled from treatments 0.12–0.48 m 3 m −3 ( p < 0.0001). Subirrigation increased shoot height, stem diameter, dry weight, leaf area, physiological parameters (leaf intracellular concentration of CO 2 , transpiration, stomatal conductance, and net photosynthesis), and water use efficiency in response to increase in VWC and FS ( p < 0.0001). Subirrigation shortened the crop cycle in 30 days, anticipating the liners transplant for grafting, allowing another cultivation cycle in the nursery during the year. VWC of 0.48 m 3 m −3 and FS concentration of 50% of the recommended value for overhead irrigation are indicated for Rangpur lime liner production in 56-cm 3 containers. [ABSTRACT FROM AUTHOR]

Water scarcity can elicit drastic changes in plant metabolic and hormonal regulation, which may be of fundamental importance to stress tolerance. The study of plant the metabolic alterations in response to water deficit, especially the effects of the rootstocks level, is important to elucidate the mechanisms associated to drought tolerance. To verify the influence of rootstock and grafting on the tolerance to drought in citrus plants, we analyzed the growth, phytohormone levels and flavonoid profiles in grafted and ungrafted citrus plants subjected to different soil water regimes on plant status (well-watered, moderate drought and severe drought and rehydrated) under field conditions. The experiments were conducted under field conditions in the Brazilian Agricultural Research Corporation (EMBRAPA), Cruz das Almas, BA, Brazil. Water deficit reduced the total leaf area per plant in all canopy/rootstock combinations. Self-grafting reduce root volume, area and length when compared to ungrafted plants. Drought-induced increases in salicylic acid and abscisic acid associated with concomitant reductions in indoleacetic acid were observed in most canopy/rootstock combinations. However, plants with 'Sunki Maravilha' rootstocks exhibited the most pronounced changes in hormonal levels upon drought stress. Associated to these hormonal changes, drought also significantly affected flavonoid content and profile in both leaves and roots of the distinct citrus combinations. Glycosylated (GFs) and polimethoxylated flavonoids were predominantly found in leaves, whereas prenylated coumarins were found in the roots. Leaf levels of GFs (vicenin, F11, rutin and rhoifolin) were particularly modulated by drought in plants with ‘Rangpur Santa Cruz’ lime rootstock, whereas root levels of prenylated coumarins were most regulated by drought in plants with the 'Sunki Maravilha' root system. Taken together, these data indicate that the impacts of water deficit restriction on growth, hormonal balance and flavonoid profiles significantly varies depending on the canopy/rootstock combinations. [ABSTRACT FROM AUTHOR]

Several in vitro biotechnological techniques have been developed, all of which require a reliable protocol to produce a responsive callus mass. One of these techniques is callus fusion in vitro, which is reliable for the early detection of (in)- compatibility of scions and rootstocks. In this paper, the possibility to obtain friable callus tissues was explored by callus induction of adult tissues of Japanese flowering cherry trees from the group Sato zakura (Prunus serrulata 'Amanogawa', 'Kanzan' and 'Kiku-shidare-zakura') and two domestic cherry rootstocks - Prunus avium and Prunus 'Colt'. The explants used in the research were: leaf petiole, leaf base with a part of a petiole, part of lamina with a midvein and a stem with an axillary bud. Among three plant growth media (MS, SH and WP) that were used in this study, the MS proved to be the most favourable for the majority of taxa during the callus induction process. For the sweet cherry tree and the cultivars 'Kanzan' and 'Colt', the SH plant growth medium was also acceptable. The best results in callogenesis were obtained for the majority of taxons with auxin at the concentration 2 mgL-1 NAA and cytokinin BAP 0.5 mgL-1. It is also possible to use 2.4-D at the same concentration as a substitute for the genotypes Prunus avium, Prunus 'Colt' and Prunus serrulata 'Kanzan', whereas IBA proved to be an inappropriate auxin for callus induction. The protocol described herein is proved to be efficient callus induction in a range of taxa of genus Prunus. [ABSTRACT FROM AUTHOR]

The behavior of six citrus rootstocks, Volkameriana, Citrumelo 'Swingle', Citrange 'Carrizo', Poncirus trifoliata 'Serra', Poncirus trifoliata 'Rubidoux' and Poncirus trifoliata 'Flying Dragon', in in vitro propagation was studied and compared for shoot proliferation and rooting. In addition, the genetic relationships among the rootstocks studied and other Citrus species, using the Inter-Simple Sequence Repeats (ISSR) molecular markers, were investigated. Nodal explants of three months old shoots were used in Murashige and Skoog medium supplemented with N6-benzyladenine (BA) for shoot proliferation and with naphthaleneacetic acid (NAA) for rooting. The rootstock Volkameriana showed a statistically significant higher number of shoots (1.81), shoot length (15.14 mm) and number of leaves per explant (5.81), while all three Poncirus trifoliata rootstocks showed the lowest numbers. The number of roots and root length per explant were evaluated at the end of the rooting phase. The rootstock 'Swingle' showed a higher number of roots per explant (4.2) followed by 'Flying Dragon' (3.93) and 'Carrizo' (3.23) rootstocks. The rootstocks 'Swingle' (140.8 mm), Volkameriana (148 mm) and 'Flying Dragon' (131.12 mm) had significantly higher root length per explant compared to 'Carrizo' (31 mm) and 'Rubidoux' (34.5 mm). The ISSR molecular marker technique used in the present study grouped successfully the different species, varieties and rootstocks studied, revealing their genetic variability. The genetic variability observed among the rootstocks ranged between 0.29 (Poncirus trifoliata 'Serra' and Citrumelo 'Swingle') and 0.60 (Volkameriana and Citrumelo 'Swingle'). The response of the rootstocks studied in in vitro propagation however is not related to their genetic affinity. [ABSTRACT FROM AUTHOR]

experiment was carried out at the private nursery located at Baquba city/ Diyala governorate during 2015 agricultural season on three years old Citrus rootstocks seedlings to study the effect foliar application of salicylic acid on seedlings tolerance to soil salinity. The experiment included 24 treatment represented three factors: soil salinity levels (1.14,4.62 and 5.30 dSm-1) , two levels of salicylic acid (0 and 250 mg.l -1) and four citrus rootstocks (Sour orange, Cleopatra mandarin, Volkamariana lemon and Troyercitrange ),and their interactions with three replications . The results showed that: increasing soil salinity reduced most studied growth parameters (number and length of branches, number of leaves and fresh weight of the vegetative and root system). Salicylic acid application caused an increment in number of leaves, fresh and dry weight of root system. Citrus rootstocks Troyercitrange was superior on other rootstocks by giving highest values branches length, whereas Cleopatra mandarin rootstock was superior in the number of leaves. [ABSTRACT FROM AUTHOR]

This study was carried out in Wadi EL- Technologia in Ismailia Governorate, Egypt, during 2010 and 2011 seasons. Washington Navel (N.O.), Valencia (V.O.) and Baladi orange (B.O.) trees budded on Sour orange (S.O.) and Volkamer lemon (V.L.) were grown in sandy soil under drip irrigation system from a well has salinty of (1100 ppm).This investigation aimed to study the effect of the two citrus rootstocks on vegetative growth, yield, fruit quality, leaf mineral content of the three studied scions as well as the effect of such scions on root system growth of both rootstocks. The obtained results indicated that, Volkamer lemon rootstock recorded the highest significant values of vegetative growth, yield and fruit quality except T.S.S% and ascorbic acid content . Sour orange rootstock gave the highest significant effect on values of leaf mineral content (N, P, K, Mg, Fe, Zn and Cu) however V.L. showed the highest significant value. while, Ca leaf content recorded insignificantly difference between both rootstocks. Leaf Mn, content was significantly the highest with S.O. in both seasons. Root fresh and dry weight were the highest significantly with V.L. rootstock. From the showed result, one can recorded that V.O. scion significantly increased the vigour of V.L. root fresh and dry weight. While, B.O. scion showed significantly the lowest vigoure of V.L. root fresh and dry weight. On the other hand, N.O. scion gave a midiate result between V.O. and B.O. scions on root fresh and dry weight.

O trabalho foi desenvolvido com o objetivo de avaliar os efeitos de concentrações de paclobutrazol (PBZ) e ácido giberélico (GA3) sobre o desenvolvimento de plantas de limoeiro 'Volkameriano' cultivadas em sacolas plásticas, contendo 2,5 dm³ de substrato. O experimento foi montado em esquema fatorial 4x 2, sendo quatro concentrações de PBZ (0; 75; 150 e 225 mg do i.a. planta-1) e duas de GA3 (0 e 20 mg do i.a. L-1), no delineamento em blocos casualizados, com quatro repetições e cinco plantas por unidade experimental. Concentrações crescentes de PBZ reduziram o comprimento e diâmetro de caule, comprimento dos entrenós e área foliar, e aumentaram a massa foliar específica e as unidades SPAD. O GA3 reverteu a ação do PBZ. A aplicação de concentrações crescentes de PBZ, na presença de GA3, aumentou o diâmetro de caule até o valor máximo de 0,973 cm, que foi alcançado com a concentração estimada de 90,0 mg planta-1 de PBZ. O aumento das concentrações de PBZ não alterou o número de folhas, enquanto o GA3, na ausência do PBZ, aumentou em 10% o número de folhas e reduziu em 17,93% o comprimento de caule.This work was carried out to evaluate the effects of concentrations of paclobutrazol (PBZ) and giberellic acid (GA3) on the development of 'Volkameriano' lemon plants cultivated in recipients. The experiment was arranged in a 4 X 2 factorial scheme, with four concentrations of PBZ (0, 75, 150 and 225 mg of i.a. plant-1) and two concentrations of GA3 (0 and 20 mg of i.a. L-1), in a randomized block design with four repetitions and 5 plants per experimental unit. Increasing PBZ concentrations reduced the length and stem diameter, length of the internodes and leaf area. They increased the specific leaf mass and the SPAD units. The GA3 reversed the action of PBZ. The application of increasing concentrations of PBZ, in the presence of GA3, increased the stem diameter to the maximum value of 0,973 cm that was reached with the estimated PBZ concentration of 90.0 mg plant-1. The leaves number was not influenced by PBZ concentrations, while GA3, in the absence of PBZ, increased the leaves number in 10% and reduced the stem length in 17.93%.

Cytokinin oxidase/dehydrogenases (CKXs) in plants are coded by a small multigene family and play important roles in maintaining cytokinin homeostasis. In this study, fourCKXgenes (i.e.PsCKX1, PsCKX2, PsCKX5, andPsCKX7) were cloned fromPoncirus trifoliata. All PsCKXs contained a highly conserved flavin adenine dinucleotide (FAD) binding domain and a cytokinin dehydrogenase 1, FAD/cytokinin binding domain. PsCKX1 and PsCKX2 shared 66.2% and 65.4% identity with AtCKX6 and AtCKX1, respectively, while PsCKX5 and PsCKX7 exhibited less than 45% identity with AtCKXs. The expression analysis under abiotic conditions (NaCl, ABA, 6-BA and drought) revealed that the fourPsCKXgenes could respond to at least one treatment, and the expression patterns were diverse in root and leaf. Overexpressing fourPsCKXgenes in tobacco led to diverse phenotypic variations in transgenic plant, including leaf shape, root architecture, and plant height. In addition, the data showed thatPsCKX2andPsCKX5hold promise to obtain citrus dwarf rootstock with a stronger root system, since the overexpression of them resulted in dwarf plants with more lateral roots. Taken together, the work lays the basis for applications ofPsCKXgenes in future. [ABSTRACT FROM PUBLISHER]

Huanglongbing (HLB) is one of the most destructive bacterial diseases of citrus. No resistant cultivars have been identified, although tolerance has been observed in the genus Poncirus and some of its hybrids with Citrus that are commonly used as rootstocks. In this study we exploited this tolerance by comparing five different tolerant hybrids with a cultivar that shows pronounced HLB sensitivity to discern potential contributing metabolic factors. Whole leaves of infected and non-infected greenhouse-grown seedlings were extracted and subjected to untargeted GC-TOF MS based metabolomics. After BinBase data filtering, 342 (experiment 1) and 650 (experiment 2) unique metabolites were quantified, of which 122 and 195, respectively, were assigned by chemical structures. The number of metabolites found to be differently regulated in the infected state compared with the non-infected state varied between the cultivars and was largest (166) in the susceptible cultivar Cleopatra mandarin ( Citrus reticulata ) and lowest (3) in the tolerant cultivars US-897 ( C . reticulata ‘Cleopatra’ × Poncirus trifoliata ) and US-942 ( C . reticulata ‘Sunki’ × P . trifoliata ) from experiment 2. Tolerance to HLB did not appear to be associated with accumulation of higher amounts of protective metabolites in response to infection. Many metabolites were found in higher concentrations in the tolerant cultivars compared with susceptible Cleopatra mandarin and may play important roles in conferring tolerance to HLB. Lower availability of specific sugars necessary for survival of the pathogen may also be a contributing factor in the decreased disease severity observed for these cultivars. [ABSTRACT FROM AUTHOR]

The microbial community plays an essential role in maintaining the ecological balance of soils. Interactions between microorganisms and plants have a major influence on the nutrition and health of the latter, and growth-promoting rhizobacteria can be used to improve plant development through a wide range of mechanisms. Therefore, the objective of the present study was to evaluate bacteria as growth-promoting agents for citrus rootstocks. A total of 30 bacterial isolates (11 of Bacillus spp., 11 actinobacteria, and 8 lactic acid bacteria) were evaluated in vitro for indoleacetic acid production, phosphate solubilization, and nitrogen (N) fixation. In vivo testing consisted of growth promotion trials of the bacterial isolates that yielded the best results on in vitro tests with three rootstocks: Swingle citrumelo [ Citrus × paradisi Macfad cv. Duncan × Poncirus trifoliata (L.) Raf.], Sunki mandarin ( Citrus sunki Hort. ex Tan), and rangpur ( Citrus × limonia Osbeck). The parameters of interest were height, number of leaves, stem diameter, shoot and root dry mass, and total dry mass at 150 days after germination. The results showed that most bacterial isolates were capable of IAA production. Only one lactic acid bacterium isolate (BL06) solubilized phosphate, with a high solubilization index (PSI > 3). In the actinobacteria group, isolates ACT01 (PSI = 2.09) and ACT07 (PSI = 2.01) exhibited moderate phosphate-solubilizing properties. Of the Bacillus spp. isolates, only CPMO6 and BM17 solubilized phosphate. The bacterial isolates that most fixated nitrogen were BM17, ACT11, and BL24. In the present study, some bacteria were able to promote growth of citrus rootstocks; however, this response was dependent on plant genotype and isolate. Bacillus spp. BM16 and CPMO4 were able to promote growth of Swingle citrumelo. In Sunki mandarin plants, the best treatment results were obtained with BM17 ( Bacillus sp.) and ACT11 (actinobacteria). For Rangpur lime rootstock, only BM05 ( Bacillus sp.) was able to promote increase in two parameters assessed, height and number of leaves. When the bacterial isolates were used in mixture there was not promoted growth of plants on rootstocks. This fact may be associated with the different mechanisms of action of each bacteria involved or with the presence of competition among the microorganisms of the mixture. [ABSTRACT FROM AUTHOR]

The objective of this study was to identify polyploid plants from citrus rootstocks and to evaluate the influence of the genetic constitution and of the environment on the frequency of chromosome duplication. Populations obtained from rootstock seeds of Trifoliata [Poncirus trifoliate (L.) Raf], citrumelo 'Swingle' [C. paradise Macf. ? P. trifoliate], citrange 'Troyer' [C. sinensis (L.) Osb. x P. trifoliate] and citranges Fepagro 'C13', 'C37' and 'C41' [C. sinensis (L.) Osb. cv. Pêra x P. trifoliata] were evaluated under field and greenhouse conditions. Flow cytometry analysis of 415 field plants and 435 greenhouse plants identified seven (1.69%) and 29 (6.67%) tetraploids, respectively. Differences in the number of tetraploid plants among genotypes and locations were observed in field progenies of 'C 37' (2.12%) and 'C 13' (2.04%) and in greenhouse progenies of 'C 13' (15.52%) and 'C 37' (6%). The frequency of autotetraploidization events in citrus rootstocks is common and appears to be associated to genetic constitution and environmental conditions. [ABSTRACT FROM AUTHOR]

Background: Limited information is available on aluminum (Al)-toxicity-responsive proteins in woody plant roots. Seedlings of 'Xuegan' (Citrus sinensis) and 'Sour pummelo' (Citrus grandis) were treated for 18 weeks with nutrient solution containing 0 (control) or 1.2 mM AlCl3 • 6H2O (+Al). Thereafter, we investigated Citrus root protein profiles using isobaric tags for relative and absolute quantification (iTRAQ). The aims of this work were to determine the molecular mechanisms of plants to deal with Al-toxicity and to identify differentially expressed proteins involved in Al-tolerance. Results: C. sinensis was more tolerant to Al-toxicity than C. grandis. We isolated 347 differentially expressed proteins from + Al Citrus roots. Among these proteins, 202 (96) proteins only presented in C. sinensis (C. grandis), and 49 proteins were shared by the two species. Of the 49 overlapping proteins, 45 proteins were regulated in the same direction upon Al exposure in the both species. These proteins were classified into following categories: sulfur metabolism, stress and defense response, carbohydrate and energy metabolism, nucleic acid metabolism, protein metabolism, cell transport, biological regulation and signal transduction, cell wall and cytoskeleton metabolism, and jasmonic acid (JA) biosynthesis. The higher Al-tolerance of C. sinensis may be related to several factors, including: (a) activation of sulfur metabolism; (b) greatly improving the total ability of antioxidation and detoxification; (c) up-regulation of carbohydrate and energy metabolism; (d) enhancing cell transport; (e) decreased (increased) abundances of proteins involved in protein synthesis (proteiolysis); (f) keeping a better balance between protein phosphorylation and dephosphorylation; and (g) increasing JA biosynthesis. Conclusions: Our results demonstrated that metabolic flexibility was more remarkable in C. sinenis than in C. grandis roots, thus improving the Al-tolerance of C. sinensis. This provided the most integrated view of the adaptive responses occurring in Al-toxicity roots. [ABSTRACT FROM AUTHOR]

There is increasing interest in the culture of satsuma citrus in the states bordering the northern Gulf of Mexico. Yield, tree size, and fruit quality of mature 'Owari' and 'Brown Select' satsuma (Citrus unshiu Marcovitch) on Poncirus trifoliata (L.) Raf. ('Rubidoux' and 'Flying Dragon') were evaluated in north Florida. Canopy area and volume, yield, and fruit quality data were analyzed as a 2 x 2 factorial design with scion and rootstock as the main effects. There were no scion x rootstock interactions. Overall average yield per tree was 16, 88, 91, 143, and 101 kg in 2010, 2011, 2012, 2013, and 2014, respectively. Yield was influenced by scion (higher for 'Brown Select') in three of five years, and by rootstock every year (higher for 'Rubidoux'). Yield per tree was ≈2-fold greater for trees on 'Rubidoux' compared with 'Flying Dragon'; the highest yield was recorded for 'Brown Select' on 'Rubidoux'. Yield per m² canopy area was often similar since canopy area was often ≈2-fold greater for trees on 'Rubidoux'. For three of the five years, fruit weight was greater for 'Brown Select' (average = 157 g) than 'Owari' (average = 146 g), with no rootstock effect. Soluble solids of juice averaged 10.0 °Brix and were higher for trees on 'Flying Dragon' than on 'Rubidoux' in three of five years. Juice pH averaged 3.67 and was unaffected by scion or rootstock. Trees were not subjected to freeze protection and were not damaged by minimum temperatures as low as --9.4 °C, except for 2014/15. A rating of defoliation after a freeze on 19 Nov. 2014 (--5.6 °C) indicated that cold hardiness varied by scion (greater for 'Brown Select') and rootstock (greater for 'Rubidoux'). Differences in cold hardiness did not persist when assessed later in the winter. Successful satsumas production can be achieved in north Florida in the absence of a severe freeze event. [ABSTRACT FROM AUTHOR]