Citrange Rootstock Research Articles

Influence of Seed Priming with Trehalase Inhibitors on Inducing Salinity Tolerance in Sour orange and Troyer citrange Rootstocks

Influence of Seed Priming with Trehalase Inhibitors on Inducing Salinity Tolerance in Sour orange and Troyer citrange Rootstocks

Effects of Iron Rates on Growth and Development of Young Huanglongbing-affected Citrus Trees in Florida

Essential nutrients for citrus [‘Bingo’ (Citrus reticulata, Blanco)] production are important for different functions, including photosynthesis, resistance to disease, and productivity. During the past 15 to 20 years, citrus production in Florida has significantly declined as a result of the devastating citrus greening disease also called huanglongbing (HLB). Therefore, a greenhouse study was conducted for 2 years, starting in 2018, at the University of Florida/Institute of Food and Agricultural Sciences Citrus Research and Education Center in Florida to evaluate the effect of varying rates of iron on the growth and development of 2-year-old HLB-affected ‘Bingo’ (Citrus reticulata, Blanco) trees on Kuharske citrange rootstock. Four treatments were used in a randomized complete block (HLB status) design with seven single tree replicates for each treatment. The treatments applied were 0.0 (control), 5.6 (standard fertilization, lx), 11.2 (2x), and 22.4 (4x) kg⋅ha−1 iron on HLB-affected and healthy (non-HLB) citrus trees. Data including trunk diameter, tree height, and leaf samples were collected, processed, and analyzed at 3-month intervals for 2 years. At the end of the second year, trees were destructively sampled and processed as above-ground and below-ground biomass. Tree heights were different among iron rates of HLB-affected trees (P < 0.001); however, they were similar for non-HLB trees for both years. Higher average trunk diameters (P < 0.001) were observed for HLB-affected trees that received the 2x rate compared with the 1x rate and the control. In 2019, non-HLB trees showed 13% to 40% higher iron concentrations in leaves than HLB-affected trees. However, leaf iron concentrations were comparable for HLB-affected and non-HLB trees in 2020. Above-ground biomass for HLB-affected trees had between 33% and 44% more biomass (P < 0.01) than below-ground biomass for the corresponding iron fertilization. Iron accumulation correlated positively with all studied nutrients in the above-ground parts for both HLB-affected and non-HLB trees. A 95% confidence interval at which total biomass was nearly maximum corresponded to an iron rate of 9.6 to 11.8 kg⋅ha−1, which was close to the 2x rate. Therefore, soil iron application using the aforementioned rates may be appropriate for better growth and development of young HLB-affected trees.

Characteristics of boron distribution in the ‘Newhall’ navel orange plant with two root systems

Grafting is a technique that provides a substantial way to enhance nutrient utilization thereby improves plant growth and yield quality. Although it is commonly practised in horticultural crops, the impact of scion-rootstock interaction on nutrient distribution is still unclear. Here, ‘Newhall’ navel orange plants grafted on Trifoliate orange (T) as the original rootstock were inarched with trifoliate orange (N/Tt combination) or carrizo citrange (N/Tc combination) rootstock seedlings. The experimental plants were treated with isotope 10B solution for 7 weeks to investigate the effect of different inarched rootstocks on B distribution and translocation by using a two-root system. From this study, the original rootstock played a more dominant role in B distribution to scion tissues than the inarching rootstock either in N/Tt or N/Tc combination. From inarched combinations, the carrizo citrange in the N/Tc combination had a higher ability to distribute B to new leaves, new twigs and old twigs than trifoliate orange in the N/Tt combination. However, the original rootstock of N/Tt distributed more B to scion tissues than N/Tc and the B concentration in old leaves and new leaves of N/Tt plants was significantly higher than that of N/Tc plants. These results suggest that scion B status is influenced by the B distribution of two inarching rootstocks in an inarching plant, as well as the affinity between the inarching rootstock and grafted plant. In addition, by either adding 10B to the inarching rootstock or original rootstock, we could detect 10B in the other rootstock root in both N/Tt and N/Tc combinations. The results further suggest that B can translocate from rootstock to leaves and then, re-translocate from scion to rootstock through the cycling of B transportation.

The Total Population Size of 'Candidatus Liberibacter asiaticus' Inside the Phloem of Citrus Trees and the Corresponding Metabolic Burden Related to Huanglongbing Disease Development.

'Candidatus Liberibacter asiaticus' (CLas) is the predominant causal agent of citrus huanglongbing, the most devastating citrus disease worldwide. CLas colonizes phloem tissue and causes phloem dysfunction. The pathogen population size in local tissues and in the whole plant is critical for the development of disease symptoms by determining the load of pathogenicity factors and metabolic burden to the host. However, the total population size of CLas in a whole plant and the ratio of CLas to citrus cells in local tissues have not been addressed previously. The total CLas population size for 2.5-year-old 'Valencia' sweet orange on 'Kuharske' citrange rootstock trees was quantified using quantitative PCR to be approximately 1.74 × 109 cells/tree, whereas 7- and 20-year-old sweet orange trees were estimated to be 4.3 × 1010 cells/tree, and 6.0 × 1010 cells/tree, respectively. The majority of CLas cells were distributed in leaf tissues (55.58%), followed by those in branch (36.78%), feeder root (4.75%), trunk (2.39%), and structural root (0.51%) tissues. The ratios of citrus cells to CLas cells for branch, leaf, trunk, feeder root, and structural root samples were within approximately 39 to 79, 44 to 124, 153 to 1,355, 191 to 1,054, and 561 to 3,760, respectively, representing the metabolic burden of CLas in different organs. It was estimated that the ratios of phloem cells to CLas cells for branch, leaf, trunk, feeder root, and structural root samples are approximately 0.39 to 0.79, 0.44 to 1.24, 1.53 to 13.55, 1.91 to 10.54, and 5.61 to 37.60, respectively. Approximately 0.01% of the total citrus phloem volume was estimated to be occupied by CLas, explaining the difficulty to observe CLas in most tissues under transmission electron microscopy. The CLas titer inside the leaf was estimated to be approximately 1.64 × 106 cells/leaf or 9.2 × 104 cells cm-2 in leaves, approximately 104 times less than that of typical apoplastic bacterial pathogens. This study provides quantitative estimates of phloem colonization by bacterial pathogens and furthers the understanding of the biology and virulence mechanisms of CLas.

Stress-inducible Arabidopsis thaliana RD29A promoter constitutively drives Citrus sinensis APETALA1 and LEAFY expression and precocious flowering in transgenic Citrus spp.

Transgenic 'Duncan' grapefruit (Citrus paradisi Macf.) and 'Valencia' sweet orange (Citrus sinensis [L.] Osbeck) plants ectopically expressing C. sinensis (cv. Washington navel orange) APETALA1 (CsAP1) or LEAFY (CsLFY) genes under control of the Arabidopsis thaliana stress-inducible promoter AtRD29A flowered under non-inductive (warm temperature, well-watered) greenhouse conditions, whereas their wild-type (WT) counterparts did not. The transgenic plants that flowered exhibited no altered morphological features, except the lack of thorns characteristic of juvenile WT plants. The most precocious T0 line, 'Duncan' grapefruit (Dun134-3) expressing the CsAP1 gene, flowered and fruited when it was 4.5years old and the T1 siblings from this line flowered and fruited when they were just over 18months old. In contrast, T1 seedlings from three lines of 'Duncan' grapefruit expressing the CsLFY gene flowered within 3months after germination, but were unable to support fruit development. Transcript levels of corresponding transgenes in leaves were not correlated with earliness of flowering. To further study the activity of AtRD29A, leaves from three 'Carrizo' citrange (C. sinensis×Poncirus trifoliata) rootstock seedlings transformed with the green fluorescent protein (GFP) gene under regulation of the AtRD29A promoter were subjected to drought stress or well-watered conditions. Expression of GFP was not stress-dependent, consistent with the observation of flowering of CsAP1 and CsLFY transgenic plants under non-inductive conditions. Taken together, the results suggest that AtRD29A is constitutively expressed in a citrus background. Despite the loss of control over flowering time, transgenic citrus lines ectopically expressing C. sinensis AP1 or LFY genes under control of the A. thaliana RD29A promoter exhibit precocious flowering, fruit development and viable transgenic seed formation. These transformed lines can be useful tools to reduce the time between generations to accelerate breeding.

Influence of Endogenous Plant Hormones on Physiological and Growth Attributes of Kinnow Mandarin Grafted on Nine Rootstocks

Citrus holds the key position in horticulture sector of Pakistan in terms of area and production. Kinnow is considered as the trademark of Pakistan’s citriculture industry. Cultivation experiment was conducted to evaluate the endogenous plant hormones, leaf gas exchange, photosynthetic pigments, vegetative performance, and yield of Kinnow mandarin grafted on nine rootstocks (Rough lemon, cox mandarin, Fraser hybrid, Troyer citrange, Cleopatra mandarin, Poncirus trifoliata, Benton, C-35, and Carrizo citrange). Maximum indole acetic acid (IAA), gibberellic acid (GA3), and zeatin (ZT) levels were recorded in scion and rootstock of Poncirus trifoliata followed by Fraser hybrid. Troyer citrange rootstock depicted maximum amount of abscisic acid in scion and rootstock. Maximum leaf gas exchange in Kinnow mandarin was recorded on Fraser hybrid rootstock. Kinnow grafted on Troyer citrange rootstock had minimum stomatal conductance and photosynthetic activity because of high ABA level. Photosynthetic pigments of Kinnow mandarin were maximum on Poncirus trifoliata and minimum on Troyer citrange. A positive correlation was observed among the levels of IAA, GA, ZT, and vegetative growth of Kinnow mandarin. It is concluded that endogenous hormones modulated the growth of Kinnow mandarin. Poncirus trifoliata and Fraser hybrid rootstocks could be an alternate rootstocks of traditional Rough lemon for Kinnow mandarin.

Improved response of triploid citrus varieties to water deficit is related to anatomical and cytological properties

Polyploidy plays a major role in citrus plant breeding to improve the adaptation of polyploid rootstocks as well as scions to adverse conditions and to enhance agronomic characteristics. In Citrus breeding programs, triploidy could be a useful tool to react to environmental issues and consumer demands because the produced fruits are seedless. In this study, we compared the physiological, biochemical, morphological, and ultrastructural responses to water deficit of triploid and diploid citrus varieties obtained from ‘Fortune’ mandarin and ‘Ellendale’ tangor hybridization. One diploid clementine tree was included and used as a reference. All studied scions were grafted on C-35 citrange rootstock. Triploidy decreased stomatal density and increased stomata size. The number of chloroplasts increased in 3x varieties. These cytological properties may explain the greater photosynthetic capacity (Pnet, gs, Fv/Fm) and enhanced water-holding capacity (RWC, proline). In addition, reduced degradation of ultrastructural organelles (chloroplasts and mitochondria) and thylakoids accompanied by less photosynthetic activity and low oxidative damages were found in 3x varieties. Triploid varieties, especially T40-3x, had a better ability to limit water loss and dissipate excess energy (NPQ) to protect photosystems. Higher starch reserves in 3x varieties suggest a better carbon and energy supply and increases in plastoglobuli size suggest less oxidative damage (H2O2, MDA), especially in T40-3x, and preservation of photosynthetic apparatus. Taken together, our results suggest that desirable cytological and ultrastructural traits induced by triploidy improve water stress response and could be a useful stress marker during environmental constraints.

Effect of some Citrus Rootstocks Types on Growth and Productivity of Gold Nugget Mandarin Trees

The present investigation was carried out during two successive seasons (2018/2019; 2019/2020) on almost 12-year old identical Gold Nuggettrees(Citrus reticulate, Blanco) (Wilking mandarin x Kincy mandarin), grafted on three rootstocks cultivated in a private orchard located in Al Qalyubia Governorate, Egypt. The trees were grown at a distance of 2 × 6 m in silt soil under the Immersion irrigation system. This investigation aimed to study the effect of some citrus rootstocks on Gold Nugget mandarin trees Growth and Productivity. Three citrus rootstocks were: Troyer citrange Citrus sinensis 'Washington' x Poncirus trifoliate (Tr.), Sour orange (Citrus aurantium L.) (SO.) and Volkamer Lemon (Citrus volkameriana) (VOL). The experiment was designed as a randomized complete block design with five replications. The obtained results showed that Gold Nugget grafted on Troyer citrange rootstock recorded the highest significant values of chlorophyll a, b, total chlorophylls, total carbohydrates, spring growth cycle, fruit set and yield. Whereas Gold Nugget grafted on Sour orange rootstock recorded the highest significant values of shoot thickness, Leaf surface area, Rate Increasing canopy, vitamin C and TSS/ acid ratio. Regarding Gold Nugget grafted on Volkamer lemon rootstock recorded the highest significant values of dray matter percentage, the number of leaves, tree Canopy, summer growth cycle, flowering, fruit Physical properties and acidity percentage.

The vascular targeted citrus FLOWERING LOCUS T3 gene promotes non-inductive early flowering in transgenic Carrizo rootstocks and grafted juvenile scions

Shortening the juvenile stage in citrus and inducing early flowering has been the focus of several citrus genetic improvement programs. FLOWERING LOCUS T (FT) is a small phloem-translocated protein that regulates precocious flowering. In this study, two populations of transgenic Carrizo citrange rootstocks expressing either Citrus clementina FT1 or FT3 genes under the control of the Arabidopsis thaliana phloem specific SUCROSE SYNTHASE 2 (AtSUC2) promoter were developed. The transgenic plants were morphologically similar to the non-transgenic controls (non-transgenic Carrizo citrange), however, only AtSUC2-CcFT3 was capable of inducing precocious flowers. The transgenic lines produced flowers 16 months after transformation and flower buds appeared 30–40 days on juvenile immature scions grafted onto transgenic rootstock. Gene expression analysis revealed that the expression of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and APETALA1 (AP1) were enhanced in the transgenics. Transcriptome profiling of a selected transgenic line showed the induction of genes in different groups including: genes from the flowering induction pathway, APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) family genes, and jasmonic acid (JA) pathway genes. Altogether, our results suggested that ectopic expression of CcFT3 in phloem tissues of Carrizo citrange triggered the expression of several genes to mediate early flowering.

Oleocellosis development in Persian lime (Citrus latifolia T.) fruit influenced by citrus rootstock

Mexico is the main producer and exporter of Persian lime worldwide. Oleocellosis is one of the main physiological disorders of acid limes which affects visual quality of the fruit and cause economic losses. The objective of this work was to determine the effect of Sour orange, Volkamerian lemon, Flying dragon, Swingle citrumelo and C-35 citrange rootstocks on the anatomy of the flavedo and its correlation with the development of oleocellosis in Persian lime (Citrus latifolia T.) fruit. Susceptibility and development of oleocellosis by postharvest handling and mechanical damage, as well as the histological characteristics of the flavedo (cuticle, epidermis, oil glands and stomata) were evaluated. There was no effect of the rootstock on thickness of cuticle, epidermis and flavedo, oil glands size, boundary cells layers and stomata. In general, fruit grown on the Flying dragon rootstock were less susceptible to develop oleocellosis compared with fruit from the other studied rootstocks. Fruit grown on Sour orange and C-35 citrange rootstocks showed the highest number of oil glands, which might be related to an increased susceptibility to develop oleocellosis. Oleocellosis induced in the present study was directly proportional to a greater mechanical damage. Flying dragon might be a promising Persian lime rootstock for reducing susceptibility to develop oleocellosis.

EFFECTS OF CITRUS ROOTSTOCKS ON SOME PLANT NUTRIENT ELEMENTS ABSORPTION OF GRAFTED CULTIVARS

Citrus rootstocks have prime effects on the size of tree and fruit, quality of fruit and micorhyza dependence, which make difference in their leaf mineral elements concentration in leaf of grafted cultivars on them. A pot factorial experiment with two factors including rootstocks (sour orange, Citrange, Rough Lemon, Citrumelo and Yozo) and grafted cultivars (Thomson Navel, Sanguine, Unshiu Tangerine) was carried out in farm conditions with three replications. The studied traits were concentrations of elements in leaves including nitrogen, phosphorus, potassium, sulfur, magnesium, iron, manganese, zinc and copper. The result of analysis of variance revealed significant mean squares of variety, rootstock and their interaction effects for the elements in leaves. Citrumelo rootstock had mainly effect on nutritional elements in leaves. Unshiu mandarin with Citrumelo rootstock had the most amount of nitrogen and sanguine variety with Citrange rootstock made the highest concentration of phosphorus and potassium in leaves of the grafted cultivar. Significant positive correlation of K with Fe and Zn indicating that all rootstocks with high mean value of K in leaf of grafted cultivar will have high amount of Fe and Zn. Significant positive correlation also detected between N and P of leaf of grafted cultivars in combination with different rootstocks; therefore, most of combinations with high mean value of N had also high mean value of P. Unshiu Tangerine had high variation for P, but Thomson Novel had lowest variation for this mineral element. Due to Significant positive correlation of S with Mg and Mn, most of rootstocks with high amount of S in leaf of grafted cultivar had high mean values of Mg and Mn in their leaf of grafted cultivars.

Full genome characterization of 12 citrus tatter leaf virus isolates for the development of a detection assay.

Citrus tatter leaf virus (CTLV) threatens citrus production worldwide because it induces bud-union crease on the commercially important Citrange (Poncirus trifoliata × Citrus sinensis) rootstocks. However, little is known about its genomic diversity and how such diversity may influence virus detection. In this study, full-length genome sequences of 12 CTLV isolates from different geographical areas, intercepted and maintained for the past 60 years at the Citrus Clonal Protection Program (CCPP), University of California, Riverside, were characterized using next generation sequencing. Genome structure and sequence for all CTLV isolates were similar to Apple stem grooving virus (ASGV), the type species of Capillovirus genus of the Betaflexiviridae family. Phylogenetic analysis highlighted CTLV's point of origin in Asia, the virus spillover to different plant species and the bottleneck event of its introduction in the United States of America (USA). A reverse transcription quantitative polymerase chain reaction assay was designed at the most conserved genome area between the coat protein and the 3'-untranslated region (UTR), as identified by the full genome analysis. The assay was validated with different parameters (e.g. specificity, sensitivity, transferability and robustness) using multiple CTLV isolates from various citrus growing regions and it was compared with other published assays. This study proposes that in the era of powerful affordable sequencing platforms the presented approach of systematic full-genome sequence analysis of multiple virus isolates, and not only a small genome area of a small number of isolates, becomes a guideline for the design and validation of molecular virus detection assays, especially for use in high value germplasm programs.

Distribution and Mobility of Foliar-Applied Boron (10B) in Citrange Rootstock Under Different Boron Conditions

Although foliar-applied boron (B) could rapidly and effectively relieve B deficiency of plants, the distribution and mobility of foliar-applied B in citrange, an important rootstock of citrus, are poorly understood. This study aimed to investigate the transportation and variation of B allocation in different parts of citrange under different B conditions by spraying 10B on the lower mature leaves of citrange rootstock for 8 weeks. The results indicated that foliar B on lower mature leaves led to higher 10B abundance and 10B concentration in different parts of plants. Compared with the low-B plants, 10B abundance in stems, lower, and upper mature leaves of medium-B plants increased 23.95, 7.22, and 8.33% respectively. Moreover, under low- and medium-B conditions, abundance and percentage of 10B were higher in roots than that in other tissues after foliar application 10B. Meanwhile, abundance and percentage of foliar-10B in stems and old leaves under B-insufficient condition were much lower than that of B-sufficient condition. Furthermore, the 10B allocation rate was the highest in roots under the two different B conditions. There were higher 10B allocation rates in new leaves and lower mature leaves, and lower 10B allocation rates in stems and upper mature leaves in medium-B plants comparing with that in low-B plants. All these results suggest that foliar-applied 10B on lower mature leaves could be translocated to every part of citrange rootstock, with the majority distributed in roots, and the mobility of foliar B from lower mature leaves to other parts was different between low- and medium-B treatments, leading to a significant variation in translocation rate for each part of citrange.

Effect of Rootstock and Arginine Spraying in Some Vegetative Growth Characteristics for Two Citrus Species

The study was carried out to study the effect of arginine spraying and rootstocks difference in some shoot growth to four cultivars. A Randomized Complete Block design (RCBD) in a factorial experiment was used with three factors, namely: Arginine levels (0 and 250 mgL-1), Citrus rootstocks (Sour orange, Volkameriana lemon and Troyer citrange) and Citrus species (Navel orange, local orange, common mandarin and Clementine mandarin) in three replications. Results analyzed according to SAS and differences between the means compared using Duncan's test at 0.05 probability level. Results showed navel orange was superior in stem diameter and carbohydrate, Clementine mandarin superior in plant length, Troyer strange superior in plant length, arginine superior in plant length, stem diameter, leaf area, carbohydrate and N. Interaction between Clementine mandarin and volkameriana superior plant length and interaction with troyer citrange superior in leaf area, and interaction with sour superior in leaves content of N, navel orange interaction with troyer citrange in stem diameter and carbohydrate. Interaction clementine mandarin with Arginine superior in plant length, interaction arginine with common mandarin in N content, interaction arginine with orange navel superior in stem diameter and carbohydrate, and interaction troyer citrange rootstock with arginine superior plant length and leaf area,Triple interaction between clementine mandarin with volkameriana rootstock and arginine superior in plant length, interaction common mandarin with sour and arginine superior in N content, and superior navel orange with troyer citrange rootstock and arginine in stem diameter and carbohydrate content, and local orange with sour rootstock and arginine superior in leaf area.

Performance of ‘Cadenera’ orange trees grafted on five rootstocks

Abstract Citriculture is an important alternative for the agribusiness development in the state of Paraná, Brazil. However, the use of a few cultivars of scion and rootstock restricts the harvest period and increases the vulnerability to pests and diseases. This study aimed to evaluate the vegetative growth, production and fruit quality of ‘Cadenera’ orange trees (Citrus sinensis (L.) Osbeck ) grafted on five rootstocks, during nine harvests, under a subtropical environmental condition. The experimental design was randomized blocks with six replications, two plants per plot, and five rootstocks: ‘Rangpur’ lime (C. limonia Osb.), ‘Cleopatra’ (C. reshni hort. ex Tanaka ) and ‘Sunki’ mandarins (C. sunki hort. ex Tanaka (L.) Raf.), ‘Swingle’ citrumelo [C. paradisi Macfad. x Poncirus trifoliata (L.) Raf.], and ‘C-13’ citrange [C. sinensis (L.) Osbeck cv. Pera x P.s trifoliata (L.) Raf.]. Biometric variables, and fruit yield and quality were analyzed. The smallest canopy size was induced by ‘Rangpur’ lime and ‘C 13’ citrange rootstocks. ‘Swingle’ citrumelo and ‘C 13’ citrange provided the highest yields for the ‘Cadenera’ sweet orange trees and were superior to ‘Rangpur’ lime. Trees grafted on ‘C 13’ citrange presented the highest yield and productive efficiency.

Trifoliate hybrids as alternative rootstocks for ‘Valencia’ sweet orange under rainfed conditions

Abstract Considering the low diversity of rootstocks in the Brazilian citrus industry, as well as in other important citrus production regions, here we investigated the yield, fruit quality, plant size and drought tolerance of ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck] grafted onto eleven rootstocks in the northern region of Sao Paulo State, Brazil. The trial was installed with no supplementary irrigation. Various combinations (scion/rootstock) were planted in March 2007 and submitted to measurements of yield and fruit quality, canopy volume, yield efficiency, growth rate, and drought tolerance. We detected high yield in ‘Valencia’ sweet orange grafted onto “CNPMF 003” ‘Rangpur’ lime rootstock. Regarding other measurements, it was also attributed to two combinations high fruit quality of ‘Valencia’ sweet orange and to other three combinations satisfactory drought tolerance compared to two ‘Rangpur’ lime clones. ‘Valencia’ sweet orange trees grafted onto two rootstocks were suitable for high-density planting. As an alternative to ‘Rangpur’ lime, the ‘Sunki’ mandarin × P. trifoliata ‘English’ and ‘C-13’ “S” citrange rootstocks showed potential as rootstocks for ‘Valencia’ sweet orange in rainfed conditions.

Rootstock evaluation for sweet orange cv. Early Gold in arid irrigated region of Punjab

The performance of sweet orange cv. Early Gold on different rootstocks was evaluated at Regional Research Station Abohar, Punjab during 2013–16. The plants budded on different rootstocks were supplied by Punjab Agri Export Corp. Ltd., imported from USA. The data was analyzed in a randomized block design, replicated fourtimes. Fruit yield was significantly higher and comparable in trees raised on Carrizo citrange (39.1 kg/tree) and Jatti khatti rootstock (37.7 kg/tree) than other rootstocks. Fruits on Carrizo rootstock registered maximum juicecontent (48.47%), which was statistically same as observed on Jatti khatti and Volkamer lemon. Total soluble solids were also highest on Carrizo. Fruit quality index (TSS: acid ratio) was comparable in Volkamer lemon, Jatti khatti and Carrizo citrange rootstocks. The trees raised on commercial Jatti khatti rootstock were quite younger but resulted comparable yield and fruit quality to that of Carrizo. Hence, Jatti khatti seem to be the most suitable rootstock for raising ‘Early Gold’ sweet orange in arid irrigated regions of Punjab.

‘JAFFA’ SWEET ORANGE PLANTS GRAFTED ONTO FIVE ROOTSTOCKS

ABSTRACT Low genetic diversity of citrus scion and rootstock cultivars makes the crop more vulnerable to diseases and pests. The objective of this study was to evaluate the performance of ‘Jaffa’ sweet orange grafted onto five rootstocks over six harvests in subtropical conditions in the north of Paraná state, Brazil. The experiment used a randomized block design, with six replications and two trees per plot, spaced at 7.0 m x 4.0 m. The rootstocks were: ‘Rangpur’ lime, ‘Cleopatra’ and ‘Sunki’ mandarins, ‘Fepagro C-13’ citrange, and ‘Swingle’ citrumelo. The variables evaluated were vigor, yield, and yield efficiency of the trees as well as the physical and chemical characteristics of the fruits. Data were subjected to analysis of variance, complemented by Scott-Knott test at 5% probability. The smallest tree canopy for ‘Jaffa’ sweet orange plants was induced by the ‘Rangpur’ lime rootstock. The trees had the same cumulative yield performance over six seasons for all rootstocks. The best yield efficiency for ‘Jaffa’ sweet orange trees was provided by ‘Fepagro C-13’ citrange rootstock. With regard to fruit quality, no differences were observed among the rootstocks and the ‘Jaffa’ sweet orange fruits met the standards required by the fresh fruit market and the fruit processing industry.

Influence of Citrus Rootstocks in Bioactive Compounds of Clementines

Citrus fruit is one of the most important commercial fruit crops in the world. It is essential to use citrus rootstocks in this crop, since all varieties, whether, oranges, tangerines, lemons and grapefruits are highly sensitive to Phytophthora spp., present in almost all soils. Selection of optimal rootstock is crucial for commercial cultivation of citrus fruit, as the effect fruit production, tree size, diseases, and adaptation to certain soil conditions. Besides, rootstock may affect internal quality parameters of citrus fruits, including juice total, soluble solids, acidity, antioxidant capacity, sugars and organic acids content, flavor. In this study, we evaluated the effect of three rootstocks (Carrizo citrange, C-35 citrange and Forner-Alcaide 5) on physicochemical parameters, sugars and organic acids, total antioxidant activity, total phenolic, crude fibre content and flavonoids, of ‘Clemenrubi’ and ‘Orogros’ clementines. The results indicate that the effect of rootstock on the physicochemical parameters, antioxidant activity, total phenolic, sugars and organic acids and flavonoids of clementines fruits is a rather complex phenomenon that greatly depends on specific interactions between the rootstock and each particular scion variety. C-35 citrange rootstock produced the heaviest and bigger size fruits, while the rootstock Forner-Alcaide 5 produced the fruit with the major flavonoid content.

Root morphology and the effect of rootstocks on leaf nutrient acquisition of Kinnow mandarin (Citrus nobilis Loureiro × Citrus reticulata Blanco)

ABSTRACTThe study aimed to understand the root morphological character of 1 year old seedling rootstock of citrus genotypes viz., rough lemon, Karna Khatta, Carrizo citrange, Rangpur lime, Troyer citrange, Jatti Khatti and sour orange as well as to investigate the effect of these rootstocks on the leaf mineral composition of Kinnow. Root morphological traits showed significant genotypic variation. Rough lemon seedlings had a higher root length, projected area, surface area, volume and the number of forks. Sour orange was moderate rootstock of the 7 genotypes for most of the root morphological characters, while citrange rootstocks expressed poor root morphology. The rootstocks also imparted significant influence on the leaf mineral composition. Leaf K, Ca and Mg content was recorded maximum in plants grown on rough lemon seedling, while N, P, Fe, Zn, Mn and Cu concentration was higher on sour orange rootstock. Kinnow trees on Rangpur lime rootstock accumulated more Na in their leaf tissue, where as Troyer citrange restricted the accumulation of Na. Considering the root morphological characters and nutrient accumulation pattern, rough lemon and sour orange for areas free from tristeza virus could be suggested as alternative rootstocks for the studied Kinnow mandarin under similar ecological conditions.