Citrus rootstocks play a vital role in imparting tolerance or resistance to diseases. Dry root rot induced by Fusarium solani is one of most destructive soil-borne diseases of citrus. The present study was conducted under the All India Coordinated Research Project (AICRP) on Fruits scheme at Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, to evaluate the tolerance of different citrus rootstocks against F. solani. A total of 8 rootstocks (NRCC-1, NRCC-2, NRCC-3, NRCC-4, CRH-12, Rangpur lime, Alemow and Jambheri) were evaluated using different screening methods, including the seedling inoculation method, leaf inoculation with injury, leaf inoculation without injury and application of culture filtrate on wounded leaf segments. All the examined rootstocks exhibited variable levels of susceptibility to dry root rot. In the seedling inoculation method, rootstock mortality ranged from 20.00 % in Rangpur lime to 60.67 % in Jambheri. Leaf lesion lengths following injury ranged from 14.45 mm (Rangpur lime) to 24.43 mm (Jambheri), whereas without injury lesions ranged from 11.95 mm (Rangpur lime) to 20.43 mm (NRCC-4). Culture filtrate bioassays produced lesion areas ranging from 1.01 cm² (Rangpur lime) to 1.69 cm² (NRCC-1). Among the evaluated rootstocks, Rangpur lime exhibited comparatively higher tolerance to F. solani. Leaf inoculation with injury was found to be a rapid and reliable method for screening citrus rootstocks against dry root rot.

An investigation on Acid lime (Citrus aurantifolia L.) cv. Kagzi is an important citrus crop valued for its high acidity, juice content and year-round demand, but seed propagation causes genetic variability and a long juvenile phase, making vegetative propagation necessary. Softwood grafting on Rangpur lime (Citrus limonia Osbeck) was standardized during 2024 -25 at KRCCH, Arabhavi, to identify the best grafting month and growing environmental conditions. Results showed significant effects of month, growing conditions and their interactions on sprouting, growth, vigour, biomass and survival, with polyhouse showing earliest sprouting (20.85 days) and superior growth, and 15th January recording maximum vigour and biomass. The combination C3M6 (15th January under poly house) recorded highest graft success (90.74%) and survival (92.86%). Thus, softwood grafting during mid-January under polyhouse conditions is recommended for producing vigorous, true-to-type, high-quality Kagzi lime plants.

The constitutive overexpression of CsNF-YA5 in transgenic Swingle citrumelo rootstocks enhanced drought tolerance by improving stomatal regulation, antioxidant defense, and root recovery capacity. These physiological and molecular adjustments, most evident in line NF52, also benefited the grafted sweet orange scion, highlighting the potential of transgenic rootstocks to enhance citrus resilience under water-deficit conditions. Drought stress represents a critical challenge for citrus cultivation, directly affecting plant development and productivity. This study investigated the potential of the CsNF-YA5 gene, an NF-Y transcription factor, to confer drought stress tolerance in citrus rootstocks. Transgenic Swingle citrumelo plants overexpressing CsNF-YA5 from rangpur lime (Citrus limonia Osb.) were developed and evaluated under different water regimes controlled by leaf water potential (Ψleaf): control (- 0.2 to - 0.4MPa), moderate stress (- 1.0 to - 1.5MPa), and severe stress (< - 1.5MPa), followed by rehydration. Through physiological (gas exchange, water-use efficiency), biochemical (H2O2 accumulation), and molecular (gene expression by RT-qPCR) parameters, we demonstrated that transgenic plants, particularly the NF52 line, exhibited improved stomatal regulation, reduced leaf dehydration rates, and decreased reactive oxygen species (ROS) accumulation compared to wild-type genotype. Additionally, the NF52 line showed faster post-rehydration recovery and enhanced root system development. Importantly, the beneficial effects were not restricted to the rootstock: 'Valencia' sweet orange grafted onto transgenic Swingle citrumelo also exhibited higher water-use efficiency, lower H2O2 accumulation, and better recovery after stress. These results provide compelling evidence that CsNF-YA5 overexpression coordinately modulates drought stress responses in both citrus rootstocks and grafted plants, representing a promising biotechnological strategy for the development of climate-resilient citrus.

Citrus seedlings are typically propagated through grafting, using rootstocks grown from seeds. However, the coating of citrus rootstock seeds can hinder germination. Therefore, applying sodium hypochlorite (NaClO) provides an alternative to manually removing the seed coat, potentially enhancing seed germination and seedling emergence. This study investigates the use of sodium hypochlorite (NaClO) as a scarification agent on freshly harvested Rangpur lime seeds to improve germination and seedling emergence. The experiment employed a completely randomized design with a 3 × 3 factorial arrangement and an additional treatment across four replications. The variables assessed included three NaClO concentrations (0.0% - distilled water; 2.5%, and 5.0% active chlorine) and three soaking durations (3, 6, and 9 hours), with a control of unsoaked seeds retaining their coats. The evaluated parameters were germination rate, first germination count, seedling emergence, speed index, and mean seedling emergence time. Results showed that NaClO effectively degrades the seed coat, with a 2.5% concentration for 6 hours optimizing germination. While NaClO treatment did not alter emergence rates, it reduced the average time to seedling emergence. Conversely, a 5.0% concentration for 9 hours detrimentally affected germination and vigor. Sodium hypochlorite soaking presents a viable alternative for seed coat removal, accelerating germination and emergence processes in Rangpur lime tree seeds, potentially enhancing seedling production efficiency.

‘Pera’ sweet orange is a key variety for the Brazilian citrus industry, but orchards rely on a limited number of clonal selections, which restricts adaptability and productivity across diverse environments. This study assessed the agronomic performance of 13 ‘Pera’ selections grafted on Rangpur lime, cultivated under rainfed conditions in subtropical Brazil. From 2002 to 2010, trees were assessed for vegetative growth, cumulative yield, alternate bearing, and fruit quality. Market-specific performance indices were calculated to determine suitability for fresh fruit or juice processing. Substantial genotypic variation was observed across traits, particularly during early orchard stage. Selections such as ‘Morretes’, ‘Seleção 11’, ‘Seleção 27’, ‘Seleção 37’, and ‘IPR 153’ demonstrated high cumulative yield, stable productivity, and favorable canopy traits, supporting their use in both conventional and high-density systems. ‘IPR 153’ combined compact growth with high yield efficiency and excellent fruit quality, while ‘Morretes’ had the highest juice content and broad market adaptability. In contrast, ‘IPR 159’ showed low vigor and yield under rainfed conditions. The results emphasize the value of regionally targeted clonal selection to improve orchard performance and market alignment. The identification of dual-purpose genotypes offers a pathway to diversify citrus production and improve profitability under subtropical growing conditions.

Citrus is one of the most key members of the Rutaceae family and a widely grown fruit crop worldwide, containing considerable amounts of vitamin C and flavonoids. Rootstocks were used because they are resistant to soil-borne diseases and promote healthy production. Seeds were taken from citrus rootstocks and cultured in MS media with different concentrations of sucrose, M1 (30 g L-1 sucrose) and M2 (15 g L-1). In this study, eight rootstocks were collected for in vitro regeneration: citrumelo (Citroncirus spp.), citron (Citrus medica), Volkamariana (Citrus volkamariana), Rangpur lime (Citrus limonia), rough lemon (Citrus jambhiri Lush), sour orange (Citrus aurantium), Kharna Khatta (Citrus Kharna) and Carrizo citrange (Citrus sinensis). These materials were used for further propagation and regeneration through tissue culture. All these rootstocks were capable of regenerating and producing in vitro plantlet shoots. Data were collected on days to initiate germination, contamination, number of leaves per plant, leaf length (mm), leaf width (mm), leaf area (mm), and plant height (mm). The data were analysed using STATISTIX 8.1, and the means were compared using the least significant difference (LSD) test at the 5% significance level. The maximum leaf area (203.55 cm²) and maximum plant height (19.07 cm) were observed in citrange grown in MS media 1 (M1). The maximum leaf number (13.77) was observed in sour orange in MS media 1 (M1). Regenerated plantlets were transplanted for acclimatisation to obtain the best results. Therefore, a maximum of 96.6% plantlets of citrange and a minimum of 86.6% plantlets of Kharna Khatta were successfully shifted from MS media 1 containing 30 g L-1 sucrose. However, a maximum of 90% of the plantlets of Kharna Khatta and a minimum of 10% of citrumelo were successfully shifted from MS media 2 containing 15 g L-1 sucrose.

Rootstock selection plays a key role in influencing graft success tree vigor, yield quality, and resilience to biotic and abiotic stresses. A study was conducted at Nagaland University in 2021-2023, in which eight citrus rootstocks (Indian wild orange, Tasi orange, Rangpur lime, Khasi papeda, Citrange, Karna Khatta, Kachai lemon, and Rough lemon) were systematically evaluated for seed germination, seedling vigor, root development, grafting success, and overall performance under shade net conditions. Among the rootstocks, rough lemons showed the highest seed germination rate and exhibited superior seedling growth, including better seedling height, diameter, shoot and leaf number, and overall vigor. Grafting success with Khasi mandarin was the highest on rough lemon and Karna khatta rootstocks. However, Citrange performed poorly on most of the growth parameters studied. The results suggested that rough lemons and Karna khatta have potential as rootstocks for Khasi mandarin grafting, seedling vigor, and strong root systems. Further evaluation at the field level is essential to determine the compatibility of the scion-stock relationship and its impact on fruit quality and yield.

Citrus greening disease (CGD), devastating phloem residing proteobacteria, Candidatus Liberibacter asiaticus, has significantly impacted various citrus species in Tamil Nadu, India. A roving survey of citrus species revealed that the infected Citrus aurantifolia from Palamedu, Madurai district, exhibited the highest susceptibility, with a disease incidence (DI) of 67.89 % and disease severity (DS) of 65.89 %. In contrast, Poncirus trifoliata from Thadiyankudisai, Dindigul district, demonstrated the highest tolerance with a DI of 10.46 % and DS of 12.56 %. Molecular assessments using PCR and LAMP techniques confirmed the infection of CGD in symptomatic samples of Citrus aurantifolia, Citrus reticulata and Citrus × limonia, while asymptomatic samples tested negative. Biochemical analyses revealed substantial changes in metabolite compositions due to infection. Healthy acid lime contained 79 metabolites, with organic acids (27.84 %) and sugars (20.25 %) being the most dominant groups, whereas infected samples showed reduced diversity with only 60 metabolites. Similarly, healthy mandarin orange contained 93 metabolites, while infected samples exhibited 68 metabolites, significantly reducing sugars and organic acids. Poncirus and Rangpur lime also demonstrated metabolic shifts under infection, reducing the number and proportion of various metabolites. Comparative metabolic analysis highlighted the changes in key metabolites, with significant upregulation of mannose, hexadecenoic acid and maltose in healthy acid lime and downregulation of talose and shikimic acid in infected samples. Metabolomics revealed that compounds like tetramethoxyflavone, quinic acid and linoleic acid were consistently more abundant in healthy citrus samples. These findings provide insights into the biochemical responses of different citrus species to CGD, emphasizing the potential of tolerant varieties such as Poncirus trifoliata and guiding future disease management strategies through targeted metabolomic interventions.

An experiment was conducted from 2021 to 2023 at the tissue culture laboratory, micro-propagation unit, Uttar Banga Krishi Viswavidyalaya, Pundibari, West Bengal, to observe the seed germination behaviour and standardise the seedling rootstock for in vitro shoot-tip grafting. The experiment was laid out in a completely randomised design with three replications, comprising eight different citrus rootstocks (viz., NRCC 1, 2, 3, 4, Rough lemon, Rangpur lime, Pummelo, and Mandarin) as a control treatment, which were cultured in Murashige and Skoog basal media. Seeds were treated with Tween 80 for 15 minutes, followed by bavistin 500 mg for 1 hour, plantomycin 50 mg for 10 minutes, and mercuric chloride 100 mg for 2 minutes before inoculation to remove toxic residues from the seeds and also to prevent fungal and bacterial contamination. Seeds were thoroughly washed with double-distilled water three times after each treatment. In each treatment, 100 seeds were inoculated, with five seeds per jam bottle. The results showed that Rough lemon had the highest seed germination rate (81.84%), followed by NRCC 4 (81.41%). The first sprouting of seed was observed in pummelo (5.49 days) followed by rangpur lime (5.59 days). The minimum days required for 50% seed sprouting were observed in NRCC 4 (7.47 days) and Mandarin (7.93 days). The minimum average number of days required for seed germination was observed in NRCC 3 (13.13), followed by NRCC 2. The germination index was found to be highest in NRCC 4 (59.00%), followed by NRCC 2 (44.16%). The polyembryony rate was observed to be highest in Mandarin (24.19%) and Rangpur lime (16.29%). The highest number of leaves was observed in rough lemon, pummelo and NRCC 4 (2.67). Rootstocks such as rough lemon, NRCC 4, pummelo, and rangpur lime have shown potential for in vitro shoot-tip grafting.

(3092) Citrus granulata Raf., Sylva Tellur.: 143. Oct–Dec 1838 [Angiosp.: Rut.], nom. utique rej. prop. Typus: deest. In a recently published account of the accepted names of Citrus species and hybrids grown in Australia (Mabberley in Telopea 25: 271–284. 2022), only synonyms commonly encountered today were indicated, but it was noted “Many of yet other published names of cultivated citrus have no type specimens and exiguous or scarcely diagnostic descriptions, making their identity dubious (…) and their continued use valueless (though some may in fact represent known hybrid combinations enumerated below - or yet others). Moreover, the literature is littered with conclusions based on misidentified taxa, besides names applied in ways completely at odds with their type specimens (where they exist), while even modern molecular work is sometimes unaccompanied by citation of herbarium vouchers, making identification of sampled taxa equivocal and thereby interpretation of consequent phylogenetic trees problematic” (p. 272). Citrus granulata Raf. (Sylva Tellur.: 143. 1838) is such a case, published as one of 14 “real new species”, many of which already had validly published names and can be readily synonymised. Rafinesque (l.c.: 141) indicated that he was basing his names on living material but no type material has ever been found and it is likely that no herbarium material was preserved. His meagre description of C. granulata is “Citrus granulata Raf. pet. lin. fol. ovatis granulatis acum. fruct. granulato --- granular Lemon. India like all Lemons.” While this description could be applied to rough lemon and could be the earliest name for that hybrid, without authentic original material, it is not possible to be certain what Rafinesque was actually discussing, particularly when “lumpy” fruits appear sporadically in several Citrus taxa. In his account of Rafinesque's plant-names, Merrill (Index Rafin.: 150. 1949) did not comment when listing Citrus granulata. The name has no currency in the fruit industry, does not appear in the literature after its initial publication and is “unplaced” in databases such as POWO (accessed 6 Mar 2025). However, C. granulata is currently accepted in the USDA GRIN Taxonomy database (accessed 6 Mar 2025) with synonyms that are now referred to Citrus ×otaitensis (Risso & Poit.) Risso (Fl. Nice: 86. 1844, ‘taitensis’, based on C. ×aurantium var. otaitensis Risso & Poit., Hist. Nat. Orangers: 66. 1819). According to Mabberley & McNeill (in Taxon 74(3 [this issue]), https://doi.org/10.1002/tax.13356), the latter combination is the accepted name for crosses (see Mabberley in Goldschmidt & Bar-Joseph, Citron Compendium: 36. 2023) between citrons (C. medica L.) and wild mandarins (C. reticulata Blanco), including Rangpur lime and rough lemon, the latter recently crossed (Mabberley in Telopea 27: 11–13. 2024a) with the Australian finger lime, C. australasica F. Muell. to give the blood-lime or Red Centre lime of commerce, C. ×sykesii Mabb. (l.c. 2024a). More significantly internationally, rough lemon was commercially important as a rootstock that is tolerant of Citrus tristeza virus (Mabberley, Citrus: A World History: 54. 2024b). ‘Citrus otaitensis’ has been used in the trade since at least early 1834, in France (Mabberley & McNeill., l.c.), but valid publication of the species name before 1844 has yet to be found. Despite the first author's sympathy for Rafinesque and his work in general (see Bull. Soc. Neuchâtel. Sci. Nat. 144: 263–275. 2025), in this case rejection of one of his names is proposed so as to remove permanently any possible threat posed by Citrus granulata to the name C. ×otaitensis or, indeed, the name of any other commercially important Citrus crop plant.

Abstract The Rangpur lime has been called “ Citrus taitensis Risso” but we show that the correct botanical name for this and other cultivars in this group is Citrus × otaitensis (Risso &amp; Poit.) Risso.

An experiment was carried out to study the influence of three commercial rootstocks, i.e., Rangpur Lime, Rough Lemon and Trifoliate Orange on the growth characteristics, grafting success, biochemical and nutrient accumulation in the leaves of Darjeeling mandarin. Data were collected 180 days after grafting for growth parameters and one year after grafting for biochemical and nutrient accumulation by the scion of Darjeeling mandarin. The results revealed significant variation across the rootstocks under study. Rough lemon recorded the highest grafting success (91.25 %) followed by Rangpur lime (87.50 %). In terms of growth parameters rough lemon demonstrated the highest rootstock length (22.26 cm), scion length (11.72 cm), and leaf area (39.59 cm²). Darjeeling mandarin was recorded highest starch content (2.9 mg/g), total sugar (1.31 mg/g), total protein (3.98 mg/g), and total phenol content (0.941mg/g). Higher proline content (1.9 mg/g) in rough lemon indicates a high stress tolerance. Trifoliate Orange recorded the lowest scion length (4.87 cm), leaf area (17.92 cm²) and total sugar content (0.89 mg/g). Concerning macronutrient and micronutrient accumulation, Rangpur Lime recorded the highest calcium (2.35 %), magnesium (0.42%) and iron content (149.8 %). Thus, the findings revealed that Rough Lemon and Rangpur Lime are the most promising rootstocks for improving growth, nutrient uptake, and biochemical traits of Darjeeling Mandarin, making them ideal rootstocks for commercial propagation on Darjeeling mandarin.

Achieving high yields and good-quality fruits is directly linked to effective management practices, including the adequate supply of nutrients. Orange trees (Citrus sinensis L.) have a high nitrogen (N) demand, and their assimilation is related to the activity of nitrate reductase, an enzyme that requires molybdenum (Mo) as a crucial cofactor. This study was aimed to assess the impact of foliar Mo application and different soil-applied nitrogen sources on leaf physiological and nutritional factors, as well as fruit quality in “Pêra” sweet orange trees grafted on Rangpur lime in a commercial orchard. The experiment used a randomized complete block design with four replications, in a 2 × 3 factorial scheme: absence or presence of Mo foliar fertilization, and application of urea (100% amide), ammonium nitrate (50% ammonium and 50% nitrate), or calcium nitrate (100% nitrate) as soil nitrogen sources. The evaluated parameters included photosynthetic variables, leaf nitrate, ammonium, and Mo contents, proline and pigment analyses, and fruit quality (physical, physicochemical, and color analyses). Principal component analysis (PCA) was employed for photosynthetic variable interpretation. PCA of physiological parameters effectively differentiated treatments based on Mo application. Mo-fertilized plants, regardless of the nitrogen source, improved fruit juice yield, increased the content of total soluble solids, and elevated the Ratio. Mo presence standardized titratable acidity and Ratio outcomes, regardless of urea, ammonium nitrate, or calcium nitrate application, while also enhancing fruit juice Ratio. Foliar Mo application, combined with the appropriate nitrogen source, enhances fruit quality and juice yield in “Pêra” oranges, optimizing commercial orchard production.

The present study was carried out during 2022 and 2023 at Research Farm, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha, Jammu, Jammu and Kashmir to study the correlation and principal component analysis in eight different citrus (Citrus spp.) rootstocks. The experiment was laid in factorial completely randomized design (FCRD) with four distinct plant growth-promoting rhizobacteria (PGPRs), viz. P1 (Bacillus subtilis); P2 (Pseudomonas fluorescens); P3 (consortia-Bacillus subtilis + Pseudomonas fluorescens); P4 (control) and eight distinct citrus rootstocks, viz. R1 (Rough lemon); R2 (Carrizo citrange); R3 (Rangpur lime); R4 (Goutoucheng); R5 (Sun Chu Sha); R6 (Swingle citrumelo); R7 (Troyer citrange) and R8 (Volkamer lemon) which were replicated thrice. The results of the investigation revealed that seedling height was positively correlated with stem girth (0.5510), root:shoot ratio (0.0399), chlorophyll content (0.5426) and leaf area (0.369) whereas, dry weight of leaves was negatively and significantly correlated with days taken for germination (-0.8693). Germination percentage was positively correlated with fresh (0.5816) and dry weight of shoots (0.5986). Moreover, chlorophyll content was negatively correlated with root: shoot ratio (-0.0912), leaf area (-0.2041) and days taken for germination (-0.1168) while, it was positively correlated with fresh leaf biomass (0.3533) and dry leaf biomass (0.3537). In principal component analysis, days taken for germination, seedling height (90 DAS) and chlorophyll content (90 DAS) showed positive contribution (PC2) whereas, number of secondary roots, dry weight of root and leaf area showed negative contribution.

The objective was to evaluate the root characteristics of citrus rootstocks grown in tubes with different substrates. Planting and development of the plants was carried out in Cazones, Veracruz, Mexico, and the evaluation was carried out at the Fruit Growing Laboratory, Colegio de Postgraduados, Montecillo, State of Mexico. The rootstocks were sour orange, Citrange C-35, Rangpur lime and Volkamerian lemon, transplanted in 1 L tubes filled with sand, peat-agrolite (4:1 v/v) and vega-tepojal soil (3:1 v/v). The experimental design was a randomized complete block factorial arrangement, with four repetitions of five experimental units. Six months after establishment, three repetitions of four plants per treatment were selected, and the following were evaluated: plant height, neck diameter, weight of fresh and dry root matter, number of roots per order and root length. The data were analyzed with the statistical package SAS, an ANOVA and Tukey's comparison of means were determined (p ≤ 0.05). The variable number of roots was subjected to polynomial regression analysis. Vega-tepojal soil gave quality to aerial and radical development, being an alternative for the development of plants in the nursery, Volkamerian lemon showed greater total root length, and second, third, fourth and fifth order roots were found in all rootstocks. In the container the roots developed up to the wall, then they went to the base, where there was natural pruning. The substrate and container influenced the development and shape of the root in the four rootstocks.

The study aimed to evaluate the performance of different rootstocks for acid lime (Citrus aurantiifolia) under salinity and nematode stress, focusing on their impact on plant growth and biochemical parameters. Grafted combinations involving acid lime (PKM 1) scions with rangpur lime and wood apple rootstocks were tested for salinity tolerance and resistance to Tylenchulus semipenetrans. The study, conducted from 2023 to 2024 at Tamil Nadu Agricultural University, HC &amp; RI, Coimbatore, Tamil Nadu, utilized varying sodium chloride (NaCl) concentrations to simulate salinity stress and nematode inoculation for biotic stress evaluation. Results indicated that the R5 combination (acid lime PKM 1 scion grafted onto rangpur lime) exhibited the highest salinity tolerance, evidenced by better chlorophyll retention, membrane stability, and enhanced activity of antioxidant enzymes such as catalase and superoxide dismutase. Similarly, T3 (acid lime PKM 1 scion grafted onto wood apple) plants demonstrated improved nematode resistance, marked by higher leaf phenol content and peroxidase activity, as well as a reduced nematode population. These findings suggest that grafting onto rangpur lime and wood apple rootstocks strengthens the physiological and biochemical mechanisms in acid lime, enabling better adaptation to environmental stresses. This study provides suitable rootstock options for enhancing acid lime productivity in areas impacted by nematode and salinity problems.

The present experiment was conducted during 2021–23 at ICAR-Indian Agricultural Research Institute, New Delhi to evaluate the response of five citrus rootstocks, viz. Rangpur lime (RL); Troyer citrange (TC); Cleopatra mandarin (CM); X-639 and Jatti khatti (JK) for leaf and root nutrient content including osmolytes and antioxidant potential in a soil pH range of 3.8–7.5. The experiment was initiated after the final establishment of plants in the pots in a factorial completely randomized block design (Factorial-CRBD) with four levels of soil pH and five different citrus rootstocks. Result indicated that RL recorded highest phosphorous content in leaf (0.43%) and root (0.36%) as well as total soluble sugars content (9.34 mg/g) in leaf. TC registered highest content of nitrogen (1.83%) and phosphorous (0.35%) in root; potassium (1.83 and 1.89%) and calcium (1.10 and 0.94%) in leaf and root, respectively, while significantly higher magnesium content (0.77%) and soluble protein (5.67 mg/g) were documented in the leaf as compared to other rootstocks. Maximum nitrogen content (3.10%), total phenols (6.76 GAE mg/g) and proline (40.27 μmol/g) were registered in leaves of CM whereas magnesium content in root (1.05%). The nitrogen content in leaves and roots of all the rootstocks as well as total soluble sugar tended to increase with decreasing levels of soil pH. Principal component analysis identified a distinct cluster of rootstocks comprising TC, X-639 and JK grouped together with notably high phenolic levels, while RL formed a separate cluster characterized by higher concentrations of total soluble sugar, proline and phosphorus. Thus, the present study demonstrated that citrus rootstocks prefer relatively lower soil pH for optimal growth. Among the investigated rootstocks, RL has demonstrated the ability to tolerate higher acidic soil conditions.

ABSTRACT The Pera sweet orange tree is the most cultivated scion variety in Brazil, mainly grafted onto Rangpur lime rootstock. Despite its drought tolerance, Rangpur lime is susceptible to various citrus diseases. More recently, trifoliate orange and its hybrids have been used as alternative rootstocks, but most genotypes are graft-incompatible with Pera. In this study, we assessed the long-term performance of Pera IAC sweet orange, which is a pre-immunized clone against citrus tristeza virus, grafted onto 11 trifoliate orange-derived rootstocks, one somatic hybrid and the standard Rangpur lime. The experiment was installed in Bebedouro, SP, Brazil, in February 2011, in a rainfed regime. The design was completely randomized with 13 treatments, 10 replications and one tree in the plot. Changsha × English Large (IAC 1711) citrandarin rootstock conjugated the tallest trees, high cumulative yield, and good drought tolerance up to 2020, followed by Rangpur lime and tetraploid citranges. The Flying Dragon trifoliate orange and tetraploid Carrizo citrange (IAC 387) rootstocks induced the highest content of soluble solids and acidity in Pera oranges. At 9 years old, four citrandarins, a citradia and one somatic hybrid rootstocks were graft-incompatible with Pera IAC sweet orange. All scion/rootstocks’ combinations were affected by huanglongbing. The IAC 1711 citrandarin, tetraploids Troyer (IAC 385) and Carrizo (IAC 387) citranges and Flying Dragon trifoliate orange have potential as graft-compatible rootstocks of Pera IAC, but evaluations should continue in the long term. In addition, the later rootstock must be evaluated in irrigated high-density orchards aiming at competitive yields.

Citrus is an important commercial fruit crop cultivated extensively in India, where the selection of suitable rootstocks plays a crucial role in enhancing productivity and imparting tolerance or resistance to diseases. Dry root rot, caused by Fusarium solani, is one of the most devastating diseases affecting citrus orchards. The present study was conducted to screen citrus rootstocks for resistance against dry root rot under the All India Coordinated Research Project (AICRP) on Fruit Crops at Dr. Panjabrao Deshmukh Krishi Vidyapeeth (PDKV), Akola, with the objective of identifying resistant or tolerant rootstocks. Screening was carried out using the seedling inoculation method. A total of eight citrus rootstocks, namely NRCC-1, NRCC-2, NRCC-3, NRCC-4, CRH-12, Rangpur lime, Alemow, and Jambheri, were evaluated. Among the tested rootstocks, Rangpur lime exhibited tolerance to Fusarium solani compared to the others. In addition, biochemical analyses were performed to assess defense-related parameters, including polyphenol oxidase, peroxidase, esterase activity, reducing and non-reducing sugars, and chlorophyll content. Rangpur lime recorded the highest levels of polyphenol oxidase and peroxidase activity, indicating a stronger oxidative defense response against the pathogen. The findings suggest that Rangpur lime is a promising rootstock for managing dry root rot disease in citrus cultivation.

Fruits and vegetables play a crucial role in addressing food security challenges posed by the growing global population. Citrus fruits are among the most widely cultivated crops worldwide; however, their production is steadily declining due to climate change. Among the various biotic and abiotic stresses affecting citrus production, water scarcity caused by climate change stands out as a significant issue. Interestingly, the rhizosphere of citrus plants is home to beneficial fungi known as arbuscular mycorrhizal fungi (AMF). AMF have been shown to enhance the growth and development of host plants. They also improve the plants’ tolerance to various stresses and enhance soil structure. This study aimed to evaluate the response of two different citrus rootstocks—Rangpur lime and Carrizo citrange—when subjected to three mycorrhizal treatments, namely, AMF+ (inoculated with AMF), AMF- (treated with fungicide to eliminate AMF), and a control (naturally occurring AMF), under conditions of water deficit. The results indicated that the AMF+ treatment had a significant positive effect on both rootstock genotypes compared to the AMF- treatment. Physiological attributes such as photosynthesis, stomatal conductance, transpiration, non-photochemical quenching, and both dark and light quantum yield exhibited significantly smaller declines under water deficit conditions in AMF+ plants compared to those in the AMF- and control groups. Conversely, stress indicators—such as malondialdehyde (MDA) and hydrogen peroxide (H2O2)—increased significantly in the AMF- treatment compared to AMF+. Additionally, the increase in antioxidative enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APx) and osmotic adjustment (proline (PRO)) was more pronounced in the AMF+ treatment in the leaves and roots of both citrus rootstocks. In conclusion, the findings suggest that the presence and application of AMF in citrus roots may enhance the plants’ ability to cope with water scarcity more effectively.