In Brazil, most orchards are not irrigated and flowering usually occurs in August/September, the season with the least rainfall, making it necessary to use drought-tolerant rootstocks. Reduced scion vigor, associated with drought tolerance, are essential factors for high-density planting systems in conditions of limited water availability. The identification of molecular markers potentially associated with these characteristics is essential to accelerate the improvement of citrus rootstocks. This study aimed to identify DArTseq molecular markers related to dwarfism and drought tolerance in citrandarin rootstocks (Citrus sunki × Poncirus trifoliata) using an in silico Bulk Segregant Analysis (BSA) approach. Experiments were conducted in Barretos, a municipality in the northern region of the São Paulo state. The bulks were selected based on vegetative development and leaf rolling scores for drought tolerance. The molecular markers were identified through differences in allele frequency between the groups, and the markers putatively associated underwent functional annotation to infer candidate genes for these characteristics using the Blast2GO program with the NCBI nr database. A total of 12 candidate markers were identified and associated with the characteristics of interest, including six related to reduced vigor and six to drought tolerance. The functional annotation enabled the identification for gene sequences associated with biological processes related to plant development, root architecture, hormonal regulation, and response to abiotic stress. The identified markers represent candidate genomic regions potentially involved in vigor regulation and drought response. These results represent valuable resources for future research in citrus rootstock breeding programs.

itrus productivity is strongly influenced by water availability and rootstock selection. This study evaluated the physiological and productive responses of two commercial scion & times; rootstock combinations: Tahiti acid lime BRS EECB IAC Ponta Firme grafted onto the dwarfing trifoliate rootstock IAC 718 Flying Dragon (PF_FD), and IAC 10 grafted onto the semi-dwarfing citrandarin IAC 3152 Itajobi (10_152). Field experiments were conducted over three years (2022-2024) under three irrigation regimes-variable (VIS), fixed (FIS), and non-irrigated (NIS)-using a 3 & times;2 factorial design with randomized blocks and drip irrigation. Physiological parameters (root length, leaf water potential, gas exchange, proline, and lipoperoxide content) and productive traits (fruit quality and cumulative yield) were assessed. The 10_152 combination showed superior root development, gas exchange performance, antioxidant regulation, and fruit yield, particularly under FIS and NIS, indicating enhanced drought tolerance. In contrast, PF_FD performed well only under VIS and was more sensitive to water deficit. Principal component analysis revealed that higher productivity and resilience were associated with greater root length, increased proline accumulation, higher CO2 assimilation, and reduced oxidative stress. Furthermore, FIS irrigation was as effective as VIS in sustaining plant performance, while optimizing water use, suggesting a sustainable management strategy. Although Tahiti acid lime IAC 10 demonstrates vigorous early orchard growth, its susceptibility to wood pocket restricts its commercial use. Overall, citrandarin IAC 3152 Itajobi proved to be the most promising rootstock, suitable for both irrigated and non-irrigated orchards, whereas PF_FD is recommended only under optimal water conditions.

Thirteen mandarin and hybrid cultivars grafted onto the commercial rootstocks Rangpur Lime and Swingle Citrumelo were comparatively assessed for vegetative growth, fruit physicochemical attributes, and field incidence and severity of Altenaria Brown Spot (ABS) and Huanglongbing (HLB). The experiment was conducted from January 2015 to December 2018 under a randomized block design, with ten replicates per scion-rootstock combination. Plant height, canopy volume, fruit mass, juice yield, acidity, soluble solids, and disease assessments were performed. RL induced greater vegetative growth but was associated with higher HLB severity, particularly in the Dekopon IAC 2009 and TM & times; LP 358 varieties. SC resulted in less vigorous trees but improved fruit quality, with higher acidity and soluble solids. Regarding ABS, the Loose Jacket IAC 515 and Muscia varieties showed high susceptibility, while Ortanique IAC 554 and Rainha BRS exhibited tolerance to both ABS and HLB. These findings suggest that although RL promotes vigorous growth, it may increase disease susceptibility, whereas SC is associated with reduced disease severity and improved fruit quality. Ortanique IAC 554 and Rainha BRS showed consistently low severity of ABS and HLB, combined with stable vegetative development and fruit quality, underscoring the importance of rootstock choice for guiding cultivar deployment in orchards under high disease pressure.

Rootstock diversification is increasingly desired and necessary for the sustainability of citriculture, which is subject to adversity, such as the occurrence of Huanglongbing (HLB), which has impacted activity in most producing regions of the world. The objective was to evaluate the productivity, water-use efficiency, vegetative growth, and HLB incidence of Valencia sweet orange grafted onto three citrandarins (dwarfing) and Swingle citrumelo (standard). The field experiment was conducted under a high-density planting spacing of 5.0 m × 1.5 m (1333 plants ha−1) for citrandarin rootstocks (IAC 1600, IAC 1697, and IAC 1711) and a conventional spacing of 6.8 m × 2.5 m (588 plants ha−1) for Swingle citrumelo. The Swingle citrumelo rootstock combination with Valencia orange exhibited a larger canopy volume and higher per-plant yield, demonstrating high productivity under conditions of adequate water availability and conventional spacing. However, this combination also demonstrated lower water-use efficiency and higher susceptibility to HLB, particularly in 2024, highlighting its limitations for use in HLB-endemic regions. In contrast, combinations with citrandarins, especially IAC 1600, showed greater water-use efficiency, smaller canopy volume, and increased drought tolerance in higher-density planting. These combinations were also less susceptible to HLB and performed well in high-density planting systems, promoting the productive efficiency (kg fruit m3 canopy). The Swingle combination is recommended to maximize production in areas with abundant water resources and low HLB pressure, while citrandarin combinations, particularly IAC 1600, are better suited for regions with limited water availability and high HLB incidence.

Tahiti lime is one of the most exported fruits in Brazil, and the state of São Paulo accounts for more than half of the country’s fruit production, and drought in the region is a growing concern as rainfall distribution has become increasingly unpredictable. Therefore, identifying the best varieties and management strategies for citrus groves has become a subject of increasing research. This experiment was conducted at the “Sylvio Moreira” Citrus Center, Brazil; the experiment focused on different planting and mulching practices and scion-rootstock combinations. Two planting/management types were tested: (i) conventional tillage – CT (no mulch in the citrus row) and no-tillage – NT (mulch maintained in the citrus row), using Urochloa ruziziensis as an intercrop. Six grafts x rootstocks were tested: Tahiti acid IACC 5, IAC 10, and BRS IAC EECB Ponta Firme grafted onto two dwarf rootstocks: trifoliate orange IAC 718 Flying Dragon and citrandarin IAC 3152 Itajobi. Over three harvests (2022–2024), this study evaluated foliar nutrition, fruit quality, root development, water potential, gas exchange, water deficit biomarkers, and overall yield. No-tillage significantly improved vital performance indicators compared to conventional tillage. Plants managed with NT exhibited superior root development, greater water uptake, and greater leaf water potential. They also showed greater photosynthetic efficiency, leading to higher yields and improved fruit quality, particularly in juice yield and soluble solids/acidity ratio. The IAC 3152 Itajobi rootstock demonstrated remarkable resilience to drought stress, outperforming Flying Dragon in root development and physiological metrics. NT promoted healthier root systems and more robust plant growth. In contrast, conventional tillage led to poorer root growth, lower nutrient uptake, and increased disease susceptibility due to soil exposure and reduced water infiltration. Despite these challenges, 3,152 rootstock maintained active physiological responses such as gas exchange and/or water potential, especially with the Firm Tip graft. In conclusion, the integration of dwarf rootstocks with NT practices offers a viable strategy to increase the sustainability and productivity. This study highlights the importance of selecting appropriate scion-rootstock combinations and adopting sustainable management practices to improve resilience to environmental stress and optimize fruit yield and quality.

Abstract The increasing incidence of diseases in tangerine orchards, including alternaria brown spot (ABS) caused by Alternaria alternata, has led to significant production losses, which requires the development of new disease control strategies. This study aimed to evaluate the effect of essential oils (EOs)extracted from the peels of different lemon genotypes at several concentrations and application methods on the ABS control. The experiments were conducted at the Sylvio Moreira Citrus Research Center, Cordeiropolis - São Paulo state,Brazil. An in vitro experiment was set up in a completely randomized design (CRD) with a 2×4×5 factorial scheme, including two control methods (preventive and curative),four lemon genotypes for EO extraction (Amber IAC 269, Eureka IAC 644, Harvey IAC 641 e IAC 262 Siciliano), and five EO concentrations (0, 2, 4, 8, and 16µL mL-1), with three replicates. Each replicate consisted of a Petri dish containingthree young Murcott tangor leaves. An in vivo experiment was also conducted in a CRD with a 2×4×3 factorial scheme, including two control methods (preventive and curative), four lemon genotypes for EO extraction, and three EO concentrations(0,8, and 16 µL mL-1), with three replicates. Each replicate consisted of one Murcott tangor plant, with four leaves from three different branches of the same plant.Disease severity assessments were conducted over seven days following fungal inoculation. The Area Under the Disease Progress Curve (AUDPC) was calculated using severity data. Data were submitted to analysis of variance, Tukey’s test(p<0.05), and regression analysis. The preventive method was more effective in controlling the fungus. The Amber genotype, at concentration of 16 µL mL-1,showed the best ABS control.

Sour rot, caused by Geotrichum citri-aurantii, is a significant post-harvest disease in citrus, resulting in economic losses due to the lack of effective fungicides. This study investigates the antifungal activity of citrus essential oils in controlling sour rot in Tahiti acid lime fruits. Essential oils were extracted via hydrodistillation with chemical composition analyzed by CG-MS and tested in vitro and in vivo. In vitro assays evaluated mycelial growth inhibition at 2 to 32 µL mL−1 concentrations. In vivo trials involved preventive and curative treatments on artificially inoculated fruits stored at 25 °C ± 2, and the results showed that Pera IAC sweet orange oil, at 32 µL mL−1, reduced disease severity by 96% in curative treatments. In contrast, Late IAC 585 willowleaf mandarin oil demonstrated moderate inhibition (44%) at the highest concentration in vitro. The oils did not affect key fruit quality parameters such as juice yield and total soluble solids. These findings suggest that citrus essential oils could be natural alternatives to synthetic fungicides for post-harvest sour rot management, combining effectiveness with maintaining fruit quality.

Alternaria brown spot (ABS) is a disease caused by the fungus A. alternata f. sp. citri, which results in lesions on the fruits, leaves, and branches of several mandarin varieties and their hybrids. Due to the high cost of fungicide application, alternative methods for controlling ABS need to be studied. Therefore, this study aimed to evaluate the use of essential oils (EOs) from different mandarin varieties to mitigate the effects of ABS. The inhibitory effect of different concentrations (1, 2, 4, 8, and 16 μL·mL−1) of the EOs of Fremont IAC 543 mandarin, IAC 2019Maria mandarin, Murcott IAC 221 tangor, and Late IAC 855 willowleaf on the in vitro mycelial growth of the fungus A. alternata was evaluated. Additionally, the curative and preventive effects of these EOs on the ABS symptoms in detached leaves of Murcott IAC 221 tangor were also assessed. The EO of IAC 2019 Maria mandarin induced less mycelial growth, and consequently, a greater inhibition of the growth of the fungus A. alternata at a concentration of 16 μL·mL−1. This EO was more effective for control than the other oils tested. In the detached leaf experiment, both the curative and preventive treatments at a concentration of 16 μL·mL−1 showed lower values of disease severity.

-Alternaria brown spot -ABS (Alternaria alternata) causes lesions on fruits, leaves and branches of mandarins. The cost of fungicide application is high and alternative managements for the control need to be studied. We aimed to eval-uate calcium (Ca) nutrition to mitigate the effects of ABS. Murcott IAC 221 tangor plants were nourished with calcium nitrate at three different concentrations (30, 150 and 300 mg Ca L-1), and the N content was standardized in the nutrient solu-tion of the treatments (245 mg L-1 of N) with ammonium nitrate. In vitro and in vivo tests were installed, evaluating the severity and area under the disease prog-ress curve (AUDPC), total proteins, peroxidase (POX), catalase (CAT), superoxide dis-mutase (SOD) and hydrogen peroxide (H2O2), during four times. In all evaluations a negative correlation was observed between leaf Ca content and the severity and AUDPC of ABS. On the other hand, there was a positive correlation between N and the occurrence of the disease. In the treatment with the lowest concentration of calcium there was accumulation of H2O2 and hypersensitivity reaction (HR), with low detoxification of H2O2 by CAT. There is potential for use of calcium supply to plants of Murcott IAC 221 tangor as an alternative management against the fungus A. alternata.

Mandarins occupy the third group among citrus produced in Brazil. Primarily aimed at the fresh fruit market, commercial orchards have suffered significant production losses due to the high incidence of diseases, such as the alternaria brown spot (ABS) and huanglongbing (HLB). The fact that 80% of the orchards are composed of two varieties, Ponkan mandarin and Murcott tangor, which are highly susceptible to both diseases, demands intensive chemical control of the diseases in the field, which has resulted in a significant increase in production costs and a negative environmental impact. A total of one hundred and seventy-three mandarin accessions, including several species and hybrids belonging to the Collections of the Instituto Agronômico de Campinas (IAC), were evaluated in the field in an endemic location for the diseases. Evaluations of the incidence and severity of the diseases showed a range of genotypes tolerant to ABS that could replace the current commercial varieties, mainly within the clementine and willow leaf mandarin groups. Although, with differences in incidence and susceptibility to HLB, there are no tolerant varieties to this disease, which significantly impacts the loss of fruit quality.

Root rot and gummosis caused by Phytophthora spp. are considered one of the most important citrus diseases in Brazil. Symptoms of Phytophthora spp. infection in citrus plants are associated with lesions on the bark at the base of the plant, roots, and even lower branches. Inappropriately performed cultural practices, such as excessive irrigation and practices that result in reduced aeration and soil drainage, favor the disease. The objective of this study was to evaluate the effect of Urochloa ruziziensis mulching provided by an ecological mower on the severity of Phytophthora nicotianae root rot and the development of citrus plants and their root system. The experiments were carried out under controlled conditions on Rangpur lime seedlings kept in pots containing soil from ‘Hamlin’ orange orchards with the use of an ecological mower or a conventional mower in the management of inter-row vegetation for six years. Urochloa ruziziensis mulching (9 t ha−1) was added or not to the pots. The inoculation of P. nicotianae in the roots occurred through infection of the soil with a solution containing mycelium and sporangia of the pathogen. A 2 × 2 × 2 factorial scheme was used, with the following factors A: soil type, B: inoculation of P. nicotianae and C: mulching of U. ruziziensis. The attributes of plant development, such as root growth, average number of leaves, leaves and dry mass of shoots and roots, in addition to assessments of the severity of disease in the roots, were evaluated. The mulch of U. ruziziensis did not promote an increase in root rot. The soil resulting from this management promoted the better development of Rangpur lime plants. Therefore, vegetation management of inter-row with an ecological mower is not associated with increased symptoms of Phytophthora root rot.

The provision and expansion of the number of mandarin varieties and hybrids are of great importance for the market of fresh fruit, as Brazilian commercial orchards are based on a small number of varieties, which contributes to cultural vulnerability. The aim of this study was to verify, by univariate analyses, the possible physicochemical and sensory differences of early mandarin varieties: Ponkan IAC172, Múscia IAC607, Span IAC595, and the hybrid TP×TM11 (Ponkan IAC172×Murcott IAC221). The variety Span IAC595 presented expressive physicochemical characteristics, besides presenting sensory characteristics compatible with consumer preferences and a relation superior to the other varieties studied. The hybrid TM×TP11 obtained the lowest preference, demonstrating that attributes such as ease of peeling, skin color, and size are important in consumer's choice, indicating an importance of the studied attributes for the preference of a mandarin, that must be considered in the production of new varieties for the fresh fruit market.

Os oleos essenciais podem ser extraidos das plantas pela tecnica de arraste a vapor ou prensagem a frio. Flores, folhas, cascas, rizomas e frutos sao materias-primas para sua producao, a exemplo dos oleos essenciais de rosas, eucalipto, canela, gengibre e laranja, respectivamente. Os oleos essenciais de citros sao importantes subprodutos do processo de fabricacao de suco. O oleo essencial de limao e um dos mais importantes agentes odorizantes, usado em perfumaria, bebidas alcoolicas, refrigerantes, doces, balas, sorvetes, gelatinas e massas, alem da industria farmaceutica. Podem ainda apresentar atividades antimicrobianas. Objetivou-se com este trabalho obter genotipo(s) de limao produtivo(s) e com alto rendimento de oleo essencial. Selecionaram-se, na Colecao de Trabalho de Citros do Centro APTA Sylvio Moreira/IAC, quatro genotipos de limao: Amber, Harvey, Rigoni e Siciliano (padrao). Avaliaram-se as caracteristicas fisico-quimicas dos frutos, desenvolvimento vegetativo e produtivo das plantas e o rendimento e produtividade de oleo essencial. As colheitas dos frutos foram realizadas em dois periodos: outubro de 2019 (Safra 1) e abril de 2020 (Safra 2). Amostras contendo cinco frutos por repeticao do ensaio foram coletadas e encaminhadas para as analises fisico-quimicas dos frutos (massa, rendimento de suco, solidos soluveis, acidez e ratio). Para extracao do oleo foram coletados 20 frutos por repeticao de cada genotipo, em outubro de 2019 (Safra 1). As avaliacoes de desenvolvimento vegetativo e produtivo das plantas foram realizadas em outubro de 2019 (Safra 1). Na safra 1, a massa dos frutos do genotipo Rigone foi superior aos genotipos Amber e Siciliano, no entanto na Safra 2, a massa do genotipo Rigone foi inferior aos demais genotipos. Nao houve diferenca no rendimento de suco entre os genotipos. Os genotipos Rigone e Siciliano apresentaram os maiores valores de acidez. O genotipo Rigone apresentou os maiores valores de solidos soluveis, nas safras 1 e 2. Na safra 2, a acidez do genotipo Rigone foi superior aos observados nos genotipos Amber e Harvey. Os genotipos Amber e Harvey apresentaram os maiores valores de ratio , na safra 1. A massa da casca e o volume de oleo essencial nao diferiu entre os genotipos avaliados. O Rendimento de oleo essencial dos genotipos Rigone e Siciliano foi superior aos demais genotipos. A qualidade e quantidade dos oleos essenciais da casca de frutos citricos dependem de muitos fatores, tais como o genotipo, porta-enxerto, condicoes edafoclimaticas, epoca de colheita do fruto, adubacao e o metodo de extracao. Os genotipos Amber e Harvey apresentam menor volume de copa, em relacao aos outros genotipos. No entanto, o genotipo Amber apresentou maior producao por planta, maior produtividade por area, maior eficiencia produtiva e maior produtividade de oleo por area na safra 1. Plantas de porte pequeno, com o genotipo Amber, pode ser boa opcao para o adensamento, visando aumentar a produtividade e diminuir os custos de producao. Conclui-se que o genotipo Amber possui maior producao por planta, produtividade por area, eficiencia produtiva e produtividade de oleo por area, sendo o que possui maior potencial para extracao de oleo essencial extraido da casca dos frutos.