Search Results (115)

Citrus leprosis (CL) and citrus zonate chlorosis (ZC) were first described in Brazil in the 1930s. Both diseases, which caused non-systemic lesions primarily characterized by chlorotic and/or necrotic spots, were associated with the presence of Brevipalpus mites. While CL has since been well characterized as being caused by viruses of the genera Cilevirus (family Kitaviridae) and Dichorhavirus (family Rhabdoviridae) and transmitted by several species of Brevipalpus mites, the causal agent of ZC remained unknown. In this study, we analyzed Citrus spp. samples exhibiting typical ZC symptoms using high-throughput sequencing (HTS) to determine the etiology of ZC. We examined historical herbarium specimens collected between 1933 and 1965 alongside fresh samples collected from 2016 to 2022. Our results identified the higrevirus hibiscus green spot virus 2 (HGSV2, Higrevirus waimanalo) as the causal agent of ZC. In addition, we report for the first time the presence of a higrevirus in continental America, expand the diversity of known kitaviruses infecting citrus in Brazil, and demonstrate the transmission of an higrevirus by Brevipalpus yothersi and B. papayensis. Full article

The extensive application of fungicides in citrus packinghouses to mitigate economic losses has resulted in the emergence of fungicide-resistant biotypes of Penicillium spp. Furthermore, many countries have implemented strict monitoring of fungicide residues to protect consumer health and the ecosystem. Maximum residue limits (MRLs) have been established in accordance with Codex Alimentarius standards, which present challenges for exports, as exceeding MRLs may restrict market access. This study aimed to identify fungicide-resistant strains of Penicillium spp. in a Moroccan citrus packinghouse and to assess the efficacy of GRAS (Generally Recognized As Safe) salts as eco-friendly alternatives for controlling these resistant strains through in vitro and in vivo tests. A total of 31 Penicillium isolates, labeled H₁ to H₃₁, were collected; 10 were identified as P. digitatum and 21 were identified as P. italicum. Resistance to thiabendazole (61.3%) and imazalil (58.1%) was notable, with some isolates showing dual resistance. In vitro, potassium sorbate, sodium benzoate, and sodium tetraborate salts were highly effective at inhibiting the mycelial growth of resistant isolates, at a concentration of 0.3% (p < 0.0001). In vivo tests on ‘Nadorcott’ fruits demonstrated that 2% and 4% salt solutions effectively prevented the development of green and blue molds caused by Penicillium spp. and showed strong curative effects, resulting in nearly 100% inhibition of most fungal isolates. Additionally, preventive salt treatments increased the accumulation of phenolic and flavonoid compounds, while in fruits treated with sodium benzoate, chitinase and peroxidase activities were significantly enhanced. Full article

The genus Fusarium comprises multiple species recognized as plant pathogens in both annual and perennial crops. Some phytopathogenic species of this genus can be transmitted by insect vectors, which introduce them into woody plant species of ecological and agroeconomic importance. Among these species, Fusarium kuroshium stands out, but studies are limited because it is a quarantine pathogen that requires special biosafety measures for its culture. This fungus produces fusaric acid (FA), a virulence factor that is widespread in Fusarium spp. To gain insight into the role of this phytotoxin in virulence, we exposed leaves of four woody host species (Liquidambar styraciflua, Persea americana, Citrus sinensis, and Populus nigra) of F. kuroshium to FA in vitro. The plant tissue exhibited varying degrees of cell death and physiological alterations, including a reduction in biomass, generation of reactive oxygen species (ROS), elevated electrolyte leakage, and loss of photosynthetic pigments. A chemical analysis demonstrated that the flavonoid and isoflavonoid pathways, in addition to linoleic and linolenic acid metabolism, were markedly affected by FA. Following the quantification of phenolic compounds in leaves, 11 metabolites were identified whose concentrations increased in response to FA stress. The findings of this study indicate that phenolic compounds play a significant role in the response to FA stress. Particularly, scopoletin has a protective effect on leaves of Liquidambar styraciflua. Full article

The objective of this work was to analyse the genetic diversity of a population of Citrus spp. in the south of the State of Espírito Santo, Brazil, for pre-breeding studies. For that, a total of sixty genotypes were analysed, including ten citrus varieties from four species of the Citrus genus. The methodology involved DNA extraction, amplification via polymerase chain reaction, and the use of a set of 16 Simple Sequence Repeat markers. These markers identified 42 alleles, with a variation of one to four alleles per locus, an average heterozygosity value of 0.53, and an average polymorphic information content of up to 0.29 per species. After the analysis, a dissimilarity matrix was generated using Jaccard distance and a dendrogram, revealing the formation of two groups: Group I, comprising Citrus sinensis varieties, and Group II, comprising varieties of Citrus latifolia, Citrus aurantifolia, and Citrus reticulata. Our study demonstrated that the combination of these markers allowed for the differentiation of genotypes within the collection. The results obtained are valuable for the future management of the collection and the efficient use of genetic diversity estimation in Citrus spp. Full article

Fruit rot seriously damages pomelo production. Given concerns regarding the safety of chemical agents, biological alternatives are becoming more preferable. Therefore, the experiment aimed to (i) identify the pathogens causing pomelo fruit rot disease and (ii) select Trichoderma spp. strains controlling the determined pathogens in Ben Tre, Vietnam. Three pathogenic fungal strains isolated from diseased pomelo fruits were selected. The three pathogenic fungal strains were randomly injected into 9 healthy pomelo fruits. The strain PCP-B02-A2 led to a completely rotten fruit on day 17 after infection, while strains PCP-B02-B2 and PCP-B03-A1 had infected spots whose lengths were 17.5 and 28.1 mm, became larger, and eventually led to the whole fruit rot. The pathogens were identified by the internal transcribed spacer (ITS) technique as Colletotrichum gloeosporioides PCP-B02-A2, Pseudopestalotiopsis camelliae sinensis PCP-B03-A1, and P. chinensis PCP-B02-B2. Twenty-five Trichoderma spp. strains were isolated. The ITS technique identified four strains, including Trichoderma asperellum TP-B01, T. harzianum TP-B08, T. harzianum TP-B09, and T. asperellum TP-C25. The PCP-B02-A2 strain had antagonism at 66.7–68.7%, while those of PCP-B02-B2 and PCP-B03-A1 were 64.2–71.1% and 55.7–57.4%, respectively. Full article

This study investigates the complex interactions between environmental, genetic, and structural factors that influence two key parameters: the density of Phytophthora spp. propagules per gram of dry soil (NPSS) and the number of colonies (NC). Using advanced statistical approaches, we examined the combined effects of variables such as soil moisture, dry weight, temporal fluctuations, and rootstocks. The results show a significant linear relationship between NPSS and soil moisture, as well as a strong positive correlation between NPSS and NC. Genetic analyses reveal a predominant contribution of environmental factors to trait variability, with high phenotypic coefficient of variation (PCV) and low broad-sense heritability. Mixed models highlight the synergistic impact of soil moisture, NC, and dry soil weight on NPSS, as well as significant temporal effects. Mediation analysis confirms that soil moisture influences NPSS primarily through an indirect effect transmitted by NC, with a mediated proportion exceeding 94%. Finally, multivariate analysis reveals significant differences between rootstocks, with Citrus Volkameriana B2 28613 (R4) and Mandarin Sunki x P.T. B2 38581 (R7) standing out as the most performant. These results highlight the importance of an integrated management of environmental variables and rootstocks to optimize soil productivity and agronomic quality. The implications of this study provide a solid foundation for guiding genetic improvement and soil management strategies, balancing environmental constraints and the opportunities offered by targeted genetic selection. Full article

The growing demand for natural preservatives in the food industry has highlighted the importance of essential oils (EOs), despite their limitations related to volatility and oxidative instability. This study addresses these challenges by developing pectin-based microcapsules for encapsulating lemon essential oil (LEO) using ultrasound-assisted ionotropic gelation. The EO, extracted from Citrus limon (Eureka variety), exhibited a high limonene content (56.18%) and demonstrated significant antioxidant (DPPH IC50: 28.43 ± 0.14 µg/mL; ABTS IC50: 35.01 ± 0.11 µg/mL) and antifungal activities, particularly against A. niger and Botrytis spp. Encapsulation efficiency improved to 82.3% with ultrasound pretreatment, and SEM imaging confirmed spherical, uniform capsules. When applied to fresh-cut apples, LEO-loaded capsules significantly reduced browning (browning score: 1.2 ± 0.3 vs. 2.8 ± 0.2 in control), microbial load (4.9 ± 0.2 vs. 6.5 ± 0.4 log CFU/g), and weight loss (4.2% vs. 6.4%) after 10 days of storage at 4 °C. These results underscore the potential of ultrasound-enhanced pectin encapsulation for improving EO stability and efficacy in food preservation systems. Full article

Citrus sooty mould caused by Capnodium spp. alters the quality of fruits on the tree and affects their productivity. Past laboratory and hand-held spectrometry tests have concluded that sooty mould exhibits a typical spectral response in the near-infrared spectrum region. For this reason, this study aims at developing an automatic method for remote sensing of this disease, combining 10 m spatial resolution Sentinel-2 satellite images and 0.25 m spatial resolution orthophotos to identify sooty mould infestation levels in small orchards, common in Mediterranean conditions. Citrus orchards of the Comunitat Valenciana region (Spain) underwent field inspection in 2022 during two months of minimum (August) and maximum (October) infestation. The inspectors categorised their observations according to three levels of infestation in three representative positions of each orchard. Two synthetic images condensing the monthly information were generated for both periods. A filtering algorithm was created, based on high-resolution images, to select informative pixels in the lower resolution images. The data were used to evaluate the performance of a Random Forest classifier in predicting intensity levels through cross-validation. Combining the information from medium- and high-resolution images improved the overall accuracy from 0.75 to 0.80, with mean producer’s accuracies of above 0.65 and mean user’s accuracies of above 0.78. Bowley–Yule skewness coefficients were +0.50 for the overall accuracy and +0.28 for the kappa index. Full article

Among the numerous diseases that affect papaya (Carica papaya L.) cultivation, anthracnose, caused by a complex of fungi from the genus Colletotrichum spp., stands out, primarily due to its damage to the commercial part of the papaya, the fruit, specifically the pulp. Although chemical control with synthetic molecules is the most commonly used method to combat anthracnose, it is not the most appropriate solution. The indiscriminate use of synthetic chemical products results in numerous harmful effects on the environment, the health of farmers, and the final consumers. Given these circumstances, the objective of this study was to analyze the efficacy of essential oils (EOs) from Citrus aurantium var. dulcis L., known as sweet orange, Citrus limon (L.), known as Sicilian lemon, and the major compound present in these oils, limonene, against the pathogens Colletotrichum okinawense, which cause anthracnose in papaya fruits. The percentage inhibition of mycelial growth was evaluated on the seventh day, with estimates of 50% and 90% inhibition, to compare the inhibitory effect among the fungal isolates. Chromatographic analysis revealed that sweet orange EO contains myrcene and limonene. Sicilian lemon essential oil includes myrcene, limonene, α- and β-pinene, and γ-terpinene. Both EOs and limonene exhibited activity against C. okinawense. The 50 µL/mL concentration was the most effective in inhibiting growth. The EOs and limonene showed similar IC₅₀ values, with limonene at 48 µL/mL, Sicilian lemon EO at 51 µL/mL, and sweet orange EO at 57 µL/mL. Full article

Peelability, a crucial commercial trait for fresh-eating citrus, has received limited research attention regarding its underlying mechanisms. This study investigated three late-maturing citrus cultivars, namely ‘Qingjian’ (QJ), ‘Mingrijian’ (MRJ), and ‘Chunjian’ (CJ), analyzing their peelability development using texture analysis and exploring the physiological and biochemical factors influencing peeling difficulty. The results showed that peelability improved with fruit maturation, reaching its peak at full ripeness, with the following order of peeling difficulty: QJ (hardest) > MRJ (intermediate) > CJ (easiest). At full maturity, QJ (the most difficult to peel) exhibited more regularly shaped peel cells with fewer intercellular spaces, lower intracellular organic matter accumulation, and higher levels of cell wall polysaccharides, calcium (Ca), and abscisic acid (ABA). These characteristics may be linked to the lower relative expression of soluble sugar (TS)-related genes (CCR4A, SPP1) and the titratable acid (TA)-related gene (CsCit1), as well as the higher relative expression of ABA biosynthesis genes (NCED1, NCED2). Correlation analyses demonstrated that citrus peel firmness and adhesion strength are significantly associated with multiple growth and developmental characteristics, including fruit morphometric parameters, peel cellular architecture, intracellular organic compound content, cell wall polysaccharide levels and related degradative enzyme activities, calcium concentrations, and endogenous phytohormone profiles. These findings provide valuable insights for studying peelability mechanisms and improving fruit quality in citrus breeding. Full article

Citrus black spot (CBS), caused by the fungus Phyllosticta citricarpa, significantly affects citrus fruit marketability and can lead to premature fruit drop. Accurate and reliable detection of this quarantine pathogen is crucial, particularly for asymptomatic plant material. This study evaluated two qPCR assays, the EPPO recommended assay PC and assay Pc-TEF1, based on TEF region, for detecting P. citricarpa through a collaborative test performance study (TPS). DNA from the isolates of Phyllosticta spp. and other fungi was spiked into citrus fruit peel extracts (lemon, orange, and pomelo) and distributed among 13 laboratories. Sample and qPCR assay stability under typical transport conditions was confirmed, although prolonged storage affected Pc-TEF1 assay performance. The assays were assessed based on sensitivity, specificity, reproducibility, and repeatability. Both assays demonstrated high performance, with repeatability and reproducibility exceeding 95%. The PC assay, as expected, detected different related Phyllosticta species, while Pc-TEF1 showed higher specificity for P. citricarpa included in the TPS alone. Additionally, inhibitory effects were observed specifically in the pomelo peel samples, suggesting matrix-dependent variability. This TPS confirms that both PC and Pc-TEF1 qPCR assays are robust. Further evaluation of the qPCR assays would support the selection of the most reliable assays for the detection of P. citricarpa, contributing to the effective management of CBS disease in citrus production and trade. Full article

Honey is a multifaceted substance whose composition is intricately affected by various biotic and abiotic elements generated in the bee colony’s surroundings, including botanical and geographical origins, climatic conditions, soil characteristics, and beekeeping techniques. Monofloral honeys are identified by pollen analysis and are derived from the nectar of a predominant plant species, exhibiting rich sensory and nutritional profiles, making them food matrices with unique characteristics and excellent qualities. To explore the monofloral honey potential harvested in different regions of Portugal, a comprehensive study was conducted including the determination of phenolic composition and the assessment of biological activities. In addition to this evaluation, the inter simple sequence repeat (ISSR) was used to help differentiate honeys by botanical origin. The phenolic content and the antioxidant capacity were evaluated by spectrophotometric methods, observing, in general, differences between monofloral honeys. The honey from Citrus sinensis (Silves) exhibited the lowest phenolic content, including total phenols, ortho-diphenols, and flavonoids, whereas honeydew (Vinhais) showed the highest values. Regarding the antioxidant capacity, honey from Lavandula stoechas (Almodôvar) presented the lowest values, while honeydew (Vinhais) displayed the highest values for both DPPH and FRAP assays. In relation to the ABTS assay, the honey from Metrosideros excelsa (Aveiro) exhibited the lowest values, whereas the honey from Eucalyptus spp. (Arouca) showed the highest. The ISSR marker analysis allows the distribution of the samples based on the honey’s botanical origin, suggesting its potential role in honey authentication. Full article

Minimally processed foods (MPFs), often considered ready-to-eat, do not undergo cooking and therefore require proper handling and preparation to ensure safety. If not handled correctly, these foods can serve as a pathway for diseases caused by pathogenic bacteria, including Escherichia coli and Salmonella spp. The antibacterial activity of essential oils (EOs) has been increasingly studied as a tool for controlling microorganisms in the food sector. Therefore, we aimed to verify the contamination of MPF by E. coli and Salmonella and to test the sensitivity of these strains to Copaifera langsdorffii, Schinus terebinthifolius, Citrus reticulata, Eucalyptus citriodora, Elettaria cardamomum, Ocimum basilicum, and Eugenia caryophyllus EOs using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. From 25 MPF samples, one E. coli strain and one Salmonella spp. were isolated. C. langsdorffii and C. reticulata EOs did not show antibacterial activity, while S. terebinthifolius and E. citriodora inhibited the growth of both strains. The E. cardamomum, O. basilicum, and E. caryophyllus EOs presented inhibitory and bactericidal responses at concentrations 0.78, 0.39, and 0.19% (v/v), respectively, compared to the two isolated strains. The present study reinforces the antibacterial potential of EOs and suggests their application in the MPF production chain. Full article

Microbiome studies aimed at combating the citrus greening devastation caused by Liberibacter asiaticus abound. However, the role of farming practices, such as the massive use of herbicides, pesticides, and inorganic fertilizers on specific taxa and plant population immunity remains an important inquiry. To test our hypothesis that agricultural practices in managed Citrus groves induce root microbiome dysbiosis, potentially rendering citrus readily susceptible to citrus greening disease (CGD), we compared the CGD and root microbiome status of citrus plants in a rare > 130-year-old grove (no anthropogenic influence) to those of managed Valencia groves (symptomatic and asymptomatic). Citrus greening disease was detected by qPCR using the HLBa/HLBs/HLBp primer/probe combination, while root microbiome community structure was determined using 16S rDNA amplicon sequencing. The prevalence of CGD among citrus growing in the undisturbed, healthy soils was zero (Ct values > 36), while symptomatic and asymptomatic Valencia from managed groves was 100% positive (Ct < 34). Known beneficial plant symbionts (Actinomycetales, Bradyrhizobium, Verrucomicrobia, etc.) from Phylum Actinobacteria and Proteobacteria were depleted in the rhizosphere of the managed sites. This dysbiotic shift was characterized by enrichment with Acidobacterium, Nitrospira, and Sphingomonas spp. In highly infected Valencia oranges, beneficial taxa of the Alphaproteobacteria declined significantly (from 20–25% to 10–15%), while Bacillus sp. (a Firmicutes) was enriched 13-fold. Simpson and Shannon diversity indices were similar for all plant microbiomes except the heavily infected Valencia, which exhibited low diversity (p < 0.05), indicating that diversity indices alone are not reliable measures of soil health or rhizobiome homeostasis. Large reservoirs of known and novel putative beneficial rhizosphere microbes in undisturbed sites supported zero CGD, despite proximity to the managed sites where diverse non-beneficial taxa coincided with high disease rates. Supplementing the use of agrochemicals with carefully designed microbial products for plant disease control and sustainable soil health deserves acute attention. Full article

Dichorhavirus is a recently accepted plant virus genus within the family Rhabdoviridae. Species assigned to the genus consist of bi-segmented, negative sense, single-stranded RNA viruses and are transmitted by Brevipalpus spp. Currently, there are five recognized species and two unclassified members in the genus Dichorhavirus. Four out of seven-orchid fleck virus (OFV), citrus leprosis virus N, citrus chlorotic spot virus, and citrus bright spot virus-can infect citrus and produce leprosis disease-like symptoms. The E-probe Diagnostic for Nucleic Acid Analysis (EDNA) was developed to reduce computational effort and then integrated within Microbe-Finder (MiFi^®) online platform to design and evaluate e-probes in raw High Throughput Sequencing (HTS) data. During this study, Dichorhavirus genomes were downloaded from public databases and e-probes were designed using the MiProbe incorporated into the MiFi^® platform. Three different sizes of e-probes, 40, 60, and 80 nucleotides, were developed and selected based on whole genome comparisons with near-neighbor genomes. For curation, each e-probe was searched in the NCBI nucleotide sequence database using BLASTn. All the e-probes that had hits with non-target species with ≥90% identities were removed. The sensitivity and specificity of Dichorhavirus genus, species, strain, and variant-specific e-probes were validated in vivo using HTS meta-transcriptomic libraries generated from Dichorhavirus-suspected citrus, orchid, and ornamentals. Through downstream analysis of HTS data, EDNA not only detected the known hosts of OFV but also discovered an unknown host leopard plant (Farfugium japonicum), and the possible existence of a new ornamental strain of OFV in nature. Full article