Red Scale Research Articles

Penerapan prosedur operasional standar budi daya tanaman jeruk ramah lingkungan untuk menekan infestasi kutu perisai merah Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae)

Jeruk merupakan tanaman hortikultura yang sudah dikembangkan diberbagai daerah di Indonesia. Setiap tahun permintaan buah jeruk selalu meningkat, namun tidak terpenuhi karena produksi rendah. Permasalahan ini disebabkan oleh adanya serangan organisme penggangu tanaman, yaitu hama kutu perisai merah Aonidiella aurantii (Maskel). Upaya yang dilakukan untuk menekan infestasi A. aurantii, yaitu dengan penerapan prosedur operasional standar (SOP) pada budi daya tanaman jeruk ramah lingkungan. Tujuan penelitian ini adalah untuk mengetahui efektifitas penerapan SOP dalam menekan populasi dan intensitas serangan hama kutu perisai merah A. aurantii pada tanaman jeruk. Penelitian dilaksanakan bulan Januari sampai Agutus 2020 di kebun jeruk milik petani di Kota Batu. Penelitian eksperimen ini menggunakan metode teori research design. Perlakuan terdiri atas petak penerapan SOP berupa pemangkasan pemeliharaan, sanitasi kebun, dan aplikasi pupuk organik; dan petak konvensional kebiasaan petani yang tidak melakukan pemangkasan, membersihkan gulma di seluruh kebun, penggunaan pupuk anorganik NKP Mutiara 16-16-16. Luas setiap petak perlakuan adalah 1.500 m2. Pada setiap pelakuan diambil 10 tanaman sampel secara sistematik. Pengamatan setaiap tanaman dilakukan pada ranting atau cabang yang tersebar pada 4 arah mata angin. Pengamatan meliputi jumlah buah terserang, kelimpahan musuh alami, populasi, dan intensitas serangan A. aurantii. Hasil penelitian menunjukkan bahwa perlakuan penerapan SOP budi daya jeruk mampu menurunkan kepadatan populasi dan intensitas serangan hama A. aurantii secara nyata serta mampu meningkatkan kelimpahan musuh alami dan kualitas buah jeruk apabila dibandingkan dengan cara budi daya jeruk pada perlakuan konvensional.

Spatial and Temporal Dynamics of Aonidiella aurantii in Orange Orchards: Implications for Control in the Subtropical Region

Spatial and Temporal Dynamics of Aonidiella aurantii in Orange Orchards: Implications for Control in the Subtropical Region

New method for rapid detection and simultaneous determination of prohibited adrenergic drugs in sports using thin layer chromatography and image processing

This study presents a new method for simultaneous determination of fenoterol, procaterol, clenbuterol, terbutaline and isoprenaline drugs using thin-layer chromatography assisted by image analysis (HPTLC-IA) combined with sensitive detection modes. Separation of the selected drugs was obtained using HPTLC Silica gel 60 F254 plates and mixture of isopropyl alcohol, ethyl acetate and ammonia (20:25:1.5 v/v/v) as mobile phase. UV detection mode combined with the use of 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 2,2'-azino-bis (3-ethylbenzothiazoline)-6-sulfonic acid (ABTS+•) radicals were applied for the first time for sensible detection of the separated drugs. Grey, green, red and blue scales respectively were selected for image analysis and accurate quantification of spot area. According to the obtained result, the use of DPPH• and ABTS+• reagents revealed a higher sensitivity in detection and accurate quantification of the analyzed drugs. Lower limit of detection (LOD = 0.07 ± 0.03 µg/spot; 0.09 ± 0.03 µg/spot and 0.10 ± 0.04 µg/spot) was obtained for fenoterol, procaterol and terbutaline using the ABTS+• radical and red scale selection for image processing. With the exception of isoprenaline, the proposed HPTLC-IA method showed a good separation of fenoterol, procaterol, clenbuterol and terbutaline drugs from other compounds in urine samples. Good recovery was obtained for these drugs in spiked urine samples.

Florida red scale, Chrysomphalus aonidum (Linnaeus, 1758) (Hemiptera: Diaspididae) in Morocco, infesting citrus orchards and an avocado tree

AbstractA study was conducted on citrus and avocado trees in north‐western Morocco between February 2023 and April 2024 to detect scale insects (Hemiptera: Coccomorpha) and their associated natural enemies. A total of 55 orchards in seven provinces were studied. The Florida red scale, Chrysomphalus aonidum (Linnaeus, 1758) (Diaspididae) was found on leaves at two sites: a moderate infestation in one citrus orchard and one specimen on an avocado tree. This work is the first record of the scale insect on avocado in Morocco, and the first morphological description of C. aonidum from the country, based on 100 adult females mounted on microscope slides. Chrysomphalus aonidum is not causing economic damage in citrus or avocado orchards in Morocco. Two ectoparasitoid wasps (Aphytis melinus DeBach and Aphytis sp.; Hymenoptera: Aphelinidae), and three predatory beetles (Rhyzobius lophanthae Blaisdell, Chilocorus bipustulatus Linnaeus, and Clitostethus arcuatus Rosso; Coleoptera: Coccinellidae), were found associated with C. aonidum on citrus leaves.

Pest categorisation of Ceroplastes rubens.

The European Commission requested the EFSA Panel on Plant Health to conduct a pest categorisation of Ceroplastes rubens Maskell (Hemiptera: Coccidae), following the commodity risk assessments of Acer palmatum plants grafted on A. davidii and Pinus parviflora bonsai plants grafted on P. thunbergii from China, in which C. rubens was identified as a pest of possible concern to the European Union (EU). The pest, which is commonly known as the pink, red or ruby wax scale, originates in Africa and is highly polyphagous attacking plants from more than 193 genera in 84 families. It has been present in Germany since 2010 in a single tropical glasshouse. It is known to attack primarily tropical and subtropical plants, but also other host plants commonly found in the EU, such as Malus sylvestris, Prunus spp., Pyrus spp. and ornamentals. It is considered an important pest of Citrus spp. The pink wax scale reproduces mainly parthenogenetically, and it has one or two generations per year. Fecundity ranges from 5 to 1178 eggs. Crawlers settle usually on young twigs and later stages are sessile. All life stages of C. rubens egest honeydew on which sooty mould grows. Host availability and climate suitability suggest that parts of the EU would be suitable for establishment. Plants for planting and cut branches provide the main pathways for entry. Crawlers could spread over short distances naturally through wind, animals, humans or machinery. C. rubens could be dispersed more rapidly and over long distances via infested plants for planting for trade. The introduction of C. rubens into the EU could lead to outbreaks causing damage to orchards, amenity ornamental trees and shrubs. Phytosanitary measures are available to inhibit the entry and spread of this species. C. rubens satisfies the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Exploring scale insects biodiversity in orange orchards: insights from Guelma province, Algeria

Scale insects are pests affecting citrus crops in the Mediterranean basin, but their significance is often overlooked in some countries due to insufficient information about the threat they pose to this type of cultivation. In Algeria, various studies have aimed to identify and highlight the most harmful species impacting citrus orchards. This research specifically focuses on compiling a list of species affecting orange orchards in three regions of Guelma province (northeast Algeria) which are Boumahra Ahmad, El Fedjoudj and Guelma. Branch samples with their leaves were collected from all cardinal directions of the trees as well as from the center of the canopy during the winter-spring period from 2014 to 2018 while examining the climatic influence on their presence. Seventeen species were identified, with Aonidiella aurantii (Maskell, 1879), Parlatoria ziziphi (Lucas, 1853) and Coccus pseudomagnoliarum (Kuwana, 1914) being dominant and Lepidosaphes beckii (Newman, 1869), Saissetia oleae (Olivier, 1791) and Saissetia coffeae (Walker, 1852) considered rare. Non-parametric richness estimators (Chao 1, Chao 2, Jack 1 and Boot) suggest the potential presence of additional species, reaching 20.15 ± 0.96, indicating that the count may extend to 21 scale insects in the surveyed orchards. Spearman correlation analysis applied to species and climatic conditions reveals their influence on species abundance, but not on their diversity. We observed a positive impact on relative humidity and a negative impact on average temperature.

Prevalence of Fish Diseases and Use of Aqua Drugs and Chemicals at Habiganj in Bangladesh

Fish farming has rapidly expanded globally, including in Bangladesh, yet this growth has brought heightened risks of disease among aquaculture species. In response, farm owners have increasingly resorted to various drugs and chemicals without stringent regulation. This study investigates the current prevalence of fish diseases in farms and hatcheries across Habiganj district, examining associated management practices. Data from 36 farms reveal frequent health monitoring, with diseases diagnosed clinically, notably Parasite (68.29%), Epizootic ulcerative syndrome (29.26%), Dropsy (31.70%), tail and fin rot (19.44%), gulping (16.67%) and cotton fungus (12.19%). Additional conditions such as red spots, scale erosion and malnutrition were also noted albeit less frequently. Hatchery operations highlighted seasonal disease spikes during winter and after striping, with prevalent issues in brood fish and fish spawn, including fungal infections, yolk sac disorders and sudden mortality. A variety of medicines and chemicals were employed, with liming of ponds a common practice. This study offers critical insights for managing fish diseases effectively in Bangladesh, emphasizing the judicious use of medications and chemicals for sustainable aquaculture.

Conventional and Green Rubber Plasticizers Classified through Nile Red [E(NR)] and Reichardt’s Polarity Scale [ET(30)

After a survey on polymer plasticization theories and conventional criteria to evaluate polymer–plasticizer compatibility through the solubility parameter, an attempt to create a polymer–plasticizer polarity scale through solvatochromic dyes has been made. Since Reichardt’s ET(30) dye is insoluble in rubber hydrocarbon polymers like polyisoprene, polybutadiene and styrene–butadiene copolymers and is not useful for the evaluation of the hydrocarbons and ester plasticizers, the Nile Red solvatochromic dye was instead used extensively and successfully for this class of compounds. A total of 53 different compounds were evaluated with the Nile Red dye and wherever possible also with Reichardt’s ET(33) dye. A very good correlation was then found between the Nile Red scale E(NR) and Reichardt’s ET(30) scale for this class of compounds focusing on diene rubbers and their typical hydrocarbons and new ester plasticizers. Furthermore, the E(NR) scale also shows a reasonable correlation with the total solubility parameter calculated according to the Van Krevelen method. Based on the above results, some conclusion was made about the compatibility between the diene rubbers and the conventional plasticizers, as well as a new and green plasticizer proposed for the rubber compounds.

Organotransition Metal Chemistry of Terpenes: Syntheses, Structures, Reactivity and Molecular Rearrangements.

The impact of organometallic chemistry on the terpene field only really blossomed in the 1960s and 1970s with the realisation that carbon-carbon bond formation under mild conditions could be achieved by using nickel or iron carbonyls as synthetic reagents. Concomitantly, the development of palladium derivatives capable of the controlled coupling of isoprene units attracted the attention of numerous highly talented researchers, including future Nobel laureates. We discuss briefly how early work on the syntheses of simple monoterpenes soon progressed to sesquiterpenes and diterpenes of increasing complexity, such as humulene, flexibilene, vitamin A, or pheromones of commercial value, in particular those used in perfumery (muscone, lavandulol), or grandisol and red scale pheromone as replacements for harmful pesticides. As the field progressed, there has been more emphasis on developing organometallic routes to enantiopure rather than racemic products, as well as gaining precise mechanistic data on the transformations, notably the course of metal-promoted molecular rearrangements that have long been a feature of terpene chemistry. We note the impact of the enormously enhanced analytical techniques, high-field NMR spectroscopy and X-ray crystallography, and their use to re-examine the originally proposed structures of terpenes and their organometallic derivatives. Finally, we highlight the very recent ground-breaking use of the crystalline sponge method to acquire structural data on low-melting or volatile terpenes. The literature cited herein covers the period 1959 to 2023.

Comparison of computed tomography perfusion and magnetic resonance dynamic susceptibility contrast perfusion-weighted imaging in canine brain.

Brain perfusion allows for the evaluation of cerebral hemodynamics, particularly in brain infarcts and tumors. Computed tomography (CT) perfusion (CTP) provides reliable data; however, it has a limited scan field of view and radiation exposure. Magnetic resonance (MR) perfusion provides detailed imaging of small structures and a wide scan field of view. However, no study has compared CTP and MR perfusion and assessed the correlation between the perfusion parameters measured using CTP and MR perfusion. The aim of the present study was to assess the correlation and agreement of the cerebral perfusion derived from dynamic susceptibility contrast (DSC)-MRI and CTP in dogs. In this crossover design study, the cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time, and time to peak were measured in the temporal cerebral cortex, caudate nucleus, thalamus, piriform lobe, and hippocampus using CTP and DSC-MRI in six healthy beagle dogs and a dog with a pituitary tumor. On the color map of healthy beagles, blood vessels and the perivascular brain parenchyma appeared as red-green, indicating high perfusion, and the areas distant from the vessels appeared as green-blue, indicating low perfusion levels in CTP and DSC-MRI. CTP parameters were highest in the piriform lobe (CBF = 121.11 ± 12.78 mL/100 g/min and CBV = 8.70 ± 2.04 mL/100 g) and lowest in the thalamus (CBF = 63.75 ± 25.24 mL/100 g/min and CBV = 4.02 ± 0.55 mL/100 g). DSC-MRI parameters were also highest in the piriform lobe (CBF = 102.31 ± 14.73 mL/100 g/min and CBV = 3.17 ± 1.23 mL/100 g) and lowest in the thalamus (CBF = 37.73 ± 25.11 mL/100 g/min and CBV = 0.81 ± 0.44 mL/100 g) although there was no statistical correlation in the quantitative perfusion parameters between CTP and DSC-MRI. In a dog with a pituitary tumor, the color map of the tumor appeared as a red scale, indicating high perfusion and higher CBF and CBV on CTP (149 mL/100 g and 20 mL/100 g/min) and on DSC-MRI (116.3 mL/100 g and 15.32 mL/100 g/min) compared to those measured in healthy dogs. These findings indicate that DSC-MRI and CTP maps exhibit comparability and interchangeability in the assessment of canine brain perfusion.

The effect of permanent protective netting on insect pest prevalence in citrus orchards in South Africa

The use of protective netting is becoming an increasingly popular practice in the citrus industry in South Africa. However, data on its effects on biotic factors, particularly insect pests, are limited. This study focused on the effect nets have on key citrus pests in the Eastern Cape province. Orchards under nets and open orchards, of similar cultivars, ages and management practices, were monitored at several sites over two seasons for pest infestation and damage. Weekly monitoring was conducted for Thaumatotibia leucotreta infestation. Other pests were monitored either monthly or once a season. During the first season, T. leucotreta infestation was higher in orchards under nets, probably because, unlike the open orchards, the nets provided protection for the existing high levels of T. leucotreta. No T. leucotreta infestation was recorded in both orchard types in 2019. This was due to generally lower than usual pest abundance and dramatically improved area-wide management of T. leucotreta. Pheromone traps were used to monitor T. leucotreta males, including sterile moths used in a sterile insect technique programme. Although higher catches of wild T. leucotreta moths were recorded in orchards under nets, so too were there higher numbers of sterile moths and a higher ratio of sterile to wild moths, indicating the potential for better pest suppression for orchards under nets. Various other key pests were monitored during this time, with variable results for each species. Pests that were elevated under nets include Planococcus citri and Aonidiella aurantii. Pests that seemed to be lower under nets were Ceratitis capitata and Scirtothrips aurantii. Nets had no effect on Empoasca distinguenda, Penthimiola bella and Eriophyes sheldoni. These differences in pest levels in netted and open orchards trigger an important debate on whether nets are beneficial for or detrimental to the successful implementation of an integrated pest management programme.

California red scale insecticide trial, 2023

California red scale insecticide trial, 2023

Innovative Transformation and Valorisation of Red Mill Scale Waste into Ferroalloys: Carbothermic Reduction in the Presence of Alumina

Primary and secondary mill scales (MSs) are waste products produced by the surface oxidation of steel during the hot (800 to 1200 °C) rolling process in downstream steelmaking. While the primary MS is comprised of FeO, Fe3O4, and Fe2O3 in a range of proportions, the secondary MS primarily contain red ferric oxide (Fe2O3) (red MS). We report a novel route for extracting iron from red MS and transforming it into ferro-aluminium alloys using carbothermic reduction in the presence of alumina. The red MS powder was blended with high-purity alumina (Al2O3) and synthetic graphite (C) in a range of proportions. The carbothermic reduction of red MS-Al2O3-C blends was carried out at 1450 °C and 1550 °C under an argon atmosphere for 30 min and then furnace-cooled. The red MS was completely reduced to iron at these temperatures with reduced iron distributed around the matrix as small droplets. However, the addition of alumina unexpectedly resulted in a significant increase in the number and sizes of iron droplets generated, much higher reactivity, and the formation of ferrous alloys. A small amount of alumina reduction into metallic aluminium was also observed at 1450 °C. There is an urgent need to identify the true potential of industrial waste and the materials within it. This study showed that red MS is a valuable material source that could be transformed into ferro-aluminium alloys. These alloys find application in a range of industrial sectors such as construction, automotive, infrastructure, etc.

Characterization of Nanocomposites Based on Poly(ε-caprolactone) Filled with Recycled Red Mill Scale

Characterization of Nanocomposites Based on Poly(ε-caprolactone) Filled with Recycled Red Mill Scale

Machine learning assisted discrimination and detection of antibiotics by using multicolor microfluidic chemiluminescence detection chip

The fabrication of multicolor chemiluminescence (CL) sensing chip for the discrimination and detection of multianalytes remains a great challenge. Herein, machine learning assisted multicolor microfluidic CL detection chip for the identification and concentration prediction of antibiotics was presented. Firstly, a three-channel microfluidic CL detection chip was fabricated. The three detection zones of the microfluidic detection chip were modified with CL catalyst Co(II) and different CL reagents including luminol, luminol mixed with fluorescein, and luminol mixed with phloxine B, respectively. Strong blue, green and pink-purple colored light emissions can be generated from the three detection zones in the presence of H2O2 solution. The three multicolor CL emissions show different degrees of reduce in intensity and change in color in the presence of different antibiotics, including diethylstilbestro (DES), metronidazole (MNZ), kanamycin (KAN), isoniazide (INH), and ceftiofur sodium (CS), resulting in distinct fingerprint-like response patterns. The red (R), green (G), blue (B) and gray scale values of the three multicolor light emissions were extracted and ten characteristic sensing parameters were chosen to obtain multicolor CL response database. Then, machine learning assisted data analysis were carried out. The five antibiotics can be facilely classified by using principal component analysis (PCA) and hierarchical clustering analysis (HCA), and further quantified by using deep neural networks (DNN) algorithm. Good results were obtained for identification of binary antibiotic mixtures, spiked antibiotics in water samples, and unknown antibiotic samples. Satisfied results were obtained for concentration prediction of antibiotics. This work provides a simple machine learning assisted and multicolor microfluidic CL detection chip based CL sensing strategy for discrimination and quantitative detection of multiple analytes.

Influence of mechanical and manual pruning on the incidence of pests in 'Clemenules' mandarins.

In Spain, citrus pruning is usually done by hand, although mechanized pruning is gradually being introduced as a cheaper alternative. The pruning strategy affects the pattern and intensity of sprouting, and the canopy characteristics, and therefore could affect pest control. In this study, the effect of three pruning strategies on the incidence of key citrus pests was analyzed: manual, mechanical (with hedging and topping) and no pruning (control). In a commercial clementine orchard, sprouting, pest density and fruit damage were evaluated through three seasons. Outside the canopy, mechanically pruned trees had a significantly higher number of shoots, and more shoots were attacked by aphids (cotton aphid, Aphis gossypii, and spirea aphid, A. spiraecola) in comparison with manual or control strategies. Inside the canopy statistically nonsignificant differences were found between strategies. Regarding the pest level of two-spotted spider mite, Tetranychus urticae, and California red scale, Aonidiella aurantii, in general, no significant differences were found between pruning strategies, and in some cases mechanical pruning resulted in a lower level of these pests and fruit damage than manual pruning. The density of aphids, which are pests associated with sprouting, was affected by the pruning strategy. However, the densities of T. urticae and A. aurantii and the level of damaged fruit were unaffected. © 2023 Society of Chemical Industry.

The contribution of cultural identity to subjective well-being in collectivist countries: a study in the context of contemporary Chinese culture.

Though the important effect of cultural identity on subjective well-being is widely acknowledged, the details of how different cultures' unique features influence well-being remain to be revealed. To address this issue in the context of Chinese culture, the present study investigates whether and how the prominent features of Chinese culture-collectivism and red culture-shape Chinese people's subjective well-being. The Red Cultural Identity Scale, Subjective Well-Being Scale, Collectivism Scale, and Perspective-Taking Scale were used to assess 1,045 Chinese residents. The results showed that red cultural identity positively predicted participants' subjective well-being through the mediated role of collectivism. Furthermore, perspective-taking was found to moderate the mediating effect of collectivism. These results demonstrate that the way cultural identity predicts subjective well-being is highly correlated to specific cultural features, e.g., the opinion of values, which was significant in practice with a cross-cultural background.

Analysis of Environmental Sustainability through a Weighting Matrix in the Oil and Gas Industry

In the oil sector, various strategies are applied to mitigate harmful effects on the environment. These strategies include, among others, compensation plans, the measurement and control of the carbon footprint and/or water footprint, the recovery of waste from activities and processes, and Environmental Management Systems (EMS). An EMS provides a formal framework that enables more efficient work on environmental issues, thereby improving performance. It aims to raise awareness of the environmental impacts associated with the oil industry in different areas through the use of weighting matrices. Additionally, it seeks to conduct sustainable studies and optimize the direct activities involved in the exploitation of hydrocarbons as a natural resource. Factors considered in decision making include ensuring that the strategy does not compromise the well-being of future generations, has economic viability, and does not hinder any oil sector activities such as exploration, drilling, production, or processing of derivatives. The purpose of this is that it allows for the creation of decision matrices based on weighting methodologies that outline possible correlations between specific activities of the oil sector such as water use, effects on soils and landscapes, greenhouse gas emissions, solid waste, liquid effluents, hazardous waste, and toxic waste, among others. The decision matrices can also help elucidate the relationship of these activities with mitigation strategies to provide a decision-making tool for environmental management plans so that activities are implemented in a way that can mitigate impacts on water, soil, and air resources. The results of this study were classified using a traffic light matrix, based on the level of technical congruence, using an optimal (green), regular (yellow), medium (orange), and at-risk (red) scale. The environmental impact of “alteration of the geoform of the land” was positioned in the at-risk category due to its assessment by experts in relation to the activity of “land adaptation”. In the medium category, a total of 23 impacts were identified, while 10 impacts fell into the regular category. These results were evaluated in the context of the environmental, social, and economic sustainability of the oil industry.

Isolation and Characterization of Bacteria Associated with Onion and First Report of Onion Diseases Caused by Five Bacterial Pathogens in Texas, U.S.A.

Bacterial diseases pose a severe challenge to growers and cause significant loss to the billion-dollar onion industry in the United States. Texas is the sixth largest onion producing state, yet the bacterial communities associated with short-day onion crops grown in Texas have not been studied. This study was conducted to identify, characterize, and understand the diversity of bacteria associated with onion production in Texas. In 2020, 190 foliar and 210 bulb samples were collected from onion crops in the Rio Grande Valley and Winter Garden regions of Texas. Sequencing of the 16s rRNA gene was used to identify each bacterial strains to a genus. The pathogenicity to onion of each bacterial strain was tested using three assays: a red onion scale assay, a yellow onion bulb assay, and a foliar assay. Whole genome sequencing was done to identify the onion-pathogenic strains to species. Collectively, isolates of 24 genera belonging to three phyla were detected, including 19 genera from foliar samples and nine genera from bulb samples. Isolates in the Phylum Proteobacteria, including 15 genera of Gram-negative bacteria, were the most abundant of the taxa, comprising 90.0% of the strains isolated. The diversity of foliar isolates was evenly distributed between Gram-positive and Gram-negative bacteria, while Gram-negative bacteria dominated the isolates from bulb samples. In total, 83.9% of the bacterial isolates were not pathogenic on onion, with only isolates of Pantoea, Pseudomonas, Burkholderia, Erwinia, Enterobacter, and Curtobacterium proving pathogenic. Strains of Burkholderia gladioli, Pseudomonas alliivorans, Pantoea agglomerans, P. ananatis, and P. allii are the first documented cases of these pathogens of onion in Texas. Identifying and characterizing the nature of onion microflora, including pathogens of onion, is vital to developing rapid disease detection techniques via pathogenomics and minimizing losses through the application of effective disease management measures.

The Genetic Requirements for HiVir-Mediated Onion Necrosis by Pantoea ananatis, a Necrotrophic Plant Pathogen.

Pantoea ananatis is an unusual bacterial pathogen that lacks typical virulence determinants yet causes extensive necrosis in onion foliage and bulb tissues. The onion necrosis phenotype is dependent on the expression of the phosphonate toxin, pantaphos, which is synthesized by putative enzymes encoded by the HiVir (high virulence) gene cluster. The genetic contributions of individual hvr genes in HiVir-mediated onion necrosis remain largely unknown, except for the first gene, hvrA (phosphoenolpyruvate mutase, pepM), whose deletion resulted in the loss of onion pathogenicity. In this study, using gene-deletion mutation and complementation, we report that, of the ten remaining genes, hvrB to hvrF are also strictly required for the HiVir-mediated onion necrosis and in-planta bacterial growth, whereas hvrG to hvrJ partially contributed to these phenotypes. As the HiVir gene cluster is a common genetic feature shared among the onion-pathogenic P. ananatis strains that could serve as a useful diagnostic marker of onion pathogenicity, we sought to understand the genetic basis of HiVir-positive yet phenotypically deviant (non-pathogenic) strains. We identified and genetically characterized inactivating single nucleotide polymorphisms in the essential hvr genes of six phenotypically deviant P. ananatis strains. Finally, inoculation of cell-free spent medium of the isopropylthio-β-galactoside (IPTG)-inducible promoter (Ptac)-driven HiVir strain caused P.ananatis-characteristic red onion scale necrosis as well as cell death symptoms in tobacco. Co-inoculation of the spent medium with essential hvr mutant strains restored in-planta populations of the strains to the wild-type level, suggesting that necrotic tissues are important for the proliferation of P. ananatis in onion. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.