Wilt Disease Research Articles

Host vegetation connectivity is decisive for the natural spread of pine wilt disease.

Pine wilt disease has caused significant economic, ecological, and social losses in China, but there is a notable lack of research on the dynamic process of its propagation and diffusion over long timescales. This study revealed the spatial and temporal spread of the natural invasion of pine wilt disease through an analysis of long time series at macroscopic scales. We analysed and verified by simulations the driving mechanisms of host and wind fields in the natural spread of pine wilt disease. The research findings indicate that from 1982 to 2019, the number of counties affected by pine wilt disease in the Yangtze River Delta region of China exhibited a pattern of 'steady increase-fluctuation-outbreak'. The host forest played a decisive role in the natural spread of the disease, while the wind field played a supporting role. The study revealed specific contributions from various factors, where host forest landscape connectivity, host forest area share, mean wind speed, and wind frequency accounted for 31.8%, 28.7%, 22.6%, and 8.8%, respectively. The interaction of increased host forest area and increased wind speed can significantly increase the risk of pine wilt disease transmission. To validate these findings, vectorial metacellular automata simulations of pine nematode transmission in the Yangtze River Delta were conducted, yielding results with an accuracy of 0.803. By quantifying the contribution of host forest connectivity to the natural spread of pine wilt disease, this research offers a scientific foundation and innovative insights for preventing and controlling its dissemination. © 2024 Society of Chemical Industry.

Surface-Imprinted Polysiloxane with Recognition Ability Based on an ITO Layer for Rapid Detection of Fusarium oxysporum f. sp. cubense by the Naked Eye.

Direct observation by the naked eye of fluorescence-stained microbes adsorbed on surface imprinted polymers (SIPs) is highly challenging and limited by speed, accuracy and the semiquantitative nature of the method. In this study, we tested for the presence of spores of Fusarium oxysporum f. sp. cubense race 4 (Foc4), which cause severe banana Fusarium wilt disease and reduces the area of banana plants. This kind of spore can become dormant in soil, which means that the detection of secreted molecules (molecular imprinting) in soil may be inaccurate; detection methods such as polymerase chain reaction (PCR) and Raman spectroscopy are more accurate but time-consuming and inconvenient. Therefore, a semiquantitative and rapid SIP detection method for Foc4 was proposed. Based on the ITO conductive layer, a reusable and naked-eye-detectable Foc4-PDMS SIP film was prepared with a site density of approximately 9000 mm-2. Adsorption experiments showed that when the Foc4 spore concentration was between 104 to 107 CFU/mL, the number of Foc4 spores adsorbed and the fluorescence intensity were strongly correlated with the concentration and could be fully distinguished by the naked eye after fluorescence staining. Adsorption tests on other microbes showed that the SIP film completely recognized only the Foc series. All the results were highly consistent with the naked-eye observations after fluorescence staining, and the results of the Foc4-infected soil experiment were also close to the ideal situation. Taken together, these results showed that Foc4-PDMS SIPs have the ability to rapidly and semiquantitatively detect the concentration of Foc in soil, which can provide good support for banana cultivation. This method also has potential applications in the detection of other fungal diseases.

Inheritance of Resistance to Chickpea Fusarium Wilt Disease (Fusarium oxysporum f. sp. ciceris Race 2) in a Wide-Cross Cicer arietinum × Cicer reticulatum Mapping Family.

Chickpea (Cicer arietinum) is a major food legume providing high quality nutrition, especially in developing regions. Chickpea wilt (Fusarium oxysporum f. sp. ciceris) causes significant annual losses. Integrated disease management of Fusarium wilt is supported by resistant varieties. Relatively few resistance genes are known so there is value in exploring genetic resources in chickpea wild relatives. This study investigates the inheritance of Fusarium wilt resistance (race 2) in recombinant inbred lines (RILs) from a cross between a cultivated susceptible chickpea variety (Gokce) and a wild resistant Cicer reticulatum line (Kayat-077). RILs, parents, resistant and susceptible tester lines were twice grown in the greenhouse with inoculation and disease symptoms scored. DNA was extracted from dried leaves and individuals were single nucleotide polymorphism (SNP) genotyped. SNPs were placed on the reference chickpea genome and quantitative trait locus (QTL) mapping was performed. Significant QTL regions were examined using PulseDB to identify candidate genes. The results showed the segregation of Fusarium wilt resistance conforming to a single gene inheritance. One significant QTL was found at the start of chromosome 8, containing 138 genes, three of which were disease-resistance candidates for chickpea breeding.

A Lightweight Pine Wilt Disease Detection Method Based on Vision Transformer-Enhanced YOLO

Pine wilt disease (PWD) is a forest disease characterized by rapid spread and extremely high lethality, posing a serious threat to the ecological security of China’s forests and causing significant economic losses in forestry. Given the extensive forestry area, limited personnel for inspection and monitoring, and high costs, utilizing UAV-based remote sensing monitoring for diseased trees represents an effective approach for controlling the spread of PWD. However, due to the small target size and uneven scale of pine wilt disease, as well as the limitations of real-time detection by drones, traditional disease tree detection algorithms based on RGB remote sensing images do not achieve an optimal balance among accuracy, detection speed, and model complexity due to real-time detection limitations. Consequently, this paper proposes Light-ViTeYOLO, a lightweight pine wilt disease detection method based on Vision Transformer-enhanced YOLO (You Only Look Once). A novel lightweight multi-scale attention module is introduced to construct an EfficientViT feature extraction network for global receptive field and multi-scale learning. A novel neck network, CACSNet(Content-Aware Cross-Scale bidirectional fusion neck network), is designed to enhance the detection of diseased trees at single granularity, and the loss function is optimized to improve localization accuracy. The algorithm effectively reduces the number of parameters and giga floating-point operations per second (GFLOPs) of the detection model while enhancing overall detection performance. Experimental results demonstrate that compared with other baseline algorithms, Light-ViTeYOLO proposed in this paper has the least parameter and computational complexity among related algorithms, with 3.89 MFLOPs and 7.4 GFLOPs, respectively. The FPS rate is 57.9 (frames/s), which is better than the original YOLOv5. Meanwhile, its mAP@0.5:0.95 is the best among the baseline algorithms, and the recall and mAP@0.5 slightly decrease. Our Light-ViTeYOLO is the first lightweight method specifically designed for detecting pine wilt disease. It not only meets the requirements for real-time detection of pine wilt disease outbreaks but also provides strong technical support for automated forestry work.

GbPP2C80 Interacts with GbWAKL14 to Negatively Co-Regulate Resistance to Fusarium and Verticillium wilt via MPK3 and ROS Signaling in Sea Island Cotton.

Fusarium wilt (FW) is widespread in global cotton production, but the mechanism underlying FW resistance in superior-fiber-quality Sea Island cotton is unclear. This study reveals that FW resistance has been the target of genetic improvement of Sea Island cotton in China since the 2010s. The key nonsynonymous single nucleotide polymorphism (SNP, T/C) of gene Gbar_D03G001670 encoding protein phosphatase 2C 80 (PP2C80) results in an amino acid shift (L/S), which is significantly associated with FW resistance of Sea Island cotton. Silencing GbPP2C80 increases FW resistance in Sea Island cotton, whereas overexpressing GbPP2C80 reduces FW resistance in Arabidopsis. GbPP2C80 and GbWAKL14 exist synergistically in Sea Island cotton accessions with haplotype forms "susceptible-susceptible" (TA) and "resistant-resistant" (CC), and interact with each other. CRISPR/Cas9-mediated knockout of GbWAKL14 enhances FW and Verticillium wilt (VW) resistance in upland cotton and overexpression of GbWAKL14 and GbPP2C80 weakens FW and VW resistance in Arabidopsis. GbPP2C80 and GbWAKL14 respond to FW and VW by modulating reactive oxygen species (ROS) content via affecting MPK3 expression. In summary, two tandem genes on chromosome D03, GbPP2C80, and GbWAKL14, functions as cooperative negative regulators in cotton wilt disease defense, providing novel genetic resources and molecular markers for the development of resistant cotton cultivars.

Resistance of complex interspecific cotton hybrids to wilt

<p>In the article, the results of determining the degree of tolerance to wilt disease in the wilt background of hybrid families obtained using the method of interspecies complex hybridization in the cotton plant are analyzed. In the F2–F4 generations of interspecies complex hybrids, a large-scale process of separation according to the sign of tolerance to wilt disease takes place, and among the hybrids, plants that are not damaged by wilt disease, partially damaged plants, and severely damaged plants are separated. With this in mind, it was confirmed that it is possible to isolate lines and varieties with different levels of wilt damage from complex hybrid combinations of interspecies with different genomes by purposefully conducting selection work by the breeder. A number of wilt disease-tolerant families compared to control cultivars have been isolated and are recommended for use as a starting source in genetic selection studies.<strong><em></em></strong></p>

A bacterial effector manipulates plant metabolism, cell death, and immune responses via independent mechanisms.

Bacterial pathogens inject effector proteins inside plant cells to manipulate cellular functions and achieve a successful infection. The soil-borne pathogen Ralstonia solanacearum (Smith), the causal agent of bacterial wilt disease, secretes > 70 different effectors inside plant cells, although only a handful of them have been thoroughly characterized. One of these effectors, named RipI, is required for full R. solanacearum pathogenicity. RipI associates with plant glutamate decarboxylases (GADs) to promote the accumulation of gamma-aminobutyric acid (GABA), which serves as bacterial nutrient. In this work, we found that RipI can also suppress plant immune responses to bacterial elicitors, which seems to be unrelated to the ability of RipI to induce GABA accumulation and plant cell death. A detailed characterization of the RipI features that contribute to its virulence activities identified two residues at the C-terminal domain that mediate RipI interaction with plant GADs and the subsequent promotion of GABA accumulation. These residues are also required for the appropriate homeostasis of RipI in plant cells and the induction of cell death, although they are partially dispensable for the suppression of plant immune responses. Altogether, we decipher and uncouple the virulence activities of an important bacterial effector at the biochemical level.

BpAFP, a Broussonetia papyrifera latex chitinase, exhibits a dual role in resisting to both Verticillium wilt disease and lepidopterous pests, Plutella xylostella and Prodenia litura

Paper mulberry (Broussonetia papyrifera) is a fast-growing tree known for its tolerance to diverse biotic and abiotic stresses. To explore genes combating Verticillium wilt, a devasting and formidable disease damage to cotton and many economically significant crops, we purified an antifungal protein, named BpAFP, from the latex of paper mulberry. Based on peptide fingerprint, we cloned the full cDNA sequence of BpAFP and revealed that BpAFP belongs to Class I chitinases, sharing 74 % identity with B. papyrifera leaf chitinase, PMAPII. We further introduced BpAFP into Arabidopsis, tobacco, and cotton. Transgenic plants exhibited significant resistance to Verticillium wilt. Importantly, BpAFP also demonstrated insecticidal activity against herbivorous pests, Plutella xylostella, and Prodenia litura, when feeding the larvae with transgenic leaves. Our finding unveils a dual role of BpAFP in conferring resistance to both plant diseases and lepidopterous pests.

Control of wilt disease caused by Fusarium sp. in the cultivation of stocks (Matthiola incana)

In greenhouse cultivation of stock (Matthiola incana), the main causative agent of its death is the fungus Fusarium sp., especially in the early phenological stages, resulting in significant losses during the first four weeks of cultivation. Therefore, the objective of this study was to evaluate phytosanitary control techniques (chemical, biological, and antibiotics) to reduce Fusarium sp. infection in stock (Matthiola incana) cultivation. The experiment was conducted in a randomized block design with five treatments (control; chemical products; biological products, antibiotics, and product combinations) and three replications. The chemical active ingredients used were aluminum phosphite, iprodione, captan, and Hymexazol. Biological solutions included Trichoderma sp. and Bacillus subtilis, while antibiotics used were Weed Pirocontrole, Kasugamicin, Polioxin B, Azoxystrobin, and Kresoxym methyl. Additionally, product combinations were evaluated, such as Fosetyl aluminum, Bacillus subtilis, Polioxin B, Hymexazol, and Azoxystrobin. Control efficacy was measured based on the severity of fungal growth in culture, while mortality represented the loss rate at the end of the experiment. The combined treatment of techniques was superior, with a mortality rate of 13.77%, compared to the 63.00% recorded in the absolute control group. These results underscore the importance of an integrated approach to Fusarium sp. control in stock cultivation, emphasizing the effectiveness of combining different phytosanitary techniques to minimize losses and promote successful production.

Aerial Image Segmentation of Nematode-Affected Pine Trees with U-Net Convolutional Neural Network

Pine wood nematode disease, commonly referred to as pine wilt, poses a grave threat to forest health, leading to profound ecological and economic impacts. Originating from the pine wood nematode, this disease not only causes the demise of pine trees but also casts a long shadow over the entire forest ecosystem. The accurate identification of infected trees stands as a pivotal initial step in developing effective prevention and control measures for pine wilt. Nevertheless, existing identification methods face challenges in precisely determining the disease status of individual pine trees, impeding early detection and efficient intervention. In this study, we leverage the capabilities of unmanned aerial vehicle (UAV) remote sensing technology and integrate the VGG classical small convolutional kernel network with U-Net to detect diseased pine trees. This cutting-edge approach captures the spatial and characteristic intricacies of infected trees, converting them into high-dimensional features through multiple convolutions within the VGG network. This method significantly reduces the parameter count while enhancing the sensing range. The results obtained from our validation set are remarkably promising, achieving a Mean Intersection over Union (MIoU) of 81.62%, a Mean Pixel Accuracy (MPA) of 85.13%, an Accuracy of 99.13%, and an F1 Score of 88.50%. These figures surpass those obtained using other methods such as ResNet50 and DeepLab v3+. The methodology presented in this research facilitates rapid and accurate monitoring of pine trees infected with nematodes, offering invaluable technical assistance in the prevention and management of pine wilt disease.

Evaluation of the novel endophytic fungus Chaetomium ascotrichoides 1-24-2 from Pinus massoniana as a biocontrol agent against pine wilt disease caused by Bursaphelenchus xylophilus.

Bursaphelenchus xylophilus, the causative agent of pine wilt disease (PWD), is an ever-increasing threat to Pinus forests worldwide. This study aimed to develop biological control of PWD by the application of endophytic fungi isolated from healthy pine trees. We successfully isolated a novel endophytic fungal strain 1-24-2 from branches of healthy Pinus massoniana. The culture filtrates (CFs) of strain 1-24-2 exhibited strong nematicidal activity against Bursaphelenchus xylophilus, with a corrected mortality rate of 99.00%. Based on the morphological and molecular characteristics, the isolated strain 1-24-2 was identified as Chaetomium ascotrichoides. In the in-planta assay, pine seedlings (2-years-old) treated with 1-24-2 CFs + pine wood nematode (T2) showed a significant control effect of 80%. A total of 24 toxic compounds were first identified from 1-24-2 CFs through gas chromatography-mass spectrometry (GC-MS) analysis, from which O-methylisourea, 2-chlorobenzothiazole, and 4,5,6-trihydroxy-7-methylphthalide showed robust binding sites at Tyr119 against phosphoethanolamine methyltransferase (PMT) protein of Bursaphelenchus xylophilus by molecular docking approach and could be used as potential compounds for developing effective nematicides. Interestingly, strain 1-24-2 produces toxic volatile organic compounds (VOCs), which disturb the natural development process of B. xylophilus, whose total number decreased by up to 83.32% in the treatment group as compared to control and also reduced Botrytis cinerea growth by up to 71.01%. Our results highlight the potential of C. ascotrichoides 1-24-2 as a promising biocontrol agent with solid nematicidal activity against B. xylophilus. This is the first report of C. ascotrichoides isolated from P. massoniana exhibiting strong biocontrol potential against B. xylophilus in the world. © 2024 Society of Chemical Industry.

Environmental behavior assessment Thiophanate methyl in the soil using different mathematical models

One of the most common fungicides, Thiophanate-methyl (TM), has been extensively used to prevent fusarium wilt disease. Understanding the kinetic behavior of the TM-fungicide in the greenhouse soil was aimed at the current research. The findings demonstrated that TM-fungicide goes through the pseudo-first-order model (PFO), which results in a rate constant K= 0.421 minutes-1. As a result, TM-fungicide needs 16.46 minutes-1 to degrade 50% of the initial concentration. The power function for TM-fungicide ranged from -1.826 to 0.0360 minutes-1, and the distribution coefficient was 6.5 mL g-1. Regarding the adsorption of Langmuir and Freundlich, TM-fungicide is more fitting to the Freundlich with the aF = 25.73 and the bF = 0.078 compared to the Langmuir model. The TM-fungicide starts to release to the soil after 4-5 hours, achieving extensive, effective control of the soil pests, Moreover, TM-fungicide is highly mobile in the soil based on the current conditions.

In vivo Studies on the Effect of Warburgia ugandensis Crude Extracts Against Bacterial wilt in Tomato

Tomato plants are susceptible to Ralstonia solanacearum, a pathogen responsible for bacterial wilt, a severe soil-borne disease with no available cure. Warburgia ugandensis crude extract has shown biocontrol capabilities against pathogenic fungi and bacteria in animals, but data on its effectiveness in plants is limited. The current study was done to evaluate the in vivo efficacy of W. ugandensis crude extracts against R. solanacearum in tomato plants. W. ugandensis leaf and stem bark crude extracts were obtained using ethanol, methanol, hexane, and dichloromethane. The obtained crude extracts were tested against R. solanacearum in tomato at the greenhouse in triplicate. The data collected on bacterial wilt incidence, severity, stem diameter, height, and the number of branches and fruits set were analyzed using analysis of variance (ANOVA) at a 5% significance level. Tukey’s test was employed to determine significant differences between means at the same significance level. Tomato plants established in soil inoculated with R. solanacearum and treated with dichloromethane crude extract of W. ugandensis stem bark showed no sign of bacterial wilt disease and were comparable to the positive control. Tomato plants established in soil inoculated with R. solanacearum but treated with W. ugandensis leaf ethanol crude extract had the highest average height of 62.50 cm which was similar to positive control. Tomato plants grown in R. solanacearum-inoculated soils and treated with methanol crude extracts from W. ugandensis stem bark produced a significantly higher average number of fruits, 22.00, compared to those treated with crude extracts from other solvents. The study proposed that W. ugandensis crude extract has the ability to be used as antibacterial biocontrol against R. solanacearum. Further research is important to determine the bioactive compounds against R. solanacearum.

Association of soil bacterial diversity and composition with Fusarium wilt disease of bananas in Yogyakarta Province, Indonesia

Abstract. Kurniasari I, Wibowo A, Subandiyah S, Pattison AB. 2024. Association of soil bacterial diversity and composition with Fusarium wilt disease of bananas in Yogyakarta Province, Indonesia. Biodiversitas 25: 2264-2275. Infection of banana plants with Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc-TR4) leads to a cascade of changes in the rhizosphere, resulting in changes to the soil physicochemical properties and bacterial community composition. This study aimed to determine the core taxa associated with different soil physicochemical properties and disease statuses and to identify the factors exerting the greatest influence on the soil bacterial community composition of bananas in Special Region of Yogyakarta Province, Indonesia. Rhizospheric soil from healthy and infected plants was collected from four banana locations, including Kulon Progo, Gunungkidul, Bantul, and Sleman districts, at 10-30 cm depth between May and September 2021. Laboratory analysis was conducted for soil physicochemical properties, and the abundance of Foc-TR4 was undertaken. Additionally, 16S rRNA gene-based metagenomics analysis was used to quantify bacterial diversity in all samples. Soil type significantly influenced the abundance and composition of the bacterial community more than disease status did. Contrarily, disease status groups influenced the complexity of bacterial network interaction more than soil type. Actinobacteriota, Proteobacteria, Chloroflexi, Acidobacteriota, and Bacteriodota are the major phyla associated with all soils. This study identified 60 bacterial genera as core members of the banana rhizosphere. These core bacterial genera include various plant growth-promoting bacteria involved in nitrogen fixation, phytohormone production, siderophore production, and biocontrol mechanisms for producing antifungal compounds. Our work provides a basis for future research on the soil bacterial composition associated with banana plants to enhance plant health against Fusarium wilt disease.

Soil nutrient levels are associated with suppression of banana Fusarium wilt disease

Soil nutrient levels are associated with suppression of banana Fusarium wilt disease

Identification and pathogenicity of Ceratocystis manginecans causing wilt disease on Acacia mangium in Sabah, Malaysia

Abstract. Yunus NM, Maid M, Yong WTL, Anthony FE, Sudin M, Taylor PWJ. 2024. Identification and pathogenicity of Ceratocystis manginecans causing wilt disease on Acacia mangium in Sabah, Malaysia. Biodiversitas 25: 2170-2182. An alarming incidence of wilt disease has been reported in an Acacia mangium plantation in Ulu Kukut, Kota Belud District, Sabah, Malaysia. Infected trees exhibited symptoms such as severe wilting, sapwood discoloration or black lesion, and a fruity-sweet odor emanating from the fermentation exudate at the wound lesion. This is the first investigation of the causal wilt pathogen in a commercial A. mangium plantation in Ulu Kukut, located in the western region of Sabah. This study aimed to identify the causal fungal pathogen from infected A. mangium trees using morphological characterization and DNA sequence comparisons for the regions of Internal Transcribed Spacer (ITS), beta-tubulin 1 (bt1), transcription elongation factor-1 alpha (tef1), guanine nucleotide-binding protein subunit beta-like protein (ms204), and second largest subunits of RNA polymerase II (rpb2). The fungal isolates shared morphological characteristics with the wilt pathogen Ceratocystis sp., including a globose base with a long neck-ended tip with ostiolar hyphae. Sequence-based phylogenetic analysis confirmed the identity of Ceratocystis manginecans, distinguishing them from all other Ceratocystis species. Bioassays inoculating phyllodes and twigs of 1-year-old A. mangium trees confirmed that C. manginecans was the cause of wilt disease. Confirming the identity of the causal agent of the increasingly destructive and severe wilt disease aids in developing effective disease management strategies for Acacia-based plantations.

Development of Tetramycin-Loaded Core–Shell Beads with Hot-/Wet-Responsive Release Properties for Control of Bacterial Wilt Disease

Plant bacterial wilt is caused by Ralstonia solanacearum, a soilborne pathogen that infects plant conduits, leading to wilt disease. It is extremely difficult to cure plants infected with Ralstonia solanacearum; however, bactericide-loaded beads with hot-/wet-responsive properties may be able to release a biocide in line with the increase in the hot-/wet-associated activity of Ralstonia solanacearum, effectively killing the pathogenic cells and providing high levels of plant protection. A biopesticide, Tetramycin, was embedded in corn kernel powder (CKP)-based cores. An oil-phase mixture was sprayed onto the core surface to form a hot-/wet-responsive intermediate shell (IMS). Subsequently, a layer of ethyl cellulose (EC) and hydroxypropyl methyl cellulose (HPMC) was coated onto the IMS to create a single wet-responsive outer shell (OTS). The ratios of the components in the cores, including the corn kernel powder (CKP), xanthan gum (XG), and Tetramycin, were optimized, as well as those of the IMS, including pentaerythrityl tetrastearate (PETS), pentaerythrityl tetraoleate (PETO), polyethylene glycol stearate (PEG400MS), and polyethylene glycol monooleate (PEG400MO), and those of the outer shell (OTS), including ethyl cellulose (EC) and hydroxypropyl methyl cellulose (HPMC). A texture performance analysis, differential scanning calorimetry (DSC) analysis, thermogravimetric analysis (TGA), temperature and humidity response performance tests, scanning electron microscope (SEM) observations, and a field effectiveness test were conducted to characterize the Tetramycin-loaded beads. The results indicated that the optimal formula for the bead cores comprised a mass ratio of CKP/Tetramycin solution/XG = 13.5:23:2. The preferred mass ratio for IMS was PETS/PETO/PEG400MO = 10:30:10, and the formula for the applicable OTS consisted of a mass ratio of EC/HPMC = 5:1. In soil with a temperature of 30–35 °C and humidity of 30%, the release period of the Tetramycin-loaded beads, with a cumulative release rate of over 95%, could last up to 35 days. Furthermore, the Tetramycin-loaded beads exhibited a gradual and multi-cyclic release process under alternating hot/wet and dry/cold environments. The relative preventive efficacy of 54.74% on tobacco was revealed at a field-testing scale. A significant reduction in the abundance of Ralstonia solanacearum was also observed under treatment with the Tetramycin-loaded beads. The early fungal community structure exhibited higher consistency compared to the control. However, in the later stage, the diversity differences between the soil layers were restored. In conclusion, Tetramycin-loaded beads that could effectively respond to temperature and humidity fluctuations were developed, resulting in enhanced disease prevention efficacy and offering broad prospects for the prevention and control of Ralstonia solanacearum in agricultural settings.

Pathogenicity and colonization of Metrosideros polymorpha by Ceratocystis huliohia

AbstractBoth Ceratocystis lukuohia and C. huliohia have been associated with Rapid ʻŌhiʻa Death (ROD), an emerging threat to ʻōhiʻa (Metrosideros polymorpha), a keystone forest tree species. The vascular wilt disease caused by C. lukuohia has been recently described and is responsible for the widespread ROD epidemic on Hawai'i Island. However, the role of C. huliohia in ROD development and tree death is not clear. Artificial inoculation of field‐grown ʻōhiʻa with C. huliohia and dissections of naturally infected, early symptomatic forest trees were conducted to confirm pathogenicity on field grown trees and the pattern of internal colonization. In two trials, crowns of trees with main stems inoculated with C. huliohia were visually healthy at the time of tree harvest after 43–55 days in the first trial, and after 91 days in the second trial. However, elliptical inner bark cankers underlain by reddish‐brown xylem were associated with the inoculation points. Similar canker and stain symptoms were found on stems and branches of ʻōhiʻa (24–26 cm trunk diameter) naturally infected by C. huliohia. This xylem stain manifested as multiple distinct elliptical cankers or the coalescing of multiple cankers. The pathogen was commonly isolated from the perimeter of the stained outer sapwood and to a depth of 4 cm. The coalescence of multiple cankers was associated with the crown symptoms observed on the naturally infected forest trees that were dissected. Multiple C. huliohia infections that lead to coalescing cankers which subsequently girdle stems likely occurs over one or more years compared to the shorter time (e.g., months) required for C. lukuohia‐caused death to occur.

Efficacy of Commercial Biocontrol Products for the Management of Verticillium and Fusarium Wilt in Greenhouse Tomatoes: Impact on Disease Severity, Fruit Yield, and Quality

Verticillium dahliae (Vd) and Fusarium oxysporum f. sp. lycopersici (Fol) are two major fungal pathogens that infect tomato plants, causing significant challenges in their control since both pathogens can persist in the soil for several years even in the absence of a host plant and no effective fungicides are available at present. This study investigated the efficacy of two biocontrol formulations, Clonotri (containing Trichoderma and Clonostachys microorganisms) and Strepse (comprising Streptomyces and Pseudomonas microorganisms), against Vd and Fol and their impact on tomato fruit quality and yield under greenhouse conditions. The pathogenicity experiment demonstrated that the Clonotri formulation, containing Trichoderma and Clonostachys spores, significantly reduced Fusarium wilt disease by 32% compared to the control group. However, in the Vd pathogenicity experiment, the formulations did not exhibit disease reduction, although treatment with Strepse, containing Streptomyces and Pseudomonas microorganisms, resulted in a preserved total fruit number when compared to uninfected plants. Analysis of fruit quality attributes revealed no significant differences among the various interventions. Furthermore, Fol infection in the first fruit set significantly increased fruit firmness, while Vd infection resulted in elevated levels of total soluble solids in fruits. These findings demonstrate that the evaluated biocontrol formulations provide a degree of protection against fungal wilt pathogens in tomato plants and can increase yield in greenhouse conditions while having minimal impact on overall fruit quality attributes.

A natural intra‐specific hybridization between populations of B. mucronatus with European and East Asian genotypes, in pine forests

AbstractBursaphelenchus mucronatus Mamiya & Enda, 1979 is a wood nematode widely distributed over Palearctic coniferous forests. It has two subspecies, that is, B. mucronatus mucronatus and B. mucronatus kolymensis, which present molecularly different East Asian and European genotypes, respectively. The European subspecies is found mainly in Europe and Siberia, while the East Asian subspecies occupies mostly Eastern regions of Asia. However, local isolates of both subspecies have been occasionally reported from various localities in Europe and Asia. Our field isolation and molecular (DNA ITS‐RFLP) identification of 21 recently collected populations of B. mucronatus revealed only 4 isolates representing clearly East Asian or European genotypes, while the remaining 17 isolates showed intermediate genotypes with electrophoretic band characters of both the above types. Further individual crossbreeding, in vitro, of nematodes representing European, East Asian, and intermediate genotypes provided experimental evidence for the process of intraspecific hybridization between both subspecies, spontaneously taking place in the forest. Such a widening of the B. mucronatus genetic variation may have its effect on a range of reported in the literature direct interactions between this native, nonpathogenic nematode species and the genetically similar, causative agent of the pine wilt disease B. xylophilus which can colonize the same host trees, use the same insect vectors, compete, and crossbreed inter‐specifically.