Plant disease最新文献

{"title":"Antifungal action by Streptomyces globisporus strain WB03 against Fusarium cugenangense causing Gastrodia elata tuber rot disease.","authors":"Jianxin Chen, Fengjinglin Wu, Youjiao Zhu, Nan Yang, Yuqian Wei, Huancheng Ma, Ziqiang Wu, Jianrong Wu","doi":"10.1094/PDIS-09-24-1994-RE","DOIUrl":"https://doi.org/10.1094/PDIS-09-24-1994-RE","url":null,"abstract":"<p><p>Tuber rot caused by Fusarium cugenangense is a serious problem in the cultivation and post-harvest preservation of Gastrodia. It is essential to explore effective biocontrol methods to control this disease. In this work, we investigated the biocontrol efficiency and defense responses of an endophytic Streptomyces globisporus strain WB03 isolated from the coralloid roots of Cycas panzhihuaensis against Gastrodia tuber rot disease. S. globisporus WB03 can secrete extracellular hydrolases that produce active compounds. Treatment with WB03 damaged the cell membranes of F. cugenangense and increased the leakage of cell contents from the pathogen's mycelia. In addition, WB03 produced phytohormones involved in root development in Arabidopsis. Spraying WB03 on Arabidopsis leaves upregulated the expression of resistance genes PR1, PR5, and PDF1.2 and downregulated the transcription factor genes WRKY38 and WRKY64 in Arabidopsis. In addition, WB03 also enhanced the activity of the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD), reduced the symptoms of rot disease, and reduced the size of the lesion in Gastrodia tuber. This study suggests that endophytic S. globisporus WB03 may be effective in controlling tuber rot disease in Gastrodia.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Weed Hosts: Hidden Reservoirs for Whitefly-Transmitted Viruses Threatening Georgia Cucurbits.","authors":"Dalvir Kaur Dhadly, Saritha Raman Kavalappara, Theodore McAvoy, Paul Severns, Alvin M Simmons, Rajagopalbabu Srinivasan, Sudeep Bag","doi":"10.1094/PDIS-12-24-2730-RE","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2730-RE","url":null,"abstract":"<p><p>The presence of weeds can undermine effective crop disease management when their role as functional reservoirs for pathogens and/or vectors is unrecognized. Weed presence and abundance can not only influence disease dynamics during the growing season but also enable year-round pathogen presence, facilitating recurrent and persistent disease outbreaks. Cucurbit leaf crumple virus (CuLCrV) and cucurbit chlorotic yellows virus (CCYV) are whitefly-transmitted viruses (WTVs) that cause severe losses in cucurbit crops in the southeastern United States. We evaluated the potential for weeds found on the margins of cucurbit fields to be reservoirs for CuLCrV and CCYV through a combination of field sampling, molecular detection, and greenhouse transmission experiments with infected weeds and uninfected, recipient yellow squash (Cucurbita pepo cv. Gold Star). Field collected cypressvine morning glory (Ipomoea quamoclit), tall morning glory (Ipomoea purpurea), pigweed (Amaranthus sp.), and wild radish (Raphanus raphanistrum) were found to harbor both viruses as mixed infections. Single-virus infections of CuLCrV and CCYV were detected in field collected lantana (Lantana camara) and prickly sida (Sida spinosa), respectively. Although virus copies in weed hosts were low during greenhouse transmission studies, whiteflies successfully acquired these viruses from infected weeds and transmitted them to previously uninfected yellow squash. CCYV-inoculated yellow squash developed typical symptoms, while CuLCrV-inoculated squash remained asymptomatic despite the presence of replicative virus forms. Since the weeds identified in this study are also known to be suitable hosts for whiteflies, they could be considered as potential targets for integrated pest management strategies.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of Infested Seed as Primary Inoculum for Cercospora Leaf Spot in Table Beet.","authors":"Pratibha Sharma, Sean Murphy, Julie R Kikkert, Sarah Jane Pethybridge","doi":"10.1094/PDIS-12-24-2624-RE","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2624-RE","url":null,"abstract":"<p><p>Cercospora leaf spot (CLS), caused by the fungus <i>Cercospora beticola</i>, is an important determinant of table beet foliar health. Primary inoculum sources include infested crop residues and alternative hosts, but seed-to-seedling transmission has also been reported. We evaluated the localization of <i>C. beticola</i> in table beet seeds and contribution of infested seeds to CLS outbreaks in field studies. In seed dissection experiments, <i>C. beticola</i> was more frequently isolated from the pericarp (95.6%) and operculum (30.4%) compared to the true seed (17.4%). Field trials in Geneva and Freeville had significantly higher CLS incidence, severity, and disease progress in plots established from an infested seed lot than those from a noninfested lot. <i>C. beticola</i> populations collected from infested seeds and field plots were genotyped using 11 microsatellite markers. The population from plants grown from an infested seed lot exhibited high genotypic diversity, mating type equilibrium, and linkage equilibrium, suggesting random mating. Two clonal lineages of <i>C. beticola</i> were identified. Populations from infested seeds and from plants that grew in plots planted with infested seed grouped into cluster 1, while cluster 2 contained populations from plants that grew in plots planted with noninfested seed. The <i>C. beticola</i> population not associated with genotypes from the infested seed in NY was dominated by a few multilocus genotypes and was genetically distinct from the infested seed lot population. Our findings highlight the potential of <i>C.beticola</i>-infested seed as a primary inoculum source.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Turnip yellows virus resistances differ in effectiveness against three diverse isolates.","authors":"Benjamin Steven Congdon, Jonathan Baulch, Alistair Hall","doi":"10.1094/PDIS-03-25-0598-RE","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0598-RE","url":null,"abstract":"<p><p>Turnip yellows virus (TuYV; species Turnip yellows virus, genus Polerovirus, family Solemoviridae) is one of the most economically important pathogens of canola (syn. oilseed rape, Brassica napus L.) worldwide. Despite this, there are few cultivars with TuYV resistance available to canola growers. Several sources of quantitative resistance have been identified in Europe and Australia in varieties of B. napus, and its progenitor species B. oleracea and B. rapa. These resistances were identified and examined in studies using only a single isolate of TuYV, which is a highly diverse virus. In this study, we evaluated the resistance responses of eight such varieties when challenged with three genetically diverse TuYV isolates under glasshouse conditions. Plants were inoculated with TuYV using its vector Myzus persicae and the infection response was measured by comparing enzyme-linked immunosorbent assay absorbance values with those of a susceptible control variety. The resistance response of each variety differed from highly resistant to highly susceptible primarily depending on the TuYV isolate but also the experiment and time after inoculation. A spectrum of resistance specificity was observed with some varieties being moderately to highly resistant against all three isolates and other varieties being resistant to one isolate and susceptible to the other two. This demonstrates that previous approaches to resistance phenotyping using a single TuYV isolate can result in the development of strain-specific resistance that is ineffective when deployed against the broader virus population. Resistance screening programs should challenge lines against a range of locally common virus strains to increase the likelihood of identifying durable resistance.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Incidence and Severity Distribution of Sweet Cherry (<i>Prunus avium</i>) and Their Influencing Factors in Southwest China.","authors":"Xiaoxia Chen, Zhi Zheng, Nannan Zhang, Hongdou Yu, Yan Wu, Fusun Shi","doi":"10.1094/PDIS-08-24-1727-RE","DOIUrl":"https://doi.org/10.1094/PDIS-08-24-1727-RE","url":null,"abstract":"<p><p>Root rot disease is a significant constraint to sweet cherry production in the highlands of southwest China, causing substantial yield losses. While the disease is prevalent, the complex interplay of climate, topography, soil, and management practices on its development remains poorly understood. To address this knowledge gap, a field survey encompassing 95 field sites was conducted to assess disease incidence (DI) and canopy damage index (_CDI). Our results showed that the average DI and _CDI were 27.04 and 20.52%, respectively. DI and _CDI were influenced by management practices: they both increased with the number of planting years and were lower with <i>Cerasus szechuanica</i> rootstock and composted animal manures compared with Da-qingye rootstock and uncomposted animal manures. Climatic and topographic factors also played an important role in observing higher DI at higher altitudes and shady slopes (<i>P</i> < 0.05). Moreover, both DI and _CDI demonstrated positive correlations with the aridity index and sunshine duration and negative correlations with mean annual temperature and mean annual precipitation (<i>P</i> < 0.05). Soil properties, including moisture content, bulk density, pH, and sand content, were positively associated with DI and _CDI, while clay content and available potassium exhibited negative correlation. The present study emphasizes the combined impact of multiple factors on root rot disease in sweet cherry, with management practices and soil properties having a more decisive effect than climate and topography. These findings provide crucial insights for developing effective disease management strategies.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS08241727RE"},"PeriodicalIF":4.4,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First report of <i>Rhizoctonia solani</i> AG-3 causing black scurf on <i>Solanum tuberosum</i> cv. Superchola in Cotopaxi, Ecuador.","authors":"Estefania Peña-Zuñiga, Noelia Barriga-Medina, Dario Ramirez-Villacis, Sol Llerena-Llerena, Jos M Raaijmakers, Corné Pieterse, Antonio Leon-Reyes","doi":"10.1094/PDIS-12-24-2575-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2575-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Rhizoctonia solani is a globally significant pathogen causing black scurf and stem canker in potatoes, resulting in considerable yield and quality losses. Among the 14 anastomosis groups (AGs), AG3 is primarily linked to potato diseases (Tsror, 2010). In November 2022, symptoms of black scurf were observed on Solanum tuberosum cv. Superchola tubers in Lasso-Cotopaxi, a major potato-growing region in the Andes of Ecuador (0°41'24.8''S, 78°41'27.7''W). The tubers exhibited dark brown, irregularly shaped sclerotia firmly attached to their surfaces. Harvested tubers showed 15% of disease incidence and exhibiting lesions covering from 10% - 50% of the potato surface, harvested from an area 20000 m2 plot (Fig S1). To isolate the causal agent, 10 symptomatic tubers were collected, surface disinfected (2.5% sodium hypochlorite, followed by 70% ethanol), and thoroughly rinsed with sterile distilled water. Tissue samples (~0.5 cm²) were excised from the margins of healthy and diseased areas, samples were plated on Potato Dextrose Agar (PDA) with gentamycin (160 mg/L). After incubation at 25°C in darkness, isolates were purified using the hyphal-tip method. Three isolates displayed brown colonies with sclerotia, consistent with R. solani. Microscopic examination revealed right-angle hyphal branching, septation near the branch points, and slight base constriction (Fig S1). For molecular identification, DNA was extracted from the three isolates using the Qiagen PowerSoil Kit. The ITS region was amplified with primers ITS5 and ITS4 (White et al. 1990), and the resulting fragments (716 bp) were sequenced and showed 100% identity to each other. The Consensus ITS sequence was deposited under GenBank accession PP532868. Similarly, the rpb2 gene (675 bp; GenBank accession PQ632810) was amplified with primers fRPB2-5F and fRPB2-7cR (Liu et al. 1999) and consensus sequence showed 99.7% identity to R. solani GenBank accession PP665463.1. Sequence alignment was constructed using ClustalW with the MEGA 11.0 software package (Tamura et al. 2021). Subsequently, phylogenetic analysis was performed using Bayesian inference using the BEAST version 1.8.4 program (Drummond and Rambaut 2007). The phylogenetic analysis of the sequence revealed that the isolate clustered in the same clade with Rhizoctonia solani AG-3, confirming its identity (Fig S2). Koch's postulates were fulfilled using five replicates of S. tuberosum cv. Superchola mini tubers. Symptomless tubers were sprouted at 18°C for 10 days and planted in pots with sterilized substrate (50% peat moss, 50% perlite). Each pot was inoculated with 20 mg of R. solani colonized rice, while controls received sterile rice (Lopez-Corrales et al. 2023). Plants were maintained under controlled greenhouse conditions for 25 days (15°C/27°C, 70% RH). Inoculated plants exhibited small stem and tuber lesions, while controls remained asymptomatic. The pathogen was successfully reisolated from symptomatic plants and confirmed as R.","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143710901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Eight Novel Diagnostic Markers Differentiate Lineages of the Highly Invasive Myrtle Rust Pathogen <i>Austropuccinia psidii</i>.","authors":"Zhenyan Luo, Jinghang Feng, Austin Bird, Mareike Moeller, Rita Tam, Luc Shepherd, Lydia Murphy, Lavi Singh, Abigail Graetz, Lilian Amorim, Nelson Sidnei Massola Júnior, M Asaduzzaman Prodhan, Louise Shuey, Douglas Beattie, Alejandro Trujillo Gonzalez, Peri A Tobias, Amanda Padovan, Rohan Kimber, Alistair McTaggart, Monica Kehoe, Benjamin Schwessinger, Thaís R Boufleur","doi":"10.1094/PDIS-10-24-2111-SR","DOIUrl":"10.1094/PDIS-10-24-2111-SR","url":null,"abstract":"<p><p><i>Austropuccinia psidii</i> is the causal agent of myrtle rust in more than 480 species within the family Myrtaceae. Lineages of <i>A. psidii</i> are structured by their hosts in the native range, and some have success in infecting newly encountered hosts. For example, the pandemic biotype has spread beyond South America, and proliferation of other lineages is an additional risk to biodiversity and industries. Efforts to manage <i>A. psidii</i> incursions, including lineage differentiation, rely on variable microsatellite markers. Testing these markers is time-consuming and complex and requires reference material that is not always readily available. We designed a novel diagnostic approach targeting eight selectively chosen loci including the fungal mating-type <i>HD</i> (homeodomain) transcription factor locus. The <i>HD</i> locus (<i>bW1/2-HD1</i> and <i>bE1/2-HD2)</i> is highly polymorphic, facilitating clear biological predictions about its inheritance from founding populations. To be considered as potentially derived from the same lineage, all four <i>HD</i> alleles must be identical. If all four <i>HD</i> alleles are identical, six additional markers can further differentiate lineage identity. Our lineage diagnostics relies on PCR amplification of eight loci in different genotypes of <i>A. psidii</i> followed by amplicon sequencing using Oxford Nanopore Technologies and comparative analysis. The lineage-specific assay was validated on four isolates with existing genomes, on uncharacterized isolates, and directly from infected leaf material. We reconstructed alleles from amplicons and confirmed their sequence identity relative to their reference. Genealogies of alleles confirmed the variations at the loci among lineages/isolates. Our study establishes a robust diagnostic tool for differentiating known lineages of <i>A. psidii</i> based on biological predictions and available nucleotide sequences. This tool is suited to detecting the origin of new pathogen incursions.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS10242111SR"},"PeriodicalIF":4.4,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142472372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First report of <i>Clavibacter nebraskensis</i>, causing Goss's bacterial leaf blight on maize (<i>Zea mays</i> L.) in South Africa.","authors":"Sonja Coertze, Beatrix Coetzee, Elaine Basson, Dore de Villiers, Tjitjila Makhura, Diane Mostert, Bernard Slippers, Lindy Rose, Cobus M Visagie, David Read","doi":"10.1094/PDIS-01-25-0164-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-01-25-0164-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Maize is a staple crop in South Africa and an important income source to both smallholder and commercial farmers (Gravelet-Blondin, 2015). Goss's bacterial leaf blight and wilt, caused by Clavibacter nebraskensis (Cn), is a significant maize disease in North America and a quarantine concern in unaffected regions, with seedborne transmission posing a risk of introduction (EPPO, 2024; Osdaghi et al. 2023). From February to April 2024, bacterial leaf blight symptoms, typical of Cn infection, were observed on maize (Zea mays L.) in the North-West, Mpumalanga and Gauteng provinces of South Africa. Lesions were tan, irregular, parallel to veins, with a shellac-like appearance and black water-soaked edges, showing characteristic \"luminous freckles\" when backlit. Symptomatic leaf samples were collected from 6 commercial maize fields. Eight samples from Carletonville and Potchefstroom (total of two fields) were evaluated at the Forestry and Agricultural Biotechnology Institute (FABI) at the University of Pretoria, and another four samples from Delmas, Leslie, and Bapsfontein (total of four fields) were evaluated at Stellenbosch University's Plant Disease Clinic. DNA was extracted either directly from lesions or from cultures isolated from lesions. For direct DNA extraction, cetyltrimethylammonium bromide was used, followed by a Cn specific PCR with primer pair 1184F/R (McNally et al. 2016). Macerates from lesion edges were streaked out onto nutrient broth yeast (NBY) agar. DNA from a single culture, with yellow-orange mucoid colonies, was extracted with a Zymo Quick-DNA Fungal/Bacterial Miniprep Kit (Zymo Research, Irvine, CA, USA), and confirmed as Cn with previously mentioned PCR primers. Simultaneously, macerates from the lesion edges were streaked onto yeast dextrose chalk agar (YDC). Yellow-orange mucoid colonies developed after four day and were purified onto NBY and incubated at 25°C for 4 days. All isolates tested gram-positive, were coryneform, aerobic, and non-spore forming. Genomic DNA was extracted and the suspension amplified using the 27F/1492R primer pair (Lane, 1991), targeting the 16S rRNA gene. The product was sequenced and confirmed as Cn. Cultures are stored in the culture collections at Stellenbosch University Plant Pathology Department (STE-U) and at FABI (CMW and CMW-IA). At both facilities, cell suspensions at a final concentration of 107 cells/mL were used to inoculate the third leaf of V3 / V4 stage maize plants (P1513, Syngenta), by wounding the middle of the main leaf vein and applying a 25µL droplet. Typical Cn symptoms appeared 4 days post inoculation and Cn was reisolated from these lesions and confirmed with PCR to complete Koch's postulates. Four isolates were selected for high-throughput sequencing (NCBI Bioproject: PRJNA1184689). Assembled genomes (NCBI accession: CP173672-CP173675) were analysed on the Type Strain Genome Server (Meier-Kolthoff and Göker, 2019) and confirmed as Cn based on 16S rRNA and Genome Blast","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143710890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First Report of <i>Taraxacum kok-saghyz</i> Rodin Root Rot Caused by <i>Alternaria tenuissima</i> in Heilongjiang Province, China.","authors":"Guoen Ao, Qinqin Nie, Xiaoyu Chen, Juanying Wang, XuChu Wang","doi":"10.1094/PDIS-12-24-2759-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2759-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;&lt;i&gt;Taraxacum kok-saghyz&lt;/i&gt; Rodin (TKS) is a perennial herb of the Asteraceae family, which is an important natural rubber supplement crop (Yang et al., 2023). In May 2023, a severe root rot disease was observed in TKS during cultivation in Harbin (45°75'N, 126°66'E), Heilongjiang Province, China. Field surveys indicated a disease incidence of approximately 10% within the 450 m&lt;sup&gt;2&lt;/sup&gt; cultivation area (500 TKS seedlings), with symptoms including leaf wilting, stunted growth, root necrosis, and plant mortality. To isolate its pathogen, nine symptomatic root segments (about 1 cm) were randomly sampled from three diseased plants and surface sterilized in 2% NaClO for 30 s, rinsed three times with sterile distilled water, and then incubated on potato dextrose agar (PDA) supplemented with 30 mg/L streptomycin at 28 °C in darkness for 3 days. Nine isolates with similar colony morphology were obtained from nine diseased root segments by mycelial tip separation. All isolates exhibited cottony colonies on the PDA medium, initially gray-white and then turned into dark gray, with the reverse side becoming black. On potato carrot agar medium, the conidia of these isolates are oval, brown in color, simple or form unbranched chains, and have 1-4 transverse septa and 0-2 longitudinal septa; they measured 10.23 to 30.57 μm in length and 5.48 to 9.96 μm in width (n = 50), exhibiting morphological characteristics consistent with members of the genus &lt;i&gt;Alternaria&lt;/i&gt; (Simmons et al., 2007). Three isolates (GURF-01, GURF-02, GURF-03) were randomly selected from different plants for further study. These isolates were molecularly characterized by amplifying the internal transcribed spacer (ITS), RNA polymerase II second largest subunit (&lt;i&gt;RPB2&lt;/i&gt;), translation elongation factor 1-α (&lt;i&gt;TEF&lt;/i&gt;), 18S small subunit rDNA (&lt;i&gt;SSU&lt;/i&gt;), 28S large subunit rDNA (&lt;i&gt;LSU&lt;/i&gt;), &lt;i&gt;Alternaria&lt;/i&gt; major allergen (&lt;i&gt;Alt-a1&lt;/i&gt;) and glyceraldehyde 3-phosphate dehydrogenase (&lt;i&gt;GAPDH&lt;/i&gt;) regions by ITS1/ITS4, fRPB2-5f/fRPB2-7cR, EF1-728F/EF1-986R, NS1/NS4, LR0R/LR5, Alt-for/Alt-rev and gpd1/gpd2 primers (Lawrence et al., 2013; Woudenberg et al., 2015; Li et al., 2023), respectively. BLASTn search revealed that ITS (PQ182566, PQ180345, PQ182567), &lt;i&gt;RPB2&lt;/i&gt; (PQ740537 to PQ740539), &lt;i&gt;TEF&lt;/i&gt; (PQ196801 to PQ196803), &lt;i&gt;SSU&lt;/i&gt; (PQ180346 to PQ180348), &lt;i&gt;LSU&lt;/i&gt; (PQ180349 to PQ180350), &lt;i&gt;Alt-a1&lt;/i&gt; (PQ196798 to PQ196800) and &lt;i&gt;GAPDH&lt;/i&gt; (PQ287275 to PQ287277) sequences of these isolates showed 99% to 100% identity with &lt;i&gt;A. tenuissima&lt;/i&gt; (ON514229, KC584435, KC584693, KC584567, KC584311, ON548915 and ON528099). A phylogenetic tree was constructed showing that GURF-01, GURF-02 and GURF-03 clustered with &lt;i&gt;A. tenuissima&lt;/i&gt;. The above three isolates were used for test pathogenicity in the 3-month-old TKS plants with three repeats. The test groups were inoculated with 50 mL spore suspension (10&lt;sup&gt;6&lt;/sup&gt; spores/mL) while distilled water was supplied for the control","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143710905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First Report of '<i>Candidatus</i> Phytoplasma pruni'-Related Strain and '<i>Candidatus</i> Phytoplasma asteris'-Related Strain Associated with North American Grapevine Yellows of Cultivated Grapevines in Minnesota.","authors":"Sara Bratsch, Bo Min Kim, Michelle Grabowski, Stefano Costanzo","doi":"10.1094/PDIS-02-25-0232-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0232-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Surveys for exotic plant pests conducted during July and August of 2023 and 2024 across 20 vineyards in 12 counties throughout Minnesota, USA, revealed that less than 2% of the approximatively 3000 vines inspected (&lt;i&gt;Vitis&lt;/i&gt; spp., hybrid grape varieties) exhibited symptoms suggestive of phytoplasma yellows disease. Observed symptoms included yellowing of leaf lamina, downward rolling of leaf margins, and necrosis of leaf margins. To investigate a potential association between these symptoms and phytoplasmas, two symptomatic plants were selected in August of 2024 from two distinct vineyards for further analysis. Petiole tissue DNA extracts were initially tested using a phytoplasma-specific real-time PCR assay (Hodgetts et al. 2009), which confirmed the presence of phytoplasma DNA in both symptomatic plants. Subsequently, the samples underwent semi-nested PCR amplification targeting the phytoplasma 16S rRNA gene, using primers P1/16S-SR followed by P1A/16S-SR (Deng and Hiruki 1991; Lee et al. 2004). The resulting amplicons were cloned and sequenced. No amplicon was produced from an asymptomatic grapevine DNA sample included as a test control. Analysis of the 16S rRNA gene sequences revealed that each plant was infected by one of two distinct phytoplasma strains, designated MN450 and MN466. Representative sequences obtained from the two samples exhibiting interoperon heterogeneity were deposited in the GenBank database under accession numbers: PQ889195 (&lt;i&gt;rrnA&lt;/i&gt;) and PQ889196 (&lt;i&gt;rrnB&lt;/i&gt;) for strain MN450, and PQ889197 (&lt;i&gt;rrnA&lt;/i&gt;) and PQ889198 (&lt;i&gt;rrnB&lt;/i&gt;), for strain MN466. Sequence analysis using the online phytoplasma classification tool &lt;i&gt;i&lt;/i&gt;PhyClassifier (Zhao et al. 2009) showed that the 16S rRNA gene sequences from MN450 shared 1491/1495 bp (99.73%) and 1492/1495 bp (99.80%) identity (&lt;i&gt;rrnA&lt;/i&gt; and &lt;i&gt;rrnB&lt;/i&gt;, respectively) with that of the ''&lt;i&gt;Ca&lt;/i&gt;. Phytoplasma pruni' rrnA' reference strain (GenBank JQ044393), identifying MN450 as a ''&lt;i&gt;Ca&lt;/i&gt;. Phytoplasma pruni' rrnA'-related strain and possibly representing a new subgroup within the 16Sr group III. For MN466, the 16S rRNA gene sequences shared 1471/1482 bp (99.26%) and 1469/1482 bp (99.12%) identity (&lt;i&gt;rrnA&lt;/i&gt; and &lt;i&gt;rrnB&lt;/i&gt;, respectively) with that of the '&lt;i&gt;Ca&lt;/i&gt;. Phytoplasma asteris' reference strain (GenBank M30790), and identifying the phytoplasma as a '&lt;i&gt;Ca&lt;/i&gt;. P. asteris'-related strain belonging to subgroup 16SrI-A. To further characterize the two phytoplasma strains, the &lt;i&gt;secY&lt;/i&gt; gene was PCR amplified from the DNA extracts as described by Lee et al. (2010). The obtained amplicons were cloned and sequenced, and representative &lt;i&gt;secY&lt;/i&gt; gene sequences were deposited in GenBank under accession numbers PQ899621 (MN450) and PQ899622 (MN466). BLASTn searches against the NCBI core nucleotide database revealed that the &lt;i&gt;secY&lt;/i&gt; gene sequence for MN450 exhibited 100% identity (1614/1614 bp) with '&lt;i&gt;Ca&lt;/i&gt;. P. pruni' (GenBank KM268860). Similarly, ","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143710886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}