Plant disease最新文献

{"title":"Evaluating management strategies for aphid-transmitted yellow dwarf viruses in perennial ryegrass seed production.","authors":"Seth J Dorman, Hannah M Rivedal, David J Maliszewski, Todd N Temple, Casey Cruse, Jing Zhou, Pete A Berry, Robert J Starchvick, Chloe Oshiro, Nicole P Anderson","doi":"10.1094/PDIS-12-24-2655-RE","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2655-RE","url":null,"abstract":"<p><p>Epidemiology and management of aphid-transmitted yellow dwarf viruses (YDVs) have received international attention in small grain crops over the past century. However, focused research regarding YDV management in grass seed production systems, including perennial ryegrass (<i>Lolium perenne</i> L.), is limited. An integrated pest management program is needed to reduce the impact of the aphid-YDV complex in perennial grass seed crops. The objectives of the study were to evaluate the effects of nitrogen fertilizer rate, and the timing and frequency of foliar insecticide applications on aphid abundance, YDV disease incidence, and seed yield in two perennial ryegrass cultivars in small-plot field trials from 2021 to 2024. Trade-offs in economic returns across treatment combinations and YDV detection using remote sensing were also observed. Aphid and natural predator densities varied across foliar insecticide treatments. The high nitrogen rate increased YDV incidence across three field seasons in both cultivars. Seed yield and economic returns were greatest for the less susceptible cultivar when fully protected with one insecticide treatment per season (autumn, spring, and summer). A higher than recommended nitrogen rate did not increase seed yield across treatment combinations in first-year stands; however, an increase was observed in second and third-year stands when YDV infection averaged >50%. Selecting resistant cultivars and reducing aphid populations during the autumn and spring aphid flights is critical for maximizing seed yield potential in perennial ryegrass. Furthermore, a lower nitrogen rate can be used in first-year stands to save input costs with no impact on seed yield potential.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143974961","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":"<i>Pratylenchus brasiliensis</i> sp. nov. (Nematoda: Pratylenchidae) - an emerging threat to soybean in an important new agricultural frontier in Brazil.","authors":"Francisco de Assis Dos Santos Diniz, Eduardo S G Mizubuti, João Igor Araújo Valadares, Silvino Intra Moreira, Paulo Sergio Santos, Thaís Ribeiro Santiago","doi":"10.1094/PDIS-01-25-0106-SR","DOIUrl":"https://doi.org/10.1094/PDIS-01-25-0106-SR","url":null,"abstract":"<p><p>Root-lesion nematodes (Pratylenchus spp.) are significant agricultural pests worldwide. From January 2021 to January 2023, 365 root and rhizosphere soil samples were collected in key soybean-producing regions, revealing a new species, Pratylenchus brasiliensis sp. nov., in Brazil's agricultural frontier. Identification employed a polyphasic approach, integrating microscopy, morphometric analyses, and multi-gene phylogenetics. Molecular species delineation targeted the D2-D3 expansion segments of the 28S rRNA gene, the internal transcribed spacer (ITS) rRNA region, and cytochrome oxidase I (COXI) mitochondrial DNA. Females of P. brasiliensis sp. nov. measure 614.25-671.98 µm in length and 26.42-27.34 µm in width, with a ventrally curved body, four lateral lines, a well-developed spermatheca, a vulva at 77-81% body length, and a conical tail with 19-25 annuli. The labial region features three annuli and a robust stylet (17-18 µm) with anchor-shaped basal knobs. Males are shorter (450-550 µm), with curved spicules (15-17 µm) and a bursa extending over the tail. Molecular analysis confirmed P. brasiliensis sp. nov. as closely related to P. bolivianus, P. curvicaudas, and P. vandenbergae. Pathogenicity tests demonstrated its ability to cause necrotic lesions and gallery formation in soybean roots, with reproduction factors (Rf > 1) in major Brazilian soybean cultivars, emphasizing its agricultural threat. The discovery emphasizes the need for surveillance and the development of management strategies to mitigate its impact on soybean yield. Further studies are needed to explore its host range and identify resistance sources in soybean cultivars.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144026714","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":"A community analysis of plant-parasitic nematodes on coastal Oregon golf course putting greens.","authors":"Emily Braithwaite, Robert J Starchvick, Alec Kowalewski, Todd N Temple, Hannah Baker, Megan Kitner, Amy B Peetz, Inga Zasada, Hannah M Rivedal","doi":"10.1094/PDIS-02-25-0431-RE","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0431-RE","url":null,"abstract":"<p><p>Plant-parasitic nematodes (PPN) are important pests affecting golf course putting greens. Recently PPN have become a pest of concern in the Pacific Northwest (PNW), but relatively little information exists on species present or their distribution across the region. A survey and community analysis of PPN across five independently managed golf courses in southwest Oregon was conducted. In 2023, soil samples were collected from 30 putting greens in January, May, August, and November, nematodes extracted using Baermann funnel and mist extraction methods, and identified using morphological and molecular methods. PPN community diversity measures were assessed. PerMANOVA testing indicated significant differences in PPN communities between season, course, and extraction method. Helicotylenchus and Meloidogyne were the most frequently encountered PPN, with maximum population densities of 20,776 and 59,100 nematodes per 100 cc soil, respectively. Indicator species analysis revealed Meloidogyne as a PPN of concern at three of the courses, particularly in January when population densities were highest, just prior to reported damage. Representative populations from each course were collected for speciation. Two PPN species were identified at all courses, Helicotylenchus pseudorobustus and Meloidogyne naasi, whilst other species were found to be course specific. An unidentified species of Heterodera was recovered from mixed stand putting greens. This is the first survey of golf course putting green PPN communities across multiple seasons in the PNW. With an increase in damage symptoms reported in this region, there is a need for further assessment of PPN impacts on PNW golf courses.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144023313","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 finding of soil-borne cereal mosaic virus (SBCMV) infecting wheat in Slovenia.","authors":"Irena Mavrič Pleško, Barbara Grubar, Marjetica Zemljič Urbančič, Janja Lamovšek, Eva Kovačec","doi":"10.1094/PDIS-02-25-0373-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0373-PDN","url":null,"abstract":"<p><p>The presence of soil-borne cereal viruses in Slovenia is understudied, therefore we conducted a small survey as part of Euphresco project Cerevir (2021-A-374). Barley (<i>Hordeum vulgare</i>) and wheat (<i>Triticum aestivum</i>) samples showing virus-like symptoms were collected in the years 2022 to 2024 in central and north-eastern Slovenia. The observed symptoms included yellow streaks and mosaic patterns, yellowing or reddening of the leaf tips. All collected samples were tested by double antibody sandwich ELISA (DAS-ELISA) for barley and cereal yellow dwarf viruses (BYDVs and CYDVs), wheat dwarf virus (WDV), barley mild mosaic virus (BaMMV), barley yellow mosaic virus (BaYMV), soil-borne cereal mosaic virus (SBCMV), soil-borne wheat mosaic virus (SBWMV), wheat spindle streak mosaic virus (WSSMV), barley stripe mosaic virus (BSMV) and wheat streak mosaic virus (WSMV), according to manufacturer's instructions (DSMZ/Bioreba). From 70 samples collected during the study period, three wheat samples from central Slovenia tested positive for SBCMV. Other viruses sporadically detected in tested samples were BYDVs, CYDVs and WDV. To confirm the DAS-ELISA results for SBCMV, total RNA was extracted from all samples using MagMAX-96 Total RNA Isolation Kit supplemented with Plant RNA Isolation Aid (both by Thermo Fischer Scientific) and reverse transcribed using High-Capacity cDNA Reverse Transcription Kit (Thermo Fischer Scientific) according to manufacturer's instructions. SBCMV was detected using qPCR described by Marra et al. (2023). Only the three DAS-ELISA-positive samples were confirmed to be positive by this method. SBCMV was shown to cause significant yield losses by up to 50% in susceptible winter wheat cultivars (Clover et al. 1999) and even by 70% when infecting durum wheat (Vallega and Rubies Autonell 1985). It was already identified in wheat, rye and their hybrid triticale, and reported from different countries, including UK, France, Germany, Denmark, Italy and Poland (Budge et al. 2008). The results indicate low abundance of the virus in Slovenian production fields. To the best of our knowledge, this is the first report of SBCMV detection in cereals in Slovenia. <i>Polymyxa graminis</i> vector of SBCMV is widespread in Europe (Kanyuka et al. 2003); however there are no records of its presence in Slovenia. Further studies on the presence and distribution of <i>P. graminis</i> in Slovenia are needed to evaluate the importance of this finding for Slovenian wheat production.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143974963","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 Record of Cyst Nematode (<i>Heterodera filipjevi</i>) on Wheat in Shaanxi Province of China.","authors":"Huan Guo, Deliang Peng, ZhiJie Chen, Yinmei Li, Feng Zhang, Huan Peng, Song Pan, Mengxin Zhao, Bo Fu","doi":"10.1094/PDIS-03-25-0518-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0518-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;The cyst nematode pathogens can cause a yield loss of 30-50% via stunting root growth on grains (Bonfil et al. 2004). Heterodera avenae, H. filipjevi, and H. latipons are identified as the most economically influential and harmful species on wheat (Toumi et al. 2016). H. filipjevi was first detected in Henan Province in 2010, and had subsequently spread to many provinces (Peng et al. 2010; Peng et al. 2016; Cui et al. 2021). In May 2022, wheat plants showing yellowing and premature senescence were observed in different wheat planting areas throughout Shaanxi Province. Nine soil samples were collected from Pucheng County (34°94'32\"N, 109°57'23\"E) of Shaanxi Province. Among them, six soil samples were detected to have cysts via the sieving-decanting method with an average cyst population density of 10.6 cysts per 100 cubic centimeters of soil. The cysts and second-stage juveniles (J2s) were identified based on both morphological and molecular identification. Morphologically, the cysts are lemon shaped, with a protruding vulval cone. The shell surface had a Z-shaped pattern and covered with a white subgrain layer. The cone of the vulva is bifenestrate in horseshoe-shape. Underbridge exists and is well-developed. The measurements of the cysts (n=16) as follows: body length 670.24 ± 60.67 (593.43 to 778.42) μm; body width 479.03 ± 54.51 (355.91 to 567.52) μm; length/width ratio 1.41 ± 0.16 (1.20 to 1.72); fenestra length 52.30 ± 4.32 (46.82 to 59.13) μm; fenestra width 27.59 ± 3.39 (22.42 to 34.91) μm; vulval slit length 9.17 ± 0.47 (8.69 to 10.37) μm. J2s measurements (n=15) as follow: body length 522.46 ± 24.18 (482.54 to 572.23) μm; body width 26.47 ± 3.08 (22.21 to 30.16) μm; stylet length 23.42 ± 3.24 (16.48 to 29.11) μm. These morphological characteristics and morphometrics are consistent with those of H. filipjevi (Peng et al. 2010). The DNA of single cyst was extracted with four replicates (Shao et al. 2022). The COI fragment sequence was amplified with the specific primers (HfF9/HafR8) according to Niu's research (Niu et al. 2016). The identities of amplification fragments (Genbank PQ650771, PQ650772 and PQ650773) are 98.77%, 99.08% and 98.77% matching the published sequences of H. filipjevi (MG523031.1 and MK093059.1), respectively. We also used the RAPD species-specific primers of H. filipjevi (HfF1/HfR1) to acquire 647bp sequences (Genbank PV165784, PV165785 and PV165786) which have 99.54%, 99.38% and 99.38%identities with published H. filipjevi sequence (KC529338.1) (Peng et al. 2013). Pathogenicity was confirmed by infecting wheat (Triticum aestivum 'Weilong 169'). The eggs of the cyst nematode population hatched at 15℃, and the emerged J2s were used for potted wheat inoculating in greenhouse under 18-24℃. Nine plants in three pots were inoculated and three plants in one pot remained served as the uninoculated control, the inoculum was 800 J2s per pot. After three months, an average of 15.7 cysts were detected from each of the inoc","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144037884","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>Neopestalotiopsis clavispora</i> causing leaf blight on <i>Schefflera octophylla</i> in China.","authors":"Qiaoling Lin, Junxian He, Kejing Chen, Xintong Chen","doi":"10.1094/PDIS-02-25-0396-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0396-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Schefflera octophylla is widely cultivated in South China due to its high ornamental and economic value. In April 2022, a leaf disease on S. octophylla was observed in Zhanjiang (21.20° N, 110.41°E), China. Disease incidence and severity were 15% and 20% (n = 100 investigated plants), respectively. Symptoms on leaves primarily appeared as small light gray spots, then enlarged and coalesced into regular or irregular light gray necrotic lesions with dark margins. Ten symptomatic leaves from 10 plants were collected. Small pieces of tissue (4 × 4 mm) were cut from lesion borders and were surfaced disinfected in 75% ethanol for 30 s, followed by 1 min in 1% NaClO, rinsed three times with sterile water, plated on potato dextrose agar (PDA), and incubated at 28°C. After 5 days, fifteen morphologically similar fungal isolates were obtained from all 10 leaf samples and three representative strains (YZM-1, YZM-2, and YZM-3) were used for morphological and molecular characterization. Colonies were white with cottony aerial mycelium. After 10 days, black viscous acervuli were scattered on the colony surface. Conidia were clavate to fusiform, four-septate, straight or slightly curved, and measured 17.57-25.70 × 4.53-6.80 μm (mean 23.13 × 5.14 μm) in size (n = 50). Basal and apical cells were colorless while the three medium cells were dark brown and versicolor. Conidia had a single basal appendage (4.5 to 5.5 μm long; n = 50) and two or three apical appendages (18.2 to 33.5 μm long; n = 50). These morphological characteristics were consistent with the description of Neopestalotiopsis clavispora (Maharachchikumbura et al. 2012). For further identification, genomic DNA was extracted by the 2% CTAB method (Lu et al. 2012). The internal transcribed spacer (ITS) region and β-tubulin 2 (tub2) and translation elongation factor 1-alpha (tef1α) genes were amplified using the primers ITS1/ITS4, T1/Bt-2b, and EF1-728F/EF-2 respectively (Maharachchikumbura et al. 2012). The ITS (OM721785-87), tub2 (OQ130413-15) and tef1α (OM810189-91) sequences were 99.38%, 99.33%, and 99.17% identical to the N. clavispora type strain MFLUCC12-0281 (accession nos. JX398979, JX399014, and JX399045, respectively). A phylogenetic tree was generated using the concatenated sequences of ITS, tub2, and tef1α. All three isolates clustered with N. clavispora strains including the type MFLUCC12-0281. For pathogenicity tests, 2-year-old S. octophylla plants (n=10) were sprayed with a conidial suspension (105 conidia/ml) on the surface of wounded leaves. Mock-inoculated controls (n=10) were sprayed with sterile distilled water. All plants were wrapped in polyethylene bags for 24 h and incubated at 28°C in a growth chamber at 90% relative humidity. After 10 days, all inoculated leaves showed similar symptoms to those observed in the field, whereas control leaves were asymptomatic. N. clavispora was re-isolated from the lesions and the identity of the fungus was confirmed based on morphology an","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144038208","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 a leaf spot disease of <i>Acer truncatum</i> by <i>Neofusicoccum parvum</i> in Jiangsu Province of China.","authors":"Xiaoyun Dong, Wei Xing, Yunzhou Lyu, Hainan Sun, Xin Wan, Longjiao Hu","doi":"10.1094/PDIS-09-24-1806-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-09-24-1806-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Acer truncatum, originating in China, is an ornamental tree species with high economic value. In September 2022, a new leaf spot disease was observed on seedlings of A. truncatum in a tree nursery from the Jiangsu Academy of Forestry (118°45'517.30″E, 24 31°51'27.94″N) in China. According to statistics, 62.5% of 1600 A. truncatum seedlings suffered from the disease. The first symptoms were black to brown spots appearing on the infected leaves. Subsequently, the spots gradually expanded into larger areas, and finally the entire leaf turned yellow and fell off. The diseased leaves were collected and sections of 3 to 4 mm were excised from the margins between healthy and diseased tissues, surface sterilized in 75% ethanol for 30 sec. and 1.5% NaClO for 90 sec., rinsed three times in sterilized distilled water, plated on potato dextrose agar (PDA) and incubated at 25℃ in darkness. Pure cultures were obtained by monosporic isolation. Six fungal cultures with similar morphological characteristics were obtained from the infected tissues, and they accounted for 70% of the total isolates. Colonies were initially white but turned dark gray following 7 days of incubation at 25°C in the dark. To induce sporulation, colonies were grown on 2% water agar and incubated under UVA light at 25°C for two weeks. The conidiophores produced conidia, and conidia were hyaline, unicellular, nonseptate, ellipsoidal to fusiform, externally smooth, thin-walled, and were 15.3 to 20.4 × 4.5 to 7.4 μm (n=35, counted from the two selected isolates). These characteristics were consistent with the description of Neofusicoccum sp. (Kirk et al. 2008). Isolates YBF2-1 and YBF5-1 were selected as representative for molecular identification. The internal transcribed spacer region (ITS), the translation elongation factor 1-alpha gene (EF1-α), and the beta-tubulin gene (TUB2), using the primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Alves et al. 2008), and Bt2a/Bt2b (Glass and Donaldson 1995) were amplified, respectively. The obtained ITS (GenBank Accession No. PP980685, PQ222752), EF1-α (No. PQ009204, PQ227810), and TUB2 sequences (No. PP993456, PQ227811) all showed &gt;99% homology with several GenBank sequences of Neofusicoccum parvum (MK370685, KC818612 for ITS; MH118932, KJ126847 for EF1-α; and MN318109, OL456719 for TUB2, respectively). A neighbor-joining phylogenetic tree was generated by combining all sequenced loci in MEGA7. The two isolates were identified as N. parvum. To test pathogenicity, 15 leaves on three one-month-old A. truncatum seedlings (five leaves from each seedling) were wounded with a sterile needle inoculated with 20 μL conidia suspension (1×106 spores/mL) on the left sides of the leaves, using isolate YBF2-1, while the same size droplet of sterilized water was used on the right sides of leaves. Each plant was separately covered with clear polyethylene bags to maintain about 80% relative humidity at 25℃. After 5 days of inoculation, typical sy","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144049964","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>Pythium aphanidermatum</i> causing crown and root rot in <i>Cannabis sativa</i> (L.) in Florida.","authors":"Eden S Blit, Richard N Philbrook, Matthew Indest, Jose Perez-Martinez, Dominick Palozzo, Jeremy Warren","doi":"10.1094/PDIS-02-25-0435-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0435-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;In October of 2023, Cannabis sativa (L.) cuttings of three different cultivars grown in rockwool at an indoor facility (1988 m2; 1300 plants) in Mt. Dora, FL were observed with brown, water-soaked stems that failed to form roots. Three symptomatic clones of each affected cultivar were selected for pathogen identification. In a laminar flow hood, their stems were surface sterilized in 1% sodium hypochlorite for 2 minutes, rinsed in sterile deionized (DI) water, and cut into 1cm segments with a heat-sterilized scalpel. The segments were embedded in water agar (WA) and incubated in darkness for 48 hours at 27oC. Hyaline filaments growing from the stem segments were subcultured onto V8 agar and PDA, then incubated for 48 hours. On V8, fast-growing mycelium grew from the stem of cultivar \"PBR\". The culture was white and had cottony aerial mycelium. On PDA (Figure 1A), the mycelium produced a radial pattern with aseptate filaments, consistent with Pythium spp. morphology (Chen Y.-A., et al. 2024). DNA was extracted from mycelium using Quick DNA Fungi/Bacterial Kit (Zymo Research Irvine, CA, USA). PCR was performed using ribosomal ITS primers ITS100/ITS4 (Riit et al. 2016), amplifying oomycete rDNA of Internal Transcribed Spacer regions. A second PCR was performed using COI primers OomCox-Levup/OomCox-Levlo, amplifying cytochrome oxidase subunit 1 (COI) (Robideau et al. 2011). Amplicons were Sanger sequenced, trimmed, and aligned using SnapGene software, and compared to known sequences using BLAST. Amplicons showed 100% identity to Pythium aphanidermatum accessions KX260336 (775bp/775bp) and 99.21% identity to AY129164 (1299bp/1299bp). Consensus sequences were deposited in GenBank with accessions OR731869 (ITS) and PP806568 (COI). A phylogenetic tree was constructed with MEGA software, illustrating the evolutionary relationships between the P. aphanidermatum isolate and other Pythium/Globisporangium species based on concatenated ITS and COI sequences (Figure 2). A 3 day old pure culture of P. aphanidermatum was diced and transferred to 250mL of V8 broth; a negative control was prepared using sterile V8 media. The broths were placed on a rotary shaker and incubated for 48 hours at 30oC and 100 rpm. Light microscopy revealed filamentous growth and motile zoospores in the inoculated suspension, and no growth in the negative control. To test Koch's postulate, 30 rockwool cubes (150cm3) were soaked in the broths: 15 in the inoculated, 15 in the control. The stems of 30 unrooted \"PBR\" C. sativa cuttings were dipped in rooting gel (Clonex Rooting Gel, Growth Technology, Somerset, UK) and embedded into each rockwool cube. Cuttings were grown indoors, at 27°C for 14 days under LED lights with an 18-hour photoperiod. Inoculated cuttings displayed brown, water-soaked stems and failed to root (Figure 1B); control cuttings were asymptomatic and successfully rooted. Stem samples from 2 infected and 2 control cuttings were plated as previously described. After 4","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144049722","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 Chilli Yellow Ringspot Virus Infecting Tomato (<i>Solanum lycopersicum</i>) in China.","authors":"Jie Zhang, Kuo Wu, Tiantian Wang, Zhong-Kai Zhang, Yu Li","doi":"10.1094/PDIS-03-25-0453-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0453-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Tomato (Solanum lycopersicum L.) is a globally important and economically valuable horticultural crop. Chilli yellow ringspot virus (CYRSV), belonging to the genus Orthotospovirus in the family Tospoviridae within the order Bunyavirales, was first reported infecting chilli peppers in Yunnan Province, China, in 2020 (Zheng et al., 2020). Subsequently, it was identified in Hymenocallis littoralis (Jacq.) in 2021. Yunnan Province has a high incidence of orthotospoviral diseases, characterized by diverse viral species and host plants with widespread distribution (Zhang et al., 2021). Three new Orthotospovirus species were initially reported in Yunnan: Tomato zonate spot virus (TZSV) (Dong et al., 2008), Hippeastrum chlorotic ringspot orthotospovirus (HCRV) (Dong et al., 2013), and CYRSV (Zheng et al., 2020). In December 2021, approximately 15 tomato fruits exhibiting symptoms of yellowing, ring spots, wrinkles, and necrosis were observed in a pre-harvest field in Yuanmou City, Yunnan Province, China. The incidence of the aforementioned symptoms in this field is approximately 50%, and the symptoms exhibited by the infected tomato plants are highly conspicuous. Transmission electron microscopy revealed orthotospovirus-like spherical particles approximately 90 nm in diameter. To identify the viral species in these samples, total RNA was extracted from the symptomatic tomato fruits using a Plant Total RNA Extraction Kit (Accurate, Hunan, China). Complementary DNA (cDNA) was synthesized using an M-MLV Reverse Transcription Kit (Accurate, Hunan, China) according to the manufacturer's instructions. PCR amplification was performed using specific primers targeting the N gene of CYRSV (CYRSV-F: 5'-TCACACTTCCAGAGAAGAACTTGGT-3', CYRSV-R: 5'-ATGTCTAACGTTAAGCAACTT-3') under the following conditions: initial denaturation at 98°C for 1 min, followed by 35 cycles of denaturation at 98°C for 10 s, annealing at 56°C for 30 s, extension at 72°C for 1.5 min, and a final extension at 72°C for 10 min. The resulting 828 bp PCR product was cloned into the pMD19-T vector (TakaRa, Japan) for sequencing (GenBank: PV197272.1). Sequence analysis using BLAST revealed that the amplicons exhibited 99.64% nucleotide identity with a CYRSV isolate from H. littoralis in Yunnan, China (GenBank: OP204905.1), and 99.52% identity with a CYRSV isolate from chilli pepper in Yunnan, China (Zheng et al., 2020). To investigate viral presence in CYRSV-infected tomatoes, Nicotiana benthamiana, Nicotiana tabacum K326, and Solanum lycopersicum were utilized as test hosts. Extracts from CYRSV-infected tomato fruits induced yellow ringspot lesions on K326 leaves, dwarfing and leaf curling in N. benthamiana, and yellowing and necrosis in tomato leaves at 9 days post-inoculation. Additionally, RT-PCR assays using specific CYRSV primers detected an 828 bp single specific fragment in all three plant samples. This study represents the first report of natural CYRSV infection in tomatoes. To our knowle","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144019026","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":"Leaf Spot Caused by <i>Irpex lacteus</i> on Tobacco in China.","authors":"Meili Sun, Chaoying Jiang, Tom Hsiang, Hancheng Wang, Liuti Cai, Mei Tang, Songbai Zhang, Feng Wang","doi":"10.1094/PDIS-12-24-2577-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2577-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Tobacco (Nicotiana tabacum L.) is an important commercial crop in China. In June 2023, disease symptoms were seen in a commercial tobacco field in Bijie City (27.09° N, 105.36° E), Guizhou province, China. Typical symptoms first appeared on the lower leaves as round brown spots, with a light center and a faint yellow small halo. Approximately 25% of the plants were symptomatic in a 3.5-ha field. From 8 plants, 16 small pieces of leaf tissue (6 × 6 mm) were cut from the edge of the lesions, including live and dead portions. These were surface sterilized in 1% hypochlorite for 30 s, and then placed on potato dextrose agar (PDA) amended with kanamycin (0.1 mg/ml). After 48 hours at 28 °C, 12 fungal strains were recovered. Eight strains presented a consistent morphology, while the remaining four strains varied in morphology. All 12 strains were tested for pathogenicity on detached leaves and only the eight (presenting a consistent morphology) showed disease. The other four strains showed no disease. A representative isolate, MDY, was selected for causal agent identification. The hyphae were white, slightly raised, thin-walled, straight, and 2.0-4.0 μm in diameter. There was no detectable odor. Conidia were numerous, clustered, ovoid, colorless, and 5-8 µm x 4-5 µm. These characteristics were similar to those reported for Irpex lacteus (Chi et al. 2002). The internal transcribed spacer (ITS), large ribosomal subunit (LSU) and small ribosomal subunit (SSU) loci of isolate MDY were, respectively, amplified with primers ITS1/ITS4, LR5/LROR, and NS1/NS4 (Schoch et al. 1998; Melnikov et al. 2012), and sequenced using both forward and reverse primers. Consensus sequences from each pair of primers were used in BLAST against the NCBI GenBank database. The ITS sequence (OR366346) showed 99.9% identity (648/649 bp) with I. lacteus (MH890689), the LSU sequence (OR878461) showed 99.6% identity (904/908 bp) with I. lacteus (MH867969), and the SSU sequence (OR878462) showed 99.5% identity (969/974 bp) with I. lacteus (MF190370). Neighbor-Joining analysis was carried out using the ITS sequence of MDY, several related sequences from GenBank, and Macrocybe gigantea OQ644634 as outgroup. MDY clustered with other I. lacteus sequences with 95% bootstrap support. Morphological and molecular results supported this isolate as I. lacteus. Pathogenicity was tested on six tobacco seedlings (cv. Yunyan 87) at the six-leaf stage using hyphal plugs from isolate MDY on non-wounded attached leaves, while controls received PDA plugs. This test involving three treated plants and three control plants was repeated three times. All tobacco seedlings were kept in a growth chamber at 25 ± 5 °C and 85% relative humidity. After 7 days, leaf spots similar to field symptoms were observed on the treated leaves, while no symptoms were observed on control leaves. Koch's postulates were fulfilled by re-isolation of the pathogen from the diseased leaves, confirmed by ITS sequencing. From pre","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144041078","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}