Plant disease最新文献

{"title":"Identification of <i>Geotrichum citri-aurantii</i> and <i>G. candidum</i> in Citrus Packinghouses in California, Their Sensitivity to Cyproconazole, and Incomplete Cross-Resistance to Propiconazole.","authors":"Albert M Nguyen, Helga Förster, James E Adaskaveg","doi":"10.1094/PDIS-08-24-1692-RE","DOIUrl":"10.1094/PDIS-08-24-1692-RE","url":null,"abstract":"<p><p>High levels of sour rot on propiconazole-treated lemon fruit that was stored for extended times in some California packinghouses in 2020 and 2021 initiated surveys on fungicide sensitivity of the causal pathogen. In isolations from diseased fruit in 2020 to 2023, 157 isolates of <i>Geotrichum</i> spp. were obtained. Using species-specific primers, 143 were determined to be <i>G. citri-aurantii</i> and 15 were <i>G. candidum</i>. Isolates of <i>G. citri-aurantii</i> were either sensitive (effective concentration of fungicide required for 50% growth inhibition [EC₅₀] 0.06 to 0.34 μg/ml), moderately resistant (EC₅₀ 1.20 to 2.34 μg/ml), or highly resistant (EC₅₀ ≥ 17.68 μg/ml) to propiconazole. There was incomplete cross-resistance to cyproconazole, another demethylation inhibitor fungicide, pending postharvest registration on citrus in the United States. Isolates sensitive to propiconazole were sensitive, isolates moderately resistant to propiconazole were sensitive, and isolates highly resistant were moderately resistant to cyproconazole (EC₅₀ 0.11 to 0.63 μg/ml, 0.19 to 0.73 μg/ml, and 2.66 to 6.79 μg/ml, respectively). All except one isolate of <i>G. candidum</i> were highly resistant to both fungicides (EC₅₀ > 9.55). Isolates of both species were all considered sensitive to natamycin (EC₅₀ 1.18 to 5.01 μg/ml). In lemon fruit inoculations with <i>G. candidum</i>, the incidence of typical sour rot increased from 4.7 to 68.2% when inoculum was amended with 2 μg/ml or 100 μg/ml cycloheximide, respectively, a compound known to suppress host defenses. In coinoculations with 1:1 mixtures of the two <i>Geotrichum</i> spp., <i>G. candidum</i> was only recovered from the centers of decay lesions, whereas <i>G. citri-aurantii</i> was also obtained from the advancing margins. We conclude that <i>G. candidum</i> is a secondary pathogen of lemons, and its presence was favored by extended late-season storage of senescent fruit with reduced defense mechanisms.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS08241692RE"},"PeriodicalIF":4.4,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142505829","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":"Assessing Pesticide Residue Levels in Sweetpotato Roots and Slips Treated with Fungicides for Management of Southern Blight and Circular Spot Disease Caused by <i>Agroathelia rolfsii</i>.","authors":"Jack Mascarenhas, Hunter Collins, Khalied Ahmed, Travis Gannon, Christie Almeyda, Lindsey Thiessen, Anders Huseth, Lina Maria Quesada-Ocampo","doi":"10.1094/PDIS-04-24-0849-RE","DOIUrl":"10.1094/PDIS-04-24-0849-RE","url":null,"abstract":"<p><p>Since 1971, North Carolina (NC) has been the leading sweetpotato-producing state in the United States and is now producing more than half of the nation's annual output. Because of the high demand for U.S. sweetpotatoes from international markets, NC allocates roughly 40% of its sweetpotatoes for export. However, low fungicide residue limits in primary export markets restrict the ability for NC producers to apply fungicides for disease management during sweetpotato production. <i>Agroathelia rolfsii</i>, the causal agent of southern blight and circular spot, is an important pathogen of sweetpotato. Field experiments were conducted in 2022 and 2023 to quantify the residue amount of various active ingredients and transplant-only versus bedding and transplant applications when managing <i>A. rolfsii</i> in the field. High-performance liquid chromatography analyses of root and vine samples confirmed that none of the tested active ingredients and application timings resulted in residue numbers exceeding the limits of export markets except for roots treated with thiabendazole. Results from this study provide information for development of application practices with acceptable residue levels for export markets while effectively managing diseases caused by <i>A. rolfsii</i>.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS04240849RE"},"PeriodicalIF":4.4,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142505815","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":"Development of a New Tool to Detect <i>Melampsora medusae</i> f. sp. <i>tremuloidae</i> Causing Rust Disease on <i>Populus tremuloides</i>.","authors":"Cécile Guinet, Marius Buronfosse, Philippe Tanguay, Pascal Frey, Renaud Ioos","doi":"10.1094/PDIS-07-24-1477-SC","DOIUrl":"10.1094/PDIS-07-24-1477-SC","url":null,"abstract":"<p><p><i>Melampsora</i> <i>medusae</i> f. sp. <i>tremuloidae</i> is a quarantine organism for the European Union. In North America, this fungus causes rust disease on <i>Populus tremuloides</i>. In Europe, <i>Populus tremula</i>, an aspen closely related to <i>P. tremuloides</i>, is widespread and plays an important ecological role. Introduction of <i>M. medusae</i> f. sp. <i>tremuloidae</i> into Europe could be a major risk if this <i>forma specialis</i> could evolve and become virulent on <i>P. tremula</i>. To date, no PCR-based assay exists to specifically detect <i>M. medusae</i> f. sp. <i>tremuloidae</i>. In this study, a sensitive and specific real-time PCR assay has been developed based on the 28S rDNA. The assay proved to be reliable using many real-time PCR kits and platforms. It can be used to monitor the introduction and the spread of <i>M. medusae</i> f. sp. <i>tremuloidae</i> in the context of phytosanitary regulations.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS07241477SC"},"PeriodicalIF":4.4,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142505816","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>Fusarium falciforme</i> Causing Branch Rot on <i>Jasminum sambac</i> in China.","authors":"Yiqing Zheng, Mingyan Sun, Yuan Su, Chunniu Li, Xianmin Li, Zhaoyang Bu","doi":"10.1094/PDIS-02-25-0229-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0229-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Jasmine (&lt;i&gt;Jasminum sambac&lt;/i&gt; (L.) Aiton) is a commercially important plant known for its fragrant flowers, which are used in tea production and essential oils extraction (Sun et al. 2023; Hong et al. 2024). In September 2022, branch rot symptoms were observed in a ~1300 m&lt;sup&gt;2&lt;/sup&gt; jasmine plantation in Hengzhou, Guangxi, China. Approximately 35% of the plants exhibited branch rot, with about 50% of the branches on each diseased plant affected. Symptoms included wilting and defoliation of leaves and brown irregular lesions on some branches. In later stages, the disease caused branch discoloration or desiccation and plant death. Twenty infected branches were collected randomly from six plants in the most severely affected area half. Branch tissues (3 mm&lt;sup&gt;2&lt;/sup&gt;) from necrotic margins were surface-sterilized (75% ethanol for 10 s, 2% NaClO solution for 2 min), rinsed three times with sterile distilled water, and then placed on potato dextrose agar (PDA) plates. After incubation at 28 °C for seven days, ten morphologically identical isolates were obtained. Two isolates (HR112-1 and HR113-1) were randomly selected for further study. Both isolates exhibited abundant white to cream aerial mycelium and produced hyaline, slightly curved macroconidia (21.2 to 46.1 × 4.4 to 8.8 µm; n = 100) with zero to three septa and oval or reniform microconidia (6.1 to 14.4 × 3.3 to 8.9 µm; n = 100) with zero to two septa on PDA. Genomic DNA was extracted from the two isolates using the CTAB method. The partial internal transcribed spacer (ITS) region, translation elongation factor subunit 1-alpha (&lt;i&gt;TEF-1α&lt;/i&gt;) and ribosomal polymerase II second largest subunit (&lt;i&gt;RPB2&lt;/i&gt;) gene sequences were amplified and sequenced using primers pairs ITS1/ITS4, EF1/EF2 and 5f2/7cr (White et al. 1990; O' Donnell et al. 2010), respectively. The sequences were deposited in GenBank (ITS: PQ625807 and PQ625808; &lt;i&gt;TEF-1α&lt;/i&gt;: PV008115 and PV008116; &lt;i&gt;RPB2&lt;/i&gt;: PQ638394 and PQ638395). BLAST analysis showed 99.08 to 99.81% identity with the ex-type strain &lt;i&gt;Fusarium falciforme&lt;/i&gt; CBS 475.67. A maximum-likelihood phylogenetic tree constructed using MEGA X based on concatenated sequences of ITS, &lt;i&gt;TEF-1α&lt;/i&gt; and &lt;i&gt;RPB2&lt;/i&gt; confirmed that both isolates (HR112-1 and HR113-1) clustered with &lt;i&gt;F. falciforme&lt;/i&gt;. Pathogenicity tests were performed on 1-year-old healthy &lt;i&gt;J. sambac&lt;/i&gt; plants grown in pots. Circular wounds (1 mm depth) were made on the branches using a sterilized needle and covered with wet cotton saturated with 100 μm conidial suspension (1 × 10&lt;sup&gt;6&lt;/sup&gt; conidia/ml). The inoculated sites were wrapped with plastic film to maintain moisture. Control plants were treated with sterile water-moistened cotton. Five plants were used for each isolate and control, with three inoculation sites per plant. All plants were enclosed in clear plastic bags and placed in a plant incubator (14 h light/10 h dark, 28 °C). After 14 days, all plants inoculated with the two i","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736160","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>Apiospora arundinis</i> Causing Leaf Spot on wheat in China.","authors":"Ruiling Lyu, Junlin Chen, Wei Li, Xia Fan, Huachong Zhang, Hailiang Zhou, Baosheng Dai","doi":"10.1094/PDIS-12-24-2776-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2776-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Wheat (Triticum aestivum L.) is one of the most important food crops. In April 2022, leaf spot disease were observed in a 1 hectare field located in the Huanggang area of Hubei, China(30°56'99″ N, 114°91'70″E). The lesions can infect the leaves and stems of wheat, initially presenting as punctate ulcerative spots . Over time, these lesions coalesce, leading to the necrosis and subsequent rotting of the stems and leaves in the field. To identify the pathogen, 30 diseased leaf pieces (5 × 5 mm) from the lesion borders were surface sterilized in 1% NaClO for 2 min, then rinsed three times with sterile distilled water. The tissues were placed on potato dextrose agar (PDA) and incubated at 25°C for 3 d in the dark. A total of 27 isolates with consistent morphological characteristics were obtained. The representative isolates HGNU2022-6 and HGNU2022-8 were used for morphological studies and phylogenetic analyses. The colonies on PDA of the two isolates were white with fluffy aerial mycelium, subsequently exhibiting yellow pigmentation. The hyphae were smooth, hyaline, branched and septate. Conidiophores were hyaline or pale brown and produced conidiogenous cells, which were pale brown, smooth, ampulliform, and 8.25 (7.53 to 12.82) μm long (n = 50). Conidia were solitary or clustered, brown or dark brown, smooth, ellipsoidal to spherical, and 11.28 (6.50 to 14.81) × 11.34 (7.17 to 14.32) μm (n = 50) in size. Based on these morphological characteristics, the fungus was identified as belonging to the genus Apiospora (Pintos and Alvarado 2021). For molecular identification, the internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF-1α) and β-tubulin 2(TUB2)genes were amplified with the primer pairs ITS1/ITS4, EF1-728F/EF-2 and T10/Bt-2b, respectively (White et al. 1990; Glass and Donaldson 1995; O'Donnell and Cigelnik 1997). The generated sequences were deposited in GenBank with accession numbers PQ135955 and PQ135957 for ITS, PQ148399 and PQ148400 for TEF-1α, and PQ148401 and PQ148402 for TUB2. All the sequences had more than 99% similarity with those of the Apiospora arundinis strain LC7252 and LC7277. In the multilocus phylogenetic analysis, the two isolates clustered together with other strains of A. arundinis with 100% bootstrap support. The two isolates were identified as A. arundinis based on morphological and molecular characteristics. For pathogenicity testing, healthy leaves of six wheat plants were inoculated with 100 μl of spore suspension (1 × 106 conidia/ml) and then incubated at 22°C, 90% relative humidity, with a 16 h light/8 h dark cycle. The inoculated leaves showed necrosis and wilt symptoms similar to those observed in the greenhouse, whereas the control leaves were asymptomatic. Apiospora arundinis was re-isolated from symptomatic plants and the identity was confirmed based on morphology and DNA sequence. No pathogenic fungus was isolated from the control leaves. The experiment was repeated six times with s","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736074","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":"Occurrence of Anthracnose Caused by <i>Colletotrichum fructicola</i> on Mulberry in Zhejiang, China.","authors":"Ping Li, Xue Dai, Siyi Wang, Huicong Shi, Zhongli Chen, Weiguo Zhao, Sheng Sheng, Fuan Wu","doi":"10.1094/PDIS-12-24-2611-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2611-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Mulberry trees (Morus L.) are economically crucial crops in China, highly valued for their roles in silk production, livestock feeding, and as sources of food and medicinal products. From 2021 to 2023, leaf spot symptoms emerged in mulberry orchard in Qiandao Lake Town, Hangzhou, Zhejiang, China (29.61° N, 118.91° E). A survey of 60 trees over 200 m2 area revealed 45% of the foliage was infected with leaf spot disease, significantly reducing leaf quality. Infection typically began at the leaf tips or edges, initially as small dark brown spots (0.6 to 1.4 mm) that expanded into irregular lesions with grayish white centers and brown margins (2.5 to 3.6 mm). The infected leaves eventually wither and decay, and in severe cases, they may drop. Twelve freshly infected leaves from ten different mulberry trees were collected, cut into 5 × 5 mm sections, disinfected with 75% ethanol for 45 s and 0.5% NaClO for 2 min, rinsed three times with sterile water, the sections were plated on potato dextrose agar (PDA) and incubated at 28°C in the dark for 5 days. Six morphologically similar isolates were obtained by transferring hyphal tips to pure cultures. After 7 days on PDA, colonies were dense with white cottony aerial mycelia and light gray-black hyphae. The average mycelial growth rate was 8.2 mm/day, ranging from 5.8 to 11.2 mm/day. Conidia were cylindrical, hyaline, aseptate, with rounded ends and an inconspicuous hilum, measuring 12.4 to 16.4 × 3.6 to 6.8 μm. The appressoria were brown to dark brown, nearly ovoid to cylindrical, and slightly irregular, measuring 6.32 to 13.65 ×5.25 to 7.68 µm. These features were consistent with the description of Colletotrichum spp. (Fuentes-Aragón et al. 2018). Genomic DNA was extracted, and the rDNA internal transcribed spacer (ITS), partial actin (ACT), chitin synthase (CHS1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and β- tubulin 2 (TUB2) genes were amplified using the primers ITS1/ITS4, ACT-512F/ACT-783R, CHS-79F/CHS-345R, GDF/GDR, T1/Bt2b (Weir et al. 2012). The sequences were submitted to GenBank with accession numbers ON042364.1 (ITS), PQ567195 (ACT), PQ56196 (CHS1), PQ567197 (GAPDH), and PQ567198 (TUB2). BLASTN analysis revealed high similarity to Colletotrichum fructicola strain ICMP 18581, with sequence identities of 99.62% (ITS), 96.20% (ACT), 98.89% (CHS1), 98.79% (GAPDH), and 99.56% (TUB2) (Weir et al., 2012). A phylogenetic tree was constructed using the Bayesian inference (BI) method in MrBayes v.3.2.7 based on concatenated sequences of five genes (ITS-ACT-CHS1-GAPDH-TUB2). Based on morphological characteristics and phylogenetic analysis, the isolates were identified as C. fructicola. To confirm pathogenicity, ten 6-month-old potted plants were used for inoculation with each representative isolate. Tested plants were sprayed with 5 ml of a conidial suspension (1 × 106 conidia/ml), and the controls plants were sprayed with sterile water. All the plants were incubated in a growth chamber at","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736201","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 Root-Knot Nematode <i>Meloidogyne hapla</i> on <i>Coptis chinensis</i> in China.","authors":"Qiaohui Zhang, Lin Li, Wei Fu, Zhenxing Zhu, Zhanghui Qin, Zhexian Zhang, Wenlu Liu, Hongqing Yin","doi":"10.1094/PDIS-12-24-2650-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2650-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Coptis chinensis Franch. 1897, commonly known as \"Huang Lian\", is a widely cultivated flowering plant in the family Ranunculaceae, especially in China (Wang et al., 2019). Rhizoma copies, the dried rhizome of C. chinensis, is extensively used in traditional Chinese medicine due to its antibacterial, anti-inflammatory, antioxidant, antitumor, and other pharmacological properties (Gai et al., 2018). In September 2023, C. chinensis plants in Lichuan City (30°36'15.36\" N; 108°59'36.45\" E) exhibited several symptoms, including stunted growth with yellowish leaves and many galls on roots. We suspected that this damage was caused by root-knot nematode. Roots were taken to the lab and maintained at 10°C for morphological and molecular identification of root-knot nematodes and pathogenicity testing. Females, second-stage juveniles (J2), and egg masses were dissected and extracted from roots with galls. The perineal pattern of females was oval with a slightly flat dorsal arch in some groups and marked in the anus. Males had high head caps that were narrower than the head region, broadening beyond the first body annuli. Morphological measurements of males (n = 20) were as follows: body length (BL) = 1,171.68 ± 85.34 µm, maximum body width (BW) = 34.04 ± 2.69 µm, stylet length (ST) = 19.19 ± 0.46 µm, dorsal pharyngeal gland orifice to stylet base (DGO) = 4.27 ± 0.26 µm, and spicule length = 26.58 ± 1.34 µm. Measurements of females were as follows: BL = 900.26 ± 35.15 µm, BW = 594.84 ± 42.16 µm, ST = 14.76 ± 0.58 µm, DGO = 5.22 ± 0.48 µm, stylet median bulb width = 31.25 ± 2.95 μm. Measurements of J2 were as follows: BL = 420.32 ± 26.85 µm, BW = 14.86 ± 1.77 µm, ST = 11.96 ± 0.69 µm, DGO = 3.53 ± 0.51 µm, tail length = 73.05 ± 11.52 µm, and hyaline tail terminus = 11.26 ± 2.31 µm. These morphological characteristics were consistent with those of Meloidogyne hapla (Whitehead, 1968). For species identification, genomic DNA was extracted from 12 single J2. The sequence of the 5.8S-18S ribosomal RNA gene was amplified and sequenced with the universal primer 194/195 (5´-TTAACTTGCCAGATCGGACG-3´/5´-TCTAATGAGCCGTACGC-3´) for confirmation of Meloidogyne spp. (Qin et al., 2022). The 768 bp sequence (GenBank accession no. PQ284213) was 99.82% identical to the 5.8S-18S rDNA sequences of M. hapla (AJ421708). Then, the variable V3 and V5 regions of the 18S rDNA gene were amplified and sequenced with the primers 18sf1/18sr1 (5´-CGCAAATTACCCACTCTC-3´/5´AGTCAAATTAAGCCGCAG-3´) (Waite et al., 2003). The sequences for the target genes (PQ284215) showed 100% identity to sequences of M. hapla (OQ642146). To confirm the pathogenicity of the population, six one-year-old healthy C. chinensis seedlings cultured in sterilized sand were each inoculated with 2,000 J2s hatched from egg masses. Four noninoculated seedlings served as negative controls. After maintenance at 25°C for 90 days, galls appeared on the roots of inoculated plants consistent with the symptoms observed in the f","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736166","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":"Multiplexed real-time and digital PCR tools to differentiate clades of <i>Plasmopara viticola</i> causing downy mildew in grapes.","authors":"Lexi Heger, Nancy Sharma, Austin Glenn McCoy, Frank N Martin, Laura Avila Miles, Martin I Chilvers, Rachel P Naegele, Timothy D Miles","doi":"10.1094/PDIS-01-25-0173-SR","DOIUrl":"https://doi.org/10.1094/PDIS-01-25-0173-SR","url":null,"abstract":"<p><p>In vineyards, downy mildew of grapes, caused by the oomycete pathogen <i>Plasmopara viticola</i>, can cause significant economic losses when left unmanaged. <i>P. viticola</i> is a species complex, made up of at least four clades, or cryptic species, causing disease on at least eight plant species within the family Vitaceae. In the United States, clades <i>aestivalis</i>, <i>riparia</i>, and <i>vinifera</i>, have been identified, as being present in the Great Lakes region on cultivated grapes. Within this study, a multiplexed TaqMan qPCR assay system capable of differentiating among these three taxa was developed using a mitochondrial gene order difference unique to <i>Plasmopara</i> species (cox1-atp1). The assay is needed to clearly differentiate among the closely related species as research investigates relationships between the clades and their varying hosts as well as fungicide resistance development. The multiplexed assay was validated using a panel of target and non-target samples of varying types, including leaves, ToughSpot stickers, and air sampling rods. The assay was also transferred to and optimized on a digital PCR (dPCR) platform. Air sampling rods and artificially inoculated mixed samples were tested using both qPCR and the dPCR assays to gauge utility of each. The multiplexed assays for each clade showed varying sensitivity of 10 to 1,000 fg of DNA and efficiency of 70-85% in qPCR. The dPCR sensitivity was the same, except for clade riparia, which showed a potential tenfold increase in sensitivity. These results suggest that the dPCR can serve as a more sensitive option than qPCR when trying to diagnose plant pathogens, but it is dependent on the assay. This assay system provides detection of the pathogen and classification of P. viticola clades allowing discrimination in areas growing multiple cultivated or wild grape species. This will continue to be relevant as wild hosts can potentially harbor different P. viticola clades and downy mildew is intensely managed in commercial vineyards.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736168","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>Aucklandia costus</i> Root Rot Caused by <i>Fusarium avenaceum</i> in China.","authors":"Duhua Li, Xuedong Cao, Qiyun Liu, Xiuguo Zhang, Jiwen Xia","doi":"10.1094/PDIS-01-25-0161-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-01-25-0161-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Aucklandia costus (syn. Saussurea costus) belongs to the Asteraceae family and has been cultivated in India and China, where its roots were used in traditional Chinese medicine. In December 2023, root rot symptoms were observed in Chengkou County (31.69°N 108.58°E), Chongqing Municipality of China. The infection started with brown roots and the overground parts showing dull leaf color and the roots gradually rotted and turned black, and the overground parts completely withered. Ten A. costus samples with a disease incidence of 10% to 30%, were collected from fields spanning about five acres. Rotted roots were disinfested with 1% NaOCl for 1 min, 75% ethanol for 30 s, and washed in sterile water. Pieces (1 cm3) were cut from the disinfested root, placed on potato dextrose agar (PDA), and incubated at 25°C for 1 week. Ten isolates with similar morphology were obtained and the isolate YMX was selected for further characterization. Colonies maintained on PDA in the dark had an average radial growth rate of 8-12 mm/d at 25°C. The colony was white to jasmine, presented velvety to felty mycelia, with a beige reverse lacking diffusible pigments (Fig. 1). On carnation leaf agar, sporodochia appeared as slimy dots, macroconidia were 3 to 7-septate, 35-85 × 3-6 μm, falcate, while microconidia and chlamydospores were absent. These morphological characteristics were consistent with descriptions of Fusarium sp. The isolate YMX was further characterized using the internal transcribed spacers (ITS) (White et al. 1990), RNA polymerase II largest subunit (RPB1) (Senatore et al. 2021), RNA polymerase II second largest subunit (RPB2) (Xia et al. 2019) and translation elongation factor 1-α gene (TEF1) (Carbone and Kohn 1999; O'Donnell et al. 2010) which were amplified using the primer pairs ITS5/ITS4, Amp3f/Amp3r, 5f2/7cr and EF1-728F/EF2, respectively. Sequences were deposited in GenBank (ITS: PQ381655; RPB1: PQ404771; RPB2: PQ404772; TEF1: PQ404773). BLASTn queries of ITS, RPB1, RPB2 and TEF1 sequences showed 100%, 99.69%, 99.04% and 98.74% identity with OL832320, OL772910, MH582370 and OL772758, respectively, of the reference strains of F. avenaceum NRRL 54939 or NRRL 36069. The isolate YMX clustered with Fusarium avenaceum (100% bootstrap) in a concatenated phylogenetic tree (Fig. 2). Pathogenicity tests were conducted on roots of ten A. costus healthy plants. A wound was created using a sterile toothpick on each root and one mycelial plug (5 mm diameter) from a 7-day-old colony of the isolate YMX was placed on the wound. Root samples inoculated with plugs of noncolonized PDA served as a control. The test was repeated three times. After 7 days of incubation at 25°C, all inoculated roots showed symptoms like those in the field while control roots remained healthy (Fig. 1). The fungi isolated from the experimental plant roots were confirmed as F. avenaceum using morphological and four-gene sequence analyses. F. avenaceum causes root rot in several species inc","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736077","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":"Characterization of <i>Puccinia sorghi</i> isolates from South Africa.","authors":"Lineo Anna Maphobole, Botma Visser, Wilku Meyer, Cornelia M Bender, Zacharias A Pretorius, Willem H P Boshoff","doi":"10.1094/PDIS-12-24-2585-SR","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2585-SR","url":null,"abstract":"<p><p>Common rust on maize, caused by <i>Puccinia sorghi</i> (<i>Ps</i>), is a regular occurring disease in South Africa. Knowledge on the race composition, effective resistance (<i>Rp</i>) genes and genotypic variation among <i>Ps</i> isolates contributes to the genetic control of the disease and our understanding of pathogen diversity and evolution. Ninety-six single pustule isolates of <i>Ps</i>, including field isolates from the 2006, 2008, 2014, 2018, 2021, and 2022 production seasons, were studied. Isolates were phenotyped on 26 maize differential lines and genotyped with 11 microsatellite markers. A total of 35 <i>Ps</i> races were identified. Races BBBHC and BGBHC were the most common and constituted 16 isolates each followed by races MBGHC and JBNHC with 12 and 5 isolates, respectively. Nineteen races were represented by one, and eight races by two isolates. No avirulence was detected to <i>Rp3-A</i>, <i>Rp8-A</i>, and <i>Rp8-B</i> and no virulence to <i>Rp7</i> and two lines with stacked gene combinations (<i>Rp5G</i> and <i>Rp5CGJ</i>). Lines with <i>Rp1-E</i>, <i>Rp1-Kr4</i>, <i>RpFJ</i>, <i>RpCJ</i>, <i>RpDJ</i>, <i>RpCFJ</i>, <i>RpDGJ</i>, and <i>RpFGJ</i> had a low susceptibility frequency (<10%). Microsatellite analysis revealed low genetic diversity amongst the <i>Ps</i> isolates, indicating a clonal population. STRUCTURE analysis of multilocus genotypes revealed a single genetic lineage. No correlation was found between the phenotypes and genotypes of the identified <i>Ps</i> races. The observed racial diversity emphasized the ability of Ps to evolve as well as the need to determine hybrid responses to assist in the control of the disease in areas considered as high risk in South Africa.</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":"143730799","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}