Plant disease最新文献

{"title":"First report of Cercospora leaf spot caused by <i>Cercospora</i> cf. <i>flagellaris</i> on industrial hemp (<i>Cannabis sativa</i>) in Arkansas and Oklahoma.","authors":"Kona Blake Swift, Burt Bluhm","doi":"10.1094/PDIS-05-25-0946-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-05-25-0946-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;In fall of 2021, a leaf spot disease was observed in outdoor plots of industrial hemp (&lt;i&gt;Cannabis sativa&lt;/i&gt;) in Fayetteville, Arkansas. Indistinguishable symptoms were also observed in outdoor plots of hemp in Adair County, Oklahoma. Leaf spots first appeared on older leaves in the lower canopy before spreading to the upper canopy. Nascent leaf spots began as yellow-green specks and developed into round, necrotic lesions 2 to 4 mm in diameter with white, tan, or grey centers and brown boarders. To isolate the pathogen, green leaves with mature lesions were collected and placed in moist chambers. After incubation for 24 to 72 hrs, melanized, erumpent conidiophores bearing hyaline conidia emerged in lesions. Conidia were picked with a sterile needle and transferred to V8 agar + carbenicillin (100 μg/ml). Cultures were incubated in the dark at 25°C. Resulting colonies were light or dark grey with white aerial hyphae. Some colonies produced a reddish-purple pigment consistent with cercosporin. Two isolates from AR (21CD76 and 21CD169) and three isolates from OK (21CD47, 21CD52, and 21CD56) were single spored and selected for pathogenicity tests and genetic identification. Conidiation was induced &lt;i&gt;in vitro&lt;/i&gt; by incubation on V8 agar at 25°C in the dark. Conidia were hyaline, needle shaped, straight or slightly curved, truncate at the base, terminal at the tip, with indistinct septa ranging from 5 to 15 per conidium. Conidium lengths ranged from 15 to 101 μm, consistent with descriptions of &lt;i&gt;Cercospora&lt;/i&gt; cf. &lt;i&gt;flagellaris&lt;/i&gt; (Chupp 1953). Koch's postulates were fulfilled via whole plant inoculations. Spores from each isolate were collected with sterile water and diluted to 10&lt;sup&gt;5&lt;/sup&gt; or 10&lt;sup&gt;6&lt;/sup&gt; spores/ml + 0.01% Tween 20. Three-week-old hemp plants of cv. Sour Space Candy and Red Kross were inoculated by spraying until run-off. Sterile water + 0.01% Tween 20 was used for negative controls. Four plants of each cultivar were used per treatment. Plants were kept in moist chambers for 72 hrs and maintained in a growth chamber with a 16/8-hr light/dark cycle. Symptoms consistent with those seen in the field began to appear after 7 days. After 14 days, all inoculated plants developed lesions, while control plants remained healthy. &lt;i&gt;C.&lt;/i&gt; cf. &lt;i&gt;flagellaris&lt;/i&gt; was reisolated from inoculated plants but not from control plants. The pathogenicity test was repeated once with the same results. For genetic identification, segments of the ribosomal internal transcribed spacer (ITS), translation elongation factor 1-α (TEF), histone H3 (HIS), calmodulin (CAL), and actin (ACT) genes were extracted from whole-genome sequences or sequenced individually (GenBank: PV178994 to PV178998 and PV335254 to PV335273). BLAST queries revealed 99-100% identity with NCBI &lt;i&gt;C.&lt;/i&gt; cf. &lt;i&gt;flagellaris&lt;/i&gt; strains for all but one sequence (PV335272), which shared 97.76% identity (ITS: KX443947; TEF: MG975845, KX443988; HIS: MG975843, KX443893; CAL: KX443","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144079419","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":"Mapping and Candidate Gene Identification for Adult Plant Resistance to Stripe Rust in the Chinese Wheat Landrace Laohongmai.","authors":"Xiaowei Xu, Jing Feng, Fengtao Wang, Syed J A Shah, Ruiming Lin","doi":"10.1094/PDIS-03-25-0615-RE","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0615-RE","url":null,"abstract":"<p><p>Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases affecting wheat production worldwide. Wheat resistant cultivars can effectively prevent and limit the occurrence and spread of the disease. Chinese wheat landrace Laohongmai (LHM) demonstrated a high level of resistance to stripe rust at the adult plant stage. To identify and map loci associated with resistance to stripe rust in LHM, a total of 224 recombinant inbred lines (RILs) were developed by crossing LHM with Taichung 29. Maximum disease severity was assessed for the parents and RILs in the fields inoculated with currently prevalent Pst races in Langfang, Hebei in 2023 and 2024 and in Chengdu, Sichuan in 2024. The wheat 55K SNP array was used to genotype the RILs. A new major adult plant resistance locus, QYr.LHM-1AL, was identified and mapped to a genetic interval of 3.51 cM between markers 45KASP1A-4 and 45SSR1A-973 on the long arm of chromosome 1AL corresponding to a 553.9 to 554.0 Mb region in the Chinese Spring reference genome. The genome region contains four genes, including TraesCS1A01G383100 encoding cysteine peptidase. The gene was found to be involved in responding to Pst invasion as confirmed by a qRT-PCR analysis. Among 50 wheat landraces tested with the three linked markers, 3 landraces had the Laohongmai haplotype. The markers are useful in molecular breeding.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144007751","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":"Screening, Identification, and Production Application of Endophytic Streptomyces W71 from Tobacco Plants in Sanmenxia.","authors":"Kai Zhu, Hui Wang, Zhengxiong Song, Haohao Li, Min Xu, Yebin Kang, Jian-Qiang Xu","doi":"10.1094/PDIS-02-25-0301-RE","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0301-RE","url":null,"abstract":"<p><p>Tobacco black shank, induced by Phytophthora nicotianae, ranks among the most destructive diseases threatening global tobacco production. Biological control constitutes a crucial method for the environmentally friendly management of this disease, with the discovery of biocontrol agents serving as the initial step in this endeavor. The present research seeks to uncover new biocontrol agents and plant growth promoters effective against P. nicotianae. A strain of endophytic actinomycete isolated from tobacco, designated W71, was identified as Streptomyces rochei. This strain exhibited strong IAA production capacity and inhibitory activity against P. nicotianae. In greenhouse trials, S. rochei W71 demonstrated significant plant growth promotion effects, markedly improving agronomic traits, root activity, root morphology indices, and antioxidant enzyme activities of tobacco plants. Field trials conducted at the rosette and prosperously growing stages revealed significant enhancements in several key crop parameters following the application of W71 treatment. These improvements encompassed increased maximum leaf length, maximum leaf width, stem girth, and plant height. Additionally, at harvest, W71 was found to facilitate a remarkable 98.91% boost in yield. In vitro inhibition tests demonstrated potent antagonism: live cells of S. rochei W71 suppressed P. nicotianae growth by 96.84%, outperforming the 70.89% inhibition rate of its cell-free culture filtrate. Greenhouse pot trials yielded an 87.53% disease control efficacy against tobacco black shank, and field trials resulted in a 72.68% control efficacy, indicating satisfactory performance. The study results demonstrate that S. rochei W71 possesses both plant growth-promoting properties and biocontrol capabilities against tobacco black shank, making it a promising candidate for use as a plant growth promoter and biological control agent.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144041079","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":"Genome-wide association mapping and genomic predictions for Bacterial fruit blotch resistance in the USDA <i>Citrullus amarus</i> collection.","authors":"Venkata Rao Ganaparthi, Patrick Wechter, Melanie Katawczik, Amnon Levi, Sandra Branham","doi":"10.1094/PDIS-12-24-2665-RE","DOIUrl":"https://doi.org/10.1094/PDIS-12-24-2665-RE","url":null,"abstract":"<p><p>Acidovorax citrulli infects seedlings, adult plants and fruits, causing bacterial fruit blotch (BFB) in watermelon. Host resistance would provide an effective and economical management option for BFB but there are currently no resistant watermelon cultivars. Several resistant accessions were previously identified in the USDA Citrullus amarus collection. Identifying the genetic basis of this resistance would allow the development of BFB-resistant cultivars through introgression from this crop wild relative. Genome-wide association studies (GWAS) are an excellent tool for dissecting the genetic architecture of a trait. The USDA Citrullus amarus collection (N=127 accessions) was genotyped with whole genome resequencing, resulting in 2,126,759 SNP markers, then phenotyped for BFB-resistance and used for GWAS of seedling resistance to A. citrulli. Four models were used for GWAS in R with the GAPIT package. MLM and MLMM analysis did not identify any significant marker associations. FarmCPU identified three quantitative trait nucleotides (QTN) on chromosomes 2, 4, and 8. BLINK identified only one significant QTN on chromosome 8. The three significant QTNs explained 65.1% of the phenotypic variance using a linear regression model. Putative candidate genes within the linkage disequilibrium blocks of significant SNPs code proteins relevant to biotic resistance, such as Patellin-6, macrophage migration inhibitory factor homolog, PRA1 family protein and trichome birefringence-like family proteins. The predictive ability of six genomic prediction models for A. citrulli seedling resistance ranged from 0.45 to 0.75. Along with identifying genomic regions associated with BFB seedling resistance, this study observed moderate to high predictive abilities across genomic prediction models.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144023314","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 leaf spot on <i>Basella alba</i> caused by <i>Dichotomophthora basellae</i> in Taiwan.","authors":"Huang-Hsi Chu, Yun-Xuan Xu, Chih-Li Wang","doi":"10.1094/PDIS-04-25-0815-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-04-25-0815-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Malabar spinach (&lt;i&gt;Basella alba&lt;/i&gt;) is a widely cultivated leafy vegetable in Asia. In July 2023, a severe leaf spot outbreak with 100% incidence occurred in multiple net houses on an organic farm in Miaoli county, Taiwan. Initial symptoms were small pale brown necrotic lesions, often with a reddish halo. As the disease progressed, the lesions enlarged, forming brown spots with concentric rings and abundant sporulation. The pathogen was isolated using two methods: tissue isolation from small non-sporulating lesions after surface-sterilization, and single conidium isolation from sporulating lesions. Four isolates, BaDpO-1, BaDpO-2, BaDpY-1, and BaDpY-2, exhibiting similar morphology were obtained from both isolation techniques. Conidiophores of these isolates were macronematous, unbranched or irregularly branched, with a swollen head at the apex. Heads were repeatedly dichotomously or trichotomously lobed, pale brown to brown, and measured 17-58.1 μm wide (n=40). Conidiogenous cells were terminally lobed and polytretic. Conidia were solitary, ellipsoidal to cylindrical rounded at ends, subhyaline to yellow brown, 2-4-distoseptate, and measured 35.8-66.2 × 11.9-18 μm (n=50). Sclerotia were ovoid to subglobose, dark brown to black, and measured 86-461 × 85-387 μm (n=50). Colonies on PDA displayed a black center with concentric sporulation and diffused yellow pigment. Genomic DNA from the four isolates was used to amplify the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase gene (&lt;i&gt;GAPDH&lt;/i&gt;), and RNA polymerase II second largest subunit gene (&lt;i&gt;RPB2&lt;/i&gt;) with the primers V9G/ITS4, gpd1/gpd2, and RPB2-5F2/fRPB2-7cR, respectively (Marín-Felix et al., 2019). The sequences were deposited in GenBank (ITS: PV336058 to PV336061; GAPDH: PV345458 to PV345461; RPB2: PV345454 to PV345457) and showed 100% identity with the ex-type strain CPC 33016 of &lt;i&gt;Dichotomophthora basellae&lt;/i&gt; Hern.-Restr., Cheew. & Crous. Phylogenetic analysis inferred from concatenated sequences of the three genes revealed that all four isolates clustered with &lt;i&gt;D. basellae&lt;/i&gt; CPC 33016, supported by a 100% bootstrap value. Pathogenicity tests were conducted by point-inoculating conidium suspension (10&lt;sup&gt;5&lt;/sup&gt; conidia/mL) of each isolate to four leaves of 1-month-old &lt;i&gt;B. alba&lt;/i&gt; plants without wounding at 25±3°C. Control leaves were treated with sterile water. The four isolates caused expanded necrotic lesions at one day post-inoculation (dpi). Later, abundant conidiophores and conidia produced on lesions were morphologically matched the original isolates. Additionally, a conidium suspension (10&lt;sup&gt;4&lt;/sup&gt; conidia/mL) of isolate BaDpY-2 was sprayed onto three 2-month-old plants, while three control plants received sterile water. Numerous necrotic lesions appeared on leaves without sporulation at one dpi. The pathogens were successfully re-isolated from symptomatic tissues and matched the original isolates, fulfilling Koch's postulates. Base","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144064442","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>Macrophomina phaseolina</i> Causing Leaf Spot of Kersting's Groundnut [<i>Macrotyloma geocarpum</i> (Harms) Maréchal et Baudet] in Benin.","authors":"Omar Yacouba Toure, Gildas Codjo Tchemadon, Enoch G Achigan-Dako, Baloua Nebie, Léonard A C Afouda","doi":"10.1094/PDIS-08-23-1661-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-08-23-1661-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Kersting's groundnut [&lt;i&gt;Macrotyloma geocarpum&lt;/i&gt; (Harms) Maréchal et Baudet] is a neglected and underutilized nutrient-rich crop grown in Benin and in other West African countries. During a survey of Kersting's groundnut production areas between September and October 2021, leaf spot disease was observed in the West Atacora, Central Benin cotton, and clay soil zones with incidence values of 12%, 7%, and 5.4%, respectively. These leaf spots were present on young plants and became more severe as the plants grew older. Symptoms appeared as small round, brown spots surrounded by yellow halos. The center of these spots was light brown and visible on the surfaces of both the lower and upper leaves. As the disease worsened, the halo became less visible. The infected tissues were cut into small pieces, disinfected in 0.35% sodium hypochlorite for 1 min, followed by 70% alcohol for 1 min, and rinsed thrice with sterile distilled water. Each sample with 2-5 mm2 of leaf area placed in a Petri dish containing Potato Dextrose Agar (PDA). The Petri dishes were then incubated for 72h at 25°C. Pure cultures of the isolated fungus were obtained by removing the mycelial fragments and transferring them to new Petri dishes containing PDA. The Petri dishes were then incubated for 5-7 days at 25°C. Initially, the colonies looked whitish gray, but as the culture progressed, the color of the fungal colonies darkened. Thirty sclerotia from a representative isolate measured 45-165 μm in length x 35-103 μm in width (average), and the isolated fungus was identified as &lt;i&gt;Macrophomina phaseolina&lt;/i&gt;. Conidia are unicellular, hyaline, and cylindrical. For further identification, the DNA regions of the internal transcribed spacer (ITS), translation elongation factor 1-α (TEF1) region, and partial β-tubulin (TUB) gene from one representative isolate were sequenced using the primer sets ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), and T1/T22 (O'Donnell and Cigelnik, 1997). These sequences have been deposited in GenBank (accession numbers OR064031 for ITS, PV344496 for TEF-1α, and PV155704 for β-tubulin). BLAST in the NCBI database showed 99.61%, 97.50%, and 99.62% identity with &lt;i&gt;M. phaseolina&lt;/i&gt; extracted from GenBank (ITS: OR501533; TEF-1α: KF531804; and TUB: MW592282). A phylogenetic tree was constructed using the maximum likelihood method and Tamura-Nei model with 1000 bootstrap replicates in MEGA 11, which showed that the isolate belonged to the same clade as &lt;i&gt;M. phaseolina&lt;/i&gt;. To confirm the pathogenicity of the fungus, surface of the medium containing the mycelium and conidia of &lt;i&gt;M. phaseolina&lt;/i&gt; was dissolved in sterile distilled water and adjusted to a concentration of 2.10&lt;sup&gt;4&lt;/sup&gt; conidia/ml. Kersting's groundnut seeds were soaked in this conidial suspension for 1 h before being dried in the shade and sown, whereas the controls were soaked in sterile distilled water. After flowering, typical leaf spot symptoms were observ","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144049719","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 Pink Snow Mold Caused by <i>Microdochium majus</i> on Wheat in Xinjiang Uygur Autonomous Region, China.","authors":"Micong Xu, Fei Liu, Wenjun Fu, Haifeng Gao, Hao Zhang, Meixin Yang, Taiguo Liu","doi":"10.1094/PDIS-02-25-0310-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0310-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Pink snow mold (PSM) is a destructive disease that primarily occurs in cold, humid regions with persistent snow cover. The main pathogens, &lt;i&gt;Microdochium nivale&lt;/i&gt; and &lt;i&gt;M. majus&lt;/i&gt;, can infect a wide range of graminaceous crops under snow cover (Ponomareva et al., 2021). In Xinjiang, PSM has caused significant damage to wheat in years with heavy snowfall. In March 2023, a detailed survey was conducted in Nilek County, Yili Prefecture, Xinjiang Uygur Autonomous Region, to investigate prevalent diseases impacting winter wheat (&lt;i&gt;Triticum aestivum&lt;/i&gt; L.) following snow melt. Widespread infection was observed on seedlings in wheat fields, with dead leaves near the soil surface covered in a typical dusky-pink mold and the upper leaves displaying watery spots. Over 50% of the wheat exhibited these symptoms in approximately 10 hectares of the field. To identify the pathogen, 12 symptomatic leaf segments approximately 0.5 cm in length were collected, surface disinfected, placed on potato dextrose agar (PDA), and incubated at 20°C for 5 days. All symptomatic tissues yielded fungal colonies that exhibited vigorous growth, and pink to orange fluffy mycelium. After 1 week, orange-red conidial mounds appeared at the edges of the PDA. The conidia measured 2.52-6.41 × 9.23-21.27 μm (av = 4.05 × 14.79 μm; n = 60), with 1-6 septa. These morphological characteristics were consistent with previous reports and all 12 isolates were identified as &lt;i&gt;M. majus&lt;/i&gt; (Glynn et al., 2005; Hernández-Restrepo et al., 2015). Molecular confirmation was performed using four primer pairs targeting the 28S ribosomal RNA (LSU) gene (Hernández-Restrepo et al., 2015), internal transcribed spacer (ITS) (White et al., 1990), RNA polymerase II second largest subunit (RPB2) gene, and β-tubulin gene (Jewell et al., 2013). BLAST analysis showed high similarity (≥ 99.58%) with the corresponding sequences of LSU (KP858937, 832/832 bp), ITS (OM949048, 509/509 bp), RPB2 (MZ734201, 727/727 bp) and β-tubulin (JX280568, 717~719/720) of &lt;i&gt;M. majus&lt;/i&gt; in the database. The new sequences were deposited in GenBank as follows: LSU: PQ319764 to PQ319775; ITS: PQ252935 to PQ252946; RPB2: PQ261093 to PQ261104; β-tubulin: PQ261081 to PQ261092. To assess the pathogenicity of the isolates, germinated seeds of the susceptible wheat cultivar Mingxian169 were grown in test tubes containing Murashige and Skoog medium, each inoculated with a 0.8 mm diameter plug of &lt;i&gt;M. majus&lt;/i&gt;. Of the 12 isolates, seven were selected for pathogenicity test. In the control group, seeds were cultivated without the fungal inoculum. The test tubes were incubated at 20°C under a 16-hour photoperiod for 20 days, with 10 replicates per isolate (Gorshkov et al., 2020). The control showed no symptoms, whereas all inoculated treatments resulted in wheat seedlings with brown discoloration at the stem base, watery leaf spots, and dusky-pink mold in severe cases, leading to plant death. No pathogens were isolated from the c","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144009539","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 Bacterial dieback of Mango Caused by <i>Dickeya fangzhongdai</i> in China.","authors":"Zhenyu Han, Huiying Zheng, Yuqing Lin, Changping Xie, Wei Wu, Weiguo Miao, Chunhua Lin","doi":"10.1094/PDIS-03-25-0587-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0587-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Mango (Mangifera indica L.), a globally significant tropical fruit, is a major economic crop in Hainan Province, China. In September 2024, serious dieback symptoms were observed in two mango plantations (plantation 1: 18.440450 °N, 109.112387 °E; plantation 2: 18.327334 °N, 109.418158 °E) following heavy rainfall during the typhoon season in Sanya City, Hainan Province. Disease incidence reached approximately 20% in plantation 1 (7 ha) and 50% in plantation 2 (13.5 ha). Initial symptoms included water-soaked interveinal lesions at leaf bases, which expanded into black necrotic streaks along veins, progressing to petioles and stems. Severe infections resulted in partial or complete branch dieback, accompanied by white milky exudates from necrotic lesions on stems, buds, and petioles. For pathogen isolation, one leaf, one fruit and one stem sample were collected from each plantation, totaling six samples. Diseased tissue segments (5 × 5 mm) were surface-sterilized in 70% ethanol for 1 minute, minced, and suspended in sterilized water. The resulting suspensions were streaked onto Luria-Bertani (LB) agar plates and incubated at 28 °C for 2 days. Small yellow-white bacterial colonies with irregular margins were predominantly observed across all six samples. Three representative isolates (MG2-2 from plantation 1, MG3-1 and MG3-2 from plantation 2) were subjected to further characterization. The isolated bacteria were rod-shaped, gram-negative, motile, facultatively anaerobic growth, and utilized D-glucose, sucrose, D-(+)-galactose, but not D-sorbitol and maltose (Li,et al., 2024). The total DNA of these bacterial cells was extracted and used to amplify the sequences of 16S rRNA (GenBank: PQ967981-PQ967983) using primers 27f and 1492r (Heuer et al., 1997). The 16S rRNA sequences exhibited 100% identity with Dickeya fangzhongdai strain B16 (CP087226) and 99.78% identity with the D. fangzhongdai strain JS5 (NR_151914). Additionally, the fusA, dnaX, gapA, gyrA, purA, recA, rplB, rpoB, rpoD, rpoS (PQ900325 to PQ900354) genes were amplified. A maximum-likelihood phylogenetic analysis based on the concatenated sequences of the 16S rRNA and the ten genes placed the three representative isolates within a clade comprising Dickeya fangzhongdai. Pathogenicity was confirmed by inoculating six 4-year-old mango seedling (cultivar: Jinhuang) with a bacterial suspension of strain MG2-2 (OD600 = 1.0). A 10 μL bacterial suspension was injected into the stems using a sterile disposable syringe, and 5 mL of the bacterial suspension was sprayed onto the leaves. Control plants inoculated with LB medium. Seven days post-inoculation, necrotic lesions with white milky gum were observed on the stems of the inoculated mango seedlings, and partial dieback symptoms appeared on the leaves, while controls remained asymptomatic. The bacterium was reisolated from the symptomatic stems and leaves, and the isolates exhibited the same cultural, physiological, biochemical characteris","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144033072","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":"Emergence of a novel Alternaria species infecting invasive garlic mustard (<i>Alliaria petiolata</i>) in the United States.","authors":"Matthew A Tancos, Jami L Thomas, Sydney McCauslin","doi":"10.1094/PDIS-03-25-0653-SC","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0653-SC","url":null,"abstract":"<p><p>The Brassicaceae invasive weed, garlic mustard (Alliaria petiolata), is a Eurasian biennial herb that has rapidly spread across North America infesting forests and field borders, negatively impacting plant biodiversity and agroecosystem health. In 2022, a severe garlic mustard dieback event occurred in a limited section of a large, forested garlic mustard population in Maryland, United States. Diseased plants were heavily defoliated with remaining intact leaves having irregular-shaped necrotic and chlorotic lesions. Two isolates of an unknown fungal pathogen were collected, sequenced and identified as Alternaria, and confirmed to be pathogenic to garlic mustard. All inoculated garlic mustard plants rapidly developed severe symptoms within 72-hours, mimicking the symptoms observed in the field. A multilocus sequence analysis identified the two strains as a distinct species that appears to be a new monotypic sister lineage to Alternaria section Sonchi and most closely related to the Japanese Apiaceae pathogen A. triangularis. This study reports the first documentation of a novel, pathogenic Alternaria species identified from the introduced range of the invasive weed garlic mustard. In addition to its potential use as a garlic mustard bioherbicide, future studies will provide critical insights in the role non-native invasive weeds play in harboring and selecting for novel pathogenic microbes, as well as biosecurity risks to U.S. agriculture.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143987766","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":"Intrinsic Natural Resistance of Various Plant Pathogens to Ipflufenoquin, a New DHODH (Dihydroorotate Dehydrogenase)-Inhibiting Fungicide, in Relation to an Unaltered Amino Acid Sequence of the Target Site.","authors":"Hideo Ishii, Izumi Okane, Yuichi Yamaoka","doi":"10.1094/PDIS-04-24-0844-RE","DOIUrl":"10.1094/PDIS-04-24-0844-RE","url":null,"abstract":"<p><p>In recent years, increasingly stringent pesticide regulations have made the development of new chemistries challenging. Under these regulations, the new fungicide ipflufenoquin (FRAC Code 52) was first released in Japan. Its mode of action is new; it inhibits dihydroorotate dehydrogenase (DHODH), a key enzyme in the biosynthesis of pyrimidine-based nucleotides. However, because it is a single-site inhibitor, the risk of resistance developing in pathogens must be carefully considered. The risk for dual use of DHODH inhibitors in agriculture and medicine has also become a great concern because a new antifungal olorofim is under development against human pathogens now, and cross-resistance has recently been reported between ipflufenoquin and olorofim in <i>Aspergillus fumigatus</i>. In this study, the sensitivity to ipflufenoquin was examined in culture and in plants using \"baseline\" isolates, which had never been exposed to DHODH inhibitors. Isolates of <i>Alternaria alternata</i>, <i>Botrytis cinerea</i>, <i>B. elliptica</i>, <i>Colletotrichum fioriniae</i>, <i>C</i>. <i>fructicola</i>, <i>C</i>. <i>nymphaeae</i>, <i>C</i>. <i>orbiculare</i>, <i>C</i>. <i>siamense</i>, <i>C</i>. <i>tropicale</i>, <i>C</i>. <i>truncatum</i>, and <i>Sclerotinia sclerotiorum</i> were highly sensitive to ipflufenoquin in culture, but isolates of <i>Coniella vitis</i>, <i>Corynespora cassiicola</i>, <i>Pseudocercospora fuligena</i>, and <i>Rhizoctonia solani</i> were inherently resistant. Ipflufenoquin had low efficacy against <i>C</i>. <i>cassiicola</i> and <i>C</i>. <i>vitis</i> after inoculation of cucumber and grapevine leaves, respectively. To understand the mechanism of natural resistance, we analyzed the partial sequence of <i>pyrE</i> genes, which encode the DHODH enzyme, but did not find any differences in the deduced amino acids that were thought to be associated with resistance. Thus, mechanisms other than target-site mutations might be involved in the intrinsic resistance.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS04240844RE"},"PeriodicalIF":4.4,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142546758","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}