Plant disease最新文献

{"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}

{"title":"First record of natural infection by <i>Chondrostereum purpureum</i> on Rhododendron in North America.","authors":"Elisa Becker, Simon Francis Shamoun","doi":"10.1094/PDIS-02-25-0303-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0303-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Chondrostereum purpureum (Pers. ex Fr.) Pouzar infects many woody plants, including fruit trees, ornamentals, and forest species (Setliff, 2002). Its broad host range and ability to cause silver leaf disease make it a significant concern in forestry and horticulture. Although C. purpureum was found on Rhododendron spp. in the UK, New Zealand, and Nepal, it was unreported in North America (Farr et al. 1996). Rhododendron is the largest genus in the Ericaceae family, comprising over 1,000 species and more than 25,000 cultivars. Introduced to Britain in 1763, R. ponticum naturalized and became invasive in some woodlands (Cross 1975). These shrubs are susceptible to infection by Phytophthora ramorum, which can cause severe disease (Willoughby et al. 2015). Mechanical cutting removes infected material, but stumps frequently resprout. C. purpureum was evaluated to control R. ponticum resprouts. Though less effective than synthetic herbicides, it may serve as an alternative where herbicides are restricted (Willoughby et al. 2015). In January 2010, a C. purpureum specimen was collected on white-flowering Rhododendron in an urban forest (Victoria, BC, Canada; GPS: 48.477244, 123.383991). Thin, undulating, woody bracket-like basidiocarps were found on stem sides and branch crooks. Upper surfaces were brown-grey with whitish hairs; new growth on edges and smooth undersides was purple. Symptoms included discoloured stem lesions and wilting leaves on infected stems. A pure culture was obtained by plating surface-sterilized, discoloured stem wood on acidified PDA. Within 7 days at 20°C, flat, white, cottony mycelia with clamp connections emerged. Guaiacol testing confirmed laccase activity (Stalpers 1978). Purified DNA was amplified with basidiomycete-specific rDNA primers (Gardes & Bruns 1993) and compared via BLASTn (core_nt). Sequences showed 99% identity to C. purpureum voucher strains LE-BIN 2764 (OR475683.1, 631/635 nt) and PDD:91629 (GQ411519.1, 634/641 nt), and were deposited as GenBank KM652470.1. To fulfill Koch's postulates, 3-year-old R. caucasicum × ponticum 'Cunningham's White' stems were cut and inoculated with either C. purpureum (4 plants) or PDA (2 plants) as a control. Two months later, inoculated plants developed symptoms including darkening stems, yellowing and wilting leaves, and browning of leaf tips. By six months after inoculation, infected plants had wilted and died, while control plants remained symptomfree. Subsequent PCR with 'APN1' C. purpureum-specific primers (Becker et al. 1999) confirmed the presence of the pathogen only in infected plants, and not in control plants. This is the first verified North American occurrence of C. purpureum naturally infecting Rhododendron. Following verification of identity and pathogenicity, the culture and an infected stem were deposited at the Pacific Forestry Centre-Forest Pathology Herbarium (DAVFP #29828). This finding expands the known host range of C. purpureum and has important impli","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":"144033057","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":"Control of <i>Pestalotiopsis</i> Leaf Spot of Palms by Fungicides, Plant Hormones, and Biological Agents.","authors":"Muhammad Zunair Latif, Lingguang Kong, Yanke Jiang, Naila Asghar, Amer Habib, ChongChong Lu, Xinhua Ding","doi":"10.1094/PDIS-09-24-1888-RE","DOIUrl":"10.1094/PDIS-09-24-1888-RE","url":null,"abstract":"<p><p>This study investigates fungal leaf spots of palm, an ever-present threat to the nursery and floriculture industry. Fungicides, plant hormones, and biological agents were used to consider their implications for <i>Pestalotiopsis</i> leaf spot disease management in palms. A survey of different locations in Pakistan's Kasur and Faisalabad districts was conducted, collecting data on disease incidence of debilitating leaf spot disease in <i>Roystonea regia</i> (royal palm) and <i>Ravenea rivularis</i> (ravenea palm). Pathogenicity tests were performed on healthy seedlings using <i>Pestalotiopsis</i> sp. The results indicate that the fungicide Flumax with 86.11% growth inhibition of the pathogenic fungus and the biological agent <i>Trichoderma asperellum</i> with 76% growth inhibition have a significant impact in suppressing pathogen growth. Compared with the fungicide or salicylic acid (SA) application alone, the combined application of SA with 50% less fungicide (Flumax) in an integrated program significantly reduced disease severity to 5.9 and 6.2% in royal and ravenea palms, respectively. Our findings highlighted that integrated disease management (IDM) could be crucial in addressing <i>Pestalotiopsis</i> leaf spot disease. Adapting to IDM can improve the aesthetic value and profitability of palms by allowing a reduction in fungicide use while maintaining effective control of the disease.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS09241888RE"},"PeriodicalIF":4.4,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142740168","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 the Species of <i>Pythium</i> Associated with Corn Seedlings in Delaware.","authors":"John T Bickel, Madeline G Henrickson, Alyssa K Betts","doi":"10.1094/PDIS-04-24-0876-RE","DOIUrl":"10.1094/PDIS-04-24-0876-RE","url":null,"abstract":"<p><p>Corn (<i>Zea mays</i> L.) is the top grain crop by hectares grown in Delaware (DE). Increased pre- and postemergence damping-off in corn caused by <i>Pythium</i> species have been observed in recent seasons. To date, no characterization studies have been performed to understand <i>Pythium</i> species diversity in DE. Symptomatic corn seedlings were collected from 33 fields across DE in 2019 and 2020. Isolates were obtained from infected root tissues and identified by molecular sequencing. In total, 14 species were recovered: <i>P. aristosporum</i>, <i>P. arrhenomanes</i>, <i>P. attrantheridium</i>, <i>P. catenulatum</i>, <i>P. dissotocum</i>, <i>P. graminicola</i>, <i>P. inflatum</i>, <i>P. irregulare</i>, <i>P. oligandrum</i>, <i>P. periplocum</i>, <i>P. spinosum</i>, <i>P. sylvaticum</i>, <i>P. tardicrescens</i>, and <i>P. torulosum</i>. The dominant species recovered was <i>P. graminicola</i>, accounting for 66% of the isolates. Five species were screened for fungicide sensitivity to calculate the EC₅₀ of mefenoxam, ethaboxam, and picarbutrazox which are the most commonly used active ingredients to manage species of <i>Pythium</i> in corn seed treatment packages. All species tested were sensitive to mefenoxam and picarbutrazox. For ethaboxam, <i>P. torulosum</i> was the only species with an EC₅₀ value >10 μg ml^-1. Ten species were screened for fungicide sensitivity to mefenoxam, ethaboxam, or picarbutrazox at 18, 21, and 25°C. As temperatures increased, percent inhibition was reduced in 40, 70, and 80% of the species screened for sensitivity to ethaboxam, picarbutrazox, and mefenoxam, respectively. Nine of these species were screened for isolate aggressiveness in greenhouse panels to examine impact on emergence, shoot height, shoot weight, and root weight. While all species were recovered from inoculated roots, <i>P. arrhenomanes</i>, <i>P. attrantheridium</i>, <i>P. spinosum</i>, and <i>P. sylvaticum</i> had the greatest root weight reduction.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":"PDIS04240876RE"},"PeriodicalIF":4.4,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142625823","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}