Plant disease最新文献

{"title":"QTL mapping and KASP Marker Development for Powdery Mildew Resistance in Watermelon.","authors":"Rahul Kumar, Bidisha Chanda, Mihir K Mandal, Jennifer Lauren Ikerd, Sandra Branham, Patrick Wechter, Phil Wadl, Amnon Levi, Azeezahmed Shaik, Umesh K Reddy, Raghupathy Karthikeyan, Chandrasekar S Kousik","doi":"10.1094/PDIS-04-25-0737-RE","DOIUrl":"10.1094/PDIS-04-25-0737-RE","url":null,"abstract":"<p><p>Powdery mildew, caused by <i>Podosphaera xanthii</i>, poses a significant threat to watermelon (<i>Citrullus lanatus</i>) cultivation. Development of resistant cultivars is one of the best strategies to manage powdery mildew. To elucidate the genetic basis of resistance, bulked segregant analysis (BSA) was conducted on an F₂ population derived from a cross between resistant (USVL608-PMR) and susceptible (USVL677-PMS) genotypes. A 570-kb region on chromosome 2 was identified using QTLseq, containing 99 single nucleotide polymorphisms (SNP) and 8 putative genes. A tightly linked kompetitive allele specific PCR (KASP) marker was developed and validated across three F2 populations (USVL608-PMR × USVL677-PMS, USVL608-PMR × 'Sugar Baby', USVL608-PMR × 'Dixie Lee'), showing a 3:1 segregation ratio and very strong linkage to resistance. Marker-disease resistance linkage was further validated in the F₃ generation of all three populations. RNAseq analysis revealed the upregulation of lipoxygenase (LOX), jasmonic acid (JA), and reactive oxygen species (ROS) pathways post-inoculation, suggesting their role in powdery mildew resistance in watermelon. The development of tightly linked KASP markers in three different backgrounds for powdery mildew resistance and a molecular understanding of disease resistance will be useful for breeding and selecting new disease-resistant watermelon cultivars.</p>","PeriodicalId":20063,"journal":{"name":"Plant disease","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144079473","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 Wilting Caused by <i>Curtobacterium flaccumfaciens</i> pv. <i>flaccumfaciens</i> on Tobacco.","authors":"Fei Dai, Yuan Xue, Quan Zhang, Shouhui Pan, Na Wang, Junxiang Zhang","doi":"10.1094/PDIS-03-25-0641-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0641-PDN","url":null,"abstract":"<p><p>Tobacco (Nicotiana tabacum) is an economically important crop, possessing a multifaceted impact on a global scale. In July 2024, wilting symptoms resembling tobacco bacterial wilt were observed on the cultivar Yunyan87 in a tobacco field (106°05'7.1″E, 26°03'9.9″N), Anshun, Guizhou, China. The infected plants initially presented chlorotic spots on the basal part of the stem, followed by wilting of leaves or stems, vascular browning, and in some cases, even death. Disease incidence is about 40%, causing yield losses over 20%. The disease samples were subjected to a moisturizing treatment overnight at room temperature. Cultured sap obtained from excised stems was diluted with sterilized water and plated onto LB agar plates. Post-incubation at 28°C for 2 days, the buff, circular, smooth colonies were picked from the plates and amplified using colony PCR with reference primers (Gonçalves et al., 2019; Osdaghi et al., 2024; Weisburg et al., 1991). The 16S rDNA sequence data (GenBank accessions PV104305 to PV104307) of three isolates (14-28-27, 14-15-19, and 15-11-17) shared 100% similarity with that of Curtobacterium faccumfaciens type strain C-S-R1-2 (GenBank accession no. MK398100) based on BLASTn search. The phylogenetic tree constructed using MEGA-X version 10.1.6 (Kumar et al., 2018) based on the recA, gyrB, atpD, ppk, and rpoB genes demonstrated that the three isolates belong to C. flaccumfaciens pv. flaccumfaciens (Cfpf). The partial sequences of the five genes were submitted to GenBank with accession numbers PV259359 to PV259373. Pathogenicity test was conducted on 55-day-old tobacco plants grown in plastic pots (8.7 cm height, 9.7 cm upper diameter, and 6.7 cm bottom diameter). Plants were inoculated as described (Urrea, et al., 2014). The plants treated with sterilized water acted as a control. The inoculated seedlings were moved to the greenhouse at 29 ± 1°C and ≥ 60% humidity. Ten days after inoculation, wilting of lower leaves and xylem discoloration were observed in inoculated plants. No symptoms appeared in the controls. Pathogenicity tests were performed three times with consistent results. The bacteria were reisolated from the inoculated plants and identified as Cfpf through colony morphology and multilocus sequence analysis of the recA, gyrB, atpD, ppk, and rpoB genes, fulfilling Koch's postulates. Cfpf, a common plant pathogen, causes the bacterial disease in Dendrobium officinale and Phaseolus vulgaris (Wang et al., 2016; Osdaghi et al., 2020). To our knowledge, this is the first report of Cfpf causing bacterial wilt in tobacco. This report broadens the host range of Cfpf and underscores the significance of this bacterium as a plant pathogen.</p>","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":"144079415","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 Leaf Spot on Sweet Potatoes Caused by <i>Acinetobacter seifertii</i> in China.","authors":"Lu Wang, Siyi Liang, Yingze Duan, Jinxin Yang, Tianhan Qin, Jing Wei, Jiahui Li, Yingzhi Zhu, Zhanbiao Li","doi":"10.1094/PDIS-03-25-0658-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-03-25-0658-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Sweet potato (Ipomoea batatas (L.) Lam), a globally essential yet underutilized staple crop, is primarily cultivated in Asia, Africa, and Latin America. In 2021, China alone accounted for 53% of global production, yielding 47 million tons and supplying essential nutrients such as proteins, minerals, and provitamin A carotenoids (Li et al. 2024). In June 2024, a new bacterial leaf spot disease was identified in a sweet potato nursery in Hengzhou City, Guangxi Province, China, with an incidence exceeding 50%. Early symptoms appeared as brownish-black necrotic spots, which progressed to widespread yellowing of stems, veins, and leaves, ultimately leading to tissue blackening and plant death. To isolate the causal agent, 12 tissue samples, including leaf blades and stalks from six symptomatic plants, were surface-sterilized (75% ethanol for 45 s, 2% NaClO for 1 min) and rinsed three times with sterilized water. A 10-fold serial dilution of homogenized tissue was prepared, and 100 μL of suspension was plated onto nutrient agar (NA) medium and incubated at 30°C for 48 h in the dark. A predominant colony type was found on purified NA, and a representative isolate, designated J-5, was selected for further study. The colonies were small, round, smooth, and white. Biochemical tests identified the isolate as gram-negative, methyl red positive, catalase positive, Voges-Proskauer negative, nonmotile, and highly salt-tolerant. The 16S rRNA gene was amplified and sequenced using primers 27F and 1492R (Lane 1991). BLAST analysis of the sequence against the NCBI database showed a 99.79% identity with Acinetobacter seifertii (GenBank accession no. OK178959.1). Additionally, partial sequences of four housekeeping genes (dnaK, fyuA, gyrB, and rpoD) were amplified and sequenced (Young et al. 2008), with sequences deposited in GenBank (16S rRNA: PQ638888; dnaK: PQ757048; fyuA: PQ757047; gyrB: PQ757043; rpoD: PQ757045). BLAST analysis confirmed a 99.15%-99.93% identity and 98%-100% coverage with A. seifertii. Pathogenicity was assessed by spraying a bacterial suspension (10⁸ CFU/mL) onto slightly scratched stems of 10 healthy sweet potato seedlings. A control group of 10 healthy sweet potato seedlings was treated with sterile nutrient broth. Seedlings were maintained in a greenhouse at 25°C with 70% relative humidity for 7 days. At seven days post-inoculation, inoculated plants developed symptoms identical to those observed in the nursery, while control plants remained asymptomatic. The pathogen was successfully reisolated from necrotic tissues and confirmed as A. seifertii through amplification in the polymerase chain reaction assay and sequencing of the 16S rRNA gene. A. seifertii, a species within the genus of the bacterium known for its ecological versatility in soil and water, plays a significant role in biodegradation (Budkum et al. 2022; Yang et al. 2016). To the best of our knowledge, this is the first report of A. seifertii that causes bacterial leaf spo","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":"144079398","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 Wilt Caused by <i>Fusarium nirenbergiae</i> on tomato (<i>Solanum lycopersicum</i>) in China.","authors":"Sheng-Li Zhang, Bingbing Fan, Bowen Jiang, Bingqian Guo, Qingyu Yin, Abdullah Gera, Jing-Jing Wang, Yanping Xu","doi":"10.1094/PDIS-02-25-0304-PDN","DOIUrl":"https://doi.org/10.1094/PDIS-02-25-0304-PDN","url":null,"abstract":"&lt;p&gt;&lt;p&gt;In May 2024, Fusarium wilt was observed in a tomato field in Weifang City, Shandong Province (36°54'6.876\" N, 118°51'17.003\" E) with an incidence of approximately 32%. The typical symptoms of the disease included leaf wilting and light brown or dirty white elongated lesions on one side of the stem. Three diseased plants were collected and labeled as FQKW24-1-FQKW24-3. Stem tissues with lesions were cut into 5 mm pieces and then surface sterilized with 75% ethanol for 45 s and 3% NaClO for 1 min. After triple rinsing with sterile distilled water, the tissue were transferred on potato dextrose agar (PDA) and incubated in darkness at 25°C for 5 days. After purification using hyphal-tip method (Leslie and Summerell. 2006), 9 isolates with consistent colony morphology were obtained. The representative strains FQKW24-1A and FQKW24-2A were selected for morphological identification. The colonies exhibited white or pale vinaceous center, with a floccose texture and abundant aerial mycelium. Reverse white or pale vinaceous in the center, lacking diffusible pigment. Microconidia on synthetic nutrient poor agar (SNA) were ellipsoidal to falcate, measuring 7.3 - 13.7 (x̄=10.1) × 2.7 - 4.7 (x̄=3.7) μm and 8.9 - 18.7(x̄=13.0) ×3.3 - 5.9 (x̄=4.6) μm for FQKW24-1A and FQKW24-2A, respectively. On carnation leaf agar (CLA), macroconidia were falcate, 3-5 septate, 33.9-50.4 (x̄=41.6) × 5.6 - 3.2 μm (x̄=4. 6) and 35.5 - 57.7 (x̄=44.7) × 3.6 - 5.8 (x̄=4.8) μm for FQKW24-1A and FQKW24-2A, respectively. The translation elongation factor 1-alpha gene (tef1), calmodulin (cmdA), and RNA polymerase II second largest subunit (rpb2) were amplified according to Wang et al. (2019). Sequences of tef1, cmdA, and rpb2 (PV018785-PV018793) of the isolates FQKW24-1A, FQKW24-2A and FQKW24-3A were submitted to GenBank. Alignment analysis of these sequences revealed similarities of 99.8% (614/615), 99.4% (871/876) and 99.8% (601/602) with the ex-type culture of F. nirenbergiae CBS 840.88 for tef1, rpb2 and cmdA, respectively. Phylogeny inferred based on the combined cmdA, tef1 and rpb2 sequences using PhyloSuite software, showed the three isolates and F. nirenbergiae were clustered into one branch. Based on morphology and phylogenetic analyses, the isolates were identified as F. nirenbergiae. Pathogenicity tests were conducted twice in an artificial climate box (12-h photoperiod at 25 °C, RH 80%) on 15-20 cm tomatoes seedlings with the pot culture. Plants were grown in sterilized soil and separately inoculated in pots with 20 ml of F. nirenbergiae spore suspension (106 conidia/ml). Control plants were mock-inoculated with water. Each treatment contained 10 plants. The first symptoms appeared 20 days after inoculation, which were a characteristic yellowing and wilting of foliage, falling off from bottom to upward. Within 3 months, stem tissues of the inoculated plants exhibited typical symptoms similar to those observed in the field. The controls remained healthy. To fulfill Koch's","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":"144079424","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 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}