Bacterial blight caused by Pseudomonas syringae pv. glycines (Psg) is a widespread foliar disease. Although four Resistance to Pseudomonas syringae pv. glycinea (Rpg) 1 ~ 4 (Rpg1~4) genes that have been observed to segregate in a Mendelian pattern have been reported to confer resistance to Psg in soybean, the genetic basis of quantitative resistance to bacterial blight in soybean remains unclear. In the present study, the Psg resistance of two soybean association panels consisting of 573 and 213 lines, respectively, were phenotyped in multiple environments in 2014 - 2016. Genome-wide association study (GWAS) were performed using 2 models FarmCPU and BLINK to identify Psg resistance loci. A total of 40 soybean varieties with high level of Psg resistance were identified, and 14 quantitative trait loci (QTLs) were detected on 12 soybean chromosomes. These QTLs were identified for the first time. The majority of the QTLs were only detected in one or the other association panels, while qRPG-18-1 was detected in both association panels for at least one growing season. A total of 46 candidate Psg resistance genes were identified from the qRpg_13_1, qRPG-15-1, and qRPG-18-1 loci based on gene function annotation. In addition, we found the genomic region covering rpg1-b and rpg1-r harbored the synteny with a genomic region on chromosome 15, and identified 16 nucleotide binding site - leucine-rich repeat (NBS-LRR) genes as the candidate Psg resistance genes from the synteny blocks. This study provides new information for dissecting the genetic control of Psg resistance in soybean.

Rhizoctonia zeae was recently identified as the major Rhizoctonia species in corn and soybean fields in Nebraska and was shown to be pathogenic on corn and soybean seedlings. Fungicide seed treatments commonly used to manage seedling diseases include prothioconazole (demethylation inhibitor), fludioxonil (phenylpyrrole), sedaxane (succinate dehydrogenase inhibitor), and azoxystrobin (quinone outside inhibitor; QoI). To establish the sensitivity of R. zeae to these fungicides, we isolated this pathogen from corn and soybean fields in Nebraska during 2015 to 2017 and estimated the relative effective concentration for 50% inhibition (EC50) of a total of 91 R. zeae isolates from Nebraska and Illinois. Average EC50 for prothioconazole, fludioxonil, sedaxane, and azoxystrobin was 0.219, 0.099, 0.078, and > 100 µgml-1, respectively. In planta assays showed that azoxystrobin did not significantly reduce the disease severity on soybean (P > 0.05). The cytochrome b gene of R. zeae did not harbor any mutation known to confer QoI resistance and had a type-I intron directly after codon 143 suggesting that a G143A mutation is unlikely to evolve in this pathogen. For prothioconazole, fludioxonil, and sedaxane, EC50 of isolates did not differ significantly among years of collection (P > 0.05) and their single discriminatory concentrations were identified as 0.1 µgml-1. This is the first study to establish non-target site resistance of R. zeae to azoxystrobin and the sensitivity of R. zeae to commonly used seed treatment fungicides in Nebraska. This information will help to guide strategies for chemical control of R. zeae and monitor sensitivity shifts in future.

Few recent investigations examine coinfection interactions between fungal and viral plant pathogens. Here, we investigated coinfections between Leptosphaeria maculans and turnip mosaic virus (TuMV) in canola (Brassica napus). Different combinations of L. maculans isolate P11 and resistance breaking isolates L. maculans UWA192 and TuMV 12.1, were inoculated to three cultivars with differing pathogen resistances/susceptibilities. They were inoculated first to entire or half cotyledons 10-12 days after emergence, and second to opposite entire or half cotyledons on the same day (day 0) or 3 or 7 days afterwards. The parameters measured were L. maculans cotyledon disease index (%CDI), and TuMV systemically infected leaf symptom intensity (SI) and virus concentration (VC). Except when both day 0 inoculations were with isolate UWA192, %CDI values were supressed strongly or only weakly when isolates P11 and/or UWA192 were inoculated to plants with L. maculans single gene resistance (SGR) or polygenic resistance, respectively. However, except when isolate P11 was inoculated first and UWA192 second, these values declined after inoculation day 0 when SGR was absent. TuMV infection suppressed %CDI values, although this decrease was usually smaller following day 0 half cotyledon inoculations. When TuMV temperature sensitive extreme resistance was present and both inoculations were with TuMV, SI and VC values diminished greatly. However, the extent of this decrease was reduced when second inoculations were with L. maculans. SI and VC values were also smaller when SGR was present and second inoculations were with L. maculans. When L. maculans resistance was lacking, SI and VC values were smaller when second inoculations to entire cotyledons were with L. maculans rather than TuMV. This also occurred after second half cotyledon inoculations with isolate P11 but not isolate UWA192. Therefore, diverse inter- or intra-pathogen interactions developed depending upon host resistance, isolate combination, cotyledon inoculation approach and second inoculation timing.

Amorphophallus konjac, commonly called voodoo lily, is a cash crop widely cultivated in southwest China (Gao et al. 2022). In August 2022, leaf spot symptoms were observed in a field (1 ha) located at Fuyuan (25.67°N; 104.25°E), Yunnan, China, resulting in substantial economic losses. Brown lesions, with an incidence ranging from 20 to 40%, typically had a whitish or gray center and were surrounded by yellow halos. Microscopic observations of the spots revealed anamorphic species Cercospora chevalieri. Conidiophores were 50-150 × 4-7 μm, cylindrical, unbranched, smooth-walled, pale brown and aggregated in dense fascicles arising from a brown stroma. The conidiogenous cells were integrated, terminal or intercalary, pale brown to brown and proliferated sympodially. The conidiogenous loci were thickened and darkened, and 2-3 μm in diam. The conidia were formed singly, obclavate-cylindrical, 90-160 × 5-7 μm, with an average of 130 × 6 μm (n = 30), 6-11 septa, thin-walled, smooth, hyaline or subhyaline, straight or curved with an obtuse apex and obconically truncate base, with thickened and darkened hilum. These morphological characteristics matched those of C. chevalieri, the causal agent of leaf spot on A. paeoniifolius (Braun et al. 2014; Saccardo et al. 1913). A conidial suspension in sterile water from lesions was used to inoculate water agar, and germinated conidia were transferred to potato dextrose agar（PDA) and incubated at 27°C for 7 days. Induction of sporulation was unsuccessful using PDA, as well as malt extract agar, potato sucrose agar and synthetic nutrient-poor agar. Two out of ten isolates were selected for molecular identification and pathogenicity assay. Genomic DNA from two pure isolates (KUNCC22-12536 and KUNCC22-12537) was extracted for PCR and amplified with primers for the internal transcribed spacers (ITS: ITS1/ITS4), calmodulin (CMD: CAL228F/CAL2Rd), translation elongation factor 1-alpha (TEF1-α: 728F/986R), actin (ACT: 512F/783R), histone H3 (HIS3: CYLH3F/CYLH3R), beta-tubulin gene (TUB2: BT-1F/BT-1R) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH: Gpd1/Gpd2), respectively (Vaghefi et al. 2021). The newly generated sequences for ITS (OP719153/OP719154), CMD(OP740904/OP740905), TEF1-α (OP740910/OP740911), ACT (OP740902/OP740903), HIS3 (OP740908/OP740909), TUB2 (OP740912/OP740913), GAPDH (OP740906/OP740907) of C. chevalieri were submitted to GenBank. So far, no sequence data of C. chevalieri were available in the GenBank database. As expected, most genes (TEF1-α, ACT, CMD, HIS, TUB2 and GAPDH) showed 91 to 95% identity to their best hits within species of the genus Cercospora. The phylogenetic tree showed that sequences retrieved from two isolates obtained from the A. konjac leaf spots clustered together within Cercospora forming a strongly supported clade. To test Koch\'s postulates, ten four-month-old healthy A. konjac plants grown in pots were used for a pathogenicity test in a greenhouse. One leaf of each plant was inoculated with mycelial plugs, and one leaf was inoculated with a sterile PDA plug. These plants were enclosed in plastic bags for 72 h. Only leaves inoculated with mycelium plugs produced brown lesions, which appeared after 10 to 14 days on inoculated leaves. Control plants treated with sterile PDA plugs remained asymptomatic. This experiment was repeated twice with the same results. C. chevalieri was reisolated from infected leaves and identified based on morphology and Sanger sequencing of the ITS region. To our knowledge, this is the first report of C. chevalieri causing leaf spot on A. konjac and the first report of this species from China (Braun et al. 2014), which provides key information for diagnosis and management of this disease.

In the summer of 2021, a field survey of several tomato-growing counties in Tennessee (TN) was conducted for plants exhibiting virus-like symptoms. While scouting in September in Grainger County, one of the largest areas under tomato (Solanum lycopersicum) production in TN, leaves from six tomato plants (cv. BHN 589) growing on a farm located near Rutledge were collected and subsequently stored at -80˚C. Only one of the plants exhibited symptoms typical of tomato yellow leaf curl virus (TYLCV) infection, which included chlorosis, leaf curling, downward cupping, thickening, and mottling. Total DNA was isolated using the DNeasy Plant Mini Kit (Qiagen, Santa Clara, CA) and subjected to PCR using primers TYv2337F (5\'-ACGTAGGTCTTGACATCTGTTGAGCTC-3\') and TYc138-R: (5\'-AAGTGGGTCCCACAATTGCAAGAC-3\') and Ex-Taq polymerase (Takara Bio, Mountain View, CA) to amplify a 634-bp genomic fragment of TYLCV (Alkowni et al. 2019). Primers against tomato elongation factor-1 served as internal PCR control (Dias et al. 2023). Each primer set amplified amplicons of expected sizes; however, the TYLCV fragment was detected only from the plant exhibiting typical symptoms of infection. Amplicons were purified with the QIAquick PCR purification kit (Qiagen) and sequenced directly bi-directionally by Eurofins USA using the above primers. The resultant sequences were edited and analyzed with CLC Genomic Workbench v. 24.0.1. Blast analysis of the sequences (606 nts) against those available in GenBank showed 93 TYLCV isolates with over 95% nucleotide sequence identity. Subsequently, the full-length genome was PCR amplified using primers TYBamHIv (5\'- GGATCCACTTCTAAATGAATTTCCTG-3\') and TYBamHI2c (5\'-GGATCCCACATAGTGCAAGACAAAC-3\') (Rojas et al. 2007), ligated into pGEM-T (Promega, Madison, WI) and cloned. Plasmids were purified using QIAprep Spin Miniprep kit (Qiagen) and five independent plasmids clones were sequenced using Oxford Nanopore sequencing (v14 library chemistry & R10.4.1 flow cell) by Eurofins USA. The resultant sequences were edited and analyzed with CLC Genomic Workbench and a consensus sequence representing the full-length genome (2,781 nts) was generated and submitted to GenBank (Accession No. PP505780). Blast analysis showed over 98% nucleotide sequence identity with 100 TYLCV isolates from GenBank. The highest sequence identity of 98.6% was with the sequence of an isolate from Florida (AY530931). To the best of our knowledge, this is the first report of the occurrence of TYLCV in TN. The virus was detected in a tomato plant grown from seed. The seed transmissibility of TYLCV remains controversial (Perry 2018; and references therein); thus, the most likely source of infection in this report is transmission by rare viruliferous vectors (Bemisia tabaci). It remains unknown, however, whether TYLCV is endemic in TN, or recently introduced by mobile vectors from neighboring states. The presence of TYLCV has been reported in Alabama (Akad et al. 2007), Kentucky (de Sá et al. 2008), Mississippi (Ingram and Henn 2001), Georgia (Momol et al. 1999) and North Carolina (Polston et al. 2002). The B. tabaci vector of the virus has sporadic occurrences in crops within TN (Li et al. 2021). Tennessee is one of the leading tomato producers exporting globally with production covering over 1,300 hectares and over 430 producers (Dias et al. 2023). Because of the potential threat of TYLCV to tomato industry in the state, additional surveillance measures need to be put in place to determine TYLCV incidence.

In November and December of 2023, samples of cultivars of chrysanthemums (Chrysanthemum morifolium) from a commercial greenhouse facility within the state were submitted to the Oklahoma State University (OSU) Plant Disease and Insect Diagnostic Laboratory (Stillwater, OK). More than 300 symptomatic and asymptomatic stems with flowers and flower buds were submitted. Symptomatic samples were like those reported for aster yellows on multiple plant species, with visible phyllody and virescence. A total of 238 cultivars were processed for phytoplasma detection. Initially, samples were processed in batches based on cultivars. Each batch was made up of 3-9 flowers and/or flower buds from plants belonging to the same cultivar. Genomic DNA was extracted from batched samples using Qiagen DNeasy Plant Mini Kit (Qiagen Inc., MD) following the manufacturer\'s instruction. A qPCR assay, using 18S gene as internal control and 23S gene for phytoplasma detection was used to confirm the presence of phytoplasma (Oberhansli et al. 2011). The number of composite samples that tested positive was 67. A nested PCR assay using P1/P7 followed by R16F2n/R16R2 primers (Gundersen and Lee 1996; Smart et al. 1996; Lee et al. 1993; Lee et al. 1998) was used to retest and confirm batched samples that tested positive. PCR products were purified and sequenced at the OSU DNA Core Facility using Sanger Sequencing. A BLAST search of generated sequences on NCBI database confirmed the sequences as aster yellows phytoplasma sequences. To confirm individual plant materials from batches that were positive for aster yellows, DNA extracted from 12 samples representing different cultivars. PCR was carried out using the P1/P7 primers, followed by R16F2n/R16R2 primers as described previously. Another PCR using primer pair L15F1/MapR1 was used to amplify the partial spc operon that includes the complete secY gene (Lee et al. 2010). All PCR products were purified and sequenced at the OSU DNA Core Facility using Sanger Sequencing. BioEdit (https://thalljiscience.github.io/ ) was used to trim and generate consensus sequences of the forward and reverse sequences of all sequenced strains. All sequences have been deposited on the NCBI database (Accession numbers: PP539932-PP539940 and PQ249170-PQ249174 for 16SrRNA and secY genes respectively). The 16S rRNA sequences of strains share between 99.71-99.88% (query coverage= 99-100%, E-value= 0.0) while the secY gene share 98.33-99.49% (query coverage=100%, E-value=0.0) similarity to the 16S rRNA and secY genes of Aster yellows witches\'-broom phytoplasma (CP000061.1; Bai et al. 2006). In silico iPhyClassifier 16Sr group/subgroup analyses (Wei et al. 2007; Zhao et al. 2009) showed that these strains belonged to the Candidatus phytoplasma asteris- related strains (subgroup 16SrI-A). Although aster yellows have been reported on other crops in Oklahoma, to our knowledge, this is the first report and confirmation of Candidatus phytoplasma asteris- related strains (subgroup 16SrI-A) causing aster yellows on chrysanthemums in Oklahoma. Considering that this was recovered in one of the major cut flowers growing facilities serving Oklahoma and other states, a concerted effort is required for improved surveillance to mitigate spread of this pathogen.

Common lambsquarters (Chenopodium album Linn.) is one of the most problematic weeds associated with crops worldwide due to its fast-growing, high fecundity, and wide tolerance to various conditions. Meanwhile, C. album is also an herbaceous vegetable plant, and the leaves and young shoots of this plant are considered nutritious in the human diet (Aman et al. 2016). In September 2023, C. album plants exhibiting yellowing, stunted growth, and extensive galled root symptoms were collected from a yam field in Fengqiu (34°54\'24\"N; 114°34\'57\"E), Henan Province, China. At the selected sampling site, we randomly selected 100 C. album plants, and the disease incidence was 73% on a 0.67-ha field. A RKN species belonging to the genus Meloidogyne was found, comprising an average of 550 second-stage juveniles (J2s) from 100 g of the 10 to 30 cm soil layer. The J2s were isolated from fresh soil with a Baermann funnel. C. album roots were thoroughly washed with tap water and dissected. Nematodes at different stages were collected and morphologically identified. Females and egg masses were obtained by dissecting galls. Females were white with a protruding neck, globular to pear-shaped. The perineal patterns of females predominantly exhibited a pronounced dorsal arch, characterized by either a square or trapezoid shape, lacking obvious lateral lines. Males isolated from root galls were vermiform, annulated, and showed a trapezoidal labial region, including a high head cap that was concaved at the center of the top end in lateral view. J2s were distinguished by the conspicuous, round stylet knobs, and they had wrinkled tails with a hyaline region and an obtuse tip. Morphological measurements are described in the supplementary material. All features were consistent with the morphological characteristics of Meloidogyne incognita (Eisenback and Hirschmann 1981). Identification was accomplished with subsequent species-specific PCR and sequencing analysis. The genomic DNA of 10 individual females was extracted, and the molecular identification was carried out with M. incognita-specific primers Mi-F/Mi-R, and Inc-K14-F/Inc-K14-R (Meng et al. 2004; Randig et al. 2002). PCR amplification generated 955 and 399 bp fragments for the analyzed samples, respectively, and the amplicons were confirmed by sequence analyses. The sequences were deposited in GenBank under accession number PP836070 and PP836071. BLASTn searches showed 100% identity with available GenBank M. incognita sequences (accession no. MK410954, OQ427638). To verify reproduction on C. album, 10 healthy plants (30 days old) grown in pots with sterilized soil were inoculated with 1,000 M. incognita J2s under greenhouse conditions (light/dark: 16 h/8 h, temperature: 25-28°C). Five uninoculated plants were used as negative control. Two months after inoculation, stunted growth and root-galling symptoms were observed similar to those in field, whereas control plants remained symptomless. Many root galls and egg masses were observed in all inoculated plants. The root galling index (scale of 0 to 10; Poudyal et al. 2005) was ~7 and nematode reproduction factor (final population density/initial population density) was 5.3. The morphological features of the nematodes reisolated from root tissue closely match the description of M. incognita, fulfilling Koch\'s postulates. The pathogenicity test was carried out twice with similar results. M. incognita is an emerging disease of economic importance in many crop plants worldwide, and may cause serious economic losses (Phani et al. 2021). This widely distributed C. album plant is likely a reservoir for the pathogen and serves as an alternate host for nematodes. The findings are significant for the integrated management practices of RKNs, particularly for crops that are infested with C. album. To our knowledge, this is the first report of the nematode parasitizing C. album in China. The development of effective short- and long-term control procedures is urgently needed for managing M. incognita.

Understanding the effects of barley yellow dwarf virus (BYDV) on crop agronomic traits and yield performance helps breeders balance their selection criteria and farmers decide if pesticides should be applied to control aphids that distribute the virus. To precisely assess the deterioration of different agronomic traits and yield components caused by different levels of BYDV infection, seeds of a BYDV-sensitive barley variety cv. RGT Planet were space sown in a field plot with 10 cm between seeds and 20 cm between rows under two consecutive years. When BYDV symptoms were shown, plants with different levels (0 - 5) of BYDV infection were tagged. For accurate comparisons, the neighbouring non/less-infected plants were also tagged. At maturity, different agronomic traits and yield components were measured on those tagged plants. Results showed a strong linear correlation between BYDV severity and the performance of agronomic traits and yield components. The yield reductions ranged from 30% for the least affected (score of 1) to 90% for the severely affected (score of 5). Our research confirmed previous findings that BYDV seriously affects crop yield and the prediction of yield loss due to BYDV infection should use the percentage of plants with different BYDV symptoms.

Gummy stem blight (GSB), caused primarily by the fungus Stagonosporopsis citrulli in the southeastern United States, affects cucurbits and is particularly destructive on watermelon. Previous epidemiological models of GSB constructed for greenhouse cucumber showed leaf wetness and temperature were the primary and secondary environmental factors, respectively, that explained epidemic progress. The objective of this study was to construct a model that predicted GSB severity on field-grown watermelon based on environmental factors. Disease and weather data from six fungicide experiments in Charleston, South Carolina, in spring and fall 1997 and fall 2017, 2018, 2019, and 2022 were used as inputs. Fungicide treatments were grouped into nonsprayed, protectant (chlorothalonil and mancozeb) and GSB-specific (cyprodinil, difenoconazole and fludioxonil) applications. Cumulative hours of leaf wetness was the primary explanatory variable that modeled the increase in proportion GSB severity ≥2% across all epidemics. Incorporation of temperature or other environmental variables did not improve the model. Fit of the overall model was evaluated with k-fold cross validation, where individual experiments were each excluded from the model fitting process. Slopes of predicted disease progress curves were lowered significantly compared to the nonsprayed treatments by applications of protectant fungicides. Applying GSB-specific fungicides alternated with chlorothalonil further reduced slope values. The model successfully predicted progress of GSB epidemics under different weather patterns and fungicide applications.

Virginia creeper (Parthenocissus quinquefolia [L.] Planch.) is a deciduous flowering vine in the Vitaceae family. Native to eastern North America, it is often used ornamentally as a climbing vine or as ground cover due to its rapid growth and foliage color in the fall. In July of 2022, along exterior walls of a private property in Lanham, MD, two Virginia creeper (VC) vines were observed displaying symptoms of yellow mottling and premature reddening of leaves. To investigate the cause of these symptoms, two symptomatic leaf samples and one asymptomatic leaf samples from a third vine in the same vicinity were collected for further analysis. A Qiagen DNeasy Plant Mini Kit was used to extract total DNA from leaf tissues according to the manufacturer\'s instructions. A phytoplasma-specific real-time PCR (Hodgetts et al. 2009) was used to test the DNA extracts, which detected the presence of phytoplasmas in the two DNA samples derived from symptomatic vines. The near full-length of the 16S ribosomal RNA gene was then amplified by seminested PCR from these samples with primers P1/16S-SR followed by P1A/16S-SR (Deng, and Hiruki 1991; Lee et al. 2004) and Sanger sequenced using primers P1A and 16S-SR. Analysis of the obtained 16S rDNA sequences revealed no variation between the two plant samples, and one sequence was deposited in GenBank representing the phytoplasma strain named VC-MD1 (GenBank PP746981). A BLASTn search of the 16S rRNA gene sequence in the NCBI nucleotide database, showed 99.93% sequence identity with the phytoplasma strain AldY-WA1 (GenBank MZ557341) from red alder in Washington, a phytoplasma associated with VC plants in southern Florida (GenBank AF305198) (Harrison et al. 2001), and other strains detected in grapevines in Europe described as \"flavescence dorée\" phytoplasma (GenBank AF176319) (Davis, and Dally 2001). The virtual restriction fragment length polymorphism pattern derived from iPhyClassifier (Zhao et al. 2009), indicated that VC-MD1 is indeed a member of the 16SrV-C phytoplasma subgroup. To confirm the identification, the partial spc operon and the partial tuf gene were amplified as previously described (Lee et al. 2010; Makarova et al. 2012). Specifically, the spc operon region was amplified using a nested PCR approach with primer set L15F1A-a/MapR1 followed by L15F1A-b/MapR1A-b. Sequence data obtained from the two loci were deposited to GenBank with accession numbers PP746982 (spc) and PP746983 (tuf). BLAST searches querying the nucleotide sequences of the spc operon and tuf gene showed 95.39% and 99.05% identity, respectively, to the corresponding loci of \'Candidatus Phytoplasma rubi\' strain RS (GenBank CP114006) and hemp dogbane yellows phytoplasma strain HD1 (GenBank FR686506). Phylogenetic analysis based on secY and tuf gene sequences suggest that the VC-MD1 strain is evolutionary closest to 16SrV-C phytoplasma strains detected in various hosts in the United States, including HD1 and AldY-WA1. These North American strains cluster together on a distinct branch within the elm yellows group phytoplasmas. For the State of Maryland, this detection represents the first report of a phytoplasma strain member of the16SrV-C subgroup infecting VC plants. A phytoplasma of the same subgroup was previously detected in Florida in asymptomatic VC vines (Harrison et al. 2001). The 16S rRNA gene sequences of the two VC phytoplasma strains are nearly identical, differing by just a single nucleotide. The disease transmission vectors of the VC-MD1 strain and the prevalence of the disease in the region remains undetermined.