Southern Corn Rust Research Articles

High-efficiency fungicide screening and field control efficacy of maize southern corn rust

Southern corn rust caused by Puccinia dothidea is becoming one of the main diseases of maize planting in China, which seriously threatens the yield of maize in China. Currently, there is no registered pesticide to control southern corn rust in China. Therefore, it is urgent to screen out efficient pesticides to control southern corn rust and reduce the harm of multistem rust to maize yield in China. In the present study, the indoor virulence determination of spore-germination method and 2 years of field efficacy tests were used to screen the fungicides with good prevention and control efficacy on maize southern rust. The results of the indoor toxicity test in 2023 showed that the EC50 of P. dothidea to benzoflumizole was 0.0085 mg/L, and the sensitivity to thifluzamide was relatively poor, with an EC50 of 1.2585 mg/L. The mixture of pyraclostrobin and benzoflumizole at a ratio of 4:1 had the optimal synergistic effect, with an EC50 of 0.0181 mg/L and a cotoxicity coefficient of 128.36. The results of the field efficacy test revealed that 60 g/ha benzovinfluconazole had a good field control effect, and the control effect was 83.09%–85.95%. The combination of 30 g/ha benzodifluconazole and 93.75 g/ha pyraclostrobin had the optimal control effect, and the control effect was 86.92%–88.58% and safe for corn. The results indicated that the application of benzovindiflupyr and its mixture with pyraclostrobin had a good effect on the prevention and control of southern corn rust, which could provide a theoretical basis for the prevention and control of southern corn rust in production and scientific medication.

QSCR4.05 and qSCR4.08, two QTLs on chromosome 4 are associated with resistance to southern corn rust in maize

Southern corn rust (SCR), caused by the fungal pathogen Puccinia polysora, is one of the most serious threats to maize production. Identification of stable QTLs is a prerequisite in maize resistance breeding programs. Bulked Segregant RNA-Seq (BSR-Seq) and QTL mapping are two effective approaches to detect genomic regions responsible for traits of interest. In the present study, BSR-Seq analysis and QTL mapping were used to detect the genomic regions/QTLs associated with the resistance to SCR. By using BSR-Seq analysis, totally 2 and 3 genomic regions were detected in F2 and BC1 populations, respectively. By using QTL mapping analysis, 3 resistance QTLs (qSCR3.02/03, qSCR4.05 and qSCR4.08) were identified in F2:3 population. Among them, qSCR4.05 and qSCR4.08 overlapped with the regions detected by using BSR-Seq method. Moreover, the two QTLs were further validated by using near isogenic lines. The identification of the two stable QTLs (qSCR4.05 and qSCR4.08) lay the foundation for further application in resistance breeding programs.

Prediction of the global occurrence of maize diseases and estimation of yield loss under climate change.

Climate change significantly impacts global maize production via yield reduction, posing a threat to global food security. Disease-related crop damage reduces quality and yield and results in economic losses. However, the occurrence of diseases caused by climate change, and thus crop yield loss, has not been given much attention. This study aims to investigate the potential impact of six major diseases on maize yield loss over the next 20 to 80 years under climate change. To this end, the Maximum Entropy model was implemented, based on Coupled Model Intercomparison Project 6 data. The results indicated that temperature and precipitation are identified as primary limiting factors for disease onset. Southern corn rust was projected to be the most severe disease in the future; with a few of the combined occurrence of all the selected diseases covered in this study were predicted to progressively worsen over time. Yield losses caused by diseases varied per continent, with North America facing the highest loss, followed by Asia, South America, Europe, Africa, and Oceania. This study provides a basis for regional projections and global control of maize diseases under future climate conditions. © 2024 Society of Chemical Industry.

Characterization of the fungal genus Sphaerellopsis associated with rust fungi: species diversity, host-specificity, biogeography, and in-vitro mycoparasitic events of S. macroconidialis on the southern corn rust, Puccinia polysora

Sphaerellopsis species are putative hyperparasites of rust fungi and may be promising biological control agents (BCA) of rust diseases. However, few detailed studies limit potential BCA development in Sphaerellopsis. Here, we explored the biogeography, host-specificity, and species diversity of Sphaerellopsis and examined the early infection stage of one species, S. macroconidialis, to infer its trophic status. We randomly screened 5,621 rust specimens spanning 99 genera at the Arthur Fungarium for the presence of Sphaerellopsis. We identified 199 rust specimens infected with Sphaerellopsis species on which we conducted morphological and multi-locus phylogenetic analyses. Five Sphaerellopsis species were recovered, infecting a total of 122 rust species in 18 genera from 34 countries. Sphaerellopsis melampsorinearum sp. nov. is described as a new species based on molecular phylogenetic data and morphological features of the sexual and asexual morphs. Sphaerellopsis paraphysata was the most commonly encountered species, found on 77 rust specimens, followed by Sphaerellopsis macroconidialis on 56 and S. melampsorinearum on 55 examined specimens. The type species, Sphaerellopsis filum, was found on 12 rust specimens and Sphaerellopsis hakeae on a single specimen. We also recovered and documented for the first time, the sexual morph of S. macroconidialis, from a specimen collected in Brazil. Our data indicate that Sphaerellopsis species are not host specific and furthermore that most species are cosmopolitan in distribution. However, S. paraphysata is more abundant in the tropics, and S. hakeae may be restricted to Australia. Finally, we confirm the mycoparasitic strategy of S. macroconidialis through in-vitro interaction tests with the urediniospores of Puccinia polysora. Shortly after germination, hyphae of S. macroconidialis began growing along the germ tubes of P. polysora and coiling around them. After 12 days of co-cultivation, turgor loss was evident in the germ tubes of P. polysora, and appressorium-like structures had formed on urediniospores. The interaction studies indicate that Sphaerellopsis species may be more effective as a BCA during the initial stages of rust establishment.

Inventarisasi Penyakit dan Analisis Pertanaman Jagung (Zea mays L.) dari Aplikasi Berbagai Jenis Biochar dan Pupuk Fosfor

Maize is a leading commodity for industrial materials and food suppliers. However, corn productivity is not maximized which is caused by several factors such as physical (climate and soil type), biology (pests, pathogens, weeds), and socio-economic factors of farmers. 25% of soil types in Indonesia are Ultisol which is characterized by low pH, available P, C-organic, and productivity. There are important maize diseases that may cause yield loss such as downy mildew, blight, rust, and midrib rot. Therefore, sustainable productivity improvements are required, specifically the application of biochar and phosphor. Biochar can increase pH, C-organic, available plant nutrients, and suppress several plant diseases. This research aimed to inventory important maize diseases, the effect of biochar, phosphor, and their interaction on disease severity and incidence, growth, production, soil pH, and C-organic. This research was designed in factorial Randomized Group Design with the factors biochar with four treatment levels included no biochar (B0), rice husk biochar (B2), corn cob biochar (B2), and cassava stalk biochar (B3) at a dose of 10 tons.ha-1 and phosphor with two treatments level included no phosphor (P0) and phosphor at a dose of 222.2 kg.ha-1 (P1). The results showed that there were four important diseases after application of biochar and phosphor, which are downy mildew (Peronisclerospora sp.), blight (Bipolaris maydis), southern corn rust (Puccinia polysora), and midrib rot (Fusarium spp.). Biochar corn cobs and cassava stems suppress the incidence of blight at 6th week. Biochars increase plant height, production, and soil pH. Interactions of biochar and phosphor increase plant stem diameter. Keywords: Biochar, Disease, Maize, Phosphor

Genome-wide association and transcriptome reveal genetic basis for Southern Corn Rust in maize

Southern corn rust (SCR) is an airborne fungal disease caused by Puccinia polysora Underw (P. polysora) that adversely impacts maize quality and yields worldwide. Screening for new elite SCR-resistant maize loci or genes has the potential to enhance overall resistance to this pathogen. Using phenotypic SCR resistance-related data collected over two years and three geographical environments, genome-wide association research was carried out in this work, which eventually identified 91 loci that were substantially correlated with SCR susceptibility. These included 13 loci that were significant in at least three environments, overlapping with 74 candidate genes (B73_RefGen_v4). Comparative transcriptomic analyses were then performed to detect genes related to SCR infection, with 2586 and 797 differentially expressed genes ultimately being identified in the resistant Qi319 and susceptible 8112 inbred lines following P. polysora infection, respectively, including 306 common genes. Subsequent integrative multi-omics investigations identified four potential candidate SCR response-related genes. Among these genes is ZmHCT9, which encodes the protein hydroxycinnamoyl transferase 9. This gene was up-regulated in susceptible inbred lines and linked to greater P. polysora resistance as confirmed through cucumber mosaic virus (CMV)-based VIGS system-mediated gene silencing. These data provide important insights into the genetic basis of maize SCR response. They are useful for researchers attempting to discover potential genes related to SCR resistance in maize.

Identification of southern corn rust resistance QTNs in Chinese summer maize germplasm via multi-locus GWAS and post-GWAS analysis.

Southern corn rust (SCR) caused by Puccinia polysora Underw is a major disease leading to severe yield losses in China Summer Corn Belt. Using six multi-locus GWAS methods, we identified a set of SCR resistance QTNs from a diversity panel of 140 inbred lines collected from China Summer Corn Belt. Thirteen QTNs on chromosomes 1, 2, 4, 5, 6, and 8 were grouped into three types of allele effects and their associations with SCR phenotypes were verified by post-GWAS case-control sampling, allele/haplotype effect analysis. Relative resistance (RRR) and relative susceptibility (RRs) catering to its inbred carrier were estimated from single QTN and QTN-QTN combos and epistatitic effects were estimated for QTN-QTN combos. By transcriptomic annotation, a set of candidate genes were predicted to be involved in transcriptional regulation (S5_145, Zm00001d01613, transcription factor GTE4), phosphorylation (S8_123, Zm00001d010672, Pgk2- phosphoglycerate kinase 2), and temperature stress response (S6_164a/S6_164b, Zm00001d038806, hsp101, and S5_211, Zm00001d017978, cellulase25). The breeding implications of the above findings were discussed.

Gene-for-gene-mediated resistance to southern corn rust in maize.

Southern corn rust (SCR) severely threatens maize production worldwide. Achieving durable control of SCR requires efficient breeding and deployment of resistant hybrids. Recently, two research teams (Chen et al. and Deng et al.) cloned two SCR resistance genes (RppC and RppK) and the cognate Avr genes (AvrRppC and AvrRppK), which will accelerate SCR resistance breeding.

Genome-wide association and genomic prediction for resistance to southern corn rust in DH and testcross populations.

Southern corn rust (SCR), caused by Puccinia polysora Underw, is a destructive disease that can severely reduce grain yield in maize (Zea mays L.). Owing to P. polysora being multi-racial, it is very important to explore more resistance genes and develop more efficient selection approaches in maize breeding programs. Here, four Doubled Haploid (DH) populations with 384 accessions originated from selected parents and their 903 testcross hybrids were used to perform genome-wide association (GWAS). Three GWAS processes included the additive model in the DH panel, additive and dominant models in the hybrid panel. As a result, five loci were detected on chromosomes 1, 7, 8, 8, and 10, with P-values ranging from 4.83×10-7 to 2.46×10-41. In all association analyses, a highly significant locus on chromosome 10 was detected, which was tight chained with the known SCR resistance gene RPPC and RPPK. Genomic prediction (GP), has been proven to be effective in plant breeding. In our study, several models were performed to explore predictive ability in hybrid populations for SCR resistance, including extended GBLUP with different genetic matrices, maker based prediction models, and mixed models with QTL as fixed factors. For GBLUP models, the prediction accuracies ranged from 0.56-0.60. Compared with traditional prediction only with additive effect, prediction ability was significantly improved by adding additive-by-additive effect (P-value< 0.05). For maker based models, the accuracy of BayesA and BayesB was 0.65, 8% higher than other models (i.e., RRBLUP, BRR, BL, BayesC). Finally, by adding QTL into the mixed linear prediction model, the accuracy can be further improved to 0.67, especially for the G_A model, the prediction performance can be increased by 11.67%. The prediction accuracy of the BayesB model can be further improved significantly by adding QTL information (P-value< 0.05). This study will provide important valuable information for understanding the genetic architecture and the application of GP for SCR in maize breeding.

Design, Synthesis, and Fungicidal Evaluation of Novel N-Methoxy Pyrazole-4-Carboxamides as Potent Succinate Dehydrogenase Inhibitors.

Succinate dehydrogenase (SDH, EC 1.3.5.1, also known as complex II) has been recognized as one of the most promising targets of fungicides. Here, based on the binding mode of pydiflumetofen with SDH, the carbon-carbon double bond was introduced into the chemical of pydiflumetofen and then produced the target compounds 6a-6o. The enzymatic inhibitory activity and structure-activity relationship (SAR) study showed that the 2-position and 4-position in terminal benzene were positive to increasing activity. Furthermore, fungicidal activity results in greenhouses indicated that compound 6o showed good control effects against wheat powdery mildew (WPM), cucumber powdery mildew (CPM), and southern corn rust (SCR), showing its broad-spectrum property. Especially, compound 6o exhibited 95 and 75% control effects against CPM and SCR at 6.25 mg/L, respectively, which are better than pydiflumetofen (80% control effects against CPM and 15% against SCR), indicating its potency that is worthy of further development.

Clonal expansion and dispersal pathways of Puccinia polysora in China.

Southern corn rust caused by Puccinia polysora Underw. is one of the most devastating diseases in the world. In recent years, SCR has been upgraded from a minor to a major disease around the world, including in China. However, little is known about its population genetics and structure in China. In this study, we analyzed 288 isolates collected from various localities during 2017 in seven Chinese provinces: Guangxi, Guangdong, Anhui, Hunan, Shandong, Henan, and Shaanxi. The isolates were analyzed using nine microsatellite markers. The population structure, genetic diversity, and reproduction mode of P. polysora were investigated based on genotype data. Strong genotypic diversity was detected and clonal reproduction was dominant. The populations collected from the pathogen's winter-reproductive regions harbored more genotypes than those collected from the pathogen's epidemic regions. The spatial differences in genotypic richness, diversity and evenness among the populations were significant, and showed a decreasing trend from south to north. Most isolates were clustered into two clonal groups. Two high-frequency genotypes, MLG1 and MLG2, were widely distributed in all populations. Our analyses confirmed that P. polysora employed clone dispersal from the pathogen's winter-reproductive regions to the pathogen's epidemic regions, and in addition to the sources from the pathogen's winter-reproductive regions, the pathogen in Anhui and Hunan might also have other sources from areas such as Taiwan, China or/and Southeast Asia, and the pathogen went through a genetic bottleneck during its dispersal. These findings provide initial insights into the reproduction mode and dispersal pathways of P. polysora in China.

Cloning southern corn rust resistant gene RppK and its cognate gene AvrRppK from Puccinia polysora

Broad-spectrum resistance has great values for crop breeding. However, its mechanisms are largely unknown. Here, we report the cloning of a maize NLR gene, RppK, for resistance against southern corn rust (SCR) and its cognate Avr gene, AvrRppK, from Puccinia polysora (the causal pathogen of SCR). The AvrRppK gene has no sequence variation in all examined isolates. It has high expression level during infection and can suppress pattern-triggered immunity (PTI). Further, the introgression of RppK into maize inbred lines and hybrids enhances resistance against multiple isolates of P. polysora, thereby increasing yield in the presence of SCR. Together, we show that RppK is involved in resistance against multiple P. polysora isolates and it can recognize AvrRppK, which is broadly distributed and conserved in P. polysora isolates.

First Report of Tar Spot on Corn Caused by Phyllachora maydis in Georgia, United States.

Tar spot is a major foliage disease of corn (Zea mays) caused by the fungus Phyllachora maydis. This disease can reduce the quality of silage, stover, husks, and grain (Valle-Torells et al. 2020). It was identified in the United States for the first time in 2015 in northern Illinois and Indiana (Ruhl et al. 2016). As of 2020, it has also been confirmed in Iowa, Michigan, Wisconsin, Ohio, Florida, Missouri, Minnesota and Pennsylvania (Telenko et al. 2020, Collins et al. 2021). In early August 2021, tar spot symptoms and signs were observed in late-planted, hybrid corn in southwestern Georgia in both Tift and Calhoun Counties. Where it occurred, incidence was nearly 100% and severity ranged from approximately 1% to 20% leaf coverage. As of November 2021, Tar spot has been confirmed in 13 counties throughout South Georgia. The symptoms on leaves were chlorotic lesions and the signs were black, raised, circular to irregular-shaped structures (stromata or clypei) ranging from 0.2 mm to 8 mm on the surface of the leaves. The stromata were present on both green and necrotic leaf tissue. Southern corn rust (Puccinia polysora) was often, but not always observed on leaves with tar spot. Microscopic observations of stromata included single and clustered ascomata (60 × magnification) that contained cylindrical, unitunicate asci with ellipsoid, hyaline, aseptate ascospores and abundant filiform paraphyses (400 × magnification). For molecular confirmation, stromata were surface sterilized with 95% ethanol and separated from the leaf tissue, then DNA was extracted using the Qiagen DNeasy Plant Mini-Kit (Qiagen, Inc., Valencia, CA). PCR was conducted with the universal ITS1 and ITS4 primers to amplify the internal transcribed spacer (ITS) region of the rDNA. The amplicons were Sanger sequenced (Genewiz, Inc., South Plainfield, NJ) and a consensus sequence of a representative lesion was deposited in GenBank (accession number OK649959). Using the BLASTN algorithm our sequence shared 100% and 99.2% coverage, and 97.2% and 98.4% similarity to P. maydis GenBank accessions MG881848 and MK184990, respectively. Phyllachora maydis is an obligate parasite that cannot be cultured, so Koch's postulates were not performed. Inoculum of P. maydis may have been transported to Georgia from Florida by wind or other weather events, but this has not been confirmed.

Genetic detection and identification of the candidate resistance gene for a major QTL resistant to Puccinia polysora in maize

Southern corn rust (SCR) is a major foliar disease in maize. Identification the major QTL and candidate resistance gene is prerequisite in maize resistance breeding programs. To identify major resistance loci/gene(s) resistant to SCR, a recombinant inbred line (RIL) population derived from a cross between 975 and 12 (resistant) and Lx9801 (susceptible) was analyzed. In total four QTLs were identified, which were located on chromosomes 5, 9 and 10, respectively. Among them, a major QTL on chromosome 10 (qSCR3), were detected in all the environments, which can explain 70.3–78.4% of the total phenotypic variation. Fine-mapping of qSCR3 delimited the QTL to an interval of ∼225 Kb. Using transcripts assembly of the 975–12 and a susceptible mutant (975-12S), an NLR gene, Zm00025ab420970, was identified as the candidate gene for qSCR3, which is a new allele/gene resistant to SCR in maize. Since qSCR3 is a major QTL resistant to SCR, it can be used as a desirable resistance source in maize resistance breeding programs.

RppM, Encoding a Typical CC-NBS-LRR Protein, Confers Resistance to Southern Corn Rust in Maize.

Southern corn rust (SCR) caused by Puccinia polysora Underw. poses a major threat to maize production worldwide. The utilization of host SCR-resistance genes and the cultivation of resistant cultivars are the most effective, economical strategies for controlling SCR. Here, we identified and cloned a new SCR resistance gene, RppM, from the elite maize inbred line Jing2416K. RppM was found to encode a typical CC-NBS-LRR protein localized in both the nucleus and cytoplasm. This gene was constitutively expressed at all developmental stages and in all tissues examined, with the strongest expression detected in leaves at the mature stage. A transcriptome analysis provided further evidence that multiple defense systems were initiated in Jing2416K, including pathogen-associated molecular pattern-triggered immunity and effector-triggered immunity, reinforcement of cell walls, accumulation of antimicrobial compounds, and activation of phytohormone signaling pathways. Finally, we developed functional Kompetitive allele-specific PCR markers for RppM using two conserved SNP sites and successfully applied these functional markers for the detection of RppM and the cultivation of resistant maize cultivars, demonstrating their great potential utility in maize breeding.

Classification of Southern Corn Rust Severity Based on Leaf-Level Hyperspectral Data Collected under Solar Illumination

Maize is one of the most important crops in China, and it is under a serious, ever-increasing threat from southern corn rust (SCR). The identification of wheat rust based on hyperspectral data has been proved effective, but little research on detecting maize rust has been reported. In this study, full-range hyperspectral data (350~2500 nm) were collected under solar illumination, and spectra collected under solar illumination (SCUSI) were separated into several groups according to the disease severity, measuring height and leaf curvature (the smoothness of the leaf surface). Ten indices were selected as candidate indicators for SCR classification, and their sensitivities to the disease severity, measuring height and leaf curvature, were subjected to analysis of variance (ANOVA). The better-performing indices according to the ANOVA test were applied to a random forest classifier, and the classification results were evaluated by using a confusion matrix. The results indicate that the PRI was the optimal index for SCR classification based on the SCUSI, with an overall accuracy of 81.30% for mixed samples. The results lay the foundation for SCR detection in the incubation period and reveal potential for SCR detection based on UAV and satellite imageries, which may provide a rapid, timely and cost-effective detection method for SCR monitoring.

Deep Learning-Based Identification of Maize Leaf Diseases Is Improved by an Attention Mechanism: Self-Attention.

Maize leaf diseases significantly reduce maize yield; therefore, monitoring and identifying the diseases during the growing season are crucial. Some of the current studies are based on images with simple backgrounds, and the realistic field settings are full of background noise, making this task challenging. We collected low-cost red, green, and blue (RGB) images from our experimental fields and public dataset, and they contain a total of four categories, namely, southern corn leaf blight (SCLB), gray leaf spot (GLS), southern corn rust (SR), and healthy (H). This article proposes a model different from convolutional neural networks (CNNs) based on transformer and self-attention. It represents visual information of local regions of images by tokens, calculates the correlation (called attention) of information between local regions with an attention mechanism, and finally integrates global information to make the classification. The results show that our model achieves the best performance compared to five mainstream CNNs at a meager computational cost, and the attention mechanism plays an extremely important role. The disease lesions information was effectively emphasized, and the background noise was suppressed. The proposed model is more suitable for fine-grained maize leaf disease identification in a complex background, and we demonstrated this idea from three perspectives, namely, theoretical, experimental, and visualization.

The RppC-AvrRppC NLR-effector interaction mediates the resistance to southern corn rust in maize

Southern corn rust (SCR), caused by the fungal pathogen Puccinia polysora, is a major threat to maize production worldwide. Efficient breeding and deployment of resistant hybrids are key to achieving durable control of SCR. Here, we report the molecular cloning and characterization of RppC, which encodes an NLR-type immune receptor and is responsible for a major SCR resistance quantitative trait locus. Furthermore, we identified the corresponding avirulence effector, AvrRppC, which is secreted by P. polysora and triggers RppC-mediated resistance. Allelic variation of AvrRppC directly determines the effectiveness of RppC-mediated resistance, indicating that monitoring of AvrRppC variants in the field can guide the rational deployment of RppC-containing hybrids in maize production. Currently, RppC is the most frequently deployed SCR resistance gene in China, and a better understanding of its mode of action is critical for extending its durability.

Investigation on types of corn rust in eastern Yunnan ecology and analysis of population genetic structure of its rusts

ABSTRACT Corn rust disease can be classified into four types: common corn rust, southern corn rust, tropical corn rust and stem corn rust. In this paper, 270 samples of corn rust gathered from Yunnan province were identified by observation of symptom and pathogen morphology, detection of specific molecular markers between Puccinia sorghi Schw and Puccinia polysora Unedrw. The results showed that 180 samples of corn rust collected form Qujing, Zhaotong, Kunming, Honghe (Mile, Kaiyuan and Jianshui) were common corn rust caused by Puccinia sorghi Schw; and 90 samples of corn rust collected form Wenshan and Honghe (Pinbian) were southern corn rust. Morphology and aspect ratio compared Puccinia sorghi Schw with Puccinia polysora Unedrw. The uredospores of Puccinia polysora Unedrw were oval and the aspect ratio of 81.6% of all uredospores from Puccinia polysora Unedrw was greater than 1.2. The uredospores of Puccinia sorghi Schw were nearly round, and their aspect ratio was 1.0-1.3. In addition, the population genetic structure of all corn rust samples was analyzed by ISSR molecular marker. Concerning Puccinia polysora Unedrw, the genetic diversity was larger in Wenshan than in Honghe. In Puccinia sorghi Schw, the population genetic diversity was larger in Zhaotong and the lowest in Kunming.

First report of the southern corn rust pathogen Puccinia polysora on Zea mays in North Dakota

Southern corn rust, caused by Puccinia polysora, is a yield-limiting disease on corn (Zea mays). As a biotrophic fungal pathogen, P. polysora requires a living host for its survival. Southern corn rust is favoured by high-temperatures and humid environmental conditions, and therefore is more prevalent in the southern United States. In August 2020, corn plants displaying signs and symptoms of southern rust were collected in a field in Grand Forks County, North Dakota. Due to its rare occurrence in the region, spores of the pathogen were isolated and analyzed morphologically, and found to be consistent with P. polysora. This identification was confirmed by PCR analysis and Sanger sequencing, and demonstrated further using Koch’s postulates. The discovery of P. polysora poses a potential threat to corn yields across North Dakota, and surveillance must be enhanced to predict possible epidemics in the future.