Journal articles: 'Phyllachora maydis'

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Telenko, Darcy E. P., Tiffanna J. Ross, Sujoung Shim, Qinhu Wang, and Raksha Singh. "Draft Genome Sequence Resource for Phyllachora maydis—An Obligate Pathogen That Causes Tar Spot of Corn with Recent Economic Impacts in the United States." Molecular Plant-Microbe Interactions® 33, no. 7 (July 2020): 884–87. http://dx.doi.org/10.1094/mpmi-03-20-0075-a.

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Phyllachora maydis is an important fungal pathogen that causes tar spot of corn and has led to significant yield loss in the United States and other countries. P. maydis is an obligate biotroph belonging to the Sordariomycetes class of Ascomycota. Due to the challenges posed by their obligate nature, there is no genome sequence available in the Phyllachora genus. P. maydis isolate PM01 was collected from a corn field in Indiana and the genome was determined by next-generation sequencing. The assembly size is 45.7 Mb, with 56.46% repetitive sequences. There are 5,992 protein-coding genes and 59 are predicted as effector proteins. This genome resource will increase our understanding of genomic features of P. maydis and will assist in studying the corn–P. maydis interaction and identifying potential resistant candidates for corn breeding programs.

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Gómez-Montiel, Noel O., Marino González-Camarillo, Miguel A. Cantú-Almaguer, Mauro Sierra-Macías, Bulmaro Coutiño-Estrada, and Margarito Manjarrez-Salgado. "‘H-563’, HÍBRIDO DE MAÍZ TROPICAL TOLERANTE A LA ENFERMEDAD “MANCHA DE ASFALTO”." Revista Fitotecnia Mexicana 36, no. 1 (March 15, 2013): 81. http://dx.doi.org/10.35196/rfm.2013.1.81.

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En el trópico y subtrópico de México se siembran un poco más de 4.0 millones de hectáreas de maíz (Zea mays L.) (Gómez et al., 2001). En estas áreas, la enfermedad foliar “Mancha de asfalto” causada por el complejo de hongos Phyllachora maydis, Monographella maydis y Conyothyrium phyllachorae (Marino et al., 2008) afecta más de 500 mil hectáreas en los Estados de Nayarit, Jalisco, Guerrero, Chiapas y Veracruz (Hock et al., 1989). Cuando la infección es severa en la etapa de embuche o en floración, la pérdida del rendimiento de grano puede ser total, y si la enfermedad incide después de la floración el rendimiento puede disminuir en 50 % debido principalmente a que el grano no completa su desarrollo y resulta con menor peso específico (Marino et al., 2008).

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Groves, Carol L., Nathan M. Kleczewski, Darcy E. P. Telenko, Martin I. Chilvers, and Damon L. Smith. "Phyllachora maydis Ascospore Release and Germination from Overwintered Corn Residue." Plant Health Progress 21, no. 1 (January 1, 2020): 26–30. http://dx.doi.org/10.1094/php-10-19-0077-rs.

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Tar spot of corn, caused by Phyllachora maydis, has been reported in several upper Midwest states in the United States. This has led to expanded efforts to more thoroughly understand the biology of P. maydis and the epidemiology of tar spot. This study determined the potential for P. maydis ascospore release and germination from overwintered P. maydis-infected corn residues from various locations in the upper Midwest. Corn residue samples collected in the spring of 2019 from 12 fields in four states were examined. Ascospore release and germination were observed in all residue samples collected. The mean total number of ascospores released per milliliter of water ranged from 3.6 × 103 to 4.8 × 106 after 4-h incubation and 3.7 × 103 to 4.4 × 106 after 24-h incubation. The mean percent spore germination ranged from 0.7 to 24.1% after 4-h incubation and 2.4 to 24.9% after 24-h incubation. There was a significant inverse relationship between total numbers of ascospores released and the percent germination of the ascospores. Samples from Illinois consistently yielded the greatest total ascospore release but were also consistently among the samples with the lowest percent ascospore germination. Samples from Wisconsin and Indiana were among the lowest for total ascospore numbers but were among the highest for total ascospore germination. These findings provide evidence that P. maydis can overwinter in multiple areas of the upper Midwest. Future research should focus on reducing infested corn residue to reduce initial infection by P. maydis.

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McCoy, A. G., M. G. Roth, R. Shay, Z. A. Noel, M. A. Jayawardana, R. W. Longley, G. Bonito, and M. I. Chilvers. "Identification of Fungal Communities Within the Tar Spot Complex of Corn in Michigan via Next-Generation Sequencing." Phytobiomes Journal 3, no. 3 (January 2019): 235–43. http://dx.doi.org/10.1094/pbiomes-03-19-0017-r.

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Tar spot is a fungal disease complex of corn that has been destructive and yield limiting in Central and South America for nearly 50 years. Phyllachora maydis, the causal agent of tar spot, is an emerging corn pathogen in the United States, first reported in 2015 from major corn producing regions of the country. The tar spot disease complex putatively includes Monographella maydis (syn. Microdochium maydis), which increases disease damage through the development of necrotic halos surrounding tar spot lesions. These necrotic halos, termed “fish-eye” symptoms, have been identified in the United States, though Monographella maydis has not yet been confirmed. A recent surge in disease severity and loss of yield attributed to tar spot in the United States has led to increased attention and expanded efforts to understand the disease complex and how to manage it. In this study, next-generation sequencing of the internal transcribed spacer 1 (ITS1) ribosomal DNA was used to identify fungal taxa that distinguish tar spot infections with or without fish-eye symptoms. Fungal communities within tar spot only lesions were significantly different from communities having fish-eye symptoms. Two low abundance operational taxonomic units (OTUs) were identified as Microdochium sp., however, neither were associated with fish-eye symptom development. Interestingly, a single OTU was found to be significantly more abundant in fish-eye lesions compared with tar spot lesions and had a 91% ITS1 identity to Neottiosporina paspali. In addition, the occurrence of this OTU was positively associated with Phyllachora maydis fish-eye symptom networks, but not in tar spot symptom networks. Neottiosporina paspali has been reported to cause necrotic lesions on various monocot grasses. Whether the related fungus we detected is part of the tar-spot complex of corn and responsible for fish-eye lesions remains to be tested. Alternatively, many OTUs identified as Phyllachora maydis, suggesting that different isolate genotypes may be capable of causing both tar spot and fish-eye symptoms, independent of other fungi. We conclude that Monographella maydis is not required for fish-eye symptoms in tar spot of corn.

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Kleczewski, Nathan M., James Donnelly, and Russ Higgins. "Phyllachora maydis, Causal Agent of Tar Spot on Corn, Can Overwinter in Northern Illinois." Plant Health Progress 20, no. 3 (January 1, 2019): 178. http://dx.doi.org/10.1094/php-04-19-0030-br.

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Tar spot on corn (Zea mays L.), caused by the obligate fungal pathogen Phyllachora maydis Maubl., was first detected in the United States in 2015. Currently, the disease has been detected in 172 counties across Florida, Illinois, Indiana, Iowa, Michigan, Ohio, and Wisconsin. Although observations indicate that P. maydis likely overwinters in the region, this has not been conclusively proven. Samples of corn foliage heavily infected with P. maydis were recovered from two fields in northern Illinois in March 2019. Ascospores were extracted and were applied to corn seedlings under controlled greenhouse conditions. Symptoms of tar spot were observed 17 days after inoculation, and ascospores were extracted from stromata to confirm P. maydis. This is the first conclusive proof that P. maydis can overwinter the United States. We also present a preliminary greenhouse method that, if optimized, may be used to study this pathosystem under controlled conditions.

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Malvick, D. K., D. E. Plewa, D. Lara, N. M. Kleczewski, C. M. Floyd, and B. E. Arenz. "First Report of Tar Spot of Corn Caused by Phyllachora maydis in Minnesota." Plant Disease 104, no. 6 (June 2020): 1865. http://dx.doi.org/10.1094/pdis-10-19-2167-pdn.

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Ríos Herrera, Erika Natalia, Yisa María Ochoa Fuentes, Ernesto Cerna Chávez, Jerónimo Landeros Flores, Melchor Cepeda Siller, and Raúl Rodríguez Guerra. "Hongos asociados a la mancha de asfalto en el cultivo de maíz en México." Revista Mexicana de Ciencias Agrícolas 8, no. 2 (August 11, 2017): 457. http://dx.doi.org/10.29312/remexca.v8i2.65.

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El objetivo de este estudio fue identificar los hongos fitopatógenos asociados a la mancha de asfalto en maíz, en dos estados de la República Mexicana, Chiapas y Guerrero. Se realizaron muestreos dirigidos de hojas con síntomas de la enfermedad. La identificación preliminar de los patógenos asociados con los síntomas, se realizó mediante criterios morfológicos con claves dicotómicas y se corroboró mediante la amplificación de los espacios internos de transcripción (ITS) secuenciados y analizados en la base de datos del NCBI. En ambos estados se encontró a Phyllachora maydis, y Curvularia lunata como primer reporte de la asociación a este síndrome denominado mancha de asfalto.

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Lipps, Sarah, Damon Smith, Darcy Telenko, Pierce Paul, Nathan Kleczewski, and Tiffany Jamann. "Identification of resistance for Phyllachora maydis of maize in exotic‐derived germplasm." Crop Science 62, no. 2 (February 12, 2022): 859–66. http://dx.doi.org/10.1002/csc2.20709.

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Dalla Lana, F., D. E. Plewa, E. S. Phillippi, D. Garzonio, R. Hesterman, N. M. Kleczewski, and P. A. Paul. "First Report of Tar Spot of Maize (Zea mays), Caused by Phyllachora maydis, in Ohio." Plant Disease 103, no. 7 (July 2019): 1780. http://dx.doi.org/10.1094/pdis-01-19-0070-pdn.

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Ruhl, G., M. K. Romberg, S. Bissonnette, D. Plewa, T. Creswell, and K. A. Wise. "First Report of Tar Spot on Corn Caused by Phyllachora maydis in the United States." Plant Disease 100, no. 7 (July 2016): 1496. http://dx.doi.org/10.1094/pdis-12-15-1506-pdn.

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Valle-Torres, J., T. J. Ross, D. Plewa, M. C. Avellaneda, J. Check, M. I. Chilvers, A. P. Cruz, et al. "Tar Spot: An Understudied Disease Threatening Corn Production in the Americas." Plant Disease 104, no. 10 (October 2020): 2541–50. http://dx.doi.org/10.1094/pdis-02-20-0449-fe.

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Tar spot of corn has been a major foliar disease in several Latin American countries since 1904. In 2015, tar spot was first documented in the United States and has led to significant yield losses of approximately 4.5 million t. Tar spot is caused by an obligate pathogen, Phyllachora maydis, and thus requires a living host to grow and reproduce. Due to its obligate nature, biological and epidemiological studies are limited and impact of disease in corn production has been understudied. Here we present the current literature and gaps in knowledge of tar spot of corn in the Americas, its etiology, distribution, impact and known management strategies as a resource for understanding the pathosystem. This will in turn guide current and future research and aid in the development of effective management strategies for this disease.

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González-Diéguez, David O., and Carlos Orozco. "Identificación de marcadores moleculares (SNP) y genes candidatos asociados a la tolerancia genética al complejo mancha de asfalto en variedades nativas de maíz (Zea mays L.)." Ciencia, Tecnología y Salud 7, no. 2 (February 15, 2021): 218–35. http://dx.doi.org/10.36829/63cts.v7i2.826.

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El complejo mancha de asfalto (CMA) en maíz (Zea mays L.), causado por los hongos Phyllachora maydis Maubl. y Monographella maydis Müller & Samuels, es una enfermedad de importancia económica en Guatemala, causando pérdida en el rendimiento entre 30 a 50%, inclusive del 100% si las condiciones son favorables. El objetivo de esta investigación fue identificar marcadores de un solo nucleótido o SNP (Single Nucleotide Polymorphism, por sus siglas en inglés) y genes candidatos asociados a la tolerancia genética al CMA. Para ello se analizaron 463 poblaciones nativas y 329,692 SNP, y se compararon dos modelos genómicos, single marker y BayesB, para la identificación de regiones asociadas a la tolerancia genética al CMA. Se identificaron 40 marcadores SNP asociados significativamente a la tolerancia genética al CMA con ambos modelos. La proporción de variación fenotípica total explicada (PVE) por los 40 SNPs fue de 56%, atribuida a efectos genéticos aditivos. Múltiples genes de resistencia fueron identificados en las regiones señaladas por los marcadores SNP, siendo sus principales funciones receptores y transductores de señal, factores de transcripción que regulan positivamente la expresión de genes de resistencia y genes de la familia kinasa, por lo que potencialmente están involucrados en el mecanismo de defensa al CMA.

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Mueller, Daren S., Kiersten A. Wise, Adam J. Sisson, Tom W. Allen, Gary C. Bergstrom, Kaitlyn M. Bissonnette, Carl A. Bradley, et al. "Corn Yield Loss Estimates Due to Diseases in the United States and Ontario, Canada, from 2016 to 2019." Plant Health Progress 21, no. 4 (January 1, 2020): 238–47. http://dx.doi.org/10.1094/php-05-20-0038-rs.

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Annual reductions in corn (Zea mays L.) yield caused by diseases were estimated by university Extension-affiliated plant pathologists in 26 corn-producing states in the United States and in Ontario, Canada, from 2016 through 2019. Estimated loss from each disease varied greatly by state or province and year. Gray leaf spot (caused by Cercospora zeae-maydis Tehon & E.Y. Daniels) caused the greatest estimated yield loss in parts of the northern United States and Ontario in all years except 2019, and Fusarium stalk rot (caused by Fusarium spp.) also greatly reduced yield. Tar spot (caused by Phyllachora maydis Maubl.), a relatively new disease in the United States, was estimated to cause substantial yield loss in 2018 and 2019 in several northern states. Gray leaf spot and southern rust (caused by Puccinia polysora Underw.) caused the most estimated yield losses in the southern United States. Unfavorable wet and delayed harvest conditions in 2018 resulted in an estimated 2.5 billion bushels (63.5 million metric tons) of grain contaminated with mycotoxins. The estimated mean economic loss due to reduced yield caused by corn diseases in the United States and Ontario from 2016 to 2019 was US$55.90 per acre (US$138.13 per hectare). Results from this survey provide scientists, corn breeders, government agencies, and educators with data to help inform and prioritize research, policy, and educational efforts in corn pathology and disease management.

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McCoy, A. G., M. K. Romberg, E. R. Zaworski, A. E. Robertson, A. Phibbs, B. D. Hudelson, D. L. Smith, et al. "First Report of Tar Spot on Corn (Zea mays) Caused by Phyllachora maydis in Florida, Iowa, Michigan, and Wisconsin." Plant Disease 102, no. 9 (September 2018): 1851. http://dx.doi.org/10.1094/pdis-02-18-0271-pdn.

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Deras F., Héctor R., Reina Flor De Serrano, Carlos Mejía, and Wenceslao Moreno. "Evaluación de híbridos tri-lineales de maíz (Zea mays L.), por su reacción al Complejo Mancha de asfalto causada por los patógenos (Phyllachora maydis, Monographella maydis y Coniothyrium phyllacorae)." Producción Agropecuaria y Desarrollo Sostenible 3 (February 1, 2015): 77–88. http://dx.doi.org/10.5377/payds.v3i0.3973.

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Durante 2013 se instaló un ensayo con el objetivo de identificar híbridos de maíz por su reacción a la enfermedad foliar conocida como Complejo Mancha de asfalto5. El ensayo se condujo en trece localidades de diferentes departamentos de El Salvador, teniendo nueve de ellas antecedentes de la enfermedad. La evaluación se desarrolló entre los meses de mayo a noviembre.Se utilizó el diseño experimental alpha-látice 4*5, con tres repeticiones y 20 tratamientos. Los tratamientos se conformaron de 17 híbridos tri-lineales experimentales y tres híbridos comerciales como testigo. Se realizó un análisis de varianza por localidad y combinado, especialmente para porcentaje de mazorcas con mala cobertura; porcentaje de pudrición de mazorcas totales y porcentaje de mazorcas podridas afectadas por el complejo y rendimiento. Se utilizó el modelo AMMI Biplot GGE-SREG para determinar la interacción genotipo-ambiente, encontrándose significancia para dicha interacción; así como para los factores individuales en las que existió significancia al 1% de probabilidad. En diez de las 13 localidades en la que se realizó el estudio, no existió presencia de la enfermedad. Pero en las restantes, la enfermedad incidió drásticamente sobre el rendimiento. El híbrido con mayor provecho en localidades sin presencia de la enfermedad fue DK-357 con 8.35 t ha-1, seguido por HES-3 y HES-1 con 7.75 y 7.1t ha-1 respectivamente. En las localidades donde hubo presencia de la enfermedad, los mejores híbridos fueron: HES-3, HES-17 y DK-357, con rendimientos de 4.04, 4.01 y 4t ha-1 respectivamente.Los porcentajes de mazorcas afectadas por la enfermedad para estos híbridos fueron 50.3%, 46.8% y 60.7%, respectivamente. El híbrido menos afectado por la enfermedad fue HES-1, con 42.9% de mazorcas infectadas y rendimiento de 3.85 t ha-1. El análisis de estabilidad reportó como los híbridos más estables a HES-27 y HES-13. Los resultados obtenidos muestran a HES-1 como híbrido tolerante y a HES-3 como resistente.Producción Agropecuaria y Desarrollo Sostenible, Vol. 3, 2014: 77-88

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Hernández-Ramos, Lervin, José S. Sandoval-Islas, George Mahuku, Ignacio Benítez-Riquelme, and Serafín Cruz-Izquierdo. "GENÉTICA DE LA RESISTENCIA AL COMPLEJO MANCHA DE ASFALTO EN 18 GENOTIPOS TROPICALES DE MAÍZ." Revista Fitotecnia Mexicana 38, no. 1 (February 23, 2015): 39. http://dx.doi.org/10.35196/rfm.2015.1.39.

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El complejo mancha de asfalto (CMA) del maíz (Zea mays L.), inducido por los hongos Phyllachora maydis Maubl., y Monographella maydis Müller & Samuels, es una enfermedad de importancia económica, debido a que provoca severas pérdidas en el rendimiento y deteriora la calidad del forraje. El mejoramiento genético de la resistencia del hospedante a través de la generación de genotipos resistentes representa la medida de control más eficiente para la enfermedad. Se conoce poco respecto a la base genética de la resistencia al CMA, por lo cual se determinaron las aptitudes combinatoria general (ACG) y específica (ACE) de 18 líneas endogámicas S7 mediante el Modelo I de frecuencias fijas de Griffing, bajo el Método II que incluyó las 18 líneas más sus 153 cruzas directas posibles. El diseño experimental fue bloques completos al azar, en 4 ambientes diferentes ubicados en los Estados de Veracruz, Guerrero, Puebla y Oaxaca. Tanto la ACG como la ACE tuvieron efecto significativo (P < 0.01), por lo que, tanto los efectos génicos de dominancia como los de aditividad son importantes en la resistencia a la enfermedad. Sin embargo, la ACG fue 45 veces más grande que la ACE, de modo que los efectos génicos aditivos son más importantes, por lo que diversos genes no alelicos están involucrados en resistencia al CMA en maíz, por lo tanto es posible acumular diversos genes en un solo genotipo mediante métodos de mejoramiento genético. Los híbridos más resistentes fueron los derivados de dos líneas con ACG y ACE negativa. Las mejores líneas para producir híbridos altamente resistentes fueron CML-329, CLRCW-105-B y [M37W/ZM607]. La selección recurrente podría ser el método de mejoramiento más útil para acumular e incrementar los niveles de resistencia a la enfermedad en poblaciones sintéticas o compuestas. Los efectos de dominancia fueron los más importantes en algunas cruzas específicas.

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"Phyllachora maydis. [Distribution map]." Distribution Maps of Plant Diseases, October (November 18, 2021). http://dx.doi.org/10.1079/dmpd/20210455189.

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Abstract A new distribution map is provided for Phyllachora maydis Maublanc. Sordariomycetes: Phyllachorales: Phyllachoraceae. Host: maize (Zea mays). Information is given on the geographical distribution in North America (Canada, Ontario, Costa Rica, Dominican Republic, El Salvador, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Panama, Puerto Rico, Trinidad and Tobago, US Virgin Islands, USA, Florida, Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, Wisconsin), and South America (Bolivia, Colombia, Ecuador, Peru, Venezuela).

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"Phyllachora maydis (black spot of maize)." CABI Compendium CABI Compendium (January 7, 2022). http://dx.doi.org/10.1079/cabicompendium.40876.

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This datasheet on Phyllachora maydis covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Seedborne Aspects, Natural Enemies, Impacts, Prevention/Control, Further Information.

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"Phyllachora maydis (black spot of maize)." PlantwisePlus Knowledge Bank Species Pages (January 7, 2022). http://dx.doi.org/10.1079/pwkb.species.40876.

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Helm, Matthew, Raksha Singh, Rachel R. Hiles, Namrata Jaiswal, Ariana Myers, Anjali S. Iyer-Pascuzzi, and Stephen Goodwin. "Candidate effector proteins from the maize tar spot pathogen Phyllachora maydis localize to diverse plant cell compartments." Phytopathology®, July 11, 2022. http://dx.doi.org/10.1094/phyto-05-22-0181-r.

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Most fungal pathogens secrete effector proteins into host cells to modulate their immune responses, thereby promoting pathogenesis and fungal growth. One such fungal pathogen is the ascomycete Phyllachora maydis, which causes tar spot disease on leaves of maize (Zea mays). Sequencing of the P. maydis genome revealed 462 putatively secreted proteins of which 40 contain expected effector-like sequence characteristics. However, the subcellular compartments targeted by P. maydis effector candidate (PmECs) proteins remain unknown and it will be important to prioritize them for further functional characterization. To test the hypothesis that PmECs target diverse subcellular compartments, cellular locations of super Yellow Fluorescent Protein (sYFP)-tagged P. maydis effector candidate proteins were identified using a Nicotiana benthamiana-based heterologous expression system. Immunoblot analyses showed that most of the PmEC-fluorescent protein fusions accumulated protein in N. benthamiana, indicating the candidate effectors could be expressed in dicot leaf cells. Laser-scanning confocal microscopy of N. benthamiana epidermal cells revealed most of the P. maydis putative effectors localized to the nucleus and cytosol. One candidate effector, PmEC01597, localized to multiple subcellular compartments including the nucleus, nucleolus, and plasma membrane while an additional putative effector, PmEC03792, preferentially labelled both the nucleus and nucleolus. Intriguingly, one candidate effector, PmEC04573, consistently localized to the stroma of chloroplasts as well as stroma-containing tubules (stromules). Collectively, these data suggest effector candidate proteins from P. maydis target diverse cellular organelles and may thus provide valuable insights into their putative functions as well as host processes potentially manipulated by this fungal pathogen.

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Rocco da Silva, Camila, Jill Check, Joshua S. MacCready, Amos E. Alakonya, Robert L. Beiriger, Kaitlyn M. Bissonnette, Alyssa Collins, et al. "Recovery Plan for Tar Spot of Corn, Caused by Phyllachora maydis." Plant Health Progress, July 19, 2021. http://dx.doi.org/10.1094/php-04-21-0074-rp.

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Tar spot is a foliar disease of corn threatening production across the Americas. The disease was first documented in Mexico in 1904 and is now present in 15 additional countries throughout Central America, South America, and the Caribbean. Researchers and growers in Central America, South America, and the Caribbean consider tar spot to be a disease complex caused by multiple fungal pathogens. When environmental conditions are conducive for infection, these regions have experienced yield losses can reach up to 100%. In 2015, tar spot was detected in the U.S. for the first time in Illinois and Indiana. Since that time tar spot has spread across the U.S. corn-growing region, and the disease has been found in Florida, Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, Pennsylvania, and Wisconsin. In 2020, tar spot was also found in southwest Ontario, Canada. Losses in the U.S. due to tar spot totaled an estimated 241 million bushels from 2018 to 2020. With the potential to continue to spread across the U.S. corn-growing states, much greater losses could result when environmental conditions are conducive.

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Pandey, Laxmi, Caroline Burks, Luisa Gómez Londoño, Larry Newsom, Jason Brock, Robert Kemerait, and Marin Brewer. "First Report of Tar Spot on Corn caused by Phyllachora maydis in Georgia, USA." Plant Disease, January 25, 2022. http://dx.doi.org/10.1094/pdis-11-21-2456-pdn.

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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.

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Telenko, Darcy E. P., Martin I. Chilvers, Keith Ames, Adam Byrne, Jill C. Check, Camila Rocco Da Silva, W. Scott Jay, et al. "Fungicide efficacy during a severe epidemic of tar spot on corn in the United States and Canada in 2021." Plant Health Progress, April 25, 2022. http://dx.doi.org/10.1094/php-02-22-0012-br.

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A 2021 epidemic of tar spot of corn caused by Phyllachora maydis led to significant yield losses in the midwestern United States and Ontario, Canada. Uniform fungicides trials consisting of nine foliar fungicides applied at the tassel (VT) or silk (R1) growth stage were evaluated for tar spot management in five field trials in the midwestern U.S. and Ontario, Canada in 2021. All nine foliar fungicide treatments significantly reduced tar spot severity, but only Delaro Complete (prothioconazole + fluopyram+ trifloxystrobin), Revytek (mefentrifluconazole + pyraclostrobin + fluxapyroxad), and Veltyma (mefentrifluconazole + pyraclostrobin) protected yield compared to the non-treated control.

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Kleczewski, Nathan M., Diane E. Plewa, Kaitlyn M. Bissonnette, Norman D. Bowman, Jan M. Byrne, Joseph LaForest, Felipe Dalla-Lana, et al. "Documenting the Establishment, Spread, and Severity of Phyllachora maydis on Corn, in the United States." Journal of Integrated Pest Management 11, no. 1 (January 1, 2020). http://dx.doi.org/10.1093/jipm/pmaa012.

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Abstract Tar spot on corn, caused by the fungus (Phyllachora maydis Maubl. [Phyllachorales: Phyllachoraceae]), is an emerging disease in the United States. In 2018 and 2019, significant but localized epidemics of tar spot occurred across the major corn producing region of the Midwest. After being first detected in 2015, tar spot was detected in 135 and 139 counties where the disease was not previously detected in 2018 and 2019, respectively, and is now established across 310 counties across the United Sates. Foliage with signs (stromata) of P. maydis and symptoms of tar spot were collected from 128 fields in 2018 and 191 fields in 2019, across seven states. Samples were assessed for severity of fungal stromata (percent leaf area covered with stromata) on foliage and the incidence of fisheye lesions (proportion of lesions with fisheye symptoms) associated with fungal stromata. Stromatal severity on samples in 2018 ranged from 0.5 to 67% and incidence of fisheye lesions ranged from 0 to 12%, whereas in 2019, stromatal severity ranged from 0.1 to 35% and incidence of fisheye lesions ranged from 0 to 80%, with 95% of samples presenting less than 6% incidence of fisheye lesions. Tar spot has spread substantially from where it was first reported in the United States. Collaborative efforts to monitor the spread and educate clientele on management are essential as this disease spreads into new areas.

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Vinces-Tachong, Rómulo Enrique, Mayra Carolina Vélez-Ruiz, Ramiro Remigio Gaibor-Fernández, and Favio Eduardo Herrera-Eguez. "Implementación del procesamiento de imágenes para la evaluación de la mancha de asfalto (Phyllachora maydis) en maíz (Zea mays)." REVISTA TERRA LATINOAMERICANA 40 (November 19, 2022). http://dx.doi.org/10.28940/terra.v40i0.1066.

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La enfermedad conocida como mancha de asfalto (Phyllachora maydis) afecta al cultivo de maíz (Zea mays). Esta enfermedad causa lesiones en las hojas que al progresar pueden ocasionar la muerte de la planta. Existen diferentes métodos para evaluar el progreso de una enfermedad en las plantas. Generalmente, se utilizan escalas de evaluación visual; sin embargo, su uso es bastante subjetivo. El procesamiento de imágenes ha sido utilizado como una alternativa para la evaluación de enfermedades. Este método evita sesgos y errores durante las evaluaciones. El objetivo de este ensayo fue utilizar el aplicativo telefónico Leaf Doctor como una alternativa a la evaluación de la enfermedad producida por P. maydis. Para el experimento se utilizó un diseño de bloques completamente al azar. Se sembraron tres variedades de maíz y se evaluó el nivel de tolerancia a la mancha de asfalto al ser tratadas con diferentes dosis de silicio. Las diferentes dosis de silicio no reducen la enfermedad, sin embargo, fue posible determinar aumento de la producción de maíz en dosis de silicio de 252 kg ha-1. Los resultados indican que el programa puede considerarse como una alternativa ef iciente para evaluar la mancha de asfalto debido a la alta correlación con la escala de evaluación visual (R2: 0.77-0.94). La variedad más resistente a la enfermedad fue INIAP-551.

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Collins, A. A., A. Y. Bandara, S. R. May, D. K. Weerasooriya, and P. D. Esker. "First Report of Tar Spot of Maize (Zea mays) Caused by Phyllachora maydis in Pennsylvania." Plant Disease, September 12, 2021, PDIS—11–20–2456. http://dx.doi.org/10.1094/pdis-11-20-2456-pdn.

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Telenko, Darcy E. P., Martin I. Chilvers, Adam Byrne, Jill Check, Camila Rocco Da Silva, Nathan Kleczewski, Emily Roggenkamp, Tiffanna J. Ross, and Damon L. Smith. "Fungicide efficacy on tar spot and yield of corn in the Midwestern United States." Plant Health Progress, January 12, 2022. http://dx.doi.org/10.1094/php-10-21-0125-rs.

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Tar spot of corn caused by Phyllachora maydis has recently led to significant yield losses in the eastern corn belt of the Midwestern United States. Foliar fungicides containing quinone outside inhibitors(QoI), demethylation inhibitors(DMI), and succinate dehydrogenase inhibitors(SDHI) are commonly used to manage foliar diseases in corn. To mitigate the losses from tar spot thirteen foliar fungicides containing single or multiple modes of action (MOA/FRAC groups) were applied at their recommended rates in a single application at the standard tassel/silk growth stage timing to evaluate their efficacy against tar spot in a total of eight field trials in Illinois, Indiana, Michigan, and Wisconsin during 2019 and 2020. The single MOA fungicides included either a QoI or DMI. The dual MOA fungicides included a DMI with either a QoI or SDHI, and fungicides containing three MOAs included a QoI, DMI, and SDHI. Tar spot severity estimated as the percentage of leaf area covered by P. maydis stroma of the non-treated control at dent growth stage ranged from 1.6 to 23.3% on the ear leaf. Averaged across eight field trials all foliar fungicide treatments reduced tar spot severity, but only prothioconazole+trifloxystrobin, mefentrifluconazole+pyraclostrobin+fluxapyroxad, and mefentrifluconazole+pyraclostrobin significantly increased yield over the non-treated control. When comparing fungicide treatments by the number of MOAs foliar fungicide products that had two or three MOAs decreased tar spot severity over not treating and products with one MOA. The fungicide group that contained all three MOAs significantly increased yield over not treating with a fungicide or using a single MOA.

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Solórzano, José E., Christian Cruz, Brett E. Arenz, Dean Malvick, and Nathan Kleczewski. "Tar Spot of Corn: A Diagnostic and Methods Guide." Plant Health Progress, August 1, 2022. http://dx.doi.org/10.1094/php-04-22-0033-dg.

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Tar spot of corn is an emerging plant disease in the continental U.S. and Canada caused by the fungal pathogen Phyllachora maydis Maubl. Tar spot has been known to occur in Mexico, the Caribbean, and Central and South America since the early-mid 1900s. In 2015, it was reported for the first time in the continental U.S. Since that time, tar spot has spread across corn-producing areas in the U.S. with epidemics as recent as 2021 resulting in significant yield losses. Although tar spot has been known to affect corn for over a century in the Americas, the biology of the pathogen, etiology, and epidemiology of the disease are not well understood. Additionally, symptoms and signs of tar spot resemble other foliar diseases and abiotic disorders of corn, which may lead to misdiagnosis. In this paper, we provide a brief description of current knowledge about tar spot of corn, including pathogen taxonomy, host range, symptoms and signs, specimen storage, pathogenicity testing, diagnostic protocols, and geographic distribution. This information will be useful to diagnosticians, researchers, and other professionals working with this disease.

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Kleczewski, Nathan M., and Norman D. Bowman. "An Observation of Corn Tar Spot Dispersal from Agricultural Fields to an Isolated Urban Plot." Plant Health Progress, December 10, 2020. http://dx.doi.org/10.1094/php-10-20-0082-br.

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Tar spot of corn is a fairly new disease to the United States, and since its introduction in 2015 it has spread to over 310 counties across nine states. Little is understood of the biology and epidemiology of the causative agent of tar spot of corn, Phyllachora maydis. Published research from Latin America indicates that spores can only travel a distance of 75 m; however, rapid progression and spread in the United States, in addition to widespread observations of top-down infection, indicate distal dispersal is likely more important. We observed an isolated plot of decorative corn in an urban setting, isolated from agricultural fields. We assessed nearby fields for crop, tar spot, cropping history, and distance from the urban site. Based on our observations, the propagules infecting the urban plot arrived from at least 560 m if from corn residue, and from at least 1,249 m if from active infections from nearby corn. Although this observation is not replicated, it does indicate that dispersal values from Latin America may not reflect the potential dispersion in Midwest topographies.

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Díaz-Morales, Federico, Carlos De León-García De Alba, Cristian Nava-Díaz, and María Del Carmen Mendoza-Castillo. "Inducción de resistencia a Puccinia sorghi y complejo mancha de asfalto (Phyllachora maydis y otros) en maíz (Zea mays)." Revista Mexicana de Fitopatología, Mexican Journal of Phytopathology 37, no. 1 (October 20, 2018). http://dx.doi.org/10.18781/r.mex.fit.1807-6.

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Para demostrar la eficiencia de productos inductores de la resistencia a enfermedades en maíz, en 2016 y 2017 se establecieron ensayos en el Campo Experimental de la Universidad Autónoma del Estado de México, Campus Toluca, con el híbrido de maíz comercial BG1384W, donde se estudió la eficiencia de seis agroquímicos como inductores de resistencia, incluyendo Fosetil-Al, Acibenzolar-S-metil, Bacillus subtilis, Tebuconazole + Trifloxystrobin, Proteína Harpin y Clotianidin + Bacillus firmus, para controlar la roya común (Puccinia sorghi Schw.) y el complejo de la mancha de asfalto (Phyllachora maydis Maubl. y otros), con dos formas de aplicación (al suelo y foliar) y tres dosis (comercial recomendada, mitad de la recomendada y recomendada más 50%) para cada agroquímico. Se registraron datos agronómicos en un ensayo de rendimiento y la severidad de las mencionadas enfermedades. En 2016, la severidad no fue afectada por ninguno de los agroquímicos, aunque se incrementó el rendimiento con las aplicaciones de Fosetil-Al y Acibenzolar-S-metil. En 2017, Bacillus subtilis disminuyó la severidad de la roya, mientras que Fosetil-Al redujo la severidad del complejo mancha de asfalto, pero mostró el rendimiento más bajo.

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Willcox, Martha C., Juan A. Burgueño, Daniel Jeffers, Enrique Rodriguez-Chanona, Armando Guadarrama-Espinoza, Zakaria Kehel, Daniel Chepetla, et al. "Mining alleles for tar spot complex resistance from CIMMYT's maize Germplasm Bank." Frontiers in Sustainable Food Systems 6 (August 2, 2022). http://dx.doi.org/10.3389/fsufs.2022.937200.

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The tar spot complex (TSC) is a devastating disease of maize (Zea mays L.), occurring in 17 countries throughout Central, South, and North America and the Caribbean, and can cause grain yield losses of up to 80%. As yield losses from the disease continue to intensify in Central America, Phyllachora maydis, one of the causal pathogens of TSC, was first detected in the United States in 2015, and in 2020 in Ontario, Canada. Both the distribution and yield losses due to TSC are increasing, and there is a critical need to identify the genetic resources for TSC resistance. The Seeds of Discovery Initiative at CIMMYT has sought to combine next-generation sequencing technologies and phenotypic characterization to identify valuable alleles held in the CIMMYT Germplasm Bank for use in germplasm improvement programs. Individual landrace accessions of the “Breeders' Core Collection” were crossed to CIMMYT hybrids to form 918 unique accessions topcrosses (F1 families) which were evaluated during 2011 and 2012 for TSC disease reaction. A total of 16 associated SNP variants were identified for TSC foliar leaf damage resistance and increased grain yield. These variants were confirmed by evaluating the TSC reaction of previously untested selections of the larger F1 testcross population (4,471 accessions) based on the presence of identified favorable SNPs. We demonstrated the usefulness of mining for donor alleles in Germplasm Bank accessions for newly emerging diseases using genomic variation in landraces.

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Lee, Da-Young, Dong-Yeop Na, Carlos Góngora-Canul, Sriram Baireddy, Brenden Lane, Andres P. Cruz, Mariela Fernández-Campos, et al. "Contour-Based Detection and Quantification of Tar Spot Stromata Using Red-Green-Blue (RGB) Imagery." Frontiers in Plant Science 12 (October 1, 2021). http://dx.doi.org/10.3389/fpls.2021.675975.

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Quantifying symptoms of tar spot of corn has been conducted through visual-based estimations of the proportion of leaf area covered by the pathogenic structures generated by Phyllachora maydis (stromata). However, this traditional approach is costly in terms of time and labor, as well as prone to human subjectivity. An objective and accurate method, which is also time and labor-efficient, is of an urgent need for tar spot surveillance and high-throughput disease phenotyping. Here, we present the use of contour-based detection of fungal stromata to quantify disease intensity using Red-Green-Blue (RGB) images of tar spot-infected corn leaves. Image blocks (n = 1,130) generated by uniform partitioning the RGB images of leaves, were analyzed for their number of stromata by two independent, experienced human raters using ImageJ (visual estimates) and the experimental stromata contour detection algorithm (SCDA; digital measurements). Stromata count for each image block was then categorized into five classes and tested for the agreement of human raters and SCDA using Cohen's weighted kappa coefficient (κ). Adequate agreements of stromata counts were observed for each of the human raters to SCDA (κ = 0.83) and between the two human raters (κ = 0.95). Moreover, the SCDA was able to recognize “true stromata,” but to a lesser extent than human raters (average median recall = 90.5%, precision = 89.7%, and Dice = 88.3%). Furthermore, we tracked tar spot development throughout six time points using SCDA and we obtained high agreement between area under the disease progress curve (AUDPC) shared by visual disease severity and SCDA. Our results indicate the potential utility of SCDA in quantifying stromata using RGB images, complementing the traditional human, visual-based disease severity estimations, and serve as a foundation in building an accurate, high-throughput pipeline for the scoring of tar spot symptoms.

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Journal articles on the topic 'Phyllachora maydis'

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