@article{singh_kumar_purayannur_chen_verma_2022, title={Ascochyta rabiei: A threat to global chickpea production}, ISSN={["1364-3703"]}, DOI={10.1111/mpp.13235}, abstractNote={AbstractThe necrotrophic fungus Ascochyta rabiei causes Ascochyta blight (AB) disease in chickpea. A. rabiei infects all aerial parts of the plant, which results in severe yield loss. At present, AB disease occurs in most chickpea‐growing countries. Globally increased incidences of A. rabiei infection and the emergence of new aggressive isolates directed the interest of researchers toward understanding the evolution of pathogenic determinants in this fungus. In this review, we summarize the molecular and genetic studies of the pathogen along with approaches that are helping in combating the disease. Possible areas of future research are also suggested.Taxonomykingdom Mycota, phylum Ascomycota, class Dothideomycetes, subclass Coelomycetes, order Pleosporales, family Didymellaceae, genus Ascochyta, species rabiei.Primary hostA. rabiei survives primarily on Cicer species.Disease symptomsA. rabiei infects aboveground parts of the plant including leaves, petioles, stems, pods, and seeds. The disease symptoms first appear as watersoaked lesions on the leaves and stems, which turn brown or dark brown. Early symptoms include small circular necrotic lesions visible on the leaves and oval brown lesions on the stem. At later stages of infection, the lesions may girdle the stem and the region above the girdle falls off. The disease severity increases at the reproductive stage and rounded lesions with concentric rings, due to asexual structures called pycnidia, appear on leaves, stems, and pods. The infected pod becomes blighted and often results in shrivelled and infected seeds.Disease management strategiesCrop failures may be avoided by judicious practices of integrated disease management based on the use of resistant or tolerant cultivars and growing chickpea in areas where conditions are least favourable for AB disease development. Use of healthy seeds free of A. rabiei, seed treatments with fungicides, and proper destruction of diseased stubbles can also reduce the fungal inoculum load. Crop rotation with nonhost crops is critical for controlling the disease. Planting moderately resistant cultivars and prudent application of fungicides is also a way to combat AB disease. However, the scarcity of AB‐resistant accessions and the continuous evolution of the pathogen challenges the disease management process.Useful websiteshttps://www.ndsu.edu/pubweb/pulse‐info/resourcespdf/Ascochyta%20blight%20of%20chickpea.pdf https://saskpulse.com/files/newsletters/180531_ascochyta_in_chickpeas‐compressed.pdf http://www.pulseaus.com.au/growing‐pulses/bmp/chickpea/ascochyta‐blight http://agriculture.vic.gov.au/agriculture/pests‐diseases‐and‐weeds/plant‐diseases/grains‐pulses‐and‐cereals/ascochyta‐blight‐of‐chickpea http://www.croppro.com.au/crop_disease_manual/ch05s02.php https://www.northernpulse.com/uploads/resources/722/handout‐chickpeaascochyta‐nov13‐2011.pdf http://oar.icrisat.org/184/1/24_2010_IB_no_82_Host_Plant https://www.crop.bayer.com.au/find‐crop‐solutions/by‐pest/diseases/ascochyta‐blight}, journal={MOLECULAR PLANT PATHOLOGY}, author={Singh, Ritu and Kumar, Kamal and Purayannur, Savithri and Chen, Weidong and Verma, Praveen Kumar}, year={2022}, month={Jul} }
 @misc{salcedo_purayannur_standish_miles_thiessen_quesada-ocampo_2021, title={Fantastic Downy Mildew Pathogens and How to Find Them: Advances in Detection and Diagnostics}, volume={10}, ISSN={["2223-7747"]}, url={https://doi.org/10.3390/plants10030435}, DOI={10.3390/plants10030435}, abstractNote={Downy mildews affect important crops and cause severe losses in production worldwide. Accurate identification and monitoring of these plant pathogens, especially at early stages of the disease, is fundamental in achieving effective disease control. The rapid development of molecular methods for diagnosis has provided more specific, fast, reliable, sensitive, and portable alternatives for plant pathogen detection and quantification than traditional approaches. In this review, we provide information on the use of molecular markers, serological techniques, and nucleic acid amplification technologies for downy mildew diagnosis, highlighting the benefits and disadvantages of the technologies and target selection. We emphasize the importance of incorporating information on pathogen variability in virulence and fungicide resistance for disease management and how the development and application of diagnostic assays based on standard and promising technologies, including high-throughput sequencing and genomics, are revolutionizing the development of species-specific assays suitable for in-field diagnosis. Our review provides an overview of molecular detection technologies and a practical guide for selecting the best approaches for diagnosis.}, number={3}, journal={PLANTS-BASEL}, publisher={MDPI AG}, author={Salcedo, Andres F. and Purayannur, Savithri and Standish, Jeffrey R. and Miles, Timothy and Thiessen, Lindsey and Quesada-Ocampo, Lina M.}, year={2021}, month={Mar} }
 @article{purayannur_munster_bertone_quesada-ocampo_2021, title={First Report of Downy Mildew Caused by Peronospora chenopodii-ambrosioidis on Epazote (Dysphania ambrosioides) in North Carolina}, volume={22}, ISSN={["1535-1025"]}, url={https://doi.org/10.1094/PHP-12-20-0110-FI}, DOI={10.1094/PHP-12-20-0110-FI}, abstractNote={ In this brief, we report the observation of downy mildew caused by Peronospora chenopodii-ambrosioidis on epazote (Dysphania ambrosioides) in North Carolina, U.S.A. We performed morphological characterization of the sporangia and sporangiophores for identification. We also confirmed the identity of the pathogen by performing an alignment and generating a maximum likelihood phylogeny of the concatenated internal transcribed spacer region and cytochrome c oxidase subunit I sequences. }, number={3}, journal={PLANT HEALTH PROGRESS}, publisher={Scientific Societies}, author={Purayannur, Savithri and Munster, Michael J. and Bertone, Matthew A. and Quesada-Ocampo, Lina M.}, year={2021}, pages={384–386} }
 @article{purayannur_gent_miles_radisek_quesada-ocampo_2021, title={The hop downy mildew pathogen Pseudoperonospora humuli}, volume={5}, ISSN={["1364-3703"]}, url={https://doi.org/10.1111/mpp.13063}, DOI={10.1111/mpp.13063}, abstractNote={AbstractPseudoperonospora humuli is an obligate biotrophic oomycete that causes downy mildew, one of the most devastating diseases of cultivated hop, Humulus lupulus. Downy mildew occurs in all production areas of the crop in the Northern Hemisphere and Argentina. The pathogen overwinters in hop crowns and roots, and causes considerable crop loss. Downy mildew is managed by sanitation practices, planting of resistant cultivars, and fungicide applications. However, the scarcity of sources of host resistance and fungicide resistance in pathogen populations complicates disease management. This review summarizes the current knowledge on the symptoms of the disease, life cycle, virulence factors, and management of hop downy mildew, including various forecasting systems available in the world. Additionally, recent developments in genomics and effector discovery, and the future prospects of using such resources in successful disease management are also discussed.TaxonomyClass: Oomycota; Order: Peronosporales; Family: Peronosporaceae; Genus: Pseudoperonospora; Species: Pseudoperonospora humuli.Disease symptomsThe disease is characterized by systemically infected chlorotic shoots called “spikes". Leaf symptoms and signs include angular chlorotic lesions and profuse sporulation on the abaxial side of the leaf. Under severe disease pressure, dark brown discolouration or lesions are observed on cones. Infected crowns have brown to black streaks when cut open. Cultivars highly susceptible to crown rot may die at this phase of the disease cycle without producing shoots. However, foliar symptoms may not be present on plants with systemically infected root systems.Infection processPathogen mycelium overwinters in buds and crowns, and emerges on infected shoots in spring. Profuse sporulation occurs on infected tissues and sporangia are released and dispersed by air currents. Under favourable conditions, sporangia germinate and produce biflagellate zoospores that infect healthy tissue, thus perpetuating the infection cycle. Though oospores are produced in infected tissues, their role in the infection cycle is not defined.ControlDowny mildew on hop is managed by a combination of sanitation practices and timely fungicide applications. Forecasting systems are used to time fungicide applications for successful management of the disease.Useful Websiteshttps://content.ces.ncsu.edu/hop‐downy‐mildew (North Carolina State University disease factsheet), https://www.canr.msu.edu/resources/michigan‐hop‐management‐guide (Michigan Hop Management Guide), http://uspest.org/risk/models (Oregon State University Integrated Plant Protection Center degree‐day model for hop downy mildew), https://www.usahops.org/cabinet/data/Field‐Guide.pdf (Field Guide for Integrated Pest Management in Hops).}, journal={MOLECULAR PLANT PATHOLOGY}, publisher={Wiley}, author={Purayannur, Savithri and Gent, David H. and Miles, Timothy D. and Radisek, Sebastjan and Quesada-Ocampo, Lina M.}, year={2021}, month={May} }
 @article{purayannur_cano_bowman_childs_gent_quesada-ocampo_2020, title={The Effector Repertoire of the Hop Downy Mildew Pathogen Pseudoperonospora humuli}, volume={11}, ISSN={["1664-8021"]}, DOI={10.3389/fgene.2020.00910}, abstractNote={Pseudoperonospora humuli is an obligate biotrophic oomycete that causes downy mildew (DM), one of the most destructive diseases of cultivated hop that can lead to 100% crop loss in susceptible cultivars. We used the published genome of P. humuli to predict the secretome and effectorome and analyze the transcriptome variation among diverse isolates and during infection of hop leaves. Mining the predicted coding genes of the sequenced isolate OR502AA of P. humuli revealed a secretome of 1,250 genes. We identified 296 RXLR and RXLR-like effector-encoding genes in the secretome. Among the predicted RXLRs, there were several WY-motif-containing effectors that lacked canonical RXLR domains. Transcriptome analysis of sporangia from 12 different isolates collected from various hop cultivars revealed 754 secreted proteins and 201 RXLR effectors that showed transcript evidence across all isolates with reads per kilobase million (RPKM) values > 0. RNA-seq analysis of OR502AA-infected hop leaf samples at different time points after infection revealed highly expressed effectors that may play a relevant role in pathogenicity. Quantitative RT-PCR analysis confirmed the differential expression of selected effectors. We identified a set of P. humuli core effectors that showed transcript evidence in all tested isolates and elevated expression during infection. These effectors are ideal candidates for functional analysis and effector-assisted breeding to develop DM resistant hop cultivars.}, journal={FRONTIERS IN GENETICS}, author={Purayannur, Savithri and Cano, Liliana M. and Bowman, Megan J. and Childs, Kevin L. and Gent, David H. and Quesada-Ocampo, Lina M.}, year={2020}, month={Aug} }