The Effector Repertoire of the Hop Downy Mildew Pathogen Pseudoperonospora humuli

Purayannur, Savithri; Cano, Liliana; Bowman, Megan J.; Childs, Kevin L.; Gent, David H.; Quesada‐Ocampo, Lina M.

doi:10.3389/fgene.2020.00910

Cited by 14 publications

(15 citation statements)

References 109 publications

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“…The number is closer to the 271 predicted RXLRs in the sister species P . cubensis (Savory et al, 2012), even though the analysis conducted by Purayannur, Cano, Bowman, et al (2020) revealed only 72 predicted RXLRs in the Savory et al (2012) P . cubensis genome, a discrepancy probably due to the RXLR prediction pipeline in the two studies.…”

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

“…Recently, a comprehensive scan of the P . humuli genome was conducted to identify putative apoplastic and cytoplasmic effectors (Purayannur, Cano, Bowman, et al, 2020). The P .…”

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

“…humuli consisted of known classes such as carbohydrate‐active enzymes (CAZymes), glucanase inhibitors, protease inhibitors, necrosis and ethylene‐inducing peptide 1‐like proteins (NLPs), and sperm coat proteins (SCPs). No CRNs were identified in the P. humuli secretome although there were 53 proteins containing the characteristic LXLFLAK and/or HVLVVVP motifs without predicted signal peptides (Purayannur, Cano, Bowman, et al, 2020). There were 296 RXLR‐like proteins in P .…”

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

“…cubensis genome, a discrepancy probably due to the RXLR prediction pipeline in the two studies. While Savory et al (2012) included proteins with different amino acids in the R1 position of the RXLR motif, Purayannur et al (2020) included such noncanonical proteins only when a downstream EER motif was present. Additionally, Purayannur et al (2020) used a modified version of the P .…”

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

“…In line with this, there were 74 such effectors in the secretome of P . humuli (Purayannur, Cano, Bowman, et al, 2020).…”

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

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The hop downy mildew pathogen Pseudoperonospora humuli

Purayannur

Gent

Miles

et al. 2021

Molecular Plant Pathology

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Pseudoperonospora 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. Taxonomy Class: Oomycota; Order: Peronosporales; Family: Peronosporaceae; Genus: Pseudoperonospora; Species: Pseudoperonospora humuli. Disease symptoms The 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 process Pathogen 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. Control Downy 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 Websites https://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).

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Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

“…Recently, a comprehensive scan of the P . humuli genome was conducted to identify putative apoplastic and cytoplasmic effectors (Purayannur, Cano, Bowman, et al, 2020). The P .…”

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

“…In line with this, there were 74 such effectors in the secretome of P . humuli (Purayannur, Cano, Bowman, et al, 2020).…”

Section: Genome Resources and Virulence Factorsmentioning

confidence: 99%

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The hop downy mildew pathogen Pseudoperonospora humuli

Purayannur

Gent

Miles

et al. 2021

Molecular Plant Pathology

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QTL mapping of resistance to Pseudoperonospora cubensis clade 2, mating type A1, in Cucumis melo and dual-clade marker development

et al. 2023

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Pseudoperonospora cubensis, causal organism of cucurbit downy mildew (CDM), causes severe necrosis and defoliation on Cucumis melo (melon). A recombinant inbred line population (N = 169) was screened against an isolate of P. cubensis (Clade 2 / mating type A1) in replicated greenhouse and growth chamber tests. SNPs (n = 5,633 bins) identi ed in the RIL population were used for quantitative trait loci (QTL) mapping. A single major QTL on chromosome 10 was consistently associated with resistance across all tests, while a second major QTL on chromosome 8 was identi ed only in greenhouse tests.These two major QTL were identi ed on the same chromosomes (8 and 10) but in different locations as two major QTL previously identi ed for resistance to P. cubensis Clade 1 / mating type A2. Kompetitive allele speci c PCR (KASP) markers were developed for these four major QTL and validated in the RIL population through QTL mapping. These markers will provide melon breeders a high-throughput genotyping toolkit for development of melon cultivars with broad tolerance to CDM. Key MessageThis is the rst identi cation of QTL underlying resistance in Cucumis melo to an isolate of Pseudoperonospora cubensis identi ed as Clade 2 / mating type A1.analyses performed in this study and by demonstrate that broad-spectrum CDM resistance may have different underlying mechanisms which are isolate-dependent. This research identi es CDM resistance QTL in C. melo to an isolate genetically related to that of the 2004 epidemic population of P. cubensis in the United States. With the predominance of Clade 2, mating type A1 isolates in the eastern United States, these QTL will be the more important to incorporate. This study and the one by represent the rst analyses of the underlying resistance mechanisms of a single C. melo breeding line with two isolates of P. cubensis with highly different genetic backgrounds. A total of 31 KASP markers were developed across four major QTL. Future breeding lines incorporating resistance alleles from MR-1 can be rapidly screened for introgression of major QTL for CDM resistance using the KASP markers developed in this study.

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