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Fletcher K, Michelmore R. Genome-Enabled Insights into Downy Mildew Biology and Evolution. ANNUAL REVIEW OF PHYTOPATHOLOGY 2023; 61:165-183. [PMID: 37268005 DOI: 10.1146/annurev-phyto-021622-103440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Oomycetes that cause downy mildew diseases are highly specialized, obligately biotrophic phytopathogens that can have major impacts on agriculture and natural ecosystems. Deciphering the genome sequence of these organisms provides foundational tools to study and deploy control strategies against downy mildew pathogens (DMPs). The recent telomere-to-telomere genome assembly of the DMP Peronospora effusa revealed high levels of synteny with distantly related DMPs, higher than expected repeat content, and previously undescribed architectures. This provides a road map for generating similar high-quality genome assemblies for other oomycetes. This review discusses biological insights made using this and other assemblies, including ancestral chromosome architecture, modes of sexual and asexual variation, the occurrence of heterokaryosis, candidate gene identification, functional validation, and population dynamics. We also discuss future avenues of research likely to be fruitful in studies of DMPs and highlight resources necessary for advancing our understanding and ability to forecast and control disease outbreaks.
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Affiliation(s)
- Kyle Fletcher
- The Genome Center, University of California, Davis, California, USA
| | - Richard Michelmore
- The Genome Center, University of California, Davis, California, USA
- Department of Plant Sciences; Department of Molecular and Cellular Biology; Department of Medical Microbiology and Immunology, University of California, Davis, California, USA;
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Jung T, Balci Y, Broders KD, Milenković I, Janoušek J, Kudláček T, Đorđević B, Horta Jung M. Synchrospora gen. nov., a New Peronosporaceae Genus with Aerial Lifestyle from a Natural Cloud Forest in Panama. J Fungi (Basel) 2023; 9:jof9050517. [PMID: 37233228 DOI: 10.3390/jof9050517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 04/20/2023] [Accepted: 04/23/2023] [Indexed: 05/27/2023] Open
Abstract
During a survey of Phytophthora diversity in Panama, fast-growing oomycete isolates were obtained from naturally fallen leaves of an unidentified tree species in a tropical cloud forest. Phylogenetic analyses of sequences from the nuclear ITS, LSU and ßtub loci and the mitochondrial cox1 and cox2 genes revealed that they belong to a new species of a new genus, officially described here as Synchrospora gen. nov., which resided as a basal genus within the Peronosporaceae. The type species S. medusiformis has unique morphological characteristics. The sporangiophores show determinate growth, multifurcating at the end, forming a stunted, candelabra-like apex from which multiple (8 to >100) long, curved pedicels are growing simultaneously in a medusa-like way. The caducous papillate sporangia mature and are shed synchronously. The breeding system is homothallic, hence more inbreeding than outcrossing, with smooth-walled oogonia, plerotic oospores and paragynous antheridia. Optimum and maximum temperatures for growth are 22.5 and 25-27.5 °C, consistent with its natural cloud forest habitat. It is concluded that S. medusiformis as adapted to a lifestyle as a canopy-dwelling leaf pathogen in tropical cloud forests. More oomycete explorations in the canopies of tropical rainforests and cloud forests are needed to elucidate the diversity, host associations and ecological roles of oomycetes and, in particular, S. medusiformis and possibly other Synchrospora taxa in this as yet under-explored habitat.
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Affiliation(s)
- Thomas Jung
- Phytophthora Research Centre, Faculty of Forestry and Wood Technology, Mendel University in Brno, 613 00 Brno, Czech Republic
- Phytophthora Research and Consultancy, 83131 Nußdorf, Germany
| | - Yilmaz Balci
- USDA-APHIS Plant Protection and Quarantine, 4700 River Road, Riverdale, MD 20737, USA
| | - Kirk D Broders
- Smithsonian Tropical Research Institute, Apartado Panamá, Panama City 0843-03092, Panama
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Mycotoxin Prevention and Applied Microbiology Research Unit, Peoria, IL 61604, USA
| | - Ivan Milenković
- Phytophthora Research Centre, Faculty of Forestry and Wood Technology, Mendel University in Brno, 613 00 Brno, Czech Republic
- Faculty of Forestry, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade, Serbia
| | - Josef Janoušek
- Phytophthora Research Centre, Faculty of Forestry and Wood Technology, Mendel University in Brno, 613 00 Brno, Czech Republic
| | - Tomáš Kudláček
- Phytophthora Research Centre, Faculty of Forestry and Wood Technology, Mendel University in Brno, 613 00 Brno, Czech Republic
| | - Biljana Đorđević
- Phytophthora Research Centre, Faculty of Forestry and Wood Technology, Mendel University in Brno, 613 00 Brno, Czech Republic
| | - Marilia Horta Jung
- Phytophthora Research Centre, Faculty of Forestry and Wood Technology, Mendel University in Brno, 613 00 Brno, Czech Republic
- Phytophthora Research and Consultancy, 83131 Nußdorf, Germany
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Fletcher K, Martin F, Isakeit T, Cavanaugh K, Magill C, Michelmore R. The genome of the oomycete Peronosclerospora sorghi, a cosmopolitan pathogen of maize and sorghum, is inflated with dispersed pseudogenes. G3 (BETHESDA, MD.) 2023; 13:jkac340. [PMID: 36592124 PMCID: PMC9997571 DOI: 10.1093/g3journal/jkac340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 11/14/2022] [Accepted: 12/05/2022] [Indexed: 01/03/2023]
Abstract
Several species in the oomycete genus Peronosclerospora cause downy mildew on maize and can result in significant yield losses in Asia. Bio-surveillance of these pathogens is a high priority to prevent epidemics on maize in the United States and consequent damage to the US economy. The unresolved taxonomy and dearth of molecular resources for Peronosclerospora spp. hinder these efforts. P. sorghi is a pathogen of sorghum and maize with a global distribution, for which limited diversity has been detected in the southern USA. We characterized the genome, transcriptome, and mitogenome of an isolate, representing the US pathotype 6. The highly homozygous genome was assembled using 10× Genomics linked reads and scaffolded using Hi-C into 13 chromosomes. The total assembled length was 303.2 Mb, larger than any other oomycete previously assembled. The mitogenome was 38 kb, similar in size to other oomycetes, although it had a unique gene order. Nearly 20,000 genes were annotated in the nuclear genome, more than described for other downy mildew causing oomycetes. The 13 chromosomes of P. sorghi were highly syntenic with the 17 chromosomes of Peronospora effusa with conserved centromeric regions and distinct chromosomal fusions. The increased assembly size and gene count of P. sorghi is due to extensive retrotransposition, resulting in putative pseudogenization. Ancestral genes had higher transcript abundance and were enriched for differential expression. This study provides foundational resources for analysis of Peronosclerospora and comparisons to other oomycete genera. Further genomic studies of global Peronosclerospora spp. will determine the suitability of the mitogenome, ancestral genes, and putative pseudogenes for marker development and taxonomic relationships.
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Affiliation(s)
- Kyle Fletcher
- The Genome Center, University of California, Davis, CA 95616, USA
| | - Frank Martin
- U.S. Department of Agriculture–Agriculture Research Service, Salinas, CA, 93905, USA
| | - Thomas Isakeit
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA
| | - Keri Cavanaugh
- The Genome Center, University of California, Davis, CA 95616, USA
| | - Clint Magill
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA
| | - Richard Michelmore
- The Genome Center, University of California, Davis, CA 95616, USA
- Departments of Plant Sciences, Molecular & Cellular Biology, Medical Microbiology & Immunology, University of California, Davis, CA 95616, USA
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Muis A, Ryley MJ, Tan YP, Suharjo R, Nonci N, Danaatmadja Y, Hidayat I, Widiastuti A, Widinugraheni S, Shivas RG, Thines M. Peronosclerospora neglecta sp. nov.—a widespread and overlooked threat to corn (maize) production in the tropics. Mycol Prog 2023. [DOI: 10.1007/s11557-022-01862-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Abstract
Downy mildew is a serious threat to corn (maize) production in the tropics and subtropics. Corn is native to Central America, and was introduced into South-East Asia by the Spanish colonisers in the 1700s. Corn is evolutionarily naïve to downy mildews of the genus Peronosclerospora. Consequently, corn monocultures are particularly susceptible to a variety of Peronosclerospora species, which spread to the crop from local grasses. Globally, corn is one of the most important crops for both humans and livestock. Several downy mildews of corn have been identified as potential threats to global food security, and trade with corn seeds is strictly regulated to avoid spreading the pathogens. Despite their importance, little is known about the biodiversity of graminicolous downy mildews, because their identification has often relied on variable morphological features, such as conidial dimensions. DNA barcodes for most species have become available only recently. During surveys for downy mildews on corn in Indonesia, a previously unrecognised species of Peronosclerospora was found and investigated using a combination of morphological characters and molecular phylogenetic analyses. The new species, introduced here as Peronosclerospora neglecta, is widely distributed in South-East Asia from Thailand to eastern Indonesia. The impact of this downy mildew can be severe, with complete crop losses in heavily affected fields. Given the aggressiveness of the species, close surveillance is warranted to restrict its further spread.
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