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Peronospora

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Peronospora
P. manshurica on soybean leaf
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: Sar
Clade: Stramenopiles
Phylum: Oomycota
Order: Peronosporales
Family: Peronosporaceae
Genus: Peronospora
Corda

Peronospora is a genus of downy mildews that are obligate plant pathogens.[1] They can cause severe damage to many different cultivated crops, as well as wild and ornamental plants.[2] Peronospora is most closely related to Pseudoperonospora, and together they form the clade of downy mildews with coloured conidia.[3] Peronospora has far more species than any other genus of the downy mildews.[3] However, many species have been moved from this genus to other genera based on phylogenetic evidence.[4] Among these are the species now in Hyaloperonospora, important pathogens of the Brassicaceae.[4] Now, the Peronospora species of most importance is likely Peronospora tabacina.[5][opinion] Peronospora tabacina causes blue mold on tobacco plants and can severely reduce yields of this economically important crop to the point where it has been classified as a bioweapon.[5][3]

History

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Peronospora was first described in 1837 by August Carl Joseph Corda, a Czech mycologist and physician, in his first of six volumes of his Icones fungorum hucusque cognitorum.[6] Since then, many of the species originally placed in Peronospora have been allocated to other genera or given rise to new genera based on new techniques such as molecular genetics.[4]

There was an epidemic in 1960 of Peronospora tabacina affecting tobacco plants leading to $25 million in losses across eleven countries, which was about 30 percent of the tobacco plants.[5] Another epidemic that was caused by Peronospora destructor reduced the yield of sweet onions by 25 percent in Georgia, USA in 2012, and led to an estimated $18.2 million in losses.[7]

Habitat and ecology

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Most of the Peronospora species are highly specific to their hosts and can generally be found anywhere the host plant grows, or is being cultivated.[3] A large portion of their life cycle is spent inside their host plant. Many species of Peronospora are seedborne pathogens, so the worldwide spread of Peronospora crop-plant pathogens is likely to be a result of unknowingly trading infected seeds to new areas.[3] There are also many Peronospora species that are spread by wind currents, which allows them to disperse over large distances.[3] Peronospora species prefer humid air and cool temperatures.[5]

One clade in the genus is known as the floricolous downy mildews. These species produce conidiophores exclusively on the flowers of their hosts.[8]

General form and structure

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The first stage in the Peronospora life history is the sporangia.[5] The sporangia are small spore-like structures about 65 um long that germinate a germ-tube when they are near a leaf stoma.[9][5] A germ tube will come from the sporangium and penetrate the leaf cell where it will form a haustorium.[5] The haustorium absorbs nutrients from the leaf, while hyphae invade the intercellular space, and the leaf will eventually develop a lesion.[5] These lesions often start out yellow and then turn brown as the leaf starts to undergo necrosis.[5] From here, Peronospora can undergo either asexual reproduction or sexual reproduction.[5] Asexual reproduction occurs when the air outside is moist making for favourable conditions.[5] During asexual reproduction, hyphae on the host plant will form sporangiophores, which will produce conidia.[5] The conidia will be dispersed by the wind is able to infect other plants.[5] The asexual cycle only takes five to seven days to complete.[5] Sexual reproduction occurs when the conditions are unfavourable and it needs to withstand harsh environmental conditions.[5] During sexual reproduction, the hyphae will undergo meiosis forming antheridia and oogonia, the only haploid structures in the Peronospora life history.[5] The antheridia will fuse to the oogonia, initiating plasmogamy and then karyogamy, and will result in the production of many oospores.[5] The oospores can then be dispersed by the wind to infect more plants.[5]

Both Peronospora and Pseudoperonospora are characterized by their ability to produce melanized sporangia, but Pseudoperonospora produces zoospores whereas Peronospora cannot.[3]

Practical importance

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The model oomycete pathogen, Peronospora parasitica, used to be included in this genus, however it has been reclassified to the genus Hyaloperonospora.[3]

Some species of Peronospora have been considered for their use as a bioweapon or have been classified as potential bioweapons.[3] Peronspora somniferi was considered for its ability to devastate fields of the opium poppy, which could have targeted areas that depend on the crop.[3] The United States has classified Peronospora tabacina as a possible bioweapon, because if it were used to target the US tobacco industry, it would lead to major economic loss.[3]

Genomics and genetics

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Only one species in the genus Peronospora has had its genome sequenced and assembled. In 2015, Derevnina et al. performed a de novo sequence assembly of the genome of two Peronospora tabacina isolates using Illumina sequencing.[10] They estimated the genome size to be 68 Mb with a mitochondrial genome of 43 kb.[10] The two assemblies had 61.8x and 128.9x coverage for the nuclear genomes and 6,824x and 43,225x coverage for the mitochondrial genomes.[10] The mitochondrial genome only differed by seven single nucleotide polymorphisms, three small indels, and one copy number variant.[10] Using a program to predict gene models, they found 18,000 potential protein coding genes.[10]

List of species

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The following species are placed in genus Peronospora:[11]

References

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  1. ^ Göker, M., García-Blázquez, G., Voglmayr, H., Tellería, M. T., & Martín, M. P. (2009). "Molecular taxonomy of phytopathogenic fungi: a case study in Peronospora". PLOS ONE. 4 (7): e6319. Bibcode:2009PLoSO...4.6319G. doi:10.1371/journal.pone.0006319. PMC 2712678. PMID 19641601.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ Lee, J. S., Shin, H. D., Lee, H. B., & Choi, Y. J. (2017). "Taxonomy and Phylogeny of Peronospora Species (Oomycota) Parasitic to Stellaria and Pseudostellaria in Korea, with the Introduction of Peronospora casparyi sp. nov". Mycobiology. 45 (4): 263–269. doi:10.5941/MYCO.2017.45.4.263. PMC 5780358. PMID 29371794.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ a b c d e f g h i j k Thines, M., & Choi, Y. J. (2015). "Evolution, diversity, and taxonomy of the Peronosporaceae, with focus on the genus Peronospora". Phytopathology. 106 (1): 6–18. doi:10.1094/PHYTO-05-15-0127-RVW. PMID 26649784.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ a b c Göker, M., Voglmayr, H., Riethmüller, A., Weiß, M., & Oberwinkler, F. (2003). "Taxonomic aspects of Peronosporaceae inferred from Bayesian molecular phylogenetics". Canadian Journal of Botany. 81 (7): 672–683. Bibcode:2003CaJB...81..672G. doi:10.1139/b03-066.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ a b c d e f g h i j k l m n o p q r Krsteska, V., Dimeska, V., Stojkov, S., & Stojanoski, P. (2015). "Peronospora tabacina A. the causing agent of Blue Mold disease on tobacco". Bulgarian Journal of Agricultural Science. 21: 132–139.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ Corda, A. C. J. (1837). Icones fungorum hucusque cognitorum, vol. 1.
  7. ^ Parkunan, V., Gitaitis, R. D., Dutta, B., Langston, D. B., & Ji, P. (2013). "An Epidemic of Downy Mildew caused by Peronospora destructor on Vidalia Sweet Onions in Georgia in 2012". Plant Health Progress. 14 (1): 54. Bibcode:2013PlaHP..14...54P. doi:10.1094/PHP-2013-0328-01-BR.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ Thines, M., Kummer, V. (1 May 2013). "Diversity and species boundaries in floricolous downy mildews". Mycological Progress. 12 (2): 321–329. Bibcode:2013MycPr..12..321T. doi:10.1007/s11557-012-0837-7. ISSN 1861-8952.
  9. ^ Langston Jr, D. B., & Sumner, D. R. (2000). "First report of downy mildew (caused by Peronospora destructor) of onion in Georgia". Plant Disease. 84 (4): 489. Bibcode:2000PlDis..84..489L. doi:10.1094/PDIS.2000.84.4.489B. PMID 30841183.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ a b c d e Derevnina, L., Chin-Wo-Reyes, S., Martin, F., Wood, K., Froenicke, L., Spring, O., & Michelmore, R. (2015). "Genome sequence and architecture of the tobacco downy mildew pathogen Peronospora tabacina". Molecular Plant-Microbe Interactions. 28 (11): 1198–1215. Bibcode:2015MPMI...28.1198D. doi:10.1094/MPMI-05-15-0112-R. PMID 26196322.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ^ "Taxonomy Browser: Peronospora ". NCBI taxonomy database. Retrieved 7 September 2023.
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