Peronospora sordida
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''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamental plants. There are 19 genera that produce downy mildew, and ''Peronospora'' has been placed alongside '' Pseudoperonospora'' in the group of
downy mildew Downy mildew refers to any of several types of oomycete microbes that are obligate parasites of plants. Downy mildews exclusively belong to the Peronosporaceae family. In commercial agriculture, they are a particular problem for growers of cruc ...
s with coloured conidia. ''Peronospora'' has far more species than any other genus of the downy mildews. However, many species have been moved from this genus to be reclassified to other or new genera. Among these was the most famous ''Peronospora'' species, formerly known as ''Peronospora parasitica'', and now known as ''
Hyaloperonospora parasitica ''Hyaloperonospora parasitica'' is an oomycete from the family Peronosporaceae. It has been considered for a long time to cause downy mildew of a variety of species within the Brassicaceae, on which the disease can cause economically important da ...
''. Now, the ''Peronospora'' species of most importance is likely the ''Peronospora tabacina''. ''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.


History

''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''. 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. 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. 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.


Habitat and ecology

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. 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. There are also many ''Peronospora'' species that are spread by wind currents, which allows them to disperse over large distances. ''Peronospora'' species prefer humid air and cool temperatures.


General form and structure

The first stage in the ''Peronospora'' life history is the sporangia. The sporangia are small spore-like structures about 65 um long that germinate a germ-tube when they are near a leaf stoma. A germ tube will come from the sporangium and penetrate the leaf cell where it will form a haustorium. The haustorium absorbs nutrients from the leaf, while hyphae invade the intercellular space, and the leaf will eventually develop a lesion. These lesions often start out yellow and then turn brown as the leaf starts to undergo necrosis. From here, ''Peronospora'' can undergo either asexual reproduction or sexual reproduction. Asexual reproduction occurs when the air outside is moist making for favourable conditions. During asexual reproduction, hyphae on the host plant will form sporangiophores, which will produce conidia. The conidia will be dispersed by the wind is able to infect other plants. The asexual cycle only takes five to seven days to complete. Sexual reproduction occurs when the conditions are unfavourable and it needs to withstand harsh environmental conditions. During sexual reproduction, the hyphae will undergo meiosis forming antheridia and oogonia, the only haploid structures in the ''Peronospora'' life history. The antheridia will fuse to the oogonia, initiating plasmogamy and then karyogamy, and will result in the production of many oospores. The oospores can then be dispersed by the wind to infect more plants. Both ''Peronospora'' and ''Pseudoperonospora'' are characterized by their ability to produce melanized sporangia, but ''Pseudoperonospora'' produces zoospores whereas ''Peronospora'' cannot.


Practical importance

The model oomycete pathogen, ''Peronospora parasitica'', used to be included in this genus, however it has been reclassified to the genus ''Hyaloperonospora''. Some species of ''Peronospora'' have been considered for their use as a bioweapon or have been classified as potential bioweapons. ''Peronspora somniferi'' was considered for its ability to devastate fields of the opium poppy, which could have targeted areas that depend on the crop. 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.


Genomics and genetics

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. They estimated the genome size to be 68 Mb with a mitochondrial genome of 43 kb. 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. The mitochondrial genome only differed by seven single nucleotide polymorphisms, three small indels, and one copy number variant. Using a program to predict gene models, they found 18,000 potential protein coding genes.


List of ''Peronospora'' species

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Peronospora aconiti ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora aestivalis'' *'' Peronospora affinis'' *''
Peronospora agrestis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora agrimoniae'' *'' Peronospora alchemillae'' *''
Peronospora alpicola ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora alsinearum'' *'' Peronospora alta'' Fuckel *'' Peronospora akatsukae'' Ito & Murayama *'' Peronospora anagallidis'' *''
Peronospora antirrhini ''Peronospora antirrhini'' is a plant pathogen. It causes downy mildew on leaves of species of ''Antirrhinum'' and related genera (e.g. ''Misopates ''Misopates'' is a genus of the family Plantaginaceae, and is one of the groups of plants comm ...
'' *''
Peronospora aparines ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora apula ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora aquatica'' *'' Peronospora arborescens'' *''
Peronospora arenariae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora argemones ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora arthurii ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora arvensis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora asperuginis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora astragalina ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora atriplicis-hastatae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora belbahrii ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora boni-henrici ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora bulbocapni ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora calotheca'' *'' Peronospora campestris'' *'' Peronospora canescens'' Benua *'' Peronospora cerastii-anomali'' *'' Peronospora cerastii-brachypetali'' *''
Peronospora chenopodii-polyspermi ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora chlorae'' *'' Peronospora chrysosplenii'' *'' Peronospora claytoniae'' *'' Peronospora conglomerata'' *'' Peronospora consolidae'' *'' Peronospora coronillae'' *'' Peronospora corydalis'' *'' Peronospora corydalis-intermediae'' *''
Peronospora cristata ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora cyparissiae'' *'' Peronospora debaryi'' *'' Peronospora destructor'' *''
Peronospora dianthicola ''Peronospora dianthicola'' is a plant pathogen. It causes downy mildew on leaves of carnation (''Dianthus caryophyllus ''Dianthus caryophyllus'' (), commonly known as the carnation or clove pink, is a species of '' Dianthus''. It is likely ...
'' *'' Peronospora dicentrae'' *'' Peronospora digitalis'' *'' Peronospora dipsaci'' *'' Peronospora echii'' *'' Peronospora effusa'' *''
Peronospora elsholtziae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora erodii'' *'' Peronospora ervi'' *'' Peronospora esulae'' *'' Peronospora farinosa'' ** ''Peronospora farinosa'' f. sp. ''betae'' ** ''Peronospora farinosa'' f. sp. ''chenopodii'' ** ''Peronospora farinosa'' f. sp. ''spinaciae'' *'' Peronospora ficariae'' *'' Peronospora flava'' *'' Peronospora fulva'' *'' Peronospora galii'' *''
Peronospora glechomae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora grisea'' *'' Peronospora hiemalis'' *'' Peronospora holostei'' *'' Peronospora honckenyae'' *''
Peronospora illyrica ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora jagei'' *'' Peronospora knautiae'' *'' Peronospora kochiae-scopariae'' *'' Peronospora lamii'' *'' Peronospora lapponica'' *''
Peronospora lathyri-verni ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora lathyrina'' *'' Peronospora lepigoni'' *'' Peronospora linariae'' *''
Peronospora linariae-genistifoliae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora lithospermi'' *''
Peronospora litoralis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora lotorum'' *''
Peronospora manshurica ''Peronospora manshurica'' is a plant pathogen. It is a widespread disease on the leaves of soybeans and other crop plants. The fungi is commonly referred to as downy mildew, "leafspot", or "leaf-spot". Symptoms The most visible symptoms of ''P ...
'' *'' Peronospora mayorii'' *''
Peronospora meconopsidis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora medicaginis-minimae'' *'' Peronospora medicaginis-orbicularis'' *''
Peronospora melandryi-noctiflori ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora meliloti'' *'' Peronospora mesembryanthemi'' *'' Peronospora minor'' *'' Peronospora myosotidis'' *'' Peronospora narbonensis'' *'' Peronospora oblatispora'' *'' Peronospora obovata'' *'' Peronospora ornithopi'' *'' Peronospora orobi'' *''
Peronospora parva ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora paula'' *'' Peronospora perillae'' *'' Peronospora phacae'' *''
Peronospora plantaginis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora polycarpi'' *'' Peronospora polygoni'' *''
Peronospora polygoni-convolvuli ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora potentillae'' *'' Peronospora potentillae-anserinae'' *''
Peronospora potentillae-reptantis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora potentillae-sterilis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora pseudostellaria'' *'' Peronospora pulveracea'' *'' Peronospora radii'' *'' Peronospora ranunculi'' *'' Peronospora aff. ranunculi'' *'' Peronospora romanica'' *''
Peronospora rubi ''Peronospora sparsa'' is an oomycete plant pathogen that causes downy mildew in berry producing plants; especially in the genus's ''Rubus'' and ''Rosa''. Downy mildew plant pathogens are often host specific and cause problems in cloudberries, bl ...
'' *'' Peronospora rumicis'' *''
Peronospora salviae-plebeiae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora sanguisorbae'' *''
Peronospora saturejae-hortensis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *''
Peronospora saxifragae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora schachtii'' *'' Peronospora scleranthi'' *'' Peronospora scutellariae'' *'' Peronospora sepium'' *''
Peronospora sherardiae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora silvatica'' *''
Peronospora silvestris ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora somniferi'' *'' Peronospora sordida'' *'' Peronospora sparsa'' *''
Peronospora stachydis ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora statices'' *'' Peronospora stellariae-aquaticae'' *''
Peronospora stellariae-uliginosae ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora stigmaticola'' *'' Peronospora swinglei'' *'' Peronospora symphyti'' *'' Peronospora tabacina'' *'' Peronospora tetragonolobi'' *''
Peronospora teucrii ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora tomentosa'' *''
Peronospora tranzscheliana ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora trifolii-alpestris'' *'' Peronospora trifolii-arvensis'' *'' Peronospora trifolii-hybridi'' *''
Peronospora trifolii-minoris ''Peronospora'' is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamenta ...
'' *'' Peronospora trifolii-repentis'' *'' Peronospora trifoliorum'' ** ''Peronospora trifoliorum'' f. ''trifolii-pratensis'' *'' Peronospora trigonellae'' *'' Peronospora trigonotidis'' *'' Peronospora trivialis'' *'' Peronospora valerianae'' *'' Peronospora valerianellae'' *'' Peronospora variabilis'' *'' Peronospora verbasci'' *'' Peronospora verbenae'' *'' Peronospora verna'' *'' Peronospora vernalis'' *'' Peronospora viciae'' ** ''Peronospora vicia''e f. sp. ''pisi'' *'' Peronospora violacea'' *'' Peronospora violae''


References

{{Taxonbar, from=Q1650703 Peronosporales Water mould plant pathogens and diseases Water mould genera