{{Short description|Downy mildew}} {{Speciesbox | image = Peronospora violacea macroscopic symptoms.jpg | image_caption = A flowerhead of ''Succisa pratensis'' infected by ''Peronospora violacea''. | genus = Peronospora | species = violacea | authority = Berkeley, 1860 }}
'''''Peronospora violacea''''' is a floricolous downy mildew which infects plants in the Caprifoliaceae. It has been reported from hosts in the genera ''Dipsacus'', ''Knautia'', ''Lomelosia'', ''Scabiosa'', and ''Succisa''.<ref name="bladmineerders">{{cite web |author=Ellis, W. N. |year=2024 |title=''Peronospora violacea'' |website=bladmineerders.nl |url=https://bladmineerders.nl/parasites/chromista/oomycota/oomycetes/peronosporales/peronosporaceae/peronospora/peronospora-violacea/ |access-date=13 September 2024}}</ref>
It produces conidiophores on the petals and styles of the host, oospores inside the petal and style tissue, and suppresses the development of the anthers. Infection is systemic, with hyphae produced in the xylem of the host rhizomes and stems.<ref name="Contribution">{{cite journal |author=Horáková, J. |author2=Skalický, V. | journal=Česká Mykologie | title=Contribution to the ecology of ''Peronospora violacea'' Berk. | volume=43 | issue=1 | pages=13–29 | date= 1989 | doi=10.33585/cmy.43102 }}</ref>
In infected plants of ''Succisa pratensis'' the flowers have longer, pinker petals on which the conidophores are produced.<ref name="Field Guide">{{cite web |author=Dalzell, J. | year=2024 | title=Pathogens in Grassland | website=Field Guide to Plant Pathogens | url=https://plantpathogens.neocities.org/habitats/grassland | access-date=19 December 2024}}</ref> However, other authors report that on the same host it causes the host corollas to be brownish and dead-looking.<ref>{{cite book |author=Chater, A. O. |author2=Woods, R. G. |author3=Stringer, R. N. |author4=Evans, D. A. |author5=Smith, P. A. | date= 2020 | title=Downy Mildews (Peronosporaceae) and White Blister-Rusts (Albuginaceae) of Wales = Llwydni Gwlannog (Peronosporaceae) a Rhydau-Pothelli Gwynion (Albuginaceae) Cymru | publisher=A.O. Chater | isbn=978-0-9565750-4-3}}</ref>
==Gallery== {{Gallery | File:Peronospora violacea conidiophores.png | Conidiophores of ''Peronospora violacea'' on a petal of ''Succisa pratensis'', viewed under the microscope (focus stacked image). | File:Peronospora violacea comparison.jpg | Flowerheads of ''Succisa pratensis'', infected (right) and uninfected (left) with ''Peronospora violacea''. | File:Peronospora violacea on Knautia arvensis.jpg | A flowerhead of ''Knautia arvensis'' infected with ''Peronospora violacea''. | File:Conidiophores of Peronospora violacea on Knautia arvensis imported from iNaturalist photo 510738365.jpg | Conidiophores of ''Peronospora violacea'' on a petal of ''Knautia arvensis''. }}
==References== {{Reflist}}
{{Plant-disease-stub}} {{taxonbar|from=Q127376334}}
violacea Category:Plant pathogens and diseases Category:Protists described in 1860