Urocystis colchici
A smut fungus on the leaves and petioles of Colchicum autumnale in the UK, visible as elongate lesions, often merging together, which rupture to expose powdery black masses of spores.
Sori in leaves and petioles as slightly elevated, pustular, elongate areas of various size and shape, often confluent, visible on both sides of the leaf, initially lead-coloured and covered by the epidermis which ruptures exposing the powdery, black mass of spores. Infection systemic. Spore balls globose, subglobose, ovoid to irregular, (15-20)-40 µm in diam., composed of 1-3(-4) spores and a more or less complete covering layer of sterile cells. Spores globose, subglobose, ovoid, irregularly oblong or subpolyhedral, 9-14.5(-15) x (11-)12-20(-23) µm, medium reddish brown, smooth. Sterile cells subglobose, ovoid to irregular, 510 x 6-15 µm, pale yellow, with smooth, 1-2 µm thick wall, collapsed in old specimens.
Description adapted from Vánky, K. (2012). Smut fungi of the world. St. Paul, Minnesota: APS press.
Not formally assessed. Assessed as Critically Endangered / B in GB & IOM in the current but unofficial Red Data List for Threatened British Fungi (Evans et al., 2006). Considered a species of ‘principal importance for the conservation of biological diversity’ in England and Wales, and listed in accordance with Section 41 of the Natural Environment and Rural Communities Act 2006, and Section 7 of the Environment (Wales) Act 2016. Recorded in recent years from only nine sites, although one has now been lost along with its host.
None known on this host.
An obligate biotrophic parasite and pathogen of some Colchicum species. In Great Britain, only known from C. autumnale in the wild, although there have been some reports from related cultivated plants. Elsewhere reported from a number of Cochicum and Merendera species throughout Europe, Asia and North America.
Historically reported from a small number of sites from North Wiltshire VC7, North Somerset VC6, West Sussex VC13, Warwickshire VC38, and North-west Yorkshire VC65. One pre-1900s collection may have been made in West Lothian VC84.
Recently only known in the wild from single sites in Herefordshire VC36, Oxfordshire VC23, North Wiltshire VC7, Worcestershire VC37 and Northamptonshire VC32 in England; and four sites (one now lost) in Breconshire VC42 in Wales.
A very few observations from gardens have also been made in Glamorgan VC41 and East Gloucestershire VC33.