A rust fungus on both sides of leaves of Gentianella amarella (autumn gentian or autumn felwort), visible as discrete 0.5 mm diameter cinnamon-brown pustules.
Uredosori amphigenous (on both sides of leaves), without spots, scattered, minute, rounded, about 0.5 mm. diam., surrounded by the ruptured epidermis, pulverulent (powdery), pale cinnamon-brown; uredospores globoid, 20-26 x 16-22 µm, wall 1-2 µm thick, echinulate (set with small spines) with 3, less commonly 2, equatorial pores. Teliosori amphigenous, resembling the uredosori, cinnamon-brown; teliospores globoid, cinnamon-brown, 15-18 x 18-21 µm, wall 1.5 µm thick, finely verrucose (covered in warts), pore with a low, hyaline papilla, pedicel (stem or stalk) hyaline, short, fragile and deciduous (falling off when mature). Possibly a hemi-form (possessing a reduced life cycle comprising only uredial and telial stages).
Description adapted from Wilson, M. & Henderson, D. M. (1966). British rust fungi.
Not formally assessed. Considered Critically Endangered / B in the current but unofficial Red Data List of Threatened British Fungi (Evans et al. 2006). In Great Britain, only reported from England, where it is a species “of principal importance for the purpose of conserving biodiversity” covered under section 41 (England) of the NERC Act (2006). The host plant, Gentianella amarella, is considered of Least Concern in Great Britain (Cheffings et al. 2005), but Near Threatened in England (Stroh et al, 2014).
None known on this host.
Uromyces gentianae is an obligate biotrophic parasite and pathogen of some Gentianella spp., originally described from Gentianella quinquefolia ssp. occidentalis in Iowa, USA.
In Great Britain, verified finds of the rust have only been found on Gentianella amarella. An early record from G. campestris has been presumed to be U. gentianae (Wilson and Henderson, 1968), but the host plant was not clearly identifiable due to heavy infection.
In Great Britain, historically recorded from North Devon VC4, Dorset VC9, South Hampshire VC11, East Kent VC15, and Worcester VC37. Recent surveys have found extant populations in North Devon VC4 (in 2015), North Hampshire VC12 (in 2006), West Sussex VC13 (several sites in 2010 and 2015), West Suffolk VC26 (in 1978), and Bedfordshire VC30 (in two sites in 2012).
Historical and extant sites are widely scattered across south England, and recent records note moderate to high levels of infection when the rust is present. However, many unsuccessful searches of host populations suggest that the rust may be genuinely rare.