Diaporthe sarothamni
Conidial morph: Phomopsis sarothamni (Sacc.) Höhn. (1906). Alpha-conidia 8-10(-12) x 2 µm; beta-conidia 30-33 x 1 µm.
Ascal morph: Stromata visible on the host surface as numerous minute pustulate erumpent elliptical to circular discs through which 1-3 ostioles are barely erumpent, entostroma evenly effuse and strongly differentiated and often somewhat limited in extent (1-5 cm), surrounded by a black zone line. Ascomata 400-500 µm diam., ± globose with a ± curved cylindrical neck to ca 700 µm diam., in clusters of 2-6 with the necks convergent. Interascal tissue of broad very thin-walled paraphyses to 7 µm diam., sparsely branched and tapering towards the apex, deliquescent at maturity. Asci 61-71 x 10.5-12.5 µm, cylindric-clavate, thin-walled and not fissitunicate, almost sessile and evanescent at the base and thus floating freely within the ascoma, the apex obtuse with a conspicuous refractive apical ring, not blueing in iodine but staining in fountain-pen ink, 8-spored . Ascospores arranged biseriately, (11-) 11.5-14.5 (-16.5) x 4-5 (-5.5) µm, fusiform-clavate, usually with a distinctly constricted median to slightly submedian septum but with a proportion of spores fusiform and aseptate, hyaline, smooth- and thin-walled, guttulate, without a gelatinous sheath or appendages.
Not formally assessed; seemingly not particularly common but certainly under-recorded.
The material examined has slightly broader ascospores than those listed for D. sarothamni (they are given as 13-16 (-17) x 3-4 (-4.5) µm by Wehmeyer 1933) and they are therefore intermediate between that species and D. inaequalis ((12-) 13-17 (-18) x 5.5-9 µm according to Wehmeyer), and the ascus length is also intermediate (45-58 x 7-14 µm in D. sarothamni versus 70-110 x 9-15 µm in D. inaequalis). The ascospore breadth in the collection examined appeared to be linked to maturity, and it is possible that only one species is involved.
The presence of paraphyses and the ascus apical ring that stains in ink and Congo red are atypical of Diaporthe and it may be that this collection and/or the two species discussed here belong outside of the genus - possibly closer to Melanconis.
On dead branches of Cytisus scoparius.
Reported from VC1 W Cornwall, VC14 E Sussex, VC16 W Kent, VC17 Surrey, VC28 W Norfolk, VC62 NE Yorkshire, VC66 Durham, VC97 W Ness, Rhum (VC104 N Ebudes) and VC105 W Ross.