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Page number:87 
Remarks (internal):Based on the original diagnosis, SERVAZZI (1937) considered Cladosporium lethiferum to be a species probably belonging in Pollaccia, but he did not introduce a formal combination. OND?EJ (1972) described this fungus as Pollaccia americana, and MORELET (1978) published the combination P. lethifera. In 1985, MORELET found the teleomorph of this North American species which he considered a variety of Venturia tremulae (var. grandidentatae), and he introduced the combination Pollaccia radiosa var. lethifera for its anamorph. RULAMORT (1986) reintroduced Pollaccia lethifera and proposed the new name Venturia moreletii for the teleomorph. However, this re-assessment was not based on any new examinations or any other new data.
Morphological analyses of the whole Fusicladium radiosum complex (RITSCHEL 2001) showed that the conidial sizes of var. radiosum and var. lethiferum are not significantly distinct. The conidia in var. lethiferum are only distinguished from those of var. radiosum by being frequently curved. These minor differences are not sufficient to treat this taxon as a separate species. We prefer to follow MORELET (1978) and maintain its status as a variety. A molecular approach would be the only way to re-assess the whole F. radiosum complex with all taxa included.
 
Description type:Non-original description 
Description:Fusicladium radiosum var. lethiferum (Peck) Ritschel & U. Braun comb. nov. Fig. 43
= Cladosporium lethiferum Peck, Rep. (Annual) New York State Mus. Nat. Hist. 40: 64 (1887); holotype: on Populus tremuloides, USA, New Hampshire, Keene, Jun. 1887, Peck (NYS); isotype: BPI 427241.
= Pollaccia lethifera (Peck) M. Morelet, Bull. Soc. Sci. Nat. Archéol. Toulon Var 34 (219): 12 (1978).
= Pollaccia radiosa [(Lib.) E. Bald. & Cif.] var. lethifera (Peck) M. Morelet, Cryptog. Mycol. 6: 113 (1985).
= Clasterosporium populi Ellis & Everh., J. Mycol. 7: 134 (1892), non Saccardo 1886; types: on Populus tremuloides, Canada, London, Dearness (DAOM, NY).
= Stigmina populi Pound & Clem., Bull. Geol. Nat. Hist. Surv. 9: 662 (1896), nom. nov., as '(Ellis & Everh.) Pound & Clem.'.
= Stigmina populi Peck, Bull. New York State Mus. Nat. Hist. 157: 34 (1912), nom. nov., as '(Ellis & Everh.) Peck'.
= Dicoccum populinum Ellis & Everh., Proc. Acad. Nat. Sci. Philadelphia 1893: 462 (1894); holotype: on Populus grandidentata, USA, Iowa, Iowa City, Jun. 1889 (NY).
= Fusicladium lageniforme Solheim & Hadfield, in Hadfield, Univ. Wyoming Publ. 1946: 18-19 (1946), nom. inval.
= Pollaccia americana Ond?ej, Eur. J. Forest Pathol. 2: 144 (1972); holotype: on Populus grandidentata, Canada, Kentville, 16 Jun. 1952, Creelman (DAOM), as Fusicladium radiosum (Lib.) Lind.
Teleomorph: Venturia tremulae [Aderh.] var. grandidentatae M. Morelet, Cryptog. Mycol. 6: 113 (1985) [= Venturia moreletii Rulamort, Bull. Soc. Bot. Centre-Ouest, N.S., 17: 191 (1986)].
Lit.: SACCARDO (1892: 604; 1895: 621; 1899: 1083), OND?EJ (1972: 144), MORELET (1978: 12; 1985: 113-115).
Ill.: OND?EJ (1972: 143, Fig. 3; 144, Fig. 5), MORELET (1985: 114, Fig. 7).
On living leaves, petioles and twigs, spots circular to irregular, 5-20 mm wide, yellowish brown, surrounded by a pale to later dark brown margin. Colonies amphigenous, pale to dark olivaceous-brown, sometimes almost black, dendritically spreading. Mycelium immersed. Stromata intraepidermal to subcuticular, composed of subglobose, pale to dark olivaceous-brown, relatively thick-walled cells, 4-9 µm diam. Conidiophores in dense fascicles, arising from the upper cells of stromata, forming sporodochial conidiomata, erumpent through the cuticle, erect, short cylindrical to doliiform or ampulliform, unbranched, 8-12 x 4-6 µm, aseptate, pale to medium olivaceous-brown, smooth, walls thickened, conidiophores reduced to conidiogenous cells, unilocal, determinate or occasionally percurrently proliferating, with a single or two inconspicuous annellations, loci truncate, (2-)3-4(-5) µm wide, neither thickened, nor darkened. Conidia solitary, oblong-ellipsoid to fusiform, often slightly curved, sometimes straight, 17-26(-33) x (5-)6-8(-10) µm, mostly 1-septate, septum in the upper third, to 2-septate, second septum in the lower third, rarely aseptate, often more or less constricted at the septa, pale to medium olivaceous-brown, smooth, walls somewhat thickened, apex pointed or rounded, truncate at the base, sometimes somewhat oblique, hila truncate to slightly convex, (2-)3-4(-5) µm wide, not or only slightly thickened, not darkened.
Hosts and distribution: on Populus spp. (Salicaceae), Europe, North America - Populus alba (North America, Canada, Ont.), P. alba x P. grandidentata (North America, Canada, Ont.), P. alba x P. jackii (North America, Canada, Que.), P. grandidentata (North America, Canada, NB., NS., Ont., PEI, USA, MD, NY, WI), P. tremuloides (Europe, BG, GB; North America, Canada, Alta., BC., Labr., Man., NB., Nfld., NS., Ont., PEI, Que., Sask., USA, AK, ID, ME, MT, NH, NY, PA, SD, WI).
Material examined: on Populus grandidentata, Canada, Nova Scotia, New Glasgow, 26 Aug. 1908 (NYS), as Cladosporium lethiferum Peck; on Populus grandidentata, USA, Maryland, Prince George's, 26 Jun. 1951, Waterman (B), as Fusicladium tremulae A.B. Frank.
 
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