A new approach to species delimitation in Septoria - CBS - KNAW

A new approach to species delimitation in SeptoriaFig. 44. Sphaerulina cornicola. A–C. Colonies CBS 102324. A. On OA. B. On CHA. C. On MEA.mainly consisting of a basal 15–25(–35) µm thick layer of angularto subglobose, subhyaline to pale brown cells 5–10 µm diam,lateral wall absent or very poorly developed, composed of similar,somewhat darker cells. Conidiogenous cells hyaline, discrete orintegrated in 1(–2)-septate conidiophores, subglobose, doliiformor ampulliform, holoblastic, proliferating percurrently with one toseveral disctinct annellations, or sympodially, sometimes bothtypes of proliferation occur in a single conidiogenous cell, 8–15(–20) × 2.5–4 µm. Conidia cylindrical, straight or more or less curved,attenuated gradually to a broadly rounded apex, attenuated moreor less abruptly to a truncate base, (1–)3-septate, conspicuouslyconstricted around the septa in fresh and rehydrated state, hyaline,contents with numerous minute oil-droplets and granular materialin each cell in the living state, with minute oil-droplets and granularcontents in the rehydrated state, (32–)37–47(–50) × 3–4 µm (living;rehydrated, 2–3 µm wide).Description in vitro. Colonies on OA 3–4 mm diam in 2 wk, with aundulating even margin; colonies restricted, irregularly pustulate,the surface buff or much darker grey to brown, locally glabrousbut mostly covered by a dense mat of finely felted white aerialmycelium, conidiomata developing on the surface releasing conidiain clear droplets, or in milky white to rosy-buff masses; reversedark greyish or brown-vinaceous. Colonies on MEA 3–4(–8) mmdiam in 2 wk, with a undulating even margin; colonies restricted,irregularly pustulate, the surface almost black provided with lowand finely felted, diffuse, grey to white aerial mycelium, conidiomatadeveloping just beneath the colony surface, releasing white cirrhiof conidia; reverse a palet of brown-vinaceous, cinnamon andolivaceous-grey.Conidia (OA) as in planta, (31–)34–50(–58) × 3.5–5 µm.Microconidia (spermatia of the Asteromella state) ellipsoid, hyaline,0-septate, 3–4 × 1.5 µm.Hosts: Acer campestre, A. circinatum, A. hyrcanum (Vanev et al.1997) and A. pseudoplatanus.Material examined: France, locality unknown, on leaves of Acer campestre,distributed in Libert, Pl. Cryptog. Ard. Fasc. 1 (1830): no. 54, isotype BR–MYCO153858-16, type of Ascochyta aceris Lib. Netherlands, prov. Utrecht, Baarn, onAcer pseudoplatanus, July 1969, I. Blok, living culture CBS 514.69; Baarn, gardenWCS, on living leaves of Acer pseudoplatanus, 23 July 1985, H.A. van der Aa9537, CBS H-14666, living culture CBS 652.85; same substr., prov. Zuid-Holland,Wassenaar, Hollandsch Duin, 14 Aug. 1994, G. Verkley 227, CBS H-18040, livingculture CBS 687.94; same substr., prov. Zuid-Holland, Wassenaar, Ganzenhoek, 8Aug. 1995, G. Verkley 307, CBS H-21239, living culture CBS 187.96; same substr.,prov. Utrecht, Baarn, Eemnesserweg, 7 May 1996, H.A. van der Aa 12120, CBSH-14665, living culture CBS 183.97; USA, Oregon, Lane Co., Proxy Falls Trail, onliving leaves of Acer circinatum, 11 Oct. 1996, J. K. Stone & G. Verkley 480, CBSH-21236, living culture CBS 655.97.Notes: This is the oldest septoria-like species described frommembers of the family Aceraceae. It occurs on several speciesof the genus Acer. In the original diagnosis of Libert, three hostspecies were mentioned, viz., A. campestre, A. pseudoplatanusand A. platanoides. Jørstad (1965) treated forms on A. platanoideswith conidia 26–60 × 2–2.5 µm as S. apatela All. (synonyms S.seminalis var. platanoidis All., Phleospora platanoidis Kabát &Bubák, Phloeospora samarigena Bubák & Krieg.), while those on A.campestre remained unsettled. According to Jørstad (1965) conidiaof S. aceris are 24–43 × 2–3 µm, with 3 septa, which agrees wellwith the sizes observed in the type specimen available in the presentstudy. This material also showed a small proportion of 4-septateconidia in one of the fruitbodies. More species with conidia longerthan 60 µm have been described from A. platanoides, and theseneed to be critically assessed in a comprehensive study includingisolates of all Septoria occurring on the genus Acer. No isolatesfrom the the type host A. campestre that would be most suitableas epitype, were available, hence no epitypification is proposedhere. The ultrastructure of conidiogenesis and conidia of S. aceriswas studied by Verkley (1998b), who showed that in a single cellpercurrent as well as sympodial proliferation can occur.A description of the sexual morph known as Mycosphaerellalatebrosa was provided by Kuijpers & Aptroot (2002), but theirspecies concept included several discrete entities that aredistinguishable by their conidial states and occur on distantly relatedhost plants. It is unlikely that these entities can be distinguishedat all by the morphology of the sexual state (Verkley & Starink-Willemse 2004).Sphaerulina cornicola (DC.: Fr.) Verkley, Quaedvlieg &Crous, comb. nov. MycoBank MB804474. Fig. 44.Basionym: Depazea cornicola DC.: Fr., in De Candolle & Lamarck,Flore Française VI: 146. 1815.≡ Septoria cornicola (DC.: Fr.) Desm., Pl. crypt. Fr., Fasc. 7, no 342.1828; Index Pl. crypt. Fr.: 24. 1851.= S. cornicola var. ampla H. C. Greene, Amer. Midl. Nat. 41: 755. 1949 (fideFarr 1991).For extended synonymy see Farr (1991). Neotype on Cornussanguinea, France (BPI, designated by Farr 1991), not seen.Description in planta: Symptoms starting as red discolorations ofthe leaf lamina and margin, which develop to scattered, circularto irregular, hologenous leaf spots, that later become pale brown,and surrounded by a dark brown to black bordering zone and adistinct red or purple periphery. Conidiomata pycnidial, epiphyllous,numerous scattered in each leaf spot, subglobose to globose,brown to black, immersed or semi-immersed, 55–100(–120) µmdiam; ostiolum central, initially circular and 25–40 µm wide, laterbecoming more irregular and up to 60 µm wide, surrounding cellsconcolorous to pale brown. Conidiomatal wall about 10–15 µmthick, composed of a outer layer of hyphal to irregular cells 3.0–8 µmdiam with brown walls, and an inner layer of hyaline cells 3–5 µmwww.studiesinmycology.org295