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

Verkley et al.to 60 µm diam, lacking distinctly differentiated cells; conidiomatalwall composed of textura angularis without distinctly differentiatedlayers, mostly 15–20 µm thick, the outer cells with brown,somewhat thickened walls and 4.5–10 µm diam, the inner cellshyaline and thin-walled and of comparable diam. Conidiogenouscells hyaline, discrete or integrated in short, 1–2-septateconidiophores, cylindrical, or ampuliform with a relatively shortneck, hyaline, holoblastic, proliferating sympodially, and sometimesalso percurrently with indistinct annellations, 6.5–10(–12.5) × 2.5–4.5 µm. Conidia cylindrical, weakly to strongly curved, or flexuous,gradually attenuated to a rounded apex, gradually or more abruptlyattenuated into a broadly truncate base, (0–)2–5(–6)-septate, notor indistinctly constricted around the septa, hyaline, contents withseveral small guttules and numerous granules in each cell in theliving state, oil-droplets rarely merged into larger guttules in therehydrated state, (20–)40–65 × 2–2.5(–3) µm (rehydrated). Sexualmorph unknown.Description in vitro: Colonies on OA 7–10 mm diam in 2 wk (22–26 mm in 6 wk), with an even, somewhat undulating, glabrous,colourless margin; colonies spreading, the surface plane, immersedmycelium pale luteous or buff, with scattered immersed andsuperficial pycnidial conidiomata, which are first dark olivaceous,then almost black, glabrous, 150–450 µm diam, with a single orseveral (up to 5!) ostioli placed on short papillae or more elongatednecks (up to 350 µm), that release buff to rosy-buff later salmonconidial slime; aerial mycelium diffuse, woolly-floccose, white;reverse honey, but isabelline to hazel in the centre. Colonies onCMA 6–8 mm diam in 2 wk (18–23 mm in 6 wk), with an even,glabrous margin; as on OA but immersed mycelium with a greenishhaze; aerial mycelium higher and reverse darker, later hazel witholivaceous and yellow tinges; conidiomata similar as on OA.Colonies on MEA 7–9 mm diam in 2 wk (18–21 mm in 6 wk), withan even or somewhat undulating, glabrous, buff to honey margin;colonies pustulate to almost hemispherical, immersed myceliumrather dark, near the margin covered by woolly to felty white aerialmycelium; mostly composed of spherical conidiomatal initials,superficial mature conidiomata releasing rosy-buff to salmon, laterhoney conidial slime; reverse dark brick in the centre, near themargin cinnamon to honey. Colonies on CHA 7–14 mm diam in 2wk (20–28 mm in 6 wk), with an irregular, buff margin covered by adiffuse, felty white, later grey aerial mycelium; further as on MEA,but the colony surface less elevated and especially near the marginwith greyish felty to tufty aerial mycelium; conidial slime abundantlyproduced, first rosy-buff, later salmon to ochreous; reverse in thecentre blood colour, dark brick to cinnamon at the margin.Conidiomata on OA see above. Conidia as in planta, mostly(0–)3–5(–6)-septate, 44–63(–70) × 2.5–3 µm.Hosts: Senecio fluviatilis and S. nemorensis.Material examined: Belgium, Château de Namur, on leaves of Senecio sarracenica,1829, A. Bellynck, isotype BR-MYCO 155500-09. Netherlands, Prov. Gelderland,Millingen a/d Rijn, Millingerwaard, on living leaves of S. fluviatilis, 6 Oct. 1999, G.Verkley 939, epitype designated here CBS H-21219 “MBT175358”, living culturesex-epitype CBS 102366, 102381.Notes: The first Septoria that was described on the genus Seneciowas S. senecionis. The type host is Senecio sarracenica (=Senecio fluviatilis), and in later literature it has also been reportedfrom several other species of Senecio (Radulescu et al. 1973).According to the diagnosis by Westendorp, the conidia are 40 ×1.5 µm and 3–4-septate. Vanev et al. (1997) described the conidiaof S. senecionis as 2–6-septate, 29–68 × 2–2.5 µm, Radulescuet al. (1973) as 3–4-septate, 33–57 × 1.2–2 µm. By examiningthe type specimen from BR it is here confirmed that conidia are infact wider than described by Westendorp. It contains a single leafwith a few lesions, and conidia observed are 30–55 × 1.5–2.5 µm,and mostly 3–5-septate. The fresh material that was collected inthe Netherlands from the same host species, Senecio fluviatilis,and from which CBS 102366 and 102381 were isolated, is insufficient agreement with the type and is therefore designated hereas epitype of S. senecionis. Differences with Septoria putrida arediscussed under that species.Septoria sii Roberge ex Desm., Pl. crypt. Fr., Fasc. 44, no2185; Annls Sci. Nat., sér. 3, Bot. 20: 92. 1853. Fig. 37.Description in planta: Symptoms leaf spots, yellow to brown, initiallyvaguely delimited but later well-delimited by veinlets, scattered,later often confluent over large areas, visible on both sides of theleaf. Conidiomata pycnidial, epiphyllous, rarely also hypophyllous,single, scattered or in small clusters, globose to subglobose,immersed, (60–)80–110 µm diam; ostiolum circular, central, 12.5–25(–35) µm wide, surrounding cells concolorous; conidiomatal wallcomposed of textura angularis 5–10 µm thick, with an outer layer ofcells 3–4.5 µm diam with brown, thickened walls, and an inner layerof hyaline and thin-walled cells, 2.5–4 µm diam. Conidiogenouscells hyaline, broadly or elongated ampulliform, normally witha distinct neck, hyaline, holoblastic, proliferating percurrently,annellations indistinct, 5–8.5 × 3–5 µm. Conidia cylindrical, straight,curved, or flexuous, gradually attenuated to a relatively broadlyrounded apex, more or less abruptly attenuated into a truncatebase, 1–3(–4)-septate, slightly to distinctly constricted around thesepta in the fresh, fully hydrated state, hyaline, containing one toseveral relatively large oil-droplets in each cell, in the rehydratedstate with irregular oil-masses (20–)29–35(–42) × 2–2.5(–3) µm(living; rehydrated, 1.5–2 µm wide). Sexual morph unknown.Description in vitro: Colonies on OA 4–9 mm diam in 2 wk [(15–)19–23 mm in 6 wk], with an even, glabrous, colourless margin;colonies remaining almost plane, immersed mycelium olivaceousblack,locally however peach is dominant, which becomes scarletafter several wk; aerial mycelium mostly well-developed, woollyfloccose,white; scattered, mostly immersed pycnidial to stromaticconidiomata developing in the centre, releasing droplets ofmilky white to rosy-buff conidial slime; reverse dark slate blue toolivaceous-black, and locally peach, the pigment not diffusing intothe medium. Colonies on CMA up to 1.5 mm diam in 2 wk [7–10(–25) mm in 6 wk], as on OA, but peach pigment diffusing into themedium, while the colony itself is predominantly olivaceous-black.Colonies frequently develop faster growing sectors that first arebuff and sporulate directly from the mycelium, later become paleluteous with a distinct scarlet pigmentation and forming numerousmostly superficial pycnidia. Colonies on MEA 3–6 mm diam in2 wk [12–14(–26) mm in 6 wk], the margin ruffled, olivaceousblack;colony concolorous, irregularly pustulate-worty, covered bydiffuse to dense felty white or greyish aerial mycelium; numerousconidiomatal initials developing at the surface, mature onesreleasing cirrhi of conidia that first are milky white, later salmon,sometimes merging to form slimy masses covering areas of thecolony surface; the agar surrounding the colony slightly discolouredby diffusing pigment(s). Colonies on CHA 5–6 mm diam in 2 wk[8–13(–15) mm in 6 wk], as on MEA; some parts of the colonies286