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

Verkley et al.0(–9–11?)-septate conidia, 70–80 × 2 µm. The multilocus sequenceanalysis indicates that S. putrida and S. senecionis are closelyrelated but genetically distinct species (Fig. 2). Morphologicallythese sister taxa can best be distinguished based on conidial length;conidia in S. putrida can be up to 85 µm long in planta and evenlonger (up to 97 µm) in culture, whereas those of S. senecionis arerarely longer than 65 in planta and not over 70 µm long in culture.Thirteen more taxa have been described in Septoria on Senecio,of which S. anaxaea Sacc. is another distinctive, long-spored speciesdescribed from Senecio grandidentatus (?= S. praealtus), andrecently also from several other Senecio spp. in Australia. Accordingto Priest (2006), conidia are 3(–6)-septate, 28–75 × 2.5–3 µm (50–130 × 3.5–5 µm, Teterevnikova-Babayan 1987). Most other Septoriaspp. on Senecio may be synonyms of S. senecionis, and this needsto be confirmed by study of the type material.Septoria rumicum Sacc. & Paol., in Saccardo, Bull. Soc. r.Bot. Belg. 28: 23. 1889.Description in vitro: Colonies on OA 3–5 mm diam in 3 wk, with aneven colourless margin; colonies restricted, irregularly pustulate,immersed mycelium olivaceous-black mostly hidden under a low,dense mat of felty grey to white aerial mycelium; reverse olivaceousgrey.Colonies on MEA 6–10(–12) mm diam in 3 wk, with an even orlobed, colourless margin; colonies restricted, irregularly pustulate,immersed mycelium appearing olivaceous-grey under a densemat of woolly-floccose, white to grayish aerial mycelium; reverseolivaceous-black. No sporulation observed.Conidia (OA) cylindrical, filiform, straight or slightly curved,attenuated gradually towards a narrowly rounded to almost pointedapex, attenuated gradually or more abruptly towards the narrowlytruncate base, 3–5(–7)-septate, mostly 60–82 × 2–3 µm.Hosts: Rumex spp. (R. acetosa, R. alpinum).Material examined: France, Corrèze, Roumignac, on leaves of Rumex acetosa,H.A. van der Aa 5338, CBS H-18050, living culture CBS 503.76 ; Haute-Savoie, Mt.Beaudin, on stem of R. alpinus, July 1978, H.A. van der Aa 9594c, CBS H-18163,living culture CBS 522.78.Notes: Jørstad (1965) noted that S. rumicis Trail, which waspublished in the same year as S. rumicum, may be conspecific.Septoria acetosae Oud. was also regarded as a synonym.According to Saccardo (1892, Syll. Fung. 10: 380), S. rumicumproduces mostly epiphyllous pycnidia 100–125 µm diam, andcontinuous (?) conidia 50–68 × 3 µm. Septoria rumicis produceschiefly epiphyllous pycnidia 90–100 µm diam and conidia 24–40× 2–2.5 µm (Teterevnikova-Babayan 1987), according to Jørstad(1965), 20–50 × 2.5–3.5, with 2–3(–5) septa. Septoria acetosaewas treated as a separate species by Teterevnikova-Babayan(1987). According to the latter author, it is characterised by1–3-septate conidia, 28–50 × 3–5 µm. As the conidial sizes of thematerial available here agree best with the original description ofS. rumicum, this name is adopted here. Several other species ofSeptoria have been described from Rumex, most of which need tobe restudied to assess their status.Septoria scabiosicola (Desm.) Desm., Annls Sci. Nat., sér.3, Bot. 20: 96. 1853. Fig. 36.Basionym: Depazea scabiosicola Desm., Annls Sci. Nat., sér. 2,Bot. 6: 247. 1836.Description in planta: Symptoms leaf spots numerous but small,circular, some merging to irregular patterns, centre white,surrounded by a relatively broad, dark margin with a distinctred or purple periphery. Conidiomata pycnidial, epiphyllous butsometimes also visible from the underside of the lesion, one toa few in each leaf spot, subglobose to globose, brown to black,usually fully immersed, 65–130 µm diam; ostiolum central,initially circular and 35–60 µm wide, later becoming moreirregular and up to 80 µm wide, surrounding cells concolorousto pale brown; conidiomatal wall about 10–15 µm thick,composed of a homogenous tissue of hyaline, angular cells2.5–6.5 µm diam, the outermost cells pale brown with somewhatthickened walls, the inner cells thin-walled. Conidiogenous cellshyaline, discrete, doliiform, or narrowly to broadly ampulliform,holoblastic, with a relatively narrow elongated neck, proliferatingpercurrently several times with distinct annellations, often alsosympodially after a few percurrent proliferations, 6–9(–12) ×2.5–3(–5) µm. Conidia filiform to filiform-cylindrical, straight,slightly curved to flexuous, attenuated gradually to a narrowlypointed apex and narrowly truncate base, (0–)3–5(–6)-septate(septa very thin and easily overlooked), not constricted aroundthe septa, hyaline, contents with several minute oil-droplets andgranular material in each cell in the living state, with minute oildropletsand granular contents in the rehydrated state, (17–)30–55 (–79) × 1–2 µm (living; rehydrated, 1–1.8 µm wide). Sexualmorph unknown.Description in vitro: Colonies on OA 9–13 mm diam in 2 wk, withan even, glabrous, colourless margin; immersed mycelium mostlyhomogeneously coral to scarlet, the pigment diffusing beyondthe colony margin; in the centre black and slightly elevated dueto immersed and more frequently superficial pycnidia, surroundedby an area with more scattered pycnidia, releasing pale fleshdroplets of conidial slime; aerial mycelium scanty, consisting ofminute white tufts; reverse scarlet to coral, the centre darker, bloodcolour. Colonies may develop sectors that are unpigmented andglabrous. Colonies on CMA 8–11 mm diam in 2 wk; similar as onOA, but generally less strongly pigmented. Colonies on MEA 6–9mm diam in 2 wk, the margin irregular; colonies restricted, thecentre elevated and cerebriform to irregularly pustulate, up to 2mm high, the surface pale brown, later black, with scanty whiteareal mycelium; reverse of the colony dark brick, paler towards themargin. Colonies on CHA 6–11 mm diam in 2 wk, with an even,glabrous, colourless margin; immersed mycelium greenish grey todark slate blue, throughout covered by well-developed, tufty whitishgrey arial mycelium that later attains a reddish haze; reverse bloodcolour, but margin paler; in the central part of the colony numerouspycnidia develop, releasing pale vinaceous to rosy-buff conidialslime; in older colonies the centre becomes cerebriform and up to3mm high, much as on MEA.Conidiomata (OA) as in planta, pycnidial, sometimes mergedinto larger complex stromata dark brown, glabrous, 80–180µm diam, with a single ostiolum, or without preformed openingand simply bursting open; conidiogenous cells as in planta, butmore often integrated in 1–2-septate conidiophores, often onlyproliferating percurrently and/or sympodially, 6–15 × 3–7.5 µm;conidia as in planta, 1–6(–7)-septate, not constricted around thesepta, hyaline, with several minute oil-droplets and numerousgranules in each cell, (30–)40–80(–100) ×1.5–2(–2.5) µm.Hosts: Knautia spp., Succisa spp. and Scabiosa spp.284