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

Verkley et al.much more profound difference is seen between cultures of thetwo species, with colonies of S. galeopsidis on OA being opaqueand dark olivaceous-black even at the margin, while colonies ofS. lamiicola are more translucent yellowish to ochreous, becomingdarker only due to the formation of pycnidia. Priest (2006) pointedtowards differences in conidial width and conidiogenesis betweenS. lamiicola and S. galeopsidis, but having compared both speciesmorphologically in planta and in vitro, we conclude that thesespecies cannot be distinguished using these criteria. These twospecies are, however, readily distinguished by DNA sequencedata, and the multilocus phylogeny provides evidence for a closerelationship with S. matricariae (CBS 109000, CBS 109001), whileother Septoria occurring on the same plant family as S. lamiicola(Lamiaceae) are all much more distant (Fig. 2). The Austrianand Dutch collections of S. lamiicola on L. album are sufficientlyhomogenous to consider them conspecific.Septoria leucanthemi Sacc. & Speg., in Saccardo, Michelia1: 191. 1878. Fig. 25.≡ Rhabdospora leucanthemi (Sacc. & Speg.) Petr., Sydowia 11: 351.1957.For addditional synonyms see Punithalingam (1967b).Description in planta: Symptoms leaf spots hologenous orepigenous, scattered, circular to irregular, pale to dull brownthroughout or with whitish central area, indefinite with concentriczones or delimited by a slightly darker margin. Conidiomatapycnidial, predominantly epiphyllous, numerous scattered in eachleaf spot, subglobose to globose, brown to black, semi-immersed,130–220(–240) µm diam; ostiolum central, circular, 35–100 µmwide, surrounding cells dark brown and with more thickenedwalls; conidiomatal wall about 8–12.5 µm thick, composed of ahomogenous tissue of hyaline, angular cells, 2.5–5 µm diam withrelatively thin, hyaline walls, surrounded by a layer of pale to darkbrown angular to more irregular cells, 3–6.5 µm diam with slightlythickened walls. Conidiogenous cells hyaline, discrete, rarelyintegrated in 1–2-septate conidiophores, cylindrical to doliiform,or ampulliform, holoblastic, proliferating percurrently with indistinctannellations, or sympodially, 6–18 × 4–6.5(–7.5) µm. Conidia filiformto filiform-cylindrical, straight, curved, sometimes slightly flexuous,attenuated gradually to a narrowly rounded to pointed apex, widestnear the base, where attenuating abruptly or more gradually into anarrowly truncate base, (5–)6–13-septate (later secondary septaare developed in some cells), not constricted around the septa,hyaline, contents with several minute oil-droplets and granularmaterial in each cell in the living state, with minute oil-droplets andgranular contents in the rehydrated state, (67–)80–100(–125) ×2.5–3.0(–3.5) µm (rehydrated). Sexual morph unknown.Description in vitro: Colonies on OA 6–8(–11) mm diam in 2 wk(11–14(–17) mm in 3 wk), with an even, glabrous, colourlessmargin; colonies spreading, the surface plane, immersed myceliumpale buff, later more or less rosy-buff; in the centre complexes ofpycnidial conidiomata with pale brown or olivaceous walls releasemasses of pale whitish to buff conidial slime; reverse concolorous,but honey in the centre. Colonies on CMA 9–11(–13) mm diam in2 wk (15–18 mm in 3 wk), as on OA, but with some white diffuseand high aerial hyphae in the centre, and later more elevated in thecentre; reverse in the centre hazel to fawn after 3 wk; conidiomatamuch more numerous and larger than on OA, developing inconcentric or random patterns as discrete, large acervuloid (lateralmost discoid to cupulate) stromata with olivaceous sterile tissues,releasing large masses of pale white to pale buff conidial slime.Colonies on MEA 7–10 mm diam in 2 wk (14–17 mm in 3 wk),with an even, colourless, glabrous margin; colonies restricted,irregularly pustulate to hemispherical, the bumpy surfaceconsisting of numerous protruding conidiomatal initials, appearingdark, with sepia, dark brick and cinnamon tinges, aerial myceliummostly absent, locally dense, pure white and woolly; reverse mostlysepia to fawn or vinaceous buff. Sporulation only observed afterabout 7 wk. Colonies on CHA 7–13 mm diam in 2 wk (15–20 mmin 3 wk), with an even, glabrous, pale vinaceous buff margin;colonies restricted, irregularly pustulate to conical, the surfacebumpy, immersed mycelium honey to hazel, covered by dense todiffuse, pure white, woolly aerial mycelium; conidiomata sparselydeveloping at the surface after 2 wk, the wall slightly darker thanthe surrounding hyphae, releasing pale white conidial slime (evenafter 3 wk); reverse cinnamon in the centre, vinaceous buff or paleochreous at the margin.Conidiomata and conidiogenous cells as in planta. Conidia asin planta, 5–13(–17)-septate, 70–125(–175) × 3–4 µm (OA).Hosts: Various species of the genera Chrysanthemum, Tagetes,Achillea, Centaurea and Helianthus (Waddell & Weber 1963,Punithalingam 1967b, c).Material examined: Austria, Tirol, Ober Inntal, Samnaun Gruppe, Böderweg onLazidalm, on living leaves of Chrysanthemum leucanthemum, 8 Aug. 2000, G.Verkley 1055, CBS H-21173, living cultures CBS 109090, 109091; Same substr.,Tirol, Zanderstal near Spiss, 11 Aug. 2000, G. Verkley 1069, CBS H-21170, livingcultures CBS 109083, 109086. Germany, Hamburg, on living leaves of Chr.maximum, Sep. 1958, R. Schneider s.n. CBS H-18111, living culture CBS 353.58 =BBA 8504 = IMI 91322. New Zealand, Coromandel distr., Coromandel peninsula,Waikawau, coast along St. Hwy 25, on living leaves of Chr. leucanthemum, 22 Jan.2003, G. Verkley 1826, CBS H-21247; same substr., North Island, Coromandel,Tairua Forest, along roadside of St. Hway 25, near crossing 25A, 23 Jan. 2003, G.Verkley 1842b, CBS H-21243, living culture CBS 113112.Notes: The six strains studied here showed minor differences inmorphological characters and DNA sequences, which show highestsimilarity to sequences of CBS 128621, an isolate originating fromCirsium setidens in South Korea, and identified as S. cirsii (Fig. 2).Septoria leucanthemi is also closely related to a number of otherSeptoria species from Asteraceae, such as S. senecionis and S.putrida (Senecio spp.), S. obesa (Chrysanthemum spp., Artemisia)and S. astericola (Aster sp.). It is confirmed here that Septoriaobesa, which has been regarded as a synonym of S. leucanthemiby Jørstad (1965), should be treated as a separate species (seealso the note on S. obesa).Septoria lycoctoni Speg. ex Sacc., Michelia 2 : 167. 1880.Fig. 26.Description in planta: Symptoms leaf spots epigenous, numerous,circular to irregular, single or confluent, white to pale greyish,surrounded by an initially red, then dark brown to black and thickenedborder. Conidiomata pycnidial, epiphyllous, inconspicuous, up to afew in each leaf spot, globose to subglobose, brown, immersed,90–145(–220) µm diam; ostiolum central, circular, more or lesspapillate, 25–55 µm wide; conidiomatal wall 17–35 µm thick,composed of textura angularis, differentiated layers absent, thecells mostly 3.5–5(–11) µm diam, the outer cells with brown,somewhat thickened walls, the inner cells with thinner, hyalinewalls. Conidiogenous cells hyaline, cylindrical, or elongatedampulliform with a relatively narrow neck which widens at the top,266