Leptographium alneum B. Strzalka , R. Jankowiak & P. Bilanski, 2020

Strzalka, Beata, Jankowiak, Robert, Bilanski, Piotr, Patel, Nikita, Hausner, Georg, Linnakoski, Riikka & Solheim, Halvor, 2020, Two new species of Ophiostomatales (Sordariomycetes) associated with the bark beetle Dryocoetes alni from Poland, MycoKeys 68, pp. 23-48 : 23

Leptographium alneum B. Strzalka, R. Jankowiak & P. Bilanski sp. nov. Fig. 6

Etymology.

The epithet ( alneum ) refers to the species name of the bark beetle vector of this fungus, Dryocoetes alni .

Type.

Poland, Paprocice, from Dryocoetes alni beetle infesting Populus tremula , 2 Nov 2017, K. Miśkiewicz, (TUR 207557 http://mus.utu.fi/TFU.207557 holotype, ex-holotype cultures: CBS 144091 = CMW 51789).

Description.

Sexual morph: Ascomata developing after 30 d on sterilized Populus twigs when two mating types were paired: superficially or partly embedded in the agar or wood, single. Bases light brown to dark brown, globose, unornamented, (59-)66-90(-108) μm in diameter, necks dark brown, cylindrical, straight or curved, (58-)68-88(-114) μm long (excluding ostiolar hyphae), (18.7-)20.7-27.9(-31) μm wide at base, (10.2-)11.8-15.3(-17.8) μm wide at the tip. Ostiolar hyphae present, pale brown, straight, non-septate or sporadically one-septate, numerous, divergent, pointed at the tip, (14.6-)15.9-19(-22.7) μm long, 5 to 12 in number. Asci not seen. Ascospores one-celled, hyaline, falcate in side view, (7.4-)8.1-11.1(-14.3) × (1.2-)1.5-2.1(-2.4) μm; fusiform in face view, (6.9-)7.4-8.8(-10.3) × (1.8-)2-2.8(-3.3) μm; end view not seen, excluding hyaline gelatinous sheath, (8.9-)10-11.5(-12.2) × (4.5-)5.5-6.7(-7) μm in face view including sheath, accumulated in orange yellow-colored mass at the tip of the neck. Gelatinous sheath 0.5-3 μm thick, oval in face view.

Asexual morph: conidiophores macronematous, arising directly from hyphae, single solitary, without rhizoidal hyphae at the bases, often with barrel-shaped or globose cells, (48.1-)59.3-84.2(-102.9) μm in length. Stipes erect, light olivaceous, 1-4 septate (mostly 2), (7.6-)14.3-39.2(-48.5) μm long (from first basal septum to below primary branches), (2-)2.4-5.4(-15.6) μm wide below primary branches, apical cell often strongly swollen, (3.2-)3.8-5.2(-6.1) μm wide at base, basal cell rarely swollen. Conidiophores often composed of barrel or globose cells. Conidiogenous apparatus (20-)26.5-38.6(-48.7) μm long (excluding conidial mass) consisting of 2-3 series of branches-type B (more than two branches) ( Jacobs and Wingfield 2001). Primary branches light olivaceous, cylindrical or swollen, smooth, (5.1-)5.8-12.7(-23.1) × (1.2-)1.6-4.2(-6.8) μm. Conidiogenous cells hyaline, tapering from base to apex, (11.6-)13.2-19(-23.7) × (0.8-)0.9-2(-3.5) μm. Conidia hyaline, mostly allantoid, sometimes oblong to obovoid (3.2-)3.7-5.9(-9.7) × (0.8-)1-1.8(-2.8) μm, accumulating around the conidiogenous apparatus as a creamy mucilaginous mass.

Cultural characteristics: Colonies with optimal growth at 30 °C on 2% MEA with radial growth rate 8.8 ( ± 0.9) mm/d, good growth observed at 35 °C (8.3 mm/d) and better than at 25 °C (7.9 mm/d). Colonies brownish gray with distinct silvery gloss, margin smooth. Hyphae olive yellow in color, smooth, submerged in the medium and aerial mycelium abundant, not constricted at the septa, 1.1-5.5 (mean 2.5 ± 1) µm diam., asexual morph very abundant, which gives a shade of gray. Club-shaped cells terminal on septate hyphal branches present, (11.5-)14.8-25.6(-33.3) × (7.7-)11.3-15.1(-18.2) μm, born on a multicelled stalk, (7.2-)14.7-82.4(-124.2) μm long, (4.4-)5.1-7.7(-9.7) μm wide below primary septa, (2.9-)4-6(-7.4) μm wide at base. Perithecia and asexual morph co-occur in culture.

Host trees.

Alnus incana , Malus sylvestris , Populus tremula

Insect vector.

Dryocoetes alni , Scolytus mali

Distribution.

Poland

Note.

Morphologically, Leptographium alneum differs from Grosmannia crassivaginata in having longer ascomatal necks ( L. alneum : 58-114 µm: G. crassivaginata : 40-60 µm), and the presence of larger club-shaped cells ( L. alneum : 11.5-33.3 × 7.7-18.2 µm; G. crassivaginata : 12-20 × 8-12 µm ( Griffin 1968), 6.5-18.5 × 5-13.5 µm (CBS 119144), (Table 4 ). In addition, L. alneum has aseptate or sporadically 1-septate ostiolar hypahe, which are septate in G. crassivaginata . Leptographium alneum frequently produces conidiophores with barrel-shaped or globose cells, while in G. crassivaginata the cells of the conidiophore are slightly swollen at most. In contrast to G. crassivaginata (CBS 119144), L. alneum has larger conidia, especially in regard to width ( L. alneum : (3.2-)3.7-5.9(-9.7) × (0.8-)1-1.8(-2.8) µm: G. crassivaginata : (2.4-)3.2-5(-8.1) × (0.7-)0.9-1.3(-1.7) µm) (Table 4 ). Leptographium alneum has brownish gray colony with silvery gloss cultures in contrast to the olive brown colored colonies of G. crassivaginata (isolate CBS 119144). The optimal growth on MEA for L. alneum and G. crassivaginata (isolate CBS 119144) is 30 °C. However, L. alneum grows much faster than G. crassivaginata ( L. alneum 8.8 mm/d, G. crassivaginata 6.9 mm/d) and grows faster at 35 °C (8.3 mm/d) than at 25 °C (7.9 mm/d). In contrast, G. crassivaginata grows much faster at 25 °C (5.6 mm/d) than 35 °C (4.4 mm/d).

Figures

Figure 6. Leptographium alneum sp. nov. (CBS 144901) a Dryocoetes alni - infested Populus tremula tree b galleries of D. alni with ascomata c ascoma d ascomatal base e ascospores f ostiolar hyphae g-i conidiophores, black arrow indicates barrel-shaped cells j conidiogenous k conidia l club-shape cells m fourteen-day-old culture on MEA. Scale bars: 50 μm (c), 25 μm (d), 10 μm (e), 10 μm (f), 25 μm (g), 25 μm (h), 50 μm (i), 10 μm (j), 10 μm (k), 50 μm (l).