Discosia ravennica Bundhun, Jeewon, Camporesi, J.C. Kang & K.D. Hyde,, 2021

Bundhun, Digvijayini, Jeewon, Rajesh, Senanayake, Indunil C., Erio Camporesi,, Aluthmuhandiram, Janith V. S., Tang, Alvin M. C., Ji-Chuan Kang,, Bhoyroo, Vishwakalyan & Hyde, Kevin D., 2021, Morpho-molecular characterization of Discosia ravennica sp. nov. and a new host record for Sporocadus rosigena, MycoKeys 79, pp. 173-192 : 173

Discosia ravennica Bundhun, Jeewon, Camporesi, J.C. Kang & K.D. Hyde, sp. nov. Figure 2

Etymology.

The specific epithet Discosia ravennica refers to the province of Ravenna, where the fungus was collected.

Holotype.

MFLU 18-0131

Description.

Saprobic on leaves of Pyrus sp. Sexual morph: Undetermined. Asexual morph: Conidiomata 45-70 µm high, 410-800 µm diam., stromatic, scattered to gregarious, superficial, rounded to unevenly outlined with complete margins, applanate, unilocular to bilocular, rugose, not glabrous, dull black, ostiolate. Ostiole 50-90 µm diam., circular to oval, opening to the exterior, central. Conidiomatal wall 10-20 µm thick at the base, dark brown in the outermost layer, comprising thick-walled cells of textura angularis, gradually becoming pale towards the inner layer; 10-20 µm thick near the apex, dark brown to black, made up of thick-walled cells of textura epidermoidea; interlocular wall composed of dark brown thick-walled cells of textura prismatica, becoming thin-walled and paler towards the outer layers. Conidiophores up to 40 µm high, originating from the innermost layer cells of the basal stroma, unbranched or at times branched, mostly 0-1-septate, rarely 2-septate or reduced to conidiogenous cells, cylindrical, hyaline, smooth. Conidiogenous cells 8-30 × 0.7-1.5 µm (x- = 14.3 × 1.1 µm, n = 15), subcylindrical to elongate-ampuliform, hyaline, smooth-walled, holoblastic. Conidia 12-16 × 1.5-3 µm (x- = 13.8 × 2.3 µm, n = 40) naviculate, to subcylindrical, narrow towards the base, straight or faintly curved, euseptate, mostly 3-septate, occasionally 2-septate, with septa thicker and darker than the periclinal wall, with cells unequal, hyaline to sub-hyaline, smooth-walled, without constriction at septa, bearing appendages on both apical and basal cells; basal cell 3-6 µm (x- = 3.8 µm) long, narrowly obconic, with truncate base bearing a conspicuous dehiscence scar; 2 median cells, together 6-10 µm (x- = 7.4 µm) long [second cell 4-6 µm (x- = 5.0 µm) long, close to apical cell, almost twice the size of the third cell 2-4 µm (x- = 3.0 µm) long, close to basal cell]; apical cell 3-5 µm (x- = 3.6 µm) long, subconical with acute apex, hyaline at apex and sub-hyaline below; appendages tubular, faintly broad at the base, unbranched, flexuous; appendage on apical cell 5-17 µm (x- = 10.1 µm) long, single, polar; appendage on basal cell 4-17 µm (x- = 9.4 µm) long, single, inserted slightly above conidium base.

Material examined.

ITALY. Province of Ravenna [RA], Oriolo dei Fichi- Faenza; on dead land leaves of Pyrus sp.; 24 Dec. 2017; Erio Camporesi; IT 3632 (MFLU 18-0131, holotype; HKAS 104973, isotype) .

Notes.

In the present study, no culture could be obtained for D. ravennica despite several trials on various media including MEA, potato dextrose agar, corn meal agar or water agar at different incubation conditions, the reason for which the species was subjected to direct DNA extraction from conidiomata. Discosia ravennica is morphologically similar to D. neofraxinea in terms of superficial conidiomata, which are not glabrous and 3-septate conidia with cells of unequal length. It also closely resembles D. fraxinea (Schwein.) Nag Raj (1993) in having uni-to bi-locular applanate conidiomata and naviculate to subcylindrical 3-septate conidia with cells of unequal length. The new species, however, also differs from the latter two species as mentioned in Table 2 .

Figures

Figure 2. Discosia ravennica (MFLU 18 - 0131, holotype) a Herbarium specimen b Conidiomata on the host c, d Vertical sections of conidiomata e Conidioma wall at the base f-h Conidiogenous cells and developing conidia i, j Conidia. Scale bars: 500 μm (b); 200 μm (c, d); 10 μm (e, g-j); 20 μm (f).