Ophiostoma pehueninum M. Zapata, M.A. Palma & E. Piontelli, 2018

Zapata, Mario, Palma, Maria Antonieta & Piontelli, Eduardo, 2018, Ophiostoma pehueninum, a new species associated with Araucaria araucana in Chile, Phytotaxa 346 (1), pp. 93-103 : 98-100

Ophiostoma pehueninum M. Zapata, M.A. Palma & E. Piontelli sp. nov. ( Fig. 3–4 )

MycoBank no.: MB822101

Etymology. The epithet pehueninum refers to the host tree name in Mapudungun (Mapuche language), Pehuén.

Sexual morph: Ascomata developing after 30 days on WA with autoclaved araucaria twigs, superficial, mostly embedded on media, only in crosses done between isolates RGM 2388 and RGM 2389. Ascomatal bases dark brown to black (10 YR 3/1), globose to subglobose, bases (105–)145–200(–210) μm in diameter, ornamented with brown, short and long twiggy hyphal hairs in the peridia and basal perithecia, 40–150 μm, up to 200 μm long. Ascomatal necks dark brown to black (10 YR 3/1), straight or curved without annuli, (105–)145–350(–800) μm long, (27–)30– 42.5(–50) wide at the base, (12–)17.5–27.5(–30) μm wide at the apex. Ostiolar hyphae divergent, tapering towards the apex, subhyaline, without septa and rounded end, (15–)30–40 × 1.5–2(–2.2) μm, 8–13 in number. Asci not observed. Ascospores accumulating in a clear white mucilaginous mass at the ascomatal apex, turning light yellow with age, hyaline, 1-celled, allantoid in side view, surrounded by a narrow gelatinous sheath, (3.8–)4.5–5.6(–6) × (1–)1.3–1.7(– 2) μm (average = 5 × 1.5 μm).

Asexual morph: After 14 days on MEA, hyalorhinocladiella-like micronematal state present. Conidiogenous cells arising directly from narrow undifferentiated hyphae or as distinct unbranched or branched conidiophores, revealing in the main axis low-profile scars on the extending conidiophore, (25–)35–50(–60) × 1.5–2.5 μm. Conidia hyaline at first, light brown in time, smooth, ellipsoidal, obovoid to round, base truncate, narrow or wide (more notable on OA), without denticles, (3.1–)3.6–5.2(–9.0) × (2.9–)3.0–4.2(–4.7) μm, often giving rise to secondary conidia. In some wide hyphae, apparent synchronic development of blastic conidia formed in small groups (3–5) by repeated percurrent proliferation at the apex of sessile conidiogenous cell. Mycelium aerial, superficial, embedded in the agar.

Colonies growing: Cultures on MEA reaching 40.3 ± 1.7 mm in diameter at 7 days, 69.0 ± 2.3 mm at 14 days and 76.8 ± 1.1 mm at 21 days, granular in appearance, brown-colored after 21 days (5 Y 6/3). Growing on PDA reaching 23.7 ± 0.7 mm in diameter at 7 days, 46.0 ± 2.0 mm at 14 days and 59.2 ± 3.7 mm at 21 days, color variable from white (5 Y 8/1) to light brown (5 Y 6/3) after 21 days. Growing on OA reaching 32.7 ± 1.7 mm in diameter at 7 days, 58.8 ± 3.7 mm at 14 days and 76.1 ± 1.9 mm at 21 days, color white forming brown fluffy masses (2.5 Y 6/4) after 21 days. No growth at 35° C.

Typification:— CHILE, Alto Bío Bío, Ralco Forest Reserve (37°56’41’’ S, 71°20’12’’ W), from Araucaria araucana , June 2016, collected by Viviana Sepúlveda, holotype RGM 2389, ex-type culture CBS 142995.

Additional specimens examined:— CHILE, Alto Bío Bío, Ralco Forest Reserve (37°56’04’’ S, 71°21’48’’ W), from Araucaria araucana , March 2017, Rodrigo Kiger, living culture RGM 2387, CBS 142996. Alto Bío Bío, Ralco Forest Reserve (37°56’02’’ S, 71°21’54’’ W), from Araucaria araucana , March 2017, Rodrigo Kiger, living culture RGM 2388, CBS 142997.

Notes: Ophiostoma species are pleomorphic and several types of asexual reproduction can be found in a single culture. In our specimen a continuum of conidial ontogeny was observed not including two of the common asexual morphs of Ophiostoma such as pesotum-like and sporothrix-like.This species has a special conidiogenesis in appearance similar to Hyalorhinocladiella because of its micronematous development and mycelial form in nature ( Upadhyay & Kendrick 1975), but differs from this group by the shape and brown color of its conidia. The conidiogenous cell also resembles Pesotum because of its conidium dehiscence, but differs from this group by the color of conidia at maturity and lacks synnematous character. The conidia observed in a percurrent proliferation of the conidiogenous cell under the light microscope (or interdiferencial contrast) is a situation that could be easily misinterpreted as arising from a sympodial proliferation by the effect of repeated incomplete dehiscence ( Benade et al. 1995).

Known hosts and substrate:— Araucaria araucana , stem and branches.

Known insect vector:—Unknown.

Known distribution:— Chile, Bío Bío Region.

Figures

FIGURE 3. Ophiostoma pehueninum (RGM 2389, holotype).A: Blastic conidia in the apex of conidiogenous cell. B, C: Conidia revealing narrowly spaced, over the conidiophore, and wide basal insertion. D: Conidia with repeated percurrent proliferations of the conidiogenous cell (in the box conidia with basal scar), E. Conidiogenous cell revealing narrowly spaced scar due to repeated percurrent proliferations, in the long axis (arrows). F: Apparent synchronic born of blastic conidia with repeated percurrent proliferations in the apex of sessile conidiogenous cell in the width mycelia, G: Secondary conidia. H: Group of ascomata in submerged water agar with sterilized Araucaria twigs. I: Perithecia with long neck and peridial hyphae around the base (in the box, ascospores with huge increase). J: Ascomata apex necks with divergent ostiolar hyphae and ascospore. Scale bar:A-G and I (small box) = 5 μm; H-I = 100 μm; J = 10 μm.

FIGURE 4. Colony morphology of Ophiostoma pehueninum (holotype) after 21 d growth at 25 °C on MEA, PDA and OA (from left to right).