Dendrostoma quercus C.M. Tian & N. Jiang

Jiang, Ning, Fan, Xin-Lei, Crous, Pedro W. & Tian, Cheng-Ming, 2019, Species of Dendrostoma (Erythrogloeaceae, Diaporthales) associated with chestnut and oak canker diseases in China, MycoKeys 48, pp. 67-96 : 83-85

Dendrostoma quercus C.M. Tian & N. Jiang sp. nov. Figure 10

Diagnosis.

Dendrostoma quercus is recognised by the existence of dimorphic conidia, which is unique in the genus.

Holotype.

CHINA. Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian (holotype: BJFC-S1547; ex-type culture: CFCC 52739).

Etymology.

Quercus, referring to the host genus, Quercus .

Description.

Sexual morph: Pseudostromata erumpent, consisting of an inconspicuous ectostromatic disc, semi-immersed to superficial, causing a pustulate bark surface, 1000-1500 µm diam. Ectostromatic disc flat or concave, pale brown to brown, sometimes concealed by ostioles, surrounded by bark flaps, 400-800 µm diam.; central column yellowish to brownish. Stromatic zones lacking. Perithecia conspicuous, umber to fuscous black, 350-500 µm diam. Ostioles 5-8 per disc, flat in the disc or sometimes slightly projecting, cylindrical, covered by an orange, umber to fuscous black crust, 60-80 µm diam. Paraphyses slightly deliquescent. Asci fusoid to slightly fusiform, 8-spored, ascospores regularly disposed, with an apical ring, 55-65 × 8-11 µm. Ascospores hyaline, fusoid to cylindrical, smooth, often containing one guttule per cell to multiguttulate, symmetrical to asymmetrical, straight curved, bicellular, (13.4 –)13.8–15.6(– 16.6) × (5.1 –)5.3–5.8(– 5.9) μm, l/w = (2.4 –)2.5–2.8(– 2.9) (n = 50). Asexual morph: Conidiomata pycnidial, conical, occurring separately, pale yellow, semi-immersed in bark, 700-1000 μm high, 700-950 μm diam.; wall of several layers of pale yellow textura angularis; central column beneath the disc conical, yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 4.5-9 × 2-4 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, dimorphic, type one (> 99%) ellipsoid to fusoid, straight to curved, (11 –)13.3–16.1(– 16.9) × (3.4 –)3.5–4.2(– 4.5) μm, l/w = (2.6 –)3.3–4.4(– 4.9) (n = 50); type two (<1%) fusoid, apex acutely rounded, 13-16 × 4-6 μm.

Culture characters.

On PDA, cultures are initially white, becoming dark grey after 2 weeks. The colonies are flat with irregular edge; texture uniform, producing concentric circles with sparse conidiomata irregularly distributed within 1 month at 25 °C in the dark.

Additional specimens examined.

CHINA. Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52734 (BJFC-S1548); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52735 (BJFC-S1541); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52736 (BJFC-S1542); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52737 (BJFC-S1543); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52738 (BJFC-S1544); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52740 (BJFC-S1545).

Notes.

Dendrostoma quercus is associated with oak branch cankers and forms both sexual and asexual fruiting structures beneath cankered bark. Within the genus, D. quercus produces the second largest conidia, smaller only than those of D. qinlingense (Table 2). The presence of dimorphic conidia in Dendrostoma , however, is a feature unique to D. quercus .