Ophiostoma aggregatum H. Wang, Q. Lu & Z. Zhang

Min Wang, Hui, Wang, Zheng, Liu, Fu, Xu Wu, Cheng, Fang Zhang, Su, Kong, Xiang Bo, Decock, Cony, Lu, Quan & Zhang, Zhen, 2019, Differential patterns of ophiostomatoid fungal communities associated with three sympatric Tomicus species infesting pines in south-western China, with a description of four new species, MycoKeys 50, pp. 93-133 : 108-111

Ophiostoma aggregatum H. Wang, Q. Lu & Z. Zhang sp. n. Fig. 13

Etymology.

‘aggregatum’ (Latin), reflects to the conidiophores aggregated in clusters.

Type.

CHINA, Yunnan, from Tomicus minor galleries in Pinus yunnanensis , Dec. 2016, HM Wang, holotype CXY 1876, culture ex-holotype CFCC 52615 = CXY 1876.

Description.

Sexual form: unknown.

Asexual form: Leptographium -like. Conidiophores macronematous, mononematous, gathered in groups up to 5, (28.5-) 34-45.5 (-52) μm long; stipes cylindrical, 1-2 septate, not constricted at septa, umber-brown to dark olivaceous, (6.3-) 7.3-14.5 (-18) μm long × (2.2-) 3.1-4.6 (-5.8) μm wide. Conidiogenous apparatus (22-) 26.5-31 (-34) μm long, with 2-3 series of cylindrical branches; primary branches olivaceous, smooth, cylindrical all over, (5.9-) 7.2-13.5 (-20.5) × (3-) 3.3-4.2 (-4.6) μm; conidiogenous cells discrete, 2-3 per branch, aseptate, cylindrical, hyaline to pale umber, (5.8) 7.2-12.1 (-18.5) × (2.1-) 2.8-4.0 (-4.7) μm; conidia 1-celled, globose, elliptical with truncate bases, hyaline to pale umber, (4.0-) 4.8-5.9 (-6.3) × (3.1-) 4.0-5.0 (-5.6) μm.

Culture characteristics.

Colonies on 2% MEA fast growing in the dark, reaching 90 mm in diam. in 8 days at 25 °C, growth rate up to 13 mm/day at the fastest; colony margin smooth. Hyphae submerged and aerial, umber-brown to dark olivaceous, flocculose or floccose; reverse hyphae umber-brown to dark olivaceous. Optimal growth temperature 25 °C, able to grow at 5 °C and 30 °C. No growth at 35 °C.

Known substrate and hosts.

Galleries of Tomicus yunnanensis and T. minor in Pinus yunnanensis .

Known insect vectors.

Tomicus minor , T. yunnanensis .

Known distribution.

Yunnan Province, China.

Additional specimens examined.

CHINA, Yunnan, from Tomicus yunnanensis and T. minor galleries in Pinus yunnanensis , Dec. 2016, Apr. 2017, HM Wang, CFCC 52616 = CXY 1875, CFCC 52617 = CXY 1874.

Note.

Ophiostoma aggregatum produced a single asexual, Leptographium -like state in vitro. This species is phylogenetically closely related to O. macrosporum , O. tingens , O. floccosum , O. tapionis and O. piliferum in LSU-, ITS- and TUB2-based phylogenetic inferences. Ophiostoma aggregatum and O. tingens are shown to be sympatric in Yunnan pine forest; both taxa were isolated from galleries and adults of T. minor and T. yunnanensis infesting P. yunnanensis (Table 2). Ophiostoma tingens was also reported from T. minor infesting P. yunnanensis in Yunnan ( Pan et al. 2017).

Ophiostoma aggregatum and O. tingens differ in their asexual state. Ophiostoma aggregatum only produces a Leptographium -like state. Inversely, the asexual states of O. tingens are variable. Our strains produced a Pesotum -like and a Sporothrix -like state whereas previously, Francke-Grosmann (1952) and de Beer et al. (2013b) reported a Hyalorhinocladiella - to Raffaelea -like state in European strains. The origin of this variability and its importance for taxonomy is uncertain.

Ophiostoma macrosporum , O. floccosum , O. tapionis and O. piliferum also differ from O. aggregatum by their asexual state. Ophiostoma macrosporum and O. floccosum produce a Pesotum -like asexual state, O. tapionis a Hyalorhinocladiella -like state and O. piliferum produces a Sporothrix -like state ( Francke-Grosmann 1952, Upadhyay 1981, Yamaoka et al. 2004, Linnakoski et al. 2008).

Ophiostoma macrosporum and O. tingens were both originally described in Trichosporium as T. tingens var. macrosporum and T. tingens ( Lagerberg 1927, Francke-Grosmann 1952). Batra (1967) transferred these two species into Ambrosiella . It is only recently that the morphological characteristics were found to agree with those of Ophiostoma ( de Beer et al. 2013b). Ophiostoma macrosporum has been reported from various Pinus spp. (including P. sylvestris ) infected by Ips acuminatus in Europe ( Francke-Grosmann 1952, Batra 1967).