Graphilbum xianjuensis G. H. Zheng & Q. Lu sp. nov.

Fig. 9

Etymology.

The epithet xianju (Latin) refers to the type locality.

Type.

China, Zhejiang, Xianju County, from Monochamus alternatus galleries and pupal chambers of Pinus massoniana infested by Bursaphelenchus xylophilus, December 2020, collected by G. H. Zheng, culture ex-holotype CFCC55738 = CXY4010 .

Description.

Sexual morph: not observed.

Asexual form: Hyalorhincladiella -like. Conidiogenous cells were simple or loosely branched, (9.12-) (15.44) - (48.64) (-62.49) × (1.25-) (1.53) - (2.21) (-2.45) μm . Conidia hyaline, smooth, cylindrical, aseptate, (4.76-) (6.07) - (9.87) (-13.41) × (0.99 -) (1.32) - (2.1) (-2.65) μm .

Culture characteristics.

Colonies on 2% MEA reaching 44.9 mm diameter, after incubation in the dark at 25 °C for 3 d, growth rate up to 14.98 mm/d at the fastest and colony margin irregular. Mycelium superficial to flocculose or floccose, hyaline, reverse grey-white. The optimal temperature for growth at 30 °C; no growth was observed at 5 °C.

Habitat and distribution.

Larval galleries and pupal chambers of Monochamus alternatus in Pinus massoniana, infested by Bursaphelenchus xylophilus, in Zhejiang Province, China.

Additional specimens examined.

China, Zhejiang, from Monochamus alternatus galleries and pupal chambers of Pinus massoniana infested by Bursaphelenchus xylophilus, December 2020, collected by G. H. Zheng, CFCC55739 = CXY4011, CXY4018 .

Note.

Only the Hyalorhincladiella -like asexual form was observed in Graphilbum xianjuensis . This is closely related to the G. acuminatum, G. anningense and G. translucens, based on the ITS, BT and TEF1-α phylogenetic trees (Figs 1, 3, 4). Four species differed according to the size of their conidia. The conidia of G. xianjuensis (6.07-9.87 μm) are longer than those of G. anningense (4.5-6.4 μm), G. acuminatum (3.5-6 μm) and G. translucens (2.4-3.5 μm) (Wang et al. 2019; Jankowiak et al. 2020). Besides, G. xianjuensis was found to be associated with M. alternatus and PWN-infested P. massoniana, whereas G. anningense was reported in galleries of T. yunnanensis and T. minor associated with P. yunnanensis in southwest China (Wang et al. 2019), G. acuminatum has been reported in galleries of Ips acuminatus and Pityogenes bidentatus associated with P. sylvestris in Europe (Jankowiak et al. 2020) and G. translucens was first reported in Cryphalus piceae associated with P. densiflora . In conclusion, four species of Graphilbum differ not only in geographical distribution, but also in hosts and vectors. The optimum growth temperature of G. xianjuensis, G. anningense and G. translucens is 30 °C and only G. acuminatum had an optimum growth temperature of 25 °C (Wang et al. 2019; Jankowiak et al. 2020).