Neothyronectria citri C.M. Tian & Q. Yang

Yang, Qin, Chen, Wen-Yan, Jiang, Ning & Tian, Cheng-Ming, 2019, Nectria-related fungi causing dieback and canker diseases in China, with Neothyronectriacitri sp. nov. described, MycoKeys 56, pp. 49-66 : 49

Neothyronectria citri C.M. Tian & Q. Yang sp. nov. Figure 4

Diagnosis.

Neothyronectria citri differs from its closest phylogenetic neighbour Neothyronectria sophorae in ITS, LSU and tub2 loci, based on the alignments deposited in TreeBASE.

Holotype.

CHINA. Jiangxi Province: Ganzhou city, 25°51'27.87"N, 114°58'18.95"E, on symptomatic branches of Citrus maxima (Burm.) Merr. cv. Shatian Yu, 11 May 2018, Q. Yang, Y.M. Liang & Y. Liu (holotype BJFC-S1770 designated here, ex-type culture CFCC 53590).

Etymology.

Named after the host genus on which it was collected, Citrus .

Description.

Mycelium not visible around ascomata or on the host. Stromata erumpent through epidermis, up to 0.6 mm high and 1 mm diam., pseudoparenchymatous, cells forming textura angularis to t. globulosa, intergrading with ascomatal wall. Ascomata superficial on well-developed stromata, scattered to aggregated in groups of 3-10, subglobose to globose, 200-270 μm diam., rarely slightly cupulate upon drying, sometimes with only a depressed apical region, yellowish-brown to grey, apical region slightly darker, no colour change in KOH or LA, sometimes surface scurfy or scaly, bright yellow to greenish-yellow. Ascomatal surface cells forming textura globulosa or t. angularis, sometimes including bright yellow scurf, 9-15 μm diam., walls pigmented, uniformly about 1.5 μm thick. Ascomatal wall 27-46 μm thick, of two regions: outer region 22-35 μm thick, intergrading with stroma, cells forming textura globulosa or t. angularis, walls pigmented, about 1.5 μm thick; inner region 9-15 μm thick, of elongate, thin-walled, hyaline cells, forming textura prismatica. Asci clavate, unitunicate, 53.5-65 × 8.5-11 μm, with inconspicuous ring at apex, 4-spored. Ascospores allantoid to short-cylindrical, uniseriate, rounded at both ends, (17 –)18–21(– 23.5) × 8 –9(– 10) μm (n = 20), muriform, hyaline to slightly yellowish-brown.

Culture characters.

Cultures incubated on PDA at 25 °C in darkness. Colony originally flat with white aerial mycelium, becoming pale yellowish due to pigment formation, conidiomata absent.

Additional specimen examined.

CHINA. Jiangxi Province: Ganzhou City, 25°51'27.87"N, 114°58'18.95"E, on symptomatic branches of Citrus maxima (Burm.) Merr. cv. Shatian Yu, 11 May 2018, Q. Yang, Y.M. Liang & Y. Liu (BJFC-S1771, living culture CFCC 53591).

Note.

Neothyronectria citri , as described here, is known from an ascomatal sexual morph phylogenetically allied to species of Allantonectria and Thyronectria (Fig. 1). In this study, two strains representing Neothyronectria citri cluster in a well-supported clade and appear most closely related to Neothyronectria sophorae , which was isolated from Sophora microphylla in New Zealand ( Crous et al. 2016). Neothyronectria citri can be distinguished, based on ITS, LSU and tub2 loci from Neothyronectria sophorae (16/464 in ITS, 9/772 in LSU and 60/494 in tub2).