Colletotrichum guangdongense J.W. Liu, Manawas. & M. Luo, 2023

Liu, Jia-Wei, Manawasinghe, Ishara S., Liao, Xuan-Ni, Mao, Jin, Dong, Zhang-Yong, Jayawardena, Ruvishika S., Wanasinghe, Dhanushka N., Shu, Yong-Xin & Luo, Mei, 2023, Endophytic Colletotrichum (Sordariomycetes, Glomerellaceae) species associated with Citrus grandis cv. " Tomentosa " in China, MycoKeys 95, pp. 163-188 : 163

Colletotrichum guangdongense J.W. Liu, Manawas. & M. Luo sp. nov.

Fig. 7

Etymology.

The epithet refers to the Guangdong Province where the fungus was collected.

Holotype.

ZHKUCC 21-0105

Description.

Isolated from a Citrus grandis cv. “Tomentosa” twig. Sexual morph: not observed. Asexual morph. Conidiomata formed directly on hyphae, conidial masses abundant, coral. Setae pale to dark brown, smooth-walled, straight or flexuous, 2-4-septate, 60-136 μm long, basal cell cylindrical, 3.5-4.8 μm diam., tip more or less acute. Conidiophores 20-70 × 3-7 μm (x- = 39.1 ± 10.7 × 4.7 ± 0.7 μm, n = 50), cylindrical, hyaline, smooth-walled, 1-4-celled, unbranched or branched at the base. Conidia 14-22 × 3-7 μm (x- = 18.2 ± 1.6 × 4.9 ± 0.5 μm, n = 50), straight, hyaline and smooth-walled. Appressoria 7-12 × 5-10 μm (x- = 10.2 ± 1.8 × 7.3 ± 0.9 μm, n = 50), single, medium brown, round, oval to irregular in outline.

Cultural characteristics.

Colonies on PDA reach 65 mm diameter after seven days, with 8-11 mm/day (x- = 10 mm, n = 6) growth rate. Colonies circular, slightly raised, flat, with pale coral red to light pink margin. Reverse dark vermillion to light ivory. Colonies on SNA flat, with entire margin, glaucous, reverse buff. Sporulates after 14 d on SNA.

Material examined.

China, Guangdong Province, Huazhou , isolated from healthy twigs of Citrus grandis cv. “Tomentosa”, May 2019, Y.X. Shu (dried cultures ZHKU 21-0089 holotype); living cultures ZHKUCC 21-0105 (= CGMCC 3.24127) ex-type, ZHKUCC 21-0106 and ZHKUCC 22-0042 isotype ).

Notes.

In the phylogenetic analysis of combined act, chs-1, gapdh, his3, ITS and β- tubulin sequences, three isolates (ZHKUCC 21-0105, ZHKUCC 21-0106 and ZHKUCC 22-0042) obtained in this study developed a sister clade to Colletotrichum sp. MH0413 with 89% ML bootstrap, 60% MP bootstrap and 1.00 BP (Fig. 5 ). Colletotrichum guangdongense is also closely related to C. magnum (CBS 519.97) and C. panamense (CBS 125386). It can be distinguished from C. magnum (CBS 519.97) by having smaller conidia (10-20 × 4-6 μm vs. 17-24 × 3.5-5 μm) and longer conidiophores (20-70 μm vs. 20 μm) ( Damm et al. 2019). Colletotrichum panamense (CBS 125386) has conidiophores shorter than C. guangdongense (30 μm vs. 20-70 μm). Colletotrichum guangdongense can be distinguished from C. magnum (CBS 519.97) also by 39 different nucleotides (4/538 in the ITS region, 9/204 in the gapdh region, 3/251 in the chs-1 region, 9/235 act, 5/431 tub2 and 9/403 his3) and from C. panamense (CBS 125386) by 39 different nucleotides (4/538 in the ITS region, 9/204 in the gapdh region, 3/251 in the chs-1 region, 9/235 act, 2/431 tub2 and 12/403 his3). The PHI test revealed no significant recombination event amongst C. guangdongense and its closely-related taxa (Fig. 6 ). Therefore, we have described this fungus as a novel species.

Figures

Figure 5. The most parsimonious tree of the Colletotrichum magnum complex using combined act, chs- 1, gapdh, his 3, ITS and β- tubulin sequences. Colletotrichum cliviicola and C. orchidearum were used as outgroup taxa. Bootstrap support values equal to or greater than 60 % in MP and ML and BP equal to or greater than 0.95 are shown as MP / ML / BP above the respective nodes. The isolates of the novel taxon described in the current study are highlighted in red. Ex-type strains are noted with T.

Figure 6. PHI analysis of combined act, chs- 1, gapdh, his 3, ITS and β- tubulin sequence data. A PHI test result (Φw) <0.05 indicates significant recombination within the dataset.

Figure 7. Colletotrichum guangdongense (ZHKUCC 21 - 0105, holotype) A, B upper and reverse sides of cultures on PDA seven days after inoculation C, D conidioma E, F setae G, H conidiophores I conidia J, K appressoria. Scale bars: 1 mm (C, D); 10 μm (E-K).