Colletotrichum berchemiae S.X. Zhou

Zhou, Si-Xuan, Bao, Dan-Feng, Zhang, Tao, Xiao, Yuan-Pin, Tang, Yuan-Jiang, Jing, Zhang, Lu, Yu-Xi & Shi, Kai-Zhi, 2024, Two new endophytic fungi of Colletotrichum and Diaporthe isolated from Berchemia polyphylla var. leioclada in Guizhou Province, China, Phytotaxa 640 (1), pp. 1-15 : 4-7

Colletotrichum berchemiae S.X. Zhou sp. nov.

Index Fungorum number: IF 900643; Facesoffungi number: FoF 15294; FIGURE. 1

Etymology: Referring to the host plant Berchemia polyphylla var. leioclada , on which the holotype was collected.

Holotype: KUN-HKAS 131984

Endophytic in fresh leaves of Berchemia polyphylla var. leioclada . Sexual morph: not observed. Asexual morph: Vegetative hyphae hyaline or pale brown, smooth-walled, septate, branched. Setae absent. Conidiomata acervular, gregarious, paleluteous. Chlamydospores not observed. Conidiophores 20–30 × 3–4(–5) µm (x = 25.3 × 3.9 μm, n = 25), formed directly on hyphae, cylindrical, hyaline, becoming brown to dark brown after maturity, hyaline to pale brown towards the apex, brown to dark brown at the base, branched, septate, smooth-walled. Conidiogenous cells 7–15 × 3–4.5 µm (x = 10.8 × 3.9 μm, n = 25), phialidic, integrated, terminal, hyaline, smooth-walled, cylindrical to clavate. Conidia 13–16 × 3.5–4.5 µm (x = 14.4 × 4.1μm, n = 40), hyaline, aseptate, guttulate, dry, cylindrical, rounded at both ends, or one end obtuse and another end round, straight or slightly curved, smooth-walled. Appressoria: not observed.

Cultural characteristics: Colonies on PDA reaching 68–70 mm diam, flat, entire margin, with black spots on the surface, grey on the surface, brown to dark grey on reverse, without pigmentation.

Material examined: CHINA, Guizhou Province, from Berchemia polyphylla var. leioclada leaves, 27 June 2022, S.X. Zhou, B11G1-1 (KUN-HKAS 131984, holotype), ex-type culture GMBCC 20001.

GenBank numbers: ITS = PP049021, ACT = PP056098, CHS-1 = PP056099, GAPDH = PP056100, TUB2 = PP056101.

Notes: In our multi-locus (ITS, ACT, CHS-1, GADPH, and TUB2) phylogenetic analyses, our new isolate Colletotrichum berchemiae formed a distinct lineage basal to C. gloeosporioides species complex ( FIGURES. 2 , S 1 ). Colletotrichum berchemiae is similar to the C. gloeosporioides species complex in having cylindrical conidia ( Weir et al. 2012) . However, considering the ingroup taxa of the C. gloeosporioides species complex are much more closely related to each other than to C. gloeosporioides . In addition, the PHI test revealed no significant recombination event between C. gloeosporioides and the closely related taxa (Φw = 0.42) ( Figure 3 ). Thus, we identified our species as singleton species.

Morphologically, C. berchemiae is similar to C. pyrifolia in having hyaline to pale brown, smooth-walled, septate and branched conidiophores, hyaline to pale brown, cylindrical to clavate conidiogenous cells and hyaline, smooth-walled, aseptate, cylindrical conidia. However, C. berchemiae is different from C. pyrifolia in having smaller conidiogenous cells (7–15 × 3–5 vs. 15–32 × 3–5 µm) and conidia (13–16 × 3–5 vs. 14–23 × 5.5–7 um). In addition, the conidia of C. berchemiae are rounded at both ends or one end obtuse and another end round. Whereas, conidia of C. pyrifolia are cylindrical with round ends ( Fu et al. 2019). Colletotrichum berchemiae can be distinguished from C. arecacearum in having hyaline to pale brown, smooth-walled, septate and branched conidiophores and hyaline to pale brown conidiogenous cells. In contrast, the conidiophores of C. arecacearum are reduced to conidiogenous cells, and conidiogenous cells are hyaline ( Liu et al. 2022).

Figures

FIGURE 1. Colletotrichum berchemiae (ex-type culture, GMBCC 20001). a, b Front and reverse colony on PDA. c–e Conidiomata on PDA. h–j Conidiophores. k–m Conidiogenous cells and conidia. n–p Conidia. Scale bars: f = 100 μm; g–i, n = 20 μm, j, k = 30um, l, m, o, p = 10 um.

FIGURE 2. Phylogenetic tree of Maximum Likelihood analyses of Colletotrichum gloeosporioides species complex and its closely related species (including sequences of our strain and a selection of related Colletotrichum spp.,), restricted according to the phylogenetic study of Supplementary Material (Figure S1). Colletotrichum hippeastri (CBS 125376) and C. boninense CBS 123755 were used as outgroup taxa. The tree was built using concatenated sequences of ITS, ACT, CHS-1, GADPH, and TUB2 datasets and the tree topology of the RAxML and Bayesian analyses are similar. The combined gene analysis included 86 strains with 2152 characters after aligned, including gaps (ITS: 593bp, ACT: 282bp, CHS-1: 299bp, GADPH: 277bp, and TUB2: 701bp). The RAxML analysis of the combined dataset yielded the best scoring tree with a final ML optimization likelihood value of -15857.131621. The matrix had 1198 distinct alignment patterns, with 23.12% undetermined characters or gaps. Estimated base frequencies were as follows: A = 0.229650, C = 0.299082, G = 0.241413, T = 0.229855; substitution rates AC = 1.009331, AG = 2.892663, AT = 1.227390, CG = 0.965860, CT = 4.527049, GT = 1.000000; gamma distribution shape parameter α = 0.449663. Bootstrap support values for RAxML equal to or greater than 70% and Bayesian posterior probabilities equal to or greater than 0.90 are given at each node. The new isolate is shown in red and bold.

FIGURE 3. Results of the PHI test of Colletotrichum berchemiae and closely related species using both LogDet transformation and splits decomposition. The PHI test results (Φw) <0.05 indicate significant recombination within the dataset. The new taxa are in red.