Diaporthe 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 : 7-9

Diaporthe berchemiae S.X. Zhou sp. nov.

Index Fungorum number: IF 900644; Facesoffungi number: FoF 15295; FIGURE. 4

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

Holotype: KUN-HKAS 131985

Endophytic in fresh leaves of Berchemia polyphylla var. leioclada . Sexual morph: not observed. Asexual morph: Conidiomata pycnidial in culture on PDA, globose or irregular, brown to dark brown, solitary or in groups, embedded, erumpent, white to cream conidial drops exuded from ostioles. Conidiomatal wall brown to dark brown, composed of several layers of brown to dark brown cells of textura angularis. Conidiophores 9–17 × 2–3 µm (x = 12.9 × 2.3μm, n = 25), cylindrical to subcylindrical, tapering to straight towards the apex, 1–2 septate, densely aggregated, hyaline, subhyaline to pale brown at the base, smooth-walled. Conidiogenous cells phialidic, terminal, cylindrical to subcylindrical, hyaline. Alpha conidia 5–6 × 1.5–2.5 µm (x = 5.6 × 2μm, n = 32), ellipsoidal to obovoid, or fusoidellipsoid, rounded or subobtuse at apex, acutate or subtruncate at the base, hyaline, aseptate, smooth-walled, with 0-1 small-guttules. Beta conidia 19–26 × 1–1.5 μm (x = 22.4 × 1.3μm, n = 30), filiform, slightly curved, tapering towards the ends, aseptate, hyaline, not guttulate. Gamma conidia not observed.

Cultural characteristics: Cultures on MEA initially white, growing slowly and entirely covering the 9cm Petri dish after 14 days, velvety appearance with whit aerial mycelium, white on surface, white to pale brown on reverse.

Material examined: CHINA, Guizhou Province, from Berchemia polyphylla var. leioclada leaves, 27 June 2022, S.X. Zhou, A12J-1 (KUN-HKAS 131985, holotype), ex-type culture GMBCC 20000.

GenBank numbers: ITS = PP049022, HIS3 = PP056095, TEF1-α = PP056096, TUB2 = PP056097.

Notes: In our phylogenetic analysis, Diaporthe berchemiae formed a distinct lineage between D. ellipsospora and the clade of D. nanjingensis and D. jinxiu ( FIGURES. 5 , S 2 ). Diaporthe ellipsospora was introduced based on the sexual morph ( Dissanayake et al. 2020), while D. berchemiae is reported by the asexual morph. Therefore, we are unable to compare the morphology between these two species, but phylogenetically they are distinct ( Figures 5 , S 2 ). The comparison of ITS region between D. berchemiae and D. ellipsospora revealed 41 bp (7.9%) differences which strongly support our new isolate as a new species.

Diaporthe berchemiae is similar to D. jinxiu and D. nanjingensis in having hyaline, cylindrical, smooth-walled conidiophores, phialidic, cylindrical conidiogenous cells, and hyaline, aseptate, ellipsoidal alpha conidia. However, D. berchemiae differs from D. jinxiu and D. nanjingensis in having 0-1 small-guttulate alpha conidia, whereases, the conidia of D. jinxiu and D. nanjingensis with two large guttules. In addition, the alpha conidia of D. jinxiu are rounded at both ends, while the alpha conidia are rounded or subobtuse at the apex and acutate or subtruncate at the base in D. berchemiae ( Wang et al. 2021) . Diaporthe berchemiae has much shorter beta conidia (19–26 vs. 29.7–37.1(-39.7) um) than those of D. nanjingensis and the conidiogenous cells of D. nanjingensis are muti-guttulate, which were not observed in D. berchemiae ( Wan et al. 2023) . The PHI test revealed no significant recombination event between Diaporthe berchemiae and the closely related taxa (Φw = 0.22) ( FIGURE. 6 ). Therefore, we introduce our new isolate as a new species based on both phylogeny and morphological analyses.

Figures

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 4. Diaporthe berchemiae (ex-type culture, GMBCC 20000). a, b Front and reverse colony on MEA. c, d Conidiomata on PDA. e–g Conidiophores. h–k Conidiogenous cells and conidia. l–o Alpha conidia. p-s Beta conidia. Scale bars: e–g, i–k = 10 μm; h, l–s = 5 μm.

FIGURE 5. Phylogenetic tree based on RAxML analyses of a combined ITS, TUB2, CAL, HIS, TEF1-α dataset, including sequences of our strain and a selection of related Diaporthe spp., restricted according to the phylogenetic study of Supplementary Material (Figure S2). Diaporthe caulivora (CBS 127268) was used as the outgroup. The combined gene analysis included 13 strains with 2409 characters after aligned, including gaps (ITS: 560bp, TUB2: 526bp, CAL: 506bp, HIS3: 494bp, TEF1-α: 323bp). The RAxML analysis of the combined dataset yielded the best scoring tree with a final ML optimization likelihood value of -7651.550919.The matrix had 572 distinct alignment patterns, with 23.26% undetermined characters or gaps. Estimated base frequencies were as follows: A = 0.203920, C = 0.334775, G = 0.247441, T = 0.213864; substitution rates AC = 1.486536, AG = 3.694646, AT = 1.459400, CG = 1.231075, CT = 5.843934, GT = 1.000000; gamma distribution shape parameter α = 0.257986. 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 6. Results of the PHI test of Diaporthe 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.