Diaporthe siamensis Udayanga, Xing Z. Liu & K. D. Hyde

Fallahi, Maryam, Armand, Alireza, Al-Otibi, Fatimah, Hyde, Kevin D. & Jayawardena, Ruvishika S., 2025, Pathogenic fungi (Sordariomycetes) associated with annual and perennial crops in Northern Thailand, MycoKeys 117, pp. 191-265 : 191-265

Diaporthe siamensis Udayanga, Xing Z. Liu & K. D. Hyde , Cryptog. Mycol. 33 (3): 298 (2012)

Fig. 18

Description.

Pathogenic to rambutan ( Nephelium lappaceum ) and causes fruit rot. Sexual morph not observed. Conidiomata pycnidial, subglobose, flasky, or erratically shaped, with individual or multiple cavities. Conidiophores cylindrical, hyaline, simple, in dense aggregates, 1.5–1.8 μm. Conidiogenus cells hyaline, phialidic, cylindrical. Paraphyses hyaline, sub-cylindrical, septate, reaching above conidiophores, straight, flexuous, branched, up to 33 μm in length. Beta conidia aseptate, hyaline, hamate, or curved, with an acutely rounded apex and truncated base, 18–32 × 1–1.8 µm (mean = 25.5 × 1.3 μm, n = 30). Gamma and alpha conidia not observed.

Culture characteristics.

Colonies on PDA reach 60–65 mm in diameter after 7 days of growth at 25 ° C in the dark, cottony, white to cream, with lobate margins. The reverse is greenish yellow, with emerging dark pigmentation spots, along with the production of enormous black stromata on PDA.

Material examined.

Thailand • Chiang Rai Province, Mueang Chiang Rai District, Ban Du , Fruit rot on rambutan ( Nephelium lappaceum ), June 2023, Maryam Fallahi, dried culture L 1-2 ( MFLU 24-0246 ), living culture, MFLUCC 24-0245 .

Notes.

MFLUCC 24-0245 strain clustered with Diaporthe siamensis ( MFLUCC 10-0573 a, ex-type) with 100 % ML bootstrap support, and 1.0 BYPP (Fig. 16 ). The base pair differences between D. siamensis strains MFLUCC 24-0245 and MFLUCC 10-0573 a revealed a 0.38 % (2 / 519 bp) difference in ITS, a 1.7 % (4 / 234 bp) difference in tef 1, a 0.64 % (3 / 469 bp) difference in tub 2, and no difference in cal. The sequence data of his 3 is not available for D. siamensis ( MFLUCC 10-0573 a). D. siamensis ( MFLUCC 24-0245 ) has larger Beta conidia with an L / W = 19.6 (18–32 × 1–1.8 µm in D. siamensis ( MFLUCC 24-0245 ) vs. 15–18 × (1.5 –) 2 μm in D. siamensis ( MFLU 12–0121 , holotype )), and it did not produce gamma and alpha conidia. Based on the phylogenetic tree of Norphanphoun et al. (2022), D. siamensis grouped in the D. sojae species complex. Previous reports indicated that D. siamensis exhibited the ability to cause disease in Citrus sinensis ( Cui et al. 2021) and Dasymaschalon sp. ( Udayanga et al. 2012). Additionally, it was identified as an endophyte in Pandanus sp. in Thailand ( Tibpromma et al. 2018) and Garcinia parvifolia in Malaysia ( Udayanga et al. 2012). Diaporthe siamensis from rambutan was isolated in Thailand by Abeywickrama et al. (2023).

Figures

Figure 16. Phylogenetic tree of the Diaporthe sojae species complex generated by maximum likelihood of combined ITS, tef 1, tub 2, cal, and his 3 sequence data. The ultrafast maximum likelihood (ML) bootstrap support values ≥ 50 % (BT) and Bayesian posterior probabilities ≥ 0.90 (BYPP) are shown, respectively, near the nodes. The ex-type strains are marked with an asterisk. The tree is rooted in D. amygdali (CBS 126679) and D. amygdali (CBS 115620).

Figure 18. Diaporthe siamensis (MFLUCC 24-0245) a fruit rot in rambutan b front, and c back view of the colony on PDA after 10 days d front and e back view of the colony on PDA after 60 days f – h conidiomata i, j section view of conidiomata k, l conidiophores and paraphyses m beta conidia. Scale bars: 100 μm (i, j); 50 μm (k); 20 μm (l, m).