Microdochium oryzicola S. Absalan, S. Lumyong and K. D. Hyde, 2025

Absalan, Sahar, Armand, Alireza, Jayawardena, Ruvishika S., Suwannarach, Nakarin, Monkai, Jutamart, Jungkhun, Nootjarin, Lumyong, Saisamorn & Hyde, Kevin D., 2025, Endophytic xylariaceous fungi from rice in northern Thailand: discovery of novel species and new host records, MycoKeys 120, pp. 1-34 : 1-34

Microdochium oryzicola S. Absalan, S. Lumyong and K. D. Hyde sp. nov.

Fig. 6

Holotype.

MFLU 25-0028

Etymology.

Oryzicola refers to the host genus Oryza from which it was isolated.

Description.

Endophytic from healthy leaf of Oryza sativa . Sexual morph: not observed. Asexual morph: hyphomycetous. Mycelium 2.5–4.5 μm wide, mostly superficial, branched, septate, smooth, hyaline. Conidiophores 22–63 × 2–4.5 µm (x ̄ = 37 × 3.5 µm, n = 10), usually reduced to conidiogenous cells, mono- or bi-verticillate, branched, smooth-walled, hyaline. Conidiogenous cells 6–24 × 2–5 µm (x ̄ = 15 × 3 µm, n = 20), cylindrical, lageniform to ampulliform, terminal or intercalary, mono- or polyblastic, hyaline. Conidia 6–16 × 2.5–4 µm (x ̄ = 8.5 × 3.3 µm, n = 30), solitary, aseptate, cylindrical to clavate, obovoid, guttulate, hyaline. Chlamydospores abundant, globose to subglobose, sometimes irregular, in chains, thick-walled, pale brown to brown.

Culture characteristics.

Colonies on PDA reaching 65–67 mm in diameter after 7 days at 28 ° C, dark olivaceous grey in the center and white to the periphery, circular, fluffy aerial mycelium; reverse buff with olivaceous grey in the center.

Material examined.

Thailand • Chiang Rai Province, Doi Luang District , from healthy tissue part of rice leaf, 7 February 2022, Nootjarin Jungkhun, (NS 62-1 = MFLU 25-0028 ); (living culture MFLUCC 24-0509 ) .

GenBank numbers.

MFLUCC 24-0509 : ITS = PV 241406, LSU = PV 241407, rpb 2 = PV 275683.

Notes.

Phylogenetic analysis of combined ITS, LSU, and rpb 2 sequences revealed that our strain ( MFLUCC 24-0509 ) is from a distinct branch, constituting a well-supported lineage (100 % ML) separate from its sister clade, which includes Microdochium nannuoshanense , M. sinense , M. miscanthi , and M. fisheri (Fig. 7 ). Microdochium oryzicola is morphologically distinct from its closely related species, M. fisheri , particularly in the characteristics of the conidiophores and conidiogenous cells. Microdochium oryzicola has branched mono- or biverticillate conidiophores with mainly lageniform to ampulliform conidiogenous cells, whereas M. fisheri is characterized by bifurcate conidiophores and cylindrical, sympodial, conidiogenous cells ( Hernández-Restrepo et al. 2016). A comparison of the nucleotide differences between M. oryzicola and M. fisheri revealed 2.88 % (across 520 nucleotides, 9 gaps), 1.48 % (across 810 nucleotides, 2 gaps), and 12.7 % (across 697 nucleotides, without gaps) base pair differences in the ITS, LSU, and rpb 2 gene regions, respectively. Thus, M. oryzicola is introduced as a new species.

Figures

Figure 6. Microdochium oryzicola (MFLUCC 24-0509, ex-type). a. Front and reverse of the colony on PDA; b – f. Conidiophores and conidiogenous cells; g. Chlamydospores; h. Conidia. Scale bars: 10 μm (b – h).

Figure 7. Phylogram of ML analysis based on combined ITS, LSU, and rpb 2 sequence data. ML bootstrap support values equal to or higher than 60 % and Bayesian probability values (PP) equal to or above 0.80 are given at the nodes (ML / PP). The tree is rooted to Zygosporium pseudomasonii (CBS 146059) and Z. mycophilum (CBS 894.69). The isolate from the current study is highlighted in red, and type strains are indicated in bold black.