Myxotrichum flavoroseum (Sigler & J.W. Carmich.) M. Mehrabi

Mehrabi, Mehdi, Asgari, Bita & Zare, Rasoul, 2024, Myxotrichum persicum sp. nov., and two new combinations in the genus Myxotrichum, Phytotaxa 649 (1), pp. 83-97 : 91-92

Myxotrichum flavoroseum (Sigler & J.W. Carmich.) M. Mehrabi , comb. nov.

MycoBank: MB851582

Basionym: Malbranchea flavorosea Sigler & J.W. Carmich., Mycotaxon 4(2): 432 (1976)

Morphological description: See Sigler and Carmichael (1976)

Notes: Malbranchea circinata Sigler & J.W. Carmich. and Malbranchea flavorosea Sigler & J.W. Carmich. , collected from soil in the United States, were introduced by Sigler and Carmichael (1976), who assigned the sexual morphs of both species to the genus Myxotrichum based on characteristics of ascomata, peridial hyphae and appendages. However, due to the lack of asci and ascosporse in both species, Sigler and Carmichael (1976) maintained them in the genus Malbranchea which is mainly characterized by the formation of alternate arthroconidia on branches from the vegetative hyphae ( Sigler & Carmichael 1976, Rodríguez-Andrade et al. 2021). In a revision of malbranchea-like fungi from clinical specimens, Rodríguez-Andrade et al. (2021) indicated that the ITS and LSU nucleotide sequences from the type strains of Malbranchea circinata (ATCC 34526) and Malbranchea flavorosea (ATCC 34529) matched with taxa in the family Myxotrichaceae , hence excluded both species from the genus.

Based on a MegaBlast search of NCBIs GenBank nucleotide database, the closest hit using the LSU, ITS, MCM7 and RPB1 sequence of Malbranchea circinata and M. flavorosea are shown in Table 2 .

Based on the presented phylogeny of ITS, LSU, MCM7 and RPB1 sequences ( Fig. 1 ), Malbranchea circinata clustered with Myxotrichum carminoparum and Myxotrichum chartarum (ML = 90%, BI = 1.0), and Malbranchea flavorosea with Myxotrichum stipitatum and Myxotrichum albicans (ML = 97%, BI = 1.0). These results largely correspond with those of Hirose et al. (2022), who conducted the multilocus phylogeny of ITS, LSU, MCM7 and RPB1 loci. In addition to the phylogenetic analyses, we compared the morphological characteristics of Malbranchea circinata and Malbranchea flavorosea with all well-documented species of Myxotrichum , which revealed that these species are closely related to Myxotrichum chartarum and Myxotrichum stipitatum , respectively, by the branching patterns of ascomata appendages. Also, like Malbranchea circinata , Myxotrichum carminoparum and Myxotrichum chartarum produce a malbranchea-like asexual form. Although Myxotrichum stipitatum has no asexual form, Myxotrichum albicans , the other closely related species to Malbranchea flavorosea also produces a malbranchea-like asexual form. Therefore, we here transfer Malbranchea circinata and Malbranchea flavorosea to the genus Myxotrichum based on morphological and molecular evidence.

Figures

FIGURE 1. Maximum likelihood phylogenetic tree inferred from the combined ITS, LSU, MCM7 and RPB1 sequence alignment of 55 strains of the Myxotrichaceae and Amorphothecaceae. Maximum likelihood bootstrap supports (≥70%) and Bayesian posterior probabilities support (≥0.9) are given above or below the branches, respectively. Dashes replace non-significant values. The branches with full statistical support (ML = 100%; PP = 1.0) are thickened. The scale bar shows the expected number of changes per site. The tree is rooted to Hyphodiscus hyaloscyphoides (NBRC 104869) and Venturiocistella japonica (NBRC 106633).