Two new species of nematode-trapping fungi: relationships inferred from morphology, rDNA and protein gene sequence analyses

Abstract

Two new nematode-trapping fungi, Dactylellina sichuanensis and D. varietas from China, which capture nematodes by both adhesive knobs and non-constricting rings, are described and illustrated. D. sichuanensis is characterized by both adhesive knobs and non-constricting rings, solitary conidiophores and 3-(4)-6 septate conidia, as compared with species such as D. appendiculata, D. candida, D. leptospora and D. lysipaga. Although D. sichuanensis shares similar types of trapping devices, the presence of simple conidiophores and spindle-shaped conidia with these species, it can be distinguished by its larger conidia and presence of more than four septa. In D. sichuanensis, a single conidium is born at the tip of conidiophore, while in D. candida, 3–10 conidia are born near the apex of conidiophore in a capitate arrangement. It produces spindle-shaped conidia with 3–6 septa, whereas D. leptospora produces cylindrical-shaped conidia with 5–15 septa. D. appendiculata captures nematodes by adhesive knobs whereas D. sichuanensis captures nematodes by both adhesive knobs and non-constricting rings. They also differ in conidial size (35–82.5 μm in D. sichuanensis as compared with 57–108 μm in D. appendiculata). D. varietas is characterized by conidiophores that are branched at right-angles, and elongate to fusoid conidia, with 7–8 septa (more than 25% of which are curved). D. varietas resembles D. asthenopaga, Dactylella oxyspora and Monacrosporium multiseptatum, but has elongate-fusoid conidia, whereas D. asthenopaga possesses obconical or clavate conidia. D. varietas forms both adhesive knobs and non-constricting rings whereas Dactylella oxyspora does not produce any trapping device. M. multiseptatum differs from D. varietas in having larger conidia with an inflated middle cell. Phylogenetic analyses based on nuclear and protein coding DNA sequences (18 S, and a combined 28 S + 5.8 S + β-tubulin dataset) indicate that these two taxa should be assigned to the family Orbiliaceae.