Pseudohalonectriaceae Hongsanan & K.D. Hyde, Fungal Diversity 84:33 (2017)

Index Fungorum number: IF 553215

Saprobic on wood and other plant material, commonly isolated in marine and terrestrial or freshwater habitats.  Sexual morph: Ascomata erumpent to immersed with a protruding neck, cylindrical, periphysate necks, greenish yellow, bright yellow to brown. Neck conical, composed of parallel hyphae, outer hyphae outwardly directed, subglobose with enlarged ends, greenish yellow, periphysate. Peridium multi-layers. Paraphyses tapering towards the apex, thin-walled, attached to ascogenous hyphae. Asci 8-spored, unitunicate, cylindrical to clavate, with a nonamyloid, thimble-shaped, refractive apical apparatus. Ascospores overlapping uniseriate to biseriate, cylindrical or ellipsoidal, straight to curved, usually multi-septate, constricted or not-constricted at the septa, hyaline to slightly coloured and pale brown, pink/orange in mass in some species, smooth-walled (Shearer and Zare-Maivan 1988; Hyde et al. 1999; Perera et al. 2016). Asexual morph: Undetermined.

Type genus: Pseudohalonectria Minoura & T. Muroi 1978

Notes: Pseudohalonectriaceae was introduced in Magnaporthales by Hongsanan et al. (2017) and comprises a single genus. Pseudohalonectria was previously placed in Lasiosphaeriaceae, Sordariales supported by the preliminary phylogenetic analysis of SSU sequence data by Chen et al. (1999). Shearer et al. (1999) transferred Pseudohalonectria to Magnaporthaceae. Klaubauf et al. (2014) found that Pseudohalonectria clustered with species of Magnaporthaceae, Pyriculariaceae and Ophioceraceae in the Magnaporthales in their phylogenetic study of Pyriculariaceae. Similar results were obtained by Maharachchikumbura et al. (2015b, 2016b), and they maintained Pseudohalonectria in Magnaporthales genera, incertae sedis.

Pseudohalonectria was introduced without being assigned to an order or family (Minoura and Muroi 1978). The genus was reviewed and added new  species by several researchers (see Perera et al. 2016). Shearer (1989) linked hyphomycetous, phialidic anamorph to P. phialidica, however, this species was transferred to Ceratosphaeria (Huhndorf et al. 2008). Thus, the asexual morph of Pseudohalonectria is still questionable. The MCC tree in Hyde et al. (2017), the stem age of Pseudohalonectria falls in the family status (95 MYA), with high support in the phylogenetic (this study) and the MCC trees.

Ecological and economic significance of PseudohalonectriaceaeMost species of Pseudohalonectria have antagonistic activity against other fungi and bacteria. Asthana & Shearer (1990) tested paired cultures on agar against representatives of Pseudohalonectria and showed that most tested species were strongly inhibited at a distance. Pseudohalonectria adversaria exhibited potent nematicidal activity against pine wood nematodes (Dong et al. 2004). Pseudohalonectria adversaria produce azaphilone compounds which are active against several pests, weeds, nematodes, bacteria and fungi (Dong et al. 2006). The azaphilone compounds can be developed as effective and alternative natural pest management products (Foremska et al. 1992, Park et al. 2005, Dong et al. 2006). Pseudohalonectria species also degrade lignocellulose and are involved in nutrient cycling.

Fig. RAxML maximum likelihood phylogenetic tree (LSU, SSU, TEF1 and RPB2). Numbers to the left of the nodes are RAxML value expressed from 1000 repetitions with values above 50% shown. Strain numbers are indicated after species names.