Morphological and Molecular Characterization of an Incertae Sedis Agaricoid Fungus Associated with Date Palm (Phoenix dactylifera L.)

Date palm (Phoenix dactylifera L.) is an economically important crop in Sudan, and symptoms of decline may be associated with diverse and poorly understood fungal communities. An unclassified agaricoid fungus was consistently isolated from basidiomata occurring on or near symptomatic date palms in an orchard in Khartoum State, Sudan. Affected palms exhibited chlorosis, reduced growth, drooping fronds, progressive browning, and desiccation. Six isolates (A–F) were examined based on their morphological characteristics and ITS1-5.8S-ITS2 sequences. Unlike the poroid basidiomata typical of Ganoderma, the isolates produced mushroom-like basidiomata with gills and a stipe. Several morphological characteristics also differed from the typical description of Hohenbuehelia, particularly the centrally positioned stipe and the free or narrowly adnate lamellae. BLASTn analysis showed only 83–89% ITS sequence identity with available Hohenbuehelia sequences. In the present ITS dataset, isolates A–F formed a strongly supported monophyletic group (bootstrap values of 99–100%) outside the sampled Hohenbuehelia and Ganoderma sequences. These results help clarify the phylogenetic position of the isolates within the taxa included in the current dataset but are insufficient for formal genus-level classification or the recognition of a new taxon. Furthermore, following 12 months of artificial inoculation, no consistent disease symptoms were observed, and the causal agents of date palm decline could not be determined. This study reports an unidentified agaricoid fungus associated with declining date palms and highlights the need for broader sampling of Agaricales, multilocus phylogenetic analyses, detailed morphological characterization, and carefully controlled pathogenicity tests before its taxonomic identity and ecological significance can be established.