Abstract
Palms (Arecaceae) are substrates for a highly diverse range of fungi. Many species are known as saprobes and many are important plant pathogens. Over the course of our studies of micro-fungi from palms in Thailand, two new taxa were discovered. Morphological characteristics and phylogenetic analyses of combined ITS, LSU, SSU, and tef1-α sequence data revealed their taxonomic positions within Massarinaceae. There are currently ten genera identified and accepted in Massarinaceae, with the addition of the two new genera of Haplohelminthosporium and Helminthosporiella, that are introduced in this paper. Each new genus is provided with a full description and notes, and each new taxon is provided with an illustration for the holotype. A list of identified and accepted species of Helminthosporium with morphology, host information, locality, sequence data, and related references of Helminthosporium reported worldwide is provided based on records in Species Fungorum 2021. This work provides a micro-fungi database of Haplohelminthosporium, Helminthosporiella, and Helminthosporium which can be modified and validated as new data come to light.