Taxonomic and phylogenetic contributions to fungi associated with the invasive weed Chromolaena odorata (Siam weed)

This article provides morphological descriptions and illustrations of microfungi associated with the invasive weed, Chromolaena odorata, which were mainly collected in northern Thailand. Seventy-seven taxa distributed in ten orders, 23 families (of which Neomassarinaceae is new), 12 new genera (Chromolaenicola, Chromolaenomyces, Longiappendispora, Pseudocapulatispora, Murichromolaenicola, Neoophiobolus, Paraleptospora, Pseudoroussoella, Pseudostaurosphaeria, Pseudothyridariella, Setoarthopyrenia, Xenoroussoella), 47 new species (Aplosporella chromolaenae, Arthrinium chromolaenae, Chromolaenicola chiangraiensis, C. lampangensis, C. nanensis, C. thailandensis, Chromolaenomyces appendiculatus, Diaporthe chromolaenae, Didymella chromolaenae, Dyfrolomyces chromolaenae, Leptospora chromolaenae, L. phraeana, Longiappendispora chromolaenae, Memnoniella chromolaenae, Montagnula chiangraiensis, M. chromolaenae, M. chromolaenicola, M. thailandica, Murichromolaenicola chiangraiensis, M. chromolaenae, Muyocopron chromolaenae, M. chromolaenicola, Neomassarina chromolaenae, Neoophiobolus chromolaenae, Neopyrenochaeta chiangraiensis, N. chromolaenae, N. thailandica, N. triseptatispora, Nigrograna chromolaenae, Nothophoma chromolaenae, Paraleptospora chromolaenae, P. chromolaenicola, Patellaria chromolaenae, Pseudocapulatispora longiappendiculata, Pseudoroussoella chromolaenae, Pseudostaurosphaeria chromolaenae, P. chromolaenicola, Pseudothyridariella chromolaenae, Pyrenochaetopsis chromolaenae, Rhytidhysteron chromolaenae, Setoarthopyrenia chromolaenae, Sphaeropsis chromolaenicola, Tremateia chiangraiensis, T. chromolaenae, T. thailandensis, Xenoroussoella triseptata, Yunnanensis chromolaenae), 12 new host records, three new taxonomic combinations (Chromolaenicola siamensis, Pseudoroussoella elaeicola, Pseudothyridariella mahakashae), and two reference specimens (Torula chromolaenae, T. fici) are described and illustrated. Unlike some other hosts, e.g. bamboo (Poaceae) and Pandanaceae, the dominant group of fungi on Siam weed were Dothideomycetes. Only 15 species previously recorded from northern Thailand were found in this study. Most of the taxa are likely to have jumped hosts from surrounding plants and are unlikely to be a specialist to Siam weed. Most fungal families found on Siam weed had divergence estimates with stem ages in the Cretaceous, which coincided with the expected origin of the host family (Asteraceae). This further indicates that the species have jumped hosts, as it is unlikely that the taxa on the alien Siam weed came from the Americas with its host. They may, however, have jumped from other Asteraceae hosts. In a preliminary screening 40 (65%) of the 62 species tested showed antimicrobial activity and thus, the fungi associated with C. odorata may be promising sources of novel bioactive compound discovery. We provide a checklist of fungi associated with C. odorata based on the USDA Systematic Mycology and Microbiology Laboratory (SMML) database, relevant literature and our study. In total, 130 taxa (116 identified and 14 unidentified species) are distributed in 20 orders, 48 families, and 85 genera. Pseudocercospora is the most commonly encountered genus on Siam weed.