Polyphasic analysis of six Chiang Mai flower isolates identifies two new Papiliotrema species

A polyphasic taxonomic study of six flower-associated yeast isolates collected in Chiang Mai Province, northern Thailand, in 2024 identified two previously undescribed species: Papiliotrema anthoicola and Papiliotrema floralis. The study combined multilocus DNA analysis with morphological, biochemical and physiological characterization to distinguish the new taxa from related species.

The six isolates came from five types of flowers. Four strains representing P. anthoicola were recovered from ylang-ylang (Cananga odorata), frangipani (Plumeria obtusa) and golden trumpet (Allamanda cathartica) flowers. The other two strains, representing P. floralis, came from Spanish needle (Bidens pilosa) and oncidium (Oncidium sp.) flowers. The authors deposited the strains in culture collections in Thailand and China and registered the new taxa in MycoBank.

Healthy flowers were collected in Chiang Mai and placed in sterile plastic bags, stored at 4 °C and processed within 24 hours. Internal floral material was aseptically suspended in 0.85% saline for 15 minutes and spread onto yeast extract-malt extract agar containing chloramphenicol. After three days at 25 °C, individual colonies were selected and subcultured. Purified strains were preserved long term in 20% glycerol at −80 °C. Morphological examinations covered colony appearance, cell structure, budding, capsule formation, pseudohyphae or true hyphae, and production of basidiospores across seven culture media.

The researchers also tested carbon and nitrogen assimilation, glucose fermentation, acid production, growth at six temperatures, tolerance of high glucose and sodium chloride concentrations, and resistance to cycloheximide. For phylogenetics, they sequenced the internal transcribed spacer region, the D1/D2 domains of large-subunit ribosomal DNA and the protein-coding genes rpb1, rpb2 and tef1-α. The concatenated dataset included 63 representatives of Rhynchogastremataceae and the outgroup Kwoniella mangrovensis CBS 8507.

Maximum-likelihood and Bayesian analyses produced similar tree topologies. Both supported division of the six isolates into two lineages with 100% maximum-likelihood bootstrap support and a Bayesian posterior probability of 1.0. The two lineages were sister taxa and clustered closely with P. pollinicola and P. rajasthanensis. The new species differed from each other by 1.19% in the ITS region, corresponding to six nucleotide substitutions, and by 0% in the D1/D2 domains. Greater separation occurred in the three protein-coding genes: 2.85% in rpb1, 5.34% in rpb2 and 5.90% in tef1-α.

Although the ITS and D1/D2 divergences were below proposed species-delimitation thresholds for basidiomycetous yeasts, the multilocus results were considered together with observed differences in morphology, carbon-source use and physiology. P. anthoicola produced circular, yellowish-white colonies measuring 2.0–3.0 mm in diameter after five days on yeast extract-malt extract agar at 25 °C. Its ovoid to ellipsoidal cells measured 2.63–5.78 by 4.48–7.79 μm, showed polar budding and had extracellular capsules 0.47–1.63 μm thick. Elongated cells and chains developed on potato dextrose agar after two weeks, while neither pseudohyphae nor true hyphae formed.

P. floralis produced yellowish-white colonies measuring 3.0–4.0 mm in diameter after five days, with a smooth, glistening and viscous appearance. Its ovoid to ellipsoidal cells measured 2.40–4.31 by 3.54–6.91 μm, showed multilateral budding and had capsules 0.53–1.93 μm thick. Under the reported culture conditions, it formed neither elongated cells nor pseudohyphae or true hyphae. Basidiospores were not obtained for either species after one month at 25 °C on the seven media tested.

Both species were negative for glucose fermentation and did not assimilate potassium nitrate or sodium nitrite. Neither grew on vitamin-free medium, medium containing 16% sodium chloride with 5% glucose, or media containing 0.01% or 0.1% cycloheximide. P. anthoicola grew weakly on media containing 50% and 60% glucose and grew at 37 °C. P. floralis grew on both high-glucose media but not at 37 °C. The species also differed in their carbon-source utilization and acid-production profiles. Their holotypes were registered as CMUB40150 and CMUB40151, with ex-type cultures SDBR-CMU883 and SDBR-CMU888, respectively.

The findings increase the number of known Papiliotrema species recorded in Thailand from 16 to 18 and the number reported from flowers there from five to seven. The study was limited to six isolates from flowers collected in one province in one sampling year, so it did not establish either species’ broader geographic distribution or characterize flower-associated yeast diversity across northern Thailand. The authors noted that whole-genome sequencing and average nucleotide identity analysis could provide further support for the placement of these closely related strains.

Subject of Research: Polyphasic identification of two new flower-associated Papiliotrema species in Chiang Mai Province, Thailand

Article Title: Two novel species of Papiliotrema ( Rhynchogastremataceae , Tremellales ) isolated from flowers in northern Thailand

Article References: Kathongthung, C., Kodchasee, P., Singsalood, S., Senwanna, C., Khunnamwong, P., Kumla, J., & Suwannarach, N. (2026). Two novel species of Papiliotrema (Rhynchogastremataceae, Tremellales) isolated from flowers in northern Thailand. MycoKeys, 137, 199-222. https://doi.org/10.3897/mycokeys.137.199289

Image Credits: AI Generated

DOI: 10.3897/mycokeys.137.199289

Keywords: Papiliotrema, new yeast species, anthophilous yeasts, flower-associated fungi, Chiang Mai, Thailand, multilocus phylogeny, fungal taxonomy, polyphasic taxonomy, novel, species, Rhynchogastremataceae