Background & Objectives: A portion of biodiversity and variability of life on earth belongs to the yeasts. The caroptenoid-producing yeasts are economically important and their distinct natural habitats are of interest. In this study, isolation and molecular identification of carotenoid-producing yeasts of the exudates of endangered birch trees (Betula pendula Roth.) at Marmisho in Northwest Iran were performed.
Materials & Methods: This cross-sectional study carried out by sampling from exudates of birch trees (Betula pendula Roth.) at a natural habitat located in West Azerbaijan Province in the Northwest of Iran. Using selective media, the isolation of the yeasts was done. The screening was initially based on the color and shape of the colonies during one-month incubation along with simple rapid tests to check the existence of carotenoid pigments. Finally, the D1/D2 region rDNA sequencing was accomplished for 19 isolates.
Results: 19 out of 45 isolates with pink-red colonies were selected for ribosomal gene sequencing. Phylogenetic results showed that the carotenoid-producing yeasts are in the Basidiomycota division including Rhodotorula, Cystofilobasidium, Cystobasidium, Rhodosporidiobolus, Ustilentyloma, and Xanthophyllomyces. 
Conclusion: The unique pattern of carotenogenic yeasts community at this ecological niche and placing in 6 genera with the capability to produce a variety of carotenoid structures indicate that the exudates of birch trees (Betula pendula Roth.) include a wide diversity for native carotenoid-producing yeasts. This study is the first report presenting the diversity of carotenoid-producing yeasts in the Northwest of Iran with a distinct consortium of native yeasts at this habitat.