| Summary: | Some soil microorganisms, especially bacteria and mycorrhizal fungi, play a role in the promotion of plant growth. However, plant growth promotion involving yeasts in soil has not yet been extensively investigated. This study aimed to isolate and identify yeast strains obtained from soils of the Assam tea plant (<i>Camellia sinensis</i> var. <i>assamica</i>) in northern Thailand and to investigate their plant growth promoting capabilities. A total of 42 yeast strains were obtained and identified by analysis of the D1/D2 domain of the large subunit ribosomal RNA gene. We identified 35 strains of six species belonging to the phylum Ascomycota, namely <i>Aureobasidium melanogenum, Kazachstania aquatica, Saturnispora diversa</i>, <i>Saturnispora sekii</i>, <i>Schwanniomyces pseudopolymorphus</i> and <i>Wickerhamomyces anomalus,</i> and six species were determined to belong to the phylum Basidiomycota, namely <i>Apiotrichum scarabaeorum, Curvibasidium pallidicorallinum</i>, <i>Papiliotrema laurentii</i>, <i>Rhodosporidiobolus ruineniae</i>, <i>Trichosporon asahii</i> and <i>Trichosporon coremiiforme</i>. Seven strains were representative of potential new species and belonged to the genera Galactomyces and Wickerhamomyces. A total of 28 strains were found to produce indole-3-acetic acid (IAA) in a range of 2.12 to 37.32 mg/L, with the highest amount of IAA produced by <i>R</i>. <i>ruineniae</i> SDBR-CMU-S1-03. All yeast strains were positive in terms of ammonia production, and only eight strains were positive for siderophore production. Two yeast species, <i>P. laurentii</i> and <i>W. anomalus</i>, were able to solubilize the insoluble form of calcium and zinc. The ability to produce amylase, endogulcanase, lipase, pectinase, protease and xylanase was dependent upon the yeast species and strain involved.
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