Yeasts from phylloplane and their capability to produce indole-3-acetic acid

Yeasts were isolated from the phylloplane of various plant species collected from seven provinces in Thailand. A total of 114 yeast strains and 10 strains of a yeast-like fungus were obtained by enrichment isolation from 91 out of 97 leaf samples (93.8 %). On the basis of the D1/D2 domain of the large subunit rRNA gene sequence similarity, 98 strains were identified to be of 36 yeast species in 18 genera belonging to Ascomycota viz. Candida, Clavispora, Cyberlindnera, Debaryomyces, Hanseniaspora, Hyphopichia, Kazachstania, Kluyveromyces, Kodamaea, Lachancea, Metschnikowia, Meyrozyma, Pichia, Starmerella, Torulaspora and Wickerhamomyces, and to Basidiomycota viz. Sporidiobolus and Trichosporon. Three strains were found to represent two novels Candida species which were previously described as C. sirachaensis and C. sakaeoensis. Ten strains of yeast-like fungus were identified as Aureobasidium pullulans of the phylum Ascomycota. Ascomycetous yeast species accounted altogether for 98.0 % of the 98 strains. The prevalent species was Candida tropicalis with a low frequency of isolation (14.3 %). Diversity of yeasts other than ballistoconidium-forming yeast in phylloplane in a tropical country in Asia has been reported for the first time. All strains obtained were accessed for the capability to produce IAA and result revealed that 39 strains in 20 species, one strain each of an undescribed and a novel species, and two unidentified strains showed the capability of producing IAA when cultivated in yeast extract peptone dextrose broth supplemented with 0.1 % L-tryptophan. All five strains of Candida maltosa produced relatively high concentrations of IAA.