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Culture-independent techniques have recently been used for evaluation of microbial diversity in the environment since it addresses the problem of unculturable microorganisms. In this study, the diversity of epiphytic yeasts from corn (Zea mays Linn.) phylloplanes in Thailand was investigated using this technique and sequence-based analysis of the D1/D2 domains of the large subunit ribosomal DNA sequences. Thirty-seven samples of corn leaf were collected randomly from 10 provinces. The DNA was extracted from leaf washing samples and the D1/D2 domains were amplified. The PCR products were cloned and then screened by colony PCR. A total of 1049 clones were obtained from 37 clone libraries. From this total, 329 clones (213 sequences) were closely related to yeast strains in the GenBank database, and they were clustered into 77 operational taxonomic units (OTUs) with a similarity threshold of 99 %. The majority of sequences (98.5 %) were classified into the phylum Basidiomycota. Sixteen known yeast species were identified. Interestingly, more than 65 % of the D1/D2 sequences obtained by this technique were suggested to be sequences from new yeast taxa. The predominant yeast sequences detected belonged to the order Ustilaginales with relative frequency of 68.0 %. The most common known yeast species detected on the leaf samples were Pseudozyma hubeiensis pro tem. and Moesziomyces antarcticus with frequency of occurrence of 24.3 and 21.6 %, respectively.

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Aureobasidium sp. DMKU-PAL144, Rhodotorula sp. DMKU-PAL99, and Solicococcus keelungensis DMKU-PAL84. VOCs produced by these microorganisms ranged from 4 to 14 compounds and included alcohols, alkenes, aromatics, esters and furans. The major VOCs produced by the closely related Aureobasidium strains were found to bedistinct. Moreover, 2-phenylethanol was the most abundant compound generated by Aureobasidium sp. DMKU-PAL120, while methyl benzeneacetate was the major compound emitted from Aureobasidium sp. DMKU-PAL144. On the other hand, 2-methyl-1-butanol and 3-methyl-1-butanol were significant compounds produced by the other three genera. These antagonists apparently inhibited A. flavus sporulation and mycelial development. Additionally, the reduction of the AFB 1 in the fungal-contaminated rice grains was observed after co-incubation with these VOC-producing strains and ranged from 37.7 ± 8.3% to 60.3 ± 3.4%. Our findings suggest that these same microorganisms are promising biological control agents for use against aflatoxin-producing fungi in rice and other agricultural products.