Yeast communities of secondary peat swamp forests in Thailand and their antagonistic activities against fungal pathogens cause of plant and postharvest fruit diseases

Abstract

Secondary peat swamp forest (PSF) arise by degradation of primary PSF as a result of fire and human activities. Yeasts diversity of Kuan Kreng (KK) and Rayong Botanical Garden (RBG) PSF, which are two secondary PSF in southern and in eastern Thailand, respectively, were investigated. Yeasts were isolated from soil and peat soil by the dilution plate and enrichment techniques. From six samples collected from KK PSF, 35 strains were obtained, and they were identified based on the sequence analysis of the D1/D2 region of the large subunit (LSU) rRNA gene 13 species in 12 genera, and one potential new species of the genus Galactomyces were detected. Thirty-two strains were obtained from six samples collected from RBG PSF and 26 strains were identified as 13 known yeast species in 11 genera, whereas six strains were found to represent two potential new species of the genera Papiliotrema and Moesziomyces. Among yeast strains isolated from KK PSF, the number of strains in the phylum Ascomycota and Basidiomycota were equal, whereas there were slightly fewer strains in Ascomycota than in Basidiomycota among the strains obtained from RBG PSF. The yeast strains were evaluated for their antagonistic activities against fungal pathogens which cause rice diseases (Fusarium moniliforme, Helminthosporium oryzae, Rhizoctonia solani, Curvularia lunata and Pyricularia grisea) and postharvest disease of fruits (Phytophthora palmivora, Lasiodiplodia theobromae and Colletotrichum gloeosporioides). Twelve strains of seven species were found to be antagonistic yeast strains. Starmerella kuoi DMKU-SPS13-6, Hanseniaspora lindneri DMKU ESS10-9 and Piskurozyma taiwanensis DMKU-SPS12-2 capable to inhibit R. solani by 70.1-76.2%, Wickerhamomyces anomalus DMKU SPS6-1 and three Rhodotorula taiwanensis strains (DMKU SPS8-1, DMKU ESS9-3, DMKU SPS9-2) inhibited C. lunata by 69.8-71.9%, Hanseniaspora lindneri DMKU ESS10-9 and Scheffersomyces spartinae DMKU SPS9-3 inhibited P. grisea by 81.9-84.4% and four Papiliotrema laurentii strains (DMKU-SPS15-1, DMKU-ESS11-2, DMKU-ESS8-2, DMKU-ESS6-4) inhibited P. palmivora by 53.2-59.5%.

Fig 1. Maps of sampling sites.

Sampling locations in Kuan Kreng and Rayong Botanical Garden peat swamp forests of Thailand.

Fig 2. Phylogenetic placement of ascomycetous yeasts.

Phylogenetic placement of known yeast species of Kuan Kreng (▲) and Rayong Botanical Garden (●) peat swamp forests belonging to the phylum Ascomycota and their closely related taxa based on the sequences analysis of the D1/D2 region of the LSU rRNA gene using maximum-likelihood method (GTR model). The names in bold type are representative strains from this study. Numbers on branches indicate percentages of bootstrap sampling (>50%), derived from 1000 samples. Bars indicate 0.05 substitutions per nucleotide position.

Fig 3. Phylogenetic placement of basidiomycetous yeasts.

Phylogenetic placement of known yeast species of Kuan Kreng (▲) and Rayong Botanical Garden (●) peat swamp forests belonging to the phylum Basidiomycota and their closely related taxa based on the sequences analysis of the D1/D2 region of the LSU rRNA gene using the maximum-likelihood method (GTR model). The names in bold type are representative strains from this study. Numbers on branches indicate percentages of bootstrap sampling (>50%), derived from 1000 samples. Bars indicate 0.05 substitutions per nucleotide position.

Fig 4. Yeast communities.

Summary of the yeast communities of Kuan Kreng and Rayong Botanical Garden peat swamp forests isolated by the dilution plate and the enrichment techniques.