Yeast Associated with Rice Phylloplane and Their Contribution to Control of Rice Sheath Blight Disease.

Parichat Into,Somjit Am-In,Savitree Limtong,Pannida Khunnamwong,Wanwilai Intanoo,Sasitorn Jindamoragot

doi:10.3390/microorganisms8030362

Abstract

The phylloplane is an important habitat for yeasts and these yeasts may have antagonistic activities against pathogens and could be used as biocontrol agents. To investigate rice phylloplane yeasts, 282 strains were isolated from 89 rice leaf samples and identified as 15 known yeast species in the phylum Ascomycota and 35 known and two potential new species in the phylum Basidiomycota. The majority of rice phylloplane yeasts belonged to the phylum Basidiomycota. The evaluation of antagonistic activities of 83 yeast strains against rice pathogenic fungi Pyricularia oryzae, Rhizoctonia solani, Fusarium moniliforme, Helminthosporium oryzae and Curvularia lunata revealed that 14 strains inhibited these pathogens. Among the antagonistic strains, Torulaspora indica DMKU-RP31, T. indica DMKU-RP35 and Wickerhamomyces anomalus DMKU-RP25 inhibited all rice pathogens tested, and the production of volatile organic compounds, fungal cell wall degrading enzymes and biofilm were the possible antagonistic mechanisms against all rice pathogens tested in vitro. These yeast strains were evaluated for controlling rice sheath blight caused by R. solani in rice plants in the greenhouse and were found to suppress the disease by 60.0–70.3%, whereas 3% validamycin suppressed by 83.8%. Therefore, they have potential for being developed to be used as biocontrol agents for rice sheath blight.

Highlights

The term phylloplane refers to the parts of plants above ground and dominated by leaves and is an important habitat for microorganisms [1]
The known ascomycetous yeast species belonged to nine genera: Blastobotrys, Candida, Debaryomyces, Hyphopichia, Kodamaea, Meyerozyma, Torulaspora, Wickerhamomyces and Yamadazyma
Among the strains belonging to the phylum Basidiomycota, 229 strains were identified to be 35 known species of yeasts and yeast-like fungi in 16 genera

Summary

Introduction

The term phylloplane refers to the parts of plants above ground and dominated by leaves and is an important habitat for microorganisms [1]. One of the major causes of decreases in rice production is diseases caused by pathogenic fungi. The major rice diseases caused by fungal pathogens in Thailand are blast (caused by P. oryzae), sheath blight (caused by R. solani), bakanae (caused by F. moniliforme), brown spot (caused by H. oryzae) and dirty panicle (caused by Cu. lunata and H. oryzae) (Rice Department, Ministry of Agriculture and Cooperatives of Thailand, 2014). Rice sheath blight disease causes yield losses of 25%–35% of Thai rice production [10]. This disease is the second most important rice disease worldwide [11]

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