감귤검은점무늬병 억제효과가 있는 식물근권세균 Rhizobacteria Showing Suppress Effect

Abstract

Citrus melanose is known as an important disease in the citrus cultivation of Jeju island. Mostly, citrus melanose is controled by spraying chemical fungicide. The frequency of using fungicide become increased which caused the fungicide resistance and environmental destruction. Recently, eco-friendly agricultural products is demanded in the citrus industry including biological control using microorganisms which can be an alternative method to pesticides. In this study three rhizobacterial strains TRH423-3, MRL408-3, THJ609-3 are selected by testing its antifungal activity against Diaporthe citri causing citrus melanose. To investigate the protect efficacy of the selected rhizobacterial strains to citrus melanose, the bacteria were pre-inoculated on citrus leaves following inoculation with melanose pathogen. Pre-inoculation with all selected rhizobacterial strains showed disease suppression in which the levels of protection rates were different by the rhizobacterial strains. Additional inoculation with the rhizobacterial strains after the pathogen inoculation was enhanced protection rates in all cases. In the orchards disease severity of citrus melanose was suppressed at 20% by the selected rhizobacteria strains, whereas at 94% by commercial fungicide Dithianon?. In the case of alternation treatment with the rhizobacteria and the fungicide the protection efficacy of the rhizobacteria could be apparent due to the fungicide. On the other hand, the strain MRL408-3 and TRH423-3 were identified as Burkholderia gladioli, THJ609-3 as Pseudomonaspudiaas a result of analyzing the internal transcript spaces(ITS) of the rhizobacterial strains rDNA. The selected rhizobacterial strains may be valuable in the environment-friendly citrus farm in which chemical application is limited.