식물근권세균이 감귤더뎅이병균 생장에 미치는 영향 및 품종 별 저항성 검정

Abstract

Citrus scab disease caused by Elsinoe fawcettii is one of major disease in citrus cultivation, resulting in fruit blemishes that reduce quality and the economic value of fruits. Like other disease in citrus, citrus scab was mainly protected by chemical fungicides. Recently, interests of safe products were increased so that alternatives of chemical control were highly required. Elsinoe fawcettii was suppressed by rhizobacterial strains such as Burkholderia gladioli MRL408-3, TRH423-3 and Pseudomonas fluorescens THJ609-3, TRH415-2 having antifungal activity. In order to investigate inhibition-behaviors of citrus scab pathogen, the leaf surface of Satsuma mandarin, which was pre-treated with the rhizobacteiral strains, was observed on the Satsuma mandarin leaves by a scanning electron microscope (SEM) after inoculation with Elsinoe fawcettii. The number of lesions was reduced on the leaves pre-treated with the rhizobacterial strains compared to those of untreated leaves. Especially, the lesions numbers was apparently reduced on the leaves pre-treated with B. gladioli MRL408-3. The observation by SEM revealed that not only the germination rate but also the length of germ tube of the pathogen were decreased on the rhizobacterial strains pre-treated leaves. These inhibition of the fungal growth was more strongly expressed on the leaves pretreated with commercial fungicide Imibenconazole, by which the lesions was rarely found on the leaves. Based on these results, it was suggested that rhizobacterial strains may inhibit the germination and growth of the Elsinoe fawcettii on the surface of citrus leaves, resulting in decrease of disease severity. Lastly, in order to test resistance of various kinds of citrus cultivar against E. fawcettii, some citrus cultivar Jigak, Frost eureka, Washington navel, Jugyeon and Satsuma mandarin (negative control) were inoculated with E. fawcettii. Consequently, The number of lesions was significantly reduced on all tested citrus cultivar leaves compared with Satsuma m mandarin. Particularly Jugyeon was the most resistant to citrus scab, but Frost eureka was the least.