Studies on Identification of the Pathogenic Actinomycete Causing Root Tumor of Melon and Ecology of this Disease

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1. In comparison of ten physiological characteristics and the pathogenicity to melon, there was no reference species of Streptomyces that were identical with the present Streptomyces sp. causing root tumor of melon.2. Selective isolation methods for the pathogen were investigated. The method that was isolated on basal medium of Lochhead and Chase incubated at 28 ^ﾟC for 5 days from pretreated sources with phenol solution (X140) for 10 minutes was more effective.3. Young growing melons inoculated with the pathogen of high concentration showed damping off, and these severities differed in sort of the soils. The occurrence of the disease in silty clay loam and clay loam were frequent more than sandy loam and loamy sand. The severest disease was able to appear at 35 ^ﾟC and pH 6.5-7.0 of the soils. In pF values of irrigation point, the disease in soil with pF 2.4 was severer than pF 1.8 and 2.7. Reappearance of the disease were observed in infested soils submerged paddy fields with cropping rice. Besides, the pathogen in inoculating soils could not be killed completely by submerging treatment for 150 days.4. The tissues of forming tumors were observed. The staining which was considering to be the pathogen could be recognized in parts of branching of roots before formation of the tumors and in the tissues around vascular bundle of tumors. In observation by SEM, small masses-like spore chains of the pathogen were found in vascular bundle, vascular bundle-like structures and tissues around ones containing in the tumors.