Abstract:

【Objective】 The objective of this study is to explain the relation of peach replant diseases and rhizosphere microorganisms. 【Method】Peach rhizosphere microorganisms were isolated with Mфller Potassium Cyanide Medium. The isolated strains were identified by 16S rDNA sequences and biological characterization. Biocontrol effect were observed in pot trials initially.【Result】 Three bacteria strains (CN-X4, CN-X9, CN-X17) which could utilize amygdalin as carbon source and produce hydrocyanic acid were separated from peach rhizophere soil, and three rhizosphere actinomyces strains（CN-G2, CN-G3, CN-G5）were also isolated, and show different antagonistic effect on the three bacterial strains by plate bacteriostasis assays. Strain CN-X4 and strain CN-X17 were identified as Agrobacterium tumefaciens, but they were different subspecies. Strains CN-X9, CN-G2 and CN-G5 were proved to belong to Pseudomonas sp, Streptomyces microflavus, Streptomyces lavendulae, respectively. Strain CN-G3 may be close or similar to a species of Streptomyces griseus. Biocontrol effect was significant in pot trials. 【Conclusion】 There were not only bacteria which could utilize amygdalin as carbon source and produce hydrocyanic acid but also actinomyces which had antagonistic effect on the bacteria in peach rhizosphere. The unbalance of the rhizosphere microorganisms is considered as a crucial factor for peach replant diseases occurrence.

Key words: peach, replant disease, bacteria, antagonists