Biological Control Of Postharvest Diseases Of Jujube Fruit Using Antagonists

This study focuses on the biological control of the postharvest diseases on the jujube fruit, including isolation and identification of the pathogens on the postharvest jujube fruit, screening of microbal antagonists against A. alternata isolated from jujube fruit, and investigation on the biological control effect and the action mode of antagonists against postharvest diseases.Jujube fruits (Zizyphus jujuba cv. Dongzao) used in this study were collected from several orchards in September and October, 2004-2005. The pathogens infecting jujube fruit in the pro- and post- harvest were isolated and their pathogenicities were determined according to the Koch' s postulates. Based on the DNA sequence analysis of ITS region (including 5.8S) and the morphological comparison, we concluded that the main fungal pathogens causing postharvest diseases on jujube fruit were A. alternata, F. decemcellulare Brick, P. expansum and Mon. fructicola.A large scale in vivo screening of antagonists were performed against A. alternata, a main pathogen of jujube fruit. A bacterial strain B501 and three yeast strains, XY103, XY201 and XY801, were obtained from fruit surfaces and wounds and showed effective biocontrol activities. Based on the 16S rDNA sequence analysis, physiological and biochemical characterization, the strain B501 was identified as P. agglomerans. Three separate groups represented by strains XY103T, XY201T and XY801T were recognized by sequence comparisons of the 26S rDNA D1/D2 domain and internal transcribed spacer (ITS) region. The morphological, physiological and molecular comparisons demonstrated that strains XY103T, XY201T and XY801T were distinct from each other and from any previously described Metschnikowia species. These three strains were identified as novel species in the genus Metschnikowia, M. sinensis sp. nov., M. zizyphicola sp. nov. and M. shanxiensis sp. nov., respectively.Biological control potential of strains B501 and XY201 on the postharvest jujube fruit were investigated. The results showed that the P. agglomerans B501 could significantly reduced disease incidence of jujube fruit caused by A. alternata when applied on wounded fruits at a relatively low concentration of 1×107 cfu mL-1, which also showed a significantly...