Pathogenicity Of Pantoea Agglomerans And Screening Of Antagonistic Pantoea Strains

The paper was made up of three parts: I. Physiological and biochemical characteristics of isolates from discoloring rice seed samples were tested; II. Pathogenicity of Pantoea agglomerans caused rice seeds discoloring was studied; III. Antagonistic strains of Pantoea on rice bacterial leaf blight and rice bacterial leaf streak were screened. 63 isolates were isolated from 15 discoloring rice seed samples gathered from 12 villages (towns) of Fuzhou, Minhou and Jian'ou. The testing results of physiological and biochemical characteristic of those isolates showed that 18 of them were identified to be genus Pantoea, among which 8 strains were Pantoea agglomerans. The pathogenicity of 8 Pantoea agglomerans strains was tested respectively. The result showed that all strains could cause rice seeds and rice ears discoloring, among which FDQ 1, FDSN4, XD2, XSH4 were stronger pathogenic and XD2 strongest. It was found that Pantoea agglomerans not only influenced the development and maturation of rice ears, but also inhibited the sprouting of rice seeds. Staining sites of Pantoea agglomerans in rice seed were proved to be the inner and outer glume tissue. The concentration of its bacterial suspension inoculated was found not to be lower than 1 O8CFU/ml for keeping its strong pathogenicity. The resistence of regional testing lines and conventional varieties against Pantoea agglomerans in Fujian province indicated that most varieties were resistant and a few susceptible. The result of testing the distribution of Pantoea agglomerans in paddy demonstrated that it could be isolated easily from healthy grains, the leaves of rice plants~ the water and soil of paddy and the leaves of weeds around the paddy. It was obviously found that the Pantoea agglomerans strains isolated from those samples in paddy were low-pathognicity to rice seeds. 18 Pantoea strains were screened antagonistic against Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola. The result showed that DAT4 (Pantoea dispera) and FDQ4 (Pantoea agglomerans) had good antagonistic effect against both pathogenic bacteria. It was found that the colonization of antagonistic bacteria on rice plants was related to the introduced bacterial concentration and the bacterial leaf blight (bacterial leaf streak) lesions on the leaves of rice plants. The result indicated that introduced at high concentration and sprayed on rice plant with lesions, the population of the antagonistic bacteria could maintain large 15 days after spraying. The ice-nucleation activity of FDQ4 was found strong and that of DAT4 weak. The result of testing antagonistic effect of DAT4 and FDQ4 on rice bacterial leaf blight and bacterial leaf streak in paddy showed that the index of morbidity of bacterial leaf blight( bacterial leaf streak) rice plants inoculated antagonistic bacteria was much lower than that of control. It was clear that the appropriate timing to spray antagonistic bacteria was one day after inoculating X. oryzae pv. oryzae (X. oryzae pv. oryzicola) and the initial concentration of introduced antagonistic bacteria could not be lower than 108 CFU/ml.