| Radopholus similis is a kind of important quarantine pathogen which infects most of plant hosts and can cause a serious damage. It leads to a potential threat on agricultural production in China. At present, because of the high toxicity of chemical nematicides, screening and obtainment of bio-control microbes with the antagonist to the nematode has an important significance for disease control.In this paper, rhizosphere soil samples were collected from the banana plantation infected by Radopholus similis, so that antagonistic bacteria for killing Radopholus similis in bioassay were screened and indentified. At the same time, preliminary study on its biological charateristics was carried, in order to understand the relationship between rhizosphere microorganisms and Radopholus similis, and to provide technical support for the development of new nematicides reagents. The specific research results were as follows:39soil samples were collected from the banana rhizosphere soil samples fields infected by Radopholus similis, and the strains were isolated by the method of gradient dilution. A total of789strains bacteria were isolated and5strains were high efficient against Radopholus similis through indoor test and greenhouse pot experiment. The results indicated that the mortality rates of Radopholus similis were above90%and100%within24h and48h respectively after the treatment by fermentation supernatant of bacteria strains HD-34, HD-46, HD-54, HD-86and HD-93. In greenhouse pot experiment, their control effect on Radopholus similis was risen and that of abamectin was decreased within42-70days after the inoculation. The control effect of fermentation supernatant of strain HD-86were77.34%and90.51%respectively at42and70day after the inoculation, but that of abamectin was63.97%only at70days after the inoculation. Compared with water control, the plant height, stem diameter and root weight of banana plants by the treatment of antagonistic bacteria were increased significantly.By using of the molecular techonology, the strains HD-34, HD-54and HD-86were identified as Burkholderia, but HD-46and HD-93were as Enterobacte. Based on the comparision with the reported16srDNA sequences and the construct of phylogenetic tree, the sequence of the strain and Burkholderia cepacia isolate MSMB10belonged to a branch, and the strain HD-86was identified as Burkholderia cepacia.Due to the Burkholderia cepacia pathogenesis associated with human disease genes, the PCR specificity primer was applicated to test the toxicity of strains HD-86. The results showed that the virulence gene of Burkholderia cepacia epidemic strain marker (BCESM) was not existed in the strain HD-86, and the safety of strain for humans and environment was confirmed.The results on stability of fermentation supernatant from strain HD-86against Radopholus similis showed that the antagonistic activity was still high under the treatment at80℃for60min, the antagonistic effect was better with the basicity increase within the scope of pH8-10, and the antagonistic activity was not effected with the ultraviolet ray treatment.The fermentation supernatant of strain HD-86diluted50-500times could promote the growth of mung bean, with the seedling length18.12cm and the single plant fresh weight0.45g in the treatment of diluted50times. Compared with clear water control, the average length and average plant fresh weight were increased by2.44cm and0.15g, and the difference was significant or extremely significant. The fermentation supernatant of diluted50times had a significant role in promoting the growth. However, the undiluted fermentation supernatant of strain HD-86had obvious inhibitory effect on the growth of mungbean seedlings.The fermentation supernatant of strain HD-86was extracted by organic solvent and the activity agianst Radopholus similis was tested. The results showed that the ethyl acetate extract was strong active to the nematode, The LC50were5.74mg/mL and2.74mg/mL at24h and48h after the treatment respectively. |
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