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Abstract Ralstonia solanacearum is the agent of bacterial wilt. In order to provide the development of plant vaccine with avirulent mutants of R.solanacearum whose genetics are stable and insetion sites, this study constructed the avirulent mutants of R.solanacearum(strain Rs91) using EZ-Tn5 transposon mutagenesis. Through electroporation and screening, thriteen avirulent mutants were obtained. Results showed that the insertion sites of the 5 mutants were found to locate in phcA and phcS genes separately. The growth curves and the relative contents of Exopolysaccharide (EPSⅠ) of the 5 mutants were significantly lower than that of the original strain Rs91, but their optimum temperature and pH for the mutants to grow changed a few. The supernatants of the 5 mutants cultured in the TTC liquid medium were scanned by the UV-spectrophotometer, and the result showed that the absorbance of the mutants was higher than that of Rs91. The result of scanning was analyzed by UPGMA dendrogram. The cluster was displayed that the 5 avirulent mutants and Rs91 could be separated into 3 groups, e.g. the original strain Rs91 was in groupⅠ, the mutants of phcA- were in groupⅡ, and the mutant of phcS- was in groupⅢ. The 5 mutants were determined by the bioassay of potted tomato (Lycopersicon esculentum) and they did not fall ill after 15 days. The 5 mutants were determined to be avirulent R.solanacearum. This study provides foundation data for developing plant vaccine against bacterial wilt.
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Received: 21 April 2010
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