Objective  Expressions of the defense-related genes in tomato plant induced by Ralstonia solanacearum of varied pathogenicity were studied to understand the biocontrol mechanisms of the avirulent FJAT1458.

  Method  Real-time PCR was used to determine the expressions of gluA and PR-1a in the salicylic acid signal pathway, loxA and pin2 in the jasmonic acid signal pathway, and Osm and PR-1a in the ethylene signal pathway in tomato plants inoculated with the virulent strain FJAT91, the avirulent strain FJAT1458, or sterile water (CK) for 0, 3, 6, 12, 24, 36, 48, and 72 h.

  Result  Both avirulent and virulent strains could induce expressions of gluA, PR-1a, loxA, pin2, Osm, and PR-1a. However, except for PR-1a and Osm, the gene expressions induced by FJAT1458 were significantly higher than those by FJAT91. Both FJAT1458 and FJAT91 inoculations raised the expressions of gluA and PR-1a to a peak followed by a decline in 12 h. The expressions of loxA and pin2 induced by FJAT1458 induction were significantly higher than CK, but FJAT91 did only initially. On the other hand, FJAT91 produced a significantly higher Osm expression than either FJAT1458 or CK, excluding the 72 h inoculation. And in the 3 h inoculation it rendered a PR-1b expression significantly stronger than FJAT1458 at 260.46 times higher than CK.

  Conclusion   Both avirulent and virulent R. solanacearum could induce expressions of the defense-related genes in tomato plants in varied degrees. The transcriptomic method applied in this study could conceivably be used to unveil additional differently expressed genes associated with the pathways in tomato plants in the future.