author(s)
Shiva Nagendran, Paranidharan Vaikuntavasan, Karthikeyan Muthusamy, Balachandar Dananjeyan and Gunasekaran Kulaiyappa

abstract
Bacterial wilt incited by Ralstonia solanacearum Yabucchi et al. is one of the most devastating disease of solanaceous crops. In this study, the bacterial wilt suppressing activity of Pseudomonas fluorescens Migula. was examined in tomato plants during plant-PGPR-pathogen interaction. The RT-PCR analysis revealed that, the transcription level of chitinase (133.06%) and β-1,3 glucanse (133.06%) in tomato plants treated with Ralstonia solanacearum + Pseudomonas fluorescens and Pseudomonas fluorescens increased with increasing time intervals (96 hpi). Unexpectedly, the defensin gene alone downregulated at 48^th hpi and interestingly the transcription fold (126.67%) increased again at 96 hpi. Comparatively, the transcription levels of all the three defense genes upregulated sequentially with the progressive time interval during tripartite interaction than in mock control and Ralstonia solanacearum inoculated plants. Collectively, the results suggest that the simultaneous upregulation of all the three defense-related genes triggers the systemic resistance in tomato plants against the bacterial wilt.