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Abstract
In a previous study, we demonstrated the ability of the rhizobacterium Bacillus cereus AR156 (AR156) to protect tomato against bacterial wilt caused by Ralstonia solanacearum and root-knot disease caused by Meloidogyne incognita. Here, we investigate the ability of AR156 to promote plant growth and its role in the systemic protection of tomatoes cultivated in greenhouses against bacterial speck disease caused by Pseudomonas syringae pv. tomato DC3000 (DC3000). In our experiments, the AR156 population reached 105–106 CFU/g rhizosphere soil, and remained at that level in the rhizosphere of tomato plants for more than 2 months. In terms of its ability to promote plant growth, AR156 increased the average biomass of the tomato by 47.7%. AR156 also elicited induced systemic resistance against DC3000, significantly reduced bacterial speck disease severity 1.6-fold, and inhibited proliferation of the pathogen by approximately 15-fold. This strain triggered the accumulation of defence-related genes (PR1 and PIN2) in tomato leaves and primed the leaves for accelerated defence-related gene expression upon challenge with DC3000. That suggested simultaneous activation of the salicylic acid and the jasmonic acid dependent signalling pathways by AR156 against DC3000. In conclusion, B. cereus AR156 was found to form robust colonies in the roots of tomato and had some beneficial effects, including biological control of bacterial speck disease via ISR and promotion of plant growth.
Acknowledgements
This research was supported by the National Natural Science Foundation of China (30971956, 31171809, 31000876), the Specialized Research Fund for the Doctoral Program of Higher Education of China (20100097120012), Program for Jiangsu Key Laboratory of Eco-Agricultural Biotechnology around Hongze Lake (HZHL1006), Open Research Fund of State Key Laboratory of Bioelectronics, Southeast University and Research and Innovation Project for College Graduates of Jiangsu Province (CXLX11_0695). We would like to thank Prof. Han-Song Dong (Nanjing Agricultural University, China), who kindly provided us with the virulent pathogen DC3000.