Insights into phytohormonal signaling response to Ralstonia solanacearum-virulence and host resistance perspectives

Ralstonia solanacearum is one of the most destructive plant pathogens, with a broad host range that infects many significant plant species and causes huge losses worldwide each year. Various management strategies have been employed to control this devastating pathogenic bacterium, but the required management level is still awaiting. It is because of its hard-to-eradicate nature, including prolonged persistence, extended survival in the environment, and a rapid multiplication rate. Developing an effective management strategy for any pathogen requires understanding its virulence mechanisms and the host response. Plant hormones are among the first signals to respond to pathogen invasion. Information on R. solanacearum, its life cycle, virulence mechanisms, and management strategies is mainly available in the literature. However, the collective information on its effects on plant hormones and the phytohormonal response to this pathogen, in the form of an analytical discussion, has yet to be published. In this review, we discussed how plant hormones act against pathogen attack in general and specifically against R. solanacearum infection. The effectors of R. solanacearum that influence plant hormones for virulence activity or act as inducers of plant immunity were also discussed in detail. Lastly, the phytohormonal cross-talk was analyzed in relation to pathogen virulence or host response. This analysis of the plant hormonal response to R. solanacearum infection and insights into the virulence mechanisms related to plant hormones will assist in developing useful and effective management practices for controlling this pathogen. Moreover, this review will pave the way for deeper research into pathogen virulence mechanisms.