Bacteriocin Production Correlates with Epidemiological Prevalence of Phylotype I Sequevar 18 Ralstonia pseudosolanacearum in Madagascar.

Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is a major threat to vegetable crops in Madagascar. For more effective disease management, surveys were carried out in the main vegetable production areas of the country, leading to the collection of 401 new RSSC isolates. Phylogenetic assignment of the isolates revealed a high prevalence of phylotype I sequevar 18. This result contrasts sharply with the epidemiological pattern of RSSC in neighboring islands, including Reunion Island, Comoros, Mayotte, Mauritius, Rodrigues, and the Seychelles, where phylotype I sequevar 31 is widespread. Molecular typing characterization of the Malagasy isolates allowed the identification of 96 haplotypes. Some are found in various plots located in different provinces, which suggests that they were probably disseminated via infected plant material. To find out a potential explanation for the observed epidemiological pattern, we examined the capacity of the Malagasy strains to produce bacteriocin. Interestingly, the highly prevalent genetic lineages I-18 produce bacteriocins that are active against all the genetic lineages present in the country. This work sheds light on the potential impact of bacteriocins in the epidemiology of Malagasy RSSC.