Genetic diversity of Ralstonia solanacearum strains from Mexico associated with Moko disease

The Ralstonia solanacearum species complex is one of the most destructive bacterial plant pathogens for many crops. Cavendish banana is an important staple food which is severely impacted by the bacterial wilt Moko disease, caused by R. solanacearum race 2. In Mexico, banana plantations comprise 75,000 ha, supporting the economy of more than 100,000 families. Moko disease is present in the states of Chiapas and Tabasco, which are responsible for >60% of the total banana production. Each year, thousands of diseased plants are eradicated there because of Moko disease. The goal of this study was to genotype and characterizes Mexican Moko strains. Most of the strains were pathogenic to banana (PB), but two strains were found to be unable to develop wilt symptoms (NPB). A phylogenetic tree based on egl placed all Mexican strains in phylotype IIA, sequevar 6. Mexican Moko strains share identical egl sequence with strains from Central America and Caribbean countries, supporting the Caribbean origin proposed for sequevar 6 by some authors. The Mexican Seq6 nonpathogenic to banana (6NPB) and pathogenic (6 PB) strains were clustered apart in sister clades, in hrpB and pga phylogenetic trees, suggesting that this lineage is under divergence in Mexico. This is the first report worldwide of race 2 NPB strains genotyped in sequevar 6, and extends the currently known phenotypic diversity of R. solanacearum.