Phylotypes of the potato bacterial wilt pathogen in the Philippines and their relationship to pathogen aggressiveness

Abstract

Three hundred seventy-two Ralstonia solanacearum isolates were collected from potato fields, in the Philippines, and characterized based on phylotypes, distribution and aggressiveness to host plants. Two major genetic group were identified: Phylotype I (Asiaticum), which were predominant in the southern region (Bukidnon), and Phylotype II (Americanum), found mainly in the northern region (Benguet). Phylotypes I and II were both pathogenic to tomato and potato host plants, but Phylotype I induced significantly earlier wilting symptoms to tomato and potato than Phylotype II (P = 0.03 – <0.01). No correlation was found between elevation and phylotype distribution (coefficient = 0.03–0.22). Based on the current taxonomic classification of R. solanacearum species complex, R. pseudosolanacearum and R. solanacearum cause potato bacterial wilt in the Philippines. Implications for quarantine regulations and breeding programs are discussed.