PM 7/21 (2) Ralstonia solanacearum, R. pseudosolanacearum and R. syzygii (Ralstonia solanacearum species complex)

摘要

This Standard describes a diagnostic protocol for Ralstonia solanacearum, Ralstonia pseudosolanacearum and Ralstonia syzygii, i.e. phylotype/sequevar strain in the Ralstonia solanacearum Species Complex (RSSC).1Ralstonia solanacearum (Smith) Yabuuchi et al. is included in the EPPO A2 List of pests recommended for regulation and in many EPPO members' lists of regulated pests. It has been described by Fegan & Prior (2005) as distributing into four phylotypes in aspecies complex. Each phylotype comprises multiple phylogenetic and pathogenic variants differing in barcoding genes (including ITS, hrpB, mutS and egl), known as sequevars. Historically, the species complex has been recognized as a number of phenotypically diverse strains that were originally placed into five pathogenic races and five biovars (Buddenhagen et al., 1962; Hayward, 1964). Recently, it has been reclassified by Safni et al. (2014) into three distinct species: R. solanacearum (Phylotype II),Ralstonia pseudosolanacearum (Phylotype I and III) and Ralstonia syzygii (Phylotype IV). Ralstonia syzygii comprises 3 subspecies: subsp. syzygii found on clove, subsp. celebesensis found on banana and subsp. indonesiensis found on Solanum tuberosum (potato), Solanum lycopersicum (tomato), Capsicum pnnuum (chilli pepper) and Syzygium aromaticum (clove). These three species are covered by this diagnostic protocol under the taxonomy of phylotype/sequevar, which clearly separate Phylotype I and III strains and other epidemiologically distinct strains in Phylotype II (causing potato brown rot or Moko disease).