9/9/2023 0 Comments Symphytum tuberosum sterile![]() ![]() ![]() The soil-borne Ralstonia solanacearum species complex (RSSC) is among the plant pathogenic bacteria that are most highly destructive to crops ( Mansfield et al., 2012), leading to significant economic losses for growers worldwide and resulting in dramatic consequences for sustainable crop production and food security. The evidence suggests, if at all, that African phylotype III strains are not efficiently transmitted through latently infected potato seed tubers. Overall, population structure of phylotype III involves individual small CCs that correlate to restricted geographic areas in Madagascar. Malagasy phylotype III strains were highly differentiated from continental African strains, suggesting no recent migration from the continent. High genetic diversity was uncovered, with 117 haplotypes grouped into 11 CCs. Phylotype III strains ( n = 217) were genotyped using the highly discriminatory MLVA scheme RS3-MLVA16. The population structure of phylotype III, described here for the first time in Madagascar, exhibited a different pattern. Additionally, the genetic structure of phylotype IIB-1 likely resulted from a bottleneck/founder effect. A regional-scale investigation suggested that phylotype IIB-1 strains were introduced and massively spread via latently infected potato seed tubers. One major CC included most of the worldwide haplotypes distributed across wide areas. In addition to reference strains, epidemic IIB-1 strains ( n = 255) were genotyped using the existing MultiLocus Variable-Number Tandem Repeat Analysis (MLVA) scheme RS2-MLVA9, producing 31 haplotypes separated into two related clonal complexes (CCs). This is the first report of phylotype IIB-1 strains in Madagascar. The marked increase of BW prevalence was found associated with phylotype IIB sequevar 1 (IIB-1) strains ( n = 879). Phylotypes I and III have been present in Madagascar for a long time but rarely associated with major potato BW outbreaks. A large collection of strains ( n = 1224) was assigned to RSSC phylotypes based on multiplex polymerase chain reaction (PCR). The genetic diversity and population structure of the RSSC were investigated in the major potato production areas of the Highlands. The first important step toward control is the characterization of strains and their putative origins. Controlling this disease is critical for Malagasy potato producers. In 2009, potato production in Madagascar was dramatically affected by several BW epidemics. The Ralstonia solanacearum species complex (RSSC) is a highly diverse cluster of bacterial strains found worldwide, many of which are destructive and cause bacterial wilt (BW) in a wide range of host plants. 6Unité Mixte de Recherche, Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Institut National de la Recherche Agronomique, Saint-Pierre, France.5Tropical Pests and Diseases Unit, Plant Health Laboratory, Agence Nationale de Sécurité Sanitaire de l’Alimentation, de l’Environnement et du Travail, Saint-Pierre, France.4Unité Mixte de Recherche, Biologie et Génétique des Interactions Plante-Parasite, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Montpellier, France.3Faculty of Sciences, University of Antananarivo, Antananarivo, Madagascar.2Unité Mixte de Recherche, Peuplements Végétaux et Bioagresseurs en Milieu Tropical, University of Réunion, Saint-Denis, France.1Unité Mixte de Recherche, Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Saint-Pierre, France.Santatra Ravelomanantsoa 1,2,3* Christian Vernière 4 Adrien Rieux 1 Laurent Costet 1 Frédéric Chiroleu 1 Sandrine Arribat 1 Gilles Cellier 5 Olivier Pruvost 1 Stéphane Poussier 2 Isabelle Robène 1 Fabien Guérin 2* Philippe Prior 6* ![]()
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