Poster Presentation Science Protecting Plant Health 2017

High prevalence of a genetic lineage of the Ralstonia solanacearum species complex in the Southwest Indian Ocean islands inferred by phylogenetic and genotyping approaches (#124)

Noura Yahiaoui 1 2 3 , Niry T Dianzinga 1 2 , Emeline Rébert 1 2 , Jean-Jacques Chéron 1 , Karine Boyer 1 , Thomas Chesneau 4 , Bobb Petrousse 5 , Rajan Jeetah 6 , Azali A Hamza 7 , Yasmina Jaufeerally-Fakim 8 , Jérôme Félicité 9 , Jacques Fillattre 10 , Bruno Hostachy 3 , Fabien Guérin 2 , Gilles Cellier 3 , Philippe Prior 11 , Stéphane Poussier 2
  1. CIRAD, UMR PVBMT, Saint-Pierre, Reunion, France
  2. University of Reunion island, UMR PVBMT, Saint-Pierre, Reunion, France
  3. ANSES, Laboratoire de Santé du Végétal (LSV) , Saint-Pierre, Reunion, France
  4. Etablissement Public National de Coconi, Coconi, Mayotte, France
  5. SAA, Victoria, Seychelles
  6. FAREI, Réduit, Mauritius
  7. University of Comoros, Moroni, Comoros
  8. University of Mauritius, Réduit, Mauritius
  9. Commission de l'Agriculture, Port-Mathurin, Rodrigues
  10. ARMEFHLOR, Saint-Pierre, Reunion, France
  11. USC INRA, UMR PVBMT, Saint-Pierre, Reunion, France

In the Southwest Indian Ocean (SWIO) islands (Comoros, Mauritius, Mayotte, Reunion, Rodrigues and Seychelles), bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is hampering many sustainable and cash crop productions. To thoroughly analyze the genetic diversity and population structure of the RSSC in the SWIO, we conducted a wide sampling survey that yielded 1871 isolates, mainly from solanaceous species. Phylogenetic assignation of isolates showed 88% of phylotype I that was prevalent in each SWIO islands; 9% of phylotype II and 3% of phylotype III that were only found in Reunion. Phylotype IV (2 strains), was reported in Mauritius, representing the first report of this group in SWIO. Partial egl sequencing, based on a selection of 143 strains covering the geographic and host diversity, inferred 10 sequevars: I-13, I-14, I-15, I-18, I-31, I-33, IIA-36, IIB-1, III-19, and IV-10. A Multilocus Sequence Analysis (MLSA) scheme based on the partial sequencing of 6 housekeeping genes (gdhA, gyrB, rplB, leuS, adk, and mutS) and 1 virulence-associated gene (egl) inferred the phylogenetic relationships between these 143 SWIO strains and 91 worldwide RSSC reference strains. Phylotype I was the most genetically diverse and recombinogenic, although recombination events were detected among all phylotypes. The Multilocus Sequence Typing (MLST) scheme has identified 31 sequence types (ST) with variable geographic distributions in SWIO. Outstanding epidemiologic feature was STI-13 (sequevar I-31) that was overrepresented in the SWIO, which obviously mirror a genetic lineage that have strongly adapted to SWIO environment. To further study the population structure of RSSC in SWIO, we developed a MultiLocus Variable number tandem repeat Analysis (MLVA) scheme based on 19 VNTR markers. This work, highlighting notably genetic links between African and SWIO strains, provides the basis for epidemiological surveillance of RSSC and bacterial wilt management in SWIO.