Diversity of the <i>Ralstonia Solanacearum</i> Species of Potato Seeds in Mali

Abstract

Potato brown rot was classified as a quarantine disease because of the complexity of the pathogen <i>Ralstonia solanacearum L</i>., formerly called <i>Pseudonomas</i> or <i>Burkholderia solanacearum</i>. This same bacterium causes the disease bacterial wilt. It is a multifaceted bacterium hence the complex name <i>Ralstonia solanacearum</i> (CeRs or RASLSSO) or BW (in English). It attacks several plant families, notably nightshades such as potatoes; the tomato; eggplant; chili pepper; tobacco…etc. The potato is the most cultivated plant worldwide. Mali is the second largest producer in West Africa after Nigeria. It imports more than 9,000 to 11,000 tons of seeds each year. Potato cultivation is faced with several biotic and abiotic attacks. Among all these attacks, those caused by bacteria cause the most significant damage. In addition, diseases caused mainly by the <i>Ralstonia solanacearum</i> complex lack adequate control solutions. Despite everything, today, very few studies are carried out to identify these bacteria in order to prevent their spread in the soil in Mali. This is why the objective of this study is to identify the bacteria responsible for brown rot in potato seeds in Mali. To achieve our objective, a total of 63 samples were taken from nine varieties of imported and locally multiplied potato seeds. The agent responsible for brown rot was isolated on the Triphenyl-Tetrazolium-chloride culture medium, and several microbiological, biochemical and molecular tests were carried out to identify the different isolates selected. As the main results of this study: twenty-seven bacterial isolates, capable of causing brown rot of potato seeds were isolated, the biochemical tests carried out on these isolates showed that they all of race3 and twenty -four isolates were biovar 3; one from biovar 2 and two from biovar 6. The molecular studies carried out using universal primers confirmed the presence of the species <i>Ralstonia solanacearum</i> with two phylotypes (I and II).