Malagasy traditional treatments of infectious plant diseases exert anti-virulence activities against pseudomonas aeruginosa and Ralstonia solanacearum

peer reviewedTraditional Malagasy farmers have developed a range of biological methods to restrict plant diseases without reliance on external or synthetic inputs. Five common Malagasy traditional practices demonstrated to be efficient against potato crop bacterial disease in experimental fields have been investigated for their antibacterial (i.e. bacteriostatic and bactericidal effects) and anti-virulence (i.e. antiquorum sensing and anti-biofilm) activities against two phytopathogens, Pseudomonas aeruginosa and Ralstonia solanacearum. Results show that polar (methanolic) extracts of recipes exert anti-virulence activities rather than bacteriostatic and/or bactericidal activities. Indeed, three recipes (R5, R7 and R9) reduce the expression of QS-dependent virulence factors whereas only recipe (R5) exhibit antibiofilm activities without affecting bacterial growth. R4 and R6 were not active, suggesting other bacterial targets and/or other bioactivity properties. Innovative approaches, inspired from ancestral practices, should be considered in the struggle against infectious diseases to limit the overuse of antibiotics for controlling infectious plant diseases and to reduce the overspread of multidrug resistant bacteria

Identification et gestion des maladies du vanillier à Madagascar

About 97% of the real vanilla come from Madagascar worldwide. Madagascar’s vanilla is well known for its quality, and its production is very important for the country’s economy. However this culture is threatened by the emergence of fungal and viral diseases that have been recorded for a decade, causing significant devaluations of the production’s level of quality and an important reduction of the quantities annually exported. In order to be able to scientifically construct a strategy of prevention and control against the main pathogens of vanilla, large sampling campaign was carried out in Madagascar’s SAVA region. Lianas showing symptoms of cryptogamic diseases such as rot, wilt, necrosis or melanosis were harvested. 75 bacteria and 61 fungi were isolated on NA and PDA medium and identified. Morphological and molecular identifications (based on the sequencing of 16S rRNA and ITS regions) of these isolates have shown that the genus Fusarium is the most present (27% of fungal isolates) and is represented by species of F. oxysporum, F. proliferatum, F. concentricum, F. equiseti, F. pseudocircinatum and F. mangiferae. While for bacteria, the genus Bacillus predominates (44% of purified bacterial strains). Many bacteria of the genus Bacillus are known for their biocontrol properties; this is why we have tested the potential antagonistic effect of all vanilla-isolated Bacillus strains against two species of Fusarium. Nine Bacillus strains were identified for reducing the growth of the fungi, and are of great potential for the development of a biocontrol strategy against Fusarium attacking vanilla in Madagascar.Intégration d’un réseau de compétences scientifiques dans la filière de production de la vanille pour une exploitation durable et de qualité dans la Région SAVA, Madagasca