Inventories of Forest Host Plants of the Xanthomonas Bacterium in Cashew Orchards in Western Burkina Faso

Abstract

The presence of forest species in cashew orchards in Burkina Faso, linked to their lack of maintenance, serves as a hotspot for the emergence of pathogens such as bacteria from the Xanthomonas citri species. Identifying these forest species acting as reservoirs for this bacterium in various cashew orchards could contribute to their management. To this end, a forest inventory allowed us to identify the forest species present in cashew orchards, mango orchards, and mixed cashew/mango orchards. Molecular identification of 11 strains was carried out through the analysis of the atpD housekeeping gene sequences. The population sizes of strains inoculated on the CE420 cashew accession were measured 21 days post-inoculation. We have proven the existence of 18 forest species in the orchards. The analysis of atpD sequences demonstrated that all our strains derive from a common ancestor, Xanthomonas citri. The population sizes of strains 5DDCF, 6BFG, and 1BFG, isolated from Ficus abutilifolia (Miq.) Miq and Combretum micranthum G. Don, reached high densities of up to 8.108 CFU 21 days post-inoculation. Xanthomonas strains isolated from Ficus abutilifolia (Miq.) Miq and Combretum micranthum G. Don demonstrated their ability to colonize the leaf tissues of cashew. Mango, Ficus abutilifolia (Miq.) Miq, and Combretum micranthum G. Don were plant species that share the same ecological niche as cashew and serve as reservoirs for Xanthomonas bacteria pathogenic to cashew.