Minotoring the Pathogenic Diversity of Xanthomonas axonopodis pv. manihotis Strains in Côte d'Ivoire, Sensitivity of Cassava Varieties and Disease-Control Approach

Background and Objective: Cassava occupies a special place in human nutrition in Côte d'Ivoire.
Cassava (Manihot esculenta Crantz) helps ensure food security for people in Africa. The world yield
was estimated at 250 million tons in 2011. In Côte d'Ivoire, it is estimated at 2.8 million tons per year,
and is the second most important food crop after yam. However, its cultivation is confronted with
many parasitic constraints, among which one of the most dreadful is bacterial blight caused by
Xanthomonas axonopodis pv. manihotis. With the exception of its confirmation, in 2015, in Côte
d'Ivoire, no substantial scientific information has been reported on this disease as well as on
appropriate control methods. This study aims at studying the pathogenic diversity of bacterial strains,
the sensitivity of the main cassava cultivars and assessing the bactericidal properties of the
biopesticide NECO.
Materials and Methods: 45-day-old plants were inoculated with Xam strains and then treated with a
range of five (5) concentrations (v/v) of NECO.
Results: Different sensitivity levels of the varieties as well as virulence variability were observed. Of
121 Xam strains tested, 109 caused typical symptoms of bacterial blight, while 12 strains proved
avirulent. The variety ''Diarrassouba'' was the most attacked, while the lowest sensitivity level was
obtained by ''Yavo'' and ''Bocou 2''. Moreover, the application of NECO at 5 ml/L after two treatments
favored a recovery of the infected plants by 92.59% against 14.81% for the reference product.
Conclusion: Therefore, NECO can be used for its proven effectiveness in cassava bacterial blight
control in Côte d’Ivoire. Despite the proven effectiveness of NECO, further studies are needed in the
field so as to determine the applicable doses depending on parasite pressure, varieties, and climatic
conditions.