Contribution to the Identification and Study of the Pathogenicity of Bacteria Responsible for Cassava Root Rot in Côte d'Ivoire Production Zones

Abstract

Background and Objective: Cassava is an important crop for the Ivorian population. However, yields are relatively low. This low productivity is due to cassava root rots, which are sometimes caused by bacteria. The general objective was to identify the main bacterial diseases responsible for cassava tuberous root rot in production areas in Côte d'Ivoire. Specifically, to identify pathogenic bacteria and then to assess the pathogenicity of the bacterial strains isolated. Material and Methods: The plant material consisted of tuberous cassava roots affected by rot. Decay-causing bacteria were isolated on YPGA (Yeast extract Peptone Glucose Agar) culture medium. Strain identification was carried out using the API 20 E and 20NE gallery. Tuberous cassava roots were perforated with a punch and inoculated with bacterial inoculum calibrated to an optical density of 0.2 at a wavelength of 600 nm, corresponding to 108. Results: 174 strains were isolated. The highest proportions of strains were obtained in the localities of Ferké and Man, with 19 and 26% respectively. The bacterial species identified were Roualtella planticola, Serratia liquefaciens, Serratia marcescens, Burkholderia cepacia, Chromobacterium violaceum, Erwinia spp, Enterobacter cloacae, Klebseilla pneumoniae spp ozaenae and Raoutellia ornithinolytica. The Erwinia species was the most frequent in five localities, with proportions of 100 and 71.4% respectively in Agboville and Yamoussoukro. Results showed that 91.5% of bacterial strains tested caused rot (soft or dry). On the other hand, 52.4% of bacterial strains induced dry rot and around 39% induced soft rot. Conclusion: Various bacterial species were identified in this study. In addition, these species vary in their germinative capacity.