Identification and molecular characterization of the phytoplasma associated with a lethal yellowing-type disease of coconut in Cote d'Ivoire

Coconut palms from the Grand-Lahou region of Cote d'Ivoire exhibiting lethal yellowing-like symptoms and infected by a phytoplasma were further tested for the characterization of the phytoplasma pathogen based on the 16S rRNA gene analysis. Nested PCR with phytoplasma universal and lethal yellowing-specific primers resulted in amplification of products of expected sizes from seven out of 17 symptomatic trees tested, while non-infected symptomless plants yielded no DNA amplification. The 16S rDNA sequence of the phytoplasma detected from Grand-Lahou in coconut trees (KC999037) affected with the Cote d'Ivoire Lethal Yellowing disease showed a 99% sequence identity with that of the Ghanaian lethal yellowing phytoplasma (Cape St. Paul Wilt strain) of group 16SrXXII. The 16S rDNA sequence-based virtual and actual RFLP and phylogenetic analyses revealed that the phytoplasma associated with Cote d'Ivoire Lethal Yellowing in Grand Lahou is as a member of a new subgroup within group 16SrXXII that was designated as 16SrXXII-B. The present results support previous suspicions of disease spread to Cote d'Ivoire from neighbouring Ghana, posing a threat to the survival of the coconut trees in the Grand-Lahou region and for the Ivorian coconut industry.