Analyses based on the16S rRNAandsecAgenes identify a new phytoplasma subgroup associated with a lethal yellowing-type disease of coconut in Côte d'Ivoire

Abstract

A lethal yellowing-like disease named as Cote d'Ivoire Lethal Yellowing (CILY) has been spreading throughout the Ivoirian coastal coconut plantations of the Grand-Lahou department in Cote d'Ivoire causing losses of about 12,000 tons of copra/year, and has also become a threat for the coconut Genebank. Leaf, stem apex, heart and inflorescence samples of coconut palms exhibiting CILY symptoms that resemble those associated with Cape Saint Paul Wilt Disease (CSPWD) in Ghana, were sampled and nested PCR-tested for phytoplasma presence. The phytoplasma identified was further characterized based on the sequences of the 16S rRNA and secA genes. Phytoplasma universal primers yielded expected amplification products from 61 out of 84 samples from symptomatic trees tested, while samples from symptomless palms yielded no DNA amplification. Both the 16S rDNA and secA sequences of the CILY phytoplasma showed a 99% sequence identity with that of the CSPWD phytoplasma from Ghana, and clustered with previously identified West Africa phytoplasma strains of group 16SrXXII that includes the Ghanaian CSPWD strain. The phytoplasma was assigned to the sub-group 16SrXXII-B based on virtual RFLP of the 16S rDNA sequences. Results support possibility of disease spread from the neighbouring Ghana, posing a threat for the Ivorian coconut industry.