Sweet Potato (Ipomea batatas L.): A New Alternative Host of Two Phytoplasmas Associated with Coconut Lethal Yellowing Disease in Côte d’Ivoire

Aims: Coconut Lethal Yellowing Disease has been threatening coconut plantations in Côte d'Ivoire for ten years and has destroyed more than 400 ha. The destruction of the coconut palm leads to phytoplasmas conservation on other plants grown in association or near of the disease outbreaks. Thus, the search for possible alternative host species was conducted.

Methodology: Surveys were carried out in infected coconut plantations, in order to describe symptoms associated with phytoplasma infections and to collect leaf samples of plant species other than coconut. Symptomatic and non-symptomatic leaves of sweet potato (Ipomea batatas L.) were collected for DNA extraction. The extracted DNA was subjected to molecular characterization.

Results: Mosaic and leaf reduction symptoms were observed on sweet potato leaves. From these samples, two phytoplasma strains were associated. Molecular analysis showed the presence of the endemic phytoplasma strain belonging to the 16SrXXII-B subgroup ʺCandidatus Phytoplasma palmicolaʺ. Sequencing and phylogenetic analysis also revealed the presence of a new phytoplasma strain, sharing 99% similarity with 16SrIV group strains ʺCandidatus Phytoplasma palmaeʺ.

Conclusion: The detection of these strains confirms sweet potato for the very first time, as an alternative host for coconut lethal yellowing phytoplasmas in Côte d'Ivoire.