Coconut lethal yellowing on the Southern Coast of the Dominican Republic is associated with a new 16Sr IV group phytoplasma

Coconut palm (Cocos nucifera.) is an important economic and landscape crop in the Dominican Republic. Lethal yellowing (LY), a phytoplasma disease of coconut palm, was first reported in the northern coastal provinces of Puerto Plata, Santiago, Dajabon and Luperon in 1962 (Pujals Nolasco & Hichez Frias, 1974). No further spread of LY was reported during 1969 to 1986, which is attributed to quarantine and eradication programs in the affected provinces but natural barriers e.g. topography, edaphic factors, and an abundance of non-host palms could also have contributed (Harries et al., 2001).

Dead or dying coconut palms with symptoms of LY were first recognized at Boca Chica on the southern coast during February 2006. Leaf, inflorescence or trunk tissues from five diseased palms were tested for phytoplasma infection using a nested PCR with primers P1/P7 followed by LY group-specific primers LY16Sf/LY16Sr (Harrison et al., 2002). A product (1.39 kb) was amplified from all five affected palms but not from a symptomless coconut palm. AluI or HinfI endonuclease digests of nested PCR products showed no differences in fragment patterns amongst the five diseased palms (Fig. 1). However, these patterns were atypical of the LY phytoplasma belonging to the 16SrIV-A subgroup (Lee et al., 1998). Comparison of near full-length 16S rRNA gene sequence obtained after amplification with primers P1/P7 (GenBank accession No. DQ631639), indicated this phytoplasma was most similar (99.9%) to the strain associated with Yucatan coconut lethal decline (LDY) (U18753), a subgroup 16SrIV-B member (Lee et al., 1998), but belonging to a newly identified subgroup, 16SrIV-E, while sharing only 98.3% identity with LY phytoplasma (AF498308, AF498309).

This is the first report of a new 16SrIV group phytoplasma associated with yellowing coconut palms in Dominican Republic.