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

R.T. Martinez^1*, M. Narvaez², S. Fabre³, N. Harrison⁴, C. Oropeza², M. Dollet³ and E. Hichez¹

¹ Instituto Dominicano de Investigaciones Agropecuarias y Forestales-IDIAF, Calle Rafael Augusto Sánchez, No. 89, ensanche Evaristo Morales, Dominican Republic
² Centro de Investigación Científica de Yucatán-CICY, CP 97200 Mérida, Yuc., Mexico
³ Centre de Coopération Internationale en Recherche Agronomique pour le Development-CIRAD; Perennial Crops Department, Campus International Baillarguet, 34398 Montpellier Cedex 5, France ; ⁴University of Florida, Research and Education Center, Fort Lauderdale, FL 33314, USA

* rmartinez@idiaf.org.do

Accepted for publication 25/05/07

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).

Figure 1: Hinf I (A) and Alu I (B) endonuclease digests of phytoplasma rDNA products amplified by nested PCR from coconut palms affected by lethal yellowing on the southern coast of the Dominican Republic and in Yucatan, Mexico. M is DNA ladder.

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.

Acknowledgements 

This study was partially funded by the Common Fund for Commodities, Stadhouderskade 1072 AB Amsterdam (FIGOOF/22).

References 

Harries HC, Herasme CJ, Hichez-Frias E, 2001. Why lethal yellowing has not become epidemic in the Dominican Republic. Palms 45, 92-96.

Harrison NA, Womack M, Carpio ML, 2002. Detection and characterization of a lethal yellowing (16SrIV) group phytoplasma in Canary Island date palms affected by lethal decline in Texas. Plant Disease 86, 676-81.

Lee I.-M, Gundersen-Rindal DE, Davis RE, Bartoszyk IM, 1998. Revised classification scheme of phytoplasmas based on RFLP analyses of 16S rRNA and ribosomal protein gene sequences. International Journal of Systematic Bacteriology 48, 1153-69.

Pujals Nolasco JP, Hichez Frias E, 1974. Informe sobre la situación del amarillo letal en las plantaciones de cocoteros en áreas de la República Dominicana. Secretaria de Estado de Agricultura, Santo Domingo, República Dominicana.