Phylogenetic relationships of phytoplasmas causing palm lethal diseases
Phytoplasmas associated with lethal diseases of coconuts and other palms are found in several regions of the world. Palm lethal yellowing phytoplasma (EPPO A1 quarantine pest) is present in several countries in the Caribbean, in Mexico, Belize, Honduras. Other lethal decline diseases have been reported in West Africa (Cape St Paul wild disease in Ghana, Kribi disease in Cameroon, Kaincopé disease in Togo and Awka disease in Nigeria) and in East Africa (Tanzania, Kenya, Mozambique). Although symptoms are similar, important differences in epidemiology and varietal susceptibility have been observed in each continent and between West and East Africa. In previous molecular studies (using DNA hybridization, RFLP analysis), it was found that pathogens from Florida, East Africa and West Africa, although similar, were distinct (EPPO RS 94/223 and 97/222). PCR was used to amplify the 16S rRNA genes and the 16S-23S spacer regions of phytoplasmas associated with lethal decline diseases of coconuts (Cocos nucifera) from Florida and the Yucatan region of Mexico, from East Africa, and from West Africa, and sequences of the amplified products were compared. Results showed that coconut lethal decline phytoplasmas constitute a separate cluster within the phytosplama clade, and that 3 coconut phytoplasma types/strains can be distinguished: the East African, the West African and the Caribbean type. During this study, specific primers have been developed and it is now possible to test plant material and determine which type/strain is present. These tools will be particularly useful for epidemiological studies concerning potential insect vectors of these devastating diseases.
Sources
Tymon, A.M.; Jones, P.; Harrison, N.A. (1998) Phylogenetic relationships of coconut phytoplasmas and the development of specific oligonucleotide PCR primers.
Annals of applied Biology, 132(3), 437-452.