DETECTION AND DIFFERENTIATION OF AFRICAN COCONUT PHYTOPLASMAS - RFLP ANALYSIS OF PCR-AMPLIFIED 16S RDNA AND DNA HYBRIDIZATION

Phytoplasmas associated with lethal decline diseases of the coconut pa lm (Cocos nucifera) in west and east Africa were detected by the speci fic amplification of their 16S rRNA genes. The primers used were based on conserved mollicute-specific and coconut-phytoplasma 16S rRNA gene sequences. Phytoplasma 16S rDNA was amplified from all African declin e affected palms, some periwinkle maintained phytoplasmas, but not fro m healthy palms, infected palms from Florida or from the Cocos spiropl asma and Acholeplasma sp. mollicutes. African phytoplasmas were also d etected by DNA hybridisation using two probes from the palm lethal yel lowing phytoplasma from Florida. Probes hybridised at moderate stringe ncy to dot blots of lethal decline affected palms from Africa, indicat ing possible genetic relationships between different coconut phytoplas mas. RFLP analysis of rDNA fragments (length c. 1.45 kbp) detected pol ymorphisms, indicating that the pathogens found in west and east Afric a are not identical. This provides a useful tool for further epidemiol ogical studies of African coconut phytoplasmal diseases.