Detection and diagnosis of lethal yellowing: conventional methods and molecular techniques

Abstract

Lethal yellowing (LY) is a fast spreading, highly destructive disease of coconut palms and 33 additional palm species. The disease presently occurs in several countries of the western Caribbean region, where it has virtually eliminated the susceptible Atlantic Tall ecotype from many localities. A mycoplasmalike organism (MLO) is believed to be the causal agent of LY. The LY MLO, like all other plant pathogenic MLOs, remains unculturable and thus precludes culture techniques for disease diagnosis. Diagnosis of LY has relied primarily upon symptom identification. Unequivocal disease diagnosis requires further visual confirmation of the presence of MLOs in affected palm tissues. This has traditionally been accomplished by either electron microscopy or DAPI staining in conjunction with epifluorescence microscopy. Although quite sensitive, both techniques are non-specific since they cannot distinguish one MLO from another. DNA-based techniques have recently been developed which enable both sensitive and specific detection of the LY MLO. Use of these new techniques as well as conventional methods for diagnosis of LY are discussed.