DETECTION OF THE MYCOPLASMA-LIKE ORGANISM ASSOCIATED WITH LETHAL YELLOWING DISEASE OF PALMS IN FLORIDA BY POLYMERASE CHAIN-REACTION

DNA amplification by polymerase chain reaction (PCR) was used specifically to detect the mycoplasma-like organism (MLO) associated with lethal yellowing disease of palms in Florida, For PCR, a pair of oligonucleotide primers was synthesized according to partial sequences of a cloned 1.3 kbp fragment of lethal yellowing MLO-specific genomic DNA isolated from a diseased windmill palm (Trachycarpus fortunei). A DNA product of about 1 kbp was specifically amplified by PCR in reaction mixtures containing template DNA derived from either heart, inflorescence or leaf tissues of lethal yellowing-affected palms. PCR performed for 35 cycles with as little as 5 pg of DNA template, in some instances, was sufficient consistently to amplify the same lethal yellowing MLO DNA product from hearts of 11 species comprising 30 symptomatic palms. Similar reliable and reproducible detection of the lethal yellowing MLO in palm inflorescence spikelets was also achieved after 35 cycles of PCR. When template DNA for PCR was derived from tissues of the the most immature emerging leaf; a 40-cycle reaction was sufficient for consistent foliar detection of the pathogen in all coconut palms including palms with earliest visible symptoms of disease.