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 specific ally to detect the mycoplasma-like organism (MLO) associated with leth al yellowing disease of palms in Florida, For PCR, a pair of oligonucl eotide primers was synthesized according to partial sequences of a clo ned 1.3 kbp fragment of lethal yellowing MLO-specific genomic DNA isol ated from a diseased windmill palm (Trachycarpus fortunei). A DNA prod uct of about 1 kbp was specifically amplified by PCR in reaction mixtu res containing template DNA derived from either heart, inflorescence o r leaf tissues of lethal yellowing-affected palms. PCR performed for 3 5 cycles with as little as 5 pg of DNA template, in some instances, wa s sufficient consistently to amplify the same lethal yellowing MLO DNA product from hearts of 11 species comprising 30 symptomatic palms. Si milar reliable and reproducible detection of the lethal yellowing MLO in palm inflorescence spikelets was also achieved after 35 cycles of P CR. When template DNA for PCR was derived from tissues of the the most immature emerging leaf; a 40-cycle reaction was sufficient for consis tent foliar detection of the pathogen in all coconut palms including p alms with earliest visible symptoms of disease.