Browsing by Author "Harrison, N.A."

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    16S rRNA interoperon sequence heterogeneity distinguishes strain populations of palm lethal yellowing phytoplasma in the Caribbean region
    (2002) Harrison, N.A.; Myrie, W.; Jones, P.; Carpio, M.L.; Castillo, M.; Doyle, M.M.; Oropeza, C.
    DNA of phytoplasmas in lethal yellowing (LY)-diseased palms was detected by a nested polymerase chain reaction (PCR) assay employing rRNA primer pair P1/P7 followed by primer pair LY16Sf/ LY16-23Sr. Polymorphisms revealed by Hinfl endonuclease digestion of rDNA products differentiated coconut-infecting phytoplasmas in Jamaica from those detected in palms in Florida, Honduras and Mexico. A three fragment profile was generated for rDNA from phytoplasmas infecting all 21 Jamaican palms whereas a five fragment profile was evident for phytoplasmas infecting the majority of Florida (20 of 21), Honduran (13 of 14) and Mexican (5 of 5) palms. The RFLP profile indicative of Florida LY phytoplasma was resolved by cloning into two patterns, one of three bands and the other of four bands, that together constituted the five fragment profile. The two patterns were attributed to presence of two sequence heterogeneous rRNA operons, rrnA and rrnB, in most phytoplasmas composing Florida, Honduran and Mexican LY strain populations. Unique three and four fragment RFLP profiles indicative of LY phytoplasmas infecting Howea forsteriana and coconut palm in Florida and Honduras, respectively, were also observed. By comparison, the Jamaican LY phytoplasma population uniformly contained one or possibly two identical rRNA operons. No correlation between rRNA interoperon heterogeneity and strain variation in virulence of the LY agent was evident from this study.
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    Detection of the mycoplasma-like organism associated with lethal yellowing disease of palms in Florida by polymerase chain reaction
    (2007-02-08) Tsai, J.H.; Harrison, N.A.; Richardson, P.A.; Kramer, B.
    DNA amplification by poiymerase 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 13 kbp fragment of lethal yellowing MLO-specific genomic DNA isolated from a diseased windmill palm (Trachycarpus fortunei). A DNA product of about I kbp was specifically amplified by PCR in reaction mixtures containing template DNA derived from cither heart, inflorescence or leaf tissues of lethal yellowing-affccted 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.