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Rapid Compression Technique for Detecting Mycoplasmalike Organisms in Leaf Midrib Sieve Tubes by Fluorescence Microscopy. J. L. Dale, Professor, Department of Plant Pathology, University of Arkansas, Fayetteville 72701; Phytopathology 78:118-120. Accepted for publication 13 August 1987. Copyright 1988 Department of Agriculture. Government of Canada. DOI: 10.1094/Phyto-78-118.

Phloem tissue from herbaceous plants infected with mycoplasmalike organisms (MLOs) was removed from small pieces of compressed and crushed leaf midribs, treated 20 min in fixative, rinsed 5 min in buffer, stained 3-5 min in 4'-6-diamidino-2-phenylindole (DAPI) solution, compressed in DAPI on a slide, and then examined by fluorescence microscopy for presence of MLOs. Causal MLOs were well fixed and stained and were readily discernible in phloem sieve tubes by this procedure. With this method it was possible to distinguish among plants infected with Spiroplasma citri or MLOs. MLOs were also detectable in unfixed phloem tissue placed and compressed directly in DAPI on a slide, but the MLOs lacked clarity. It is believed that this compression technique, either with or without tissue fixation, would be useful for rapid screening of herbaceous plants for presence of MLOs.