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Alkaline-Induced Metaxylem Autofluorescence: A Diagnostic Symptom of Ratoon Stunting Disease of Sugarcane. Kenneth E. Damann, Jr., Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Experiment Station, Baton Rouge 70803; Phytopathology 78:233-236. Accepted for publication 25 June 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-233.

Ratoon stunting disease (RSD) of sugarcane caused by the vascular limited bacterium Clavibacter xyli subsp. xyli can be diagnosed by a host response, alkaline-induced metaxylem autofluorescence. Mature basal internodes of sugarcane cut in cross sections and treated with 0.1 M Tris (tris[hydroxymethyl]aminomethane), pH 10, exhibited red autofluorescence in the secondary walls of metaxylem cells when the plant was infected, but not when healthy. The sections were viewed by fluorescence microscopy (exciting filter 530–560 nm, beam-splitting mirror 580 nm, suppression filter 580 nm). One person using the fluorescence microscopy technique can easily determine the RSD-status of 400 samples per day.