Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 25, 2005
Publication Date: June 20, 2005
Citation: Grisham, M.P., Pan, Y. 2005. Detection and Quantification of Leifsonia xyli subsp. xyli in Sugarcane by Real-Time PCR. Phytopathology. 95(6) (Supplement):S36. Technical Abstract: Leifsonia xyli subsp. xyli (Lxx) is a xylem-limited, Gram-positive bacterium that causes ratoon stunting disease in sugarcane. The detection of Lxx by tissue-blot immunoassay (TBIA) or conventional polymerase chain reaction (PCR) is inconsistent for plants younger than 6 months old. The efficiency of these commonly used diagnostic methods depends on the titer of the bacterium in stalk sap that increases during the growing season. Due to the fact that 5-6 month-old stalks of sugarcane are used as seed cane to plant a new crop in Louisiana, a diagnostic procedure is needed for use earlier in the growing season. A real-time PCR assay was developed to increase the sensitivity of Lxx detection and to provide a method to quantify susceptibility of cultivars to Lxx infection. Sap from mature month-old stalks of 20 cultivars of sugarcane was tested for the presence of Lxx using both real-time PCR and TBIA. Detection of Lxx by the two methods was in agreement. Real-time PCR results were also used to rank the tested cultivars for susceptibility to Lxx infection according to the relative titer of bacteria in the sap. The real-time PCR assay also correctly detected Lxx in leaf tissue of one-month-old sugarcane plants. Detection of Lxx this early in plant development with an immunoassay or conventional PCR assay has not been previously successful.