Detection of Leifsonia xyli subsp. xyli in presprouted seedcane

ABSTRACT The first great change in recent years in the Brazilian sugarcane industry occurred when mechanical harvest replaced manual cuttings of burned canes. The second transformation has started with mechanization of planting materials thanks to new methodology such as presprouted seedcane (MPB in Portuguese). To ensure the success of such innovation, the use of healthy MPB is fundamental, especially against ratoon stunt, caused by Leifsonia xyli subsp. xyli (Lxx). This is considered the most important disease of sugarcane and the only means of introducing it to new areas is by the planting of contaminated propagative materials. Therefore, the aim of this study was to develop a diagnostic assay for early detection of Lxx in MPB. In the first assay, the efficacy of four primer pairs (Cxx ITSf#5/Cxx ITSr#5, Cxx1/Cxx2, C2F/C2R, LX23SF/LX23SR) was examined to identify adult plants contaminated with various titers of Lxx, under original conditions, as well as adapted conditions proposed in this study, our own modifications. Thus, adult sugarcane was used. In the second assay, the two best primers/conditions were tested in 45- and 60-day-old MPB derived from Lxx-contaminated materials. Data of the present study showed that the primer pair CXX ITSF # 5/CxxITSr # 5, under our modification conditions, was the most accurate since Lxx was detected in all 52 MPB aged 45 days from propagative materials contaminated with 109 to 106 CFU/mL.