To detect the presence of the bacterium Leifsonia xyli subsp. xyli (Lxx) in propagation material is important for the control of the ratoon stunting disease. The objective of this work was to improve a serological method for detection of the pathogen and to evaluate the policlonal antiserum specificity produced against Lxx. The antigen was prepared by resuspending pure culture in PBS and dialyzing it in glutaraldehyde 2% in PBS. The immunization schedule in rabbit constituted of two intramuscularly injections of 1:1 mixture of the antigen: Freund adjuvant (complete and incomplete, with interval of 21 days) and two subcutaneous injections of the antigen, with ten-day intervals. The antiserum was tested by Dot Blot and revealed by peroxidase to determine: (i) title of the antibody, (ii) reaction and specificity against Lxx, Xanthomonas axonopodis pv. vesicatoria and endophytic sugarcane (Saccharum sp.) bacteria (Azospirillum brasilense, A. lipoferum, Hebaspirillum rubrisubalbicans, H. seropedicae, Gluconacetobacter diazotrophicus). The highest dilution of antiserum (1:20.000) presented strong positive reaction and high specificity against Lxx. The purification of the IgG fraction did not improve the antiserum reactivity and specificity. In bacterial cell suspension the level of detection was estimated in 2x10(6) cells/ml.
