Preliminary Assay of Gold Immunochromatographic Strip for Lettuce Witches'-broom Phytoplasma Detection

Tri-sodium citrate with aqueous gold chloride was warmed up and mixed to make 25 nm colloidal gold particles and the colloidal gold-antibody complex substance was formed under the conditions of pH 8.5 and 21 g/mL rabbit anti-immunodominant membrane protein antibody of Lettuce witches'-broom phytoplasma (LeWB). The rabbit anti-Imp of LeWB IgG and goat anti-rabbit IgG were coated on the surface of nitrocellulose membrane as the test line (T line) and control line (C line) to assemble the immunostrip. The results indicated that not only lettuce witches'-broom phytoplasma, but also chicory witches'-broom, lentils virescence, water spinach witches'-broom and parthenium virescence phytoplasma could be tested specifically by the immunostrip. All of these phytoplasma strains have the same characteristics of immunomembrane proteins and belong to subgroup A of phytoplasma 16SrII group. The detection limit was 100 dilution of the crudes infected by lettuce witches'-broom phytoplasma.