Comparison of Monoclonal Antibodies and Polyclonal Antibodies in Detection of the Aster Yellows Mycoplasmalike Organism

Abstract

Monoclonal antibodies (MA) against the aster yellow (AY) agent, a noncultivable mycoplasmalike organism (MLO), were produced by hybridoma techniques. Polyclonal antibodies (PA) were purified from the antisera collected from immunized mice during splenectomy. Both the MA and PA were used in the in vitro and in situ detection of the AY-agent. In in vitro detection by indirect enzyme-linked immunosorbent assay, the MA reacted specifically with the AY-infected plants and differentiated the AY agent from other MLOs. Both the plant antigen-absorbed and the nonabsorbed PA, however, cross reacted with plant antigens. In in situ detection by immunofluorescent staining, cross- or longitudinal sections of leaf midribs from healthy and AY-infected lettuce were made. The acetone-fixed sections were treated with either the MA or PA, then stained with fluorescein isothiocyanate-conjugated antimouse IgG. MA bound specificially to the AY-MLO in the sieve tubes of diseased plants, while PA treatment showed fluorescence throughout the sections in both healthy and diseased plants suggesting nonspecific binding to cell wall and membrane.