Serological Methods for Detection of Polymyxa graminis, an Obligate Root Parasite and Vector of Plant Viruses

A purification procedure was developed to separate Polymyxa graminisresting spores from sorghum root materials. The spores were used as im-munogen to produce a polyclonal antiserum. In a direct antigen coating enzyme-linked immunosorbent assay (DAC ELISA), the antiserum could detect one sporosorus per well of the ELISA plate. In spiked root samples, the procedure detected one sporosorus per mg of dried sorghum roots. The majority of isolates of P. graminis from Europe, North America, and India reacted strongly with the antiserum. Interestingly, P. graminis isolates from the state of Rajasthan (northern India), from Pakistan, and an isolate from Senegal (West Africa) reacted weakly with the antiserum. The cross-reactivity of the serum with P. betae isolates from Belgium and Turkey was about 40% of that observed for the homologous isolate. There was no reaction with common fungi infecting roots or with the obligate parasite Olpidium brassicae. However, two isolates of Spongospora sub-terranea gave an absorbance similar to that observed with the homologous antigen. The DAC ELISA procedure was successfully used to detect various stages in the life cycle of P. graminis and to detect infection that occurred under natural and controlled environments. A simple procedure to conjugate antibodies to fluorescein 5-isothiocyanate (FITC) is described. Resting spores could be detected in root sections by using FITC-labeled antibodies. The potential for application of the two serological techniques for studying the epidemiology of peanut clump disease and for the characterization of Polymyxa isolates from various geographical origins is discussed.

Production and characterization of monoclonal antibodies for aflatoxin B1

Hybridomas that secreted antibodies for aflatoxin B1 were selected using two immunization protocols referred to as A and B. Protocol A is a standard immunization method and resulted in the selection of only two clones that produced monoclonal antibodies against aflatoxin B1. In protocol B a unique immunization schedule which resulted in the generation of 10 hybridomas is described. Of the 10, one antibody was highly specific to B1, four antibodies reacted equally strongly with B1, G1 and weakly with B2. Another four reacted strongly with B1 and weakly with B2 and G1. One clone reacted equally strongly with B1, G1 and B2. Interestingly all the 10 antibodies showed little or no cross-reaction with G2.