Development of monoclonal antibodies against the fungi of the ‘Ascochyta complex’

Two monoclonal antibodies (MAbs) were produced against soluble antigens from the ‘Ascochyta complex’ fungi. Specificity of MAbs was tested by ELISA using antigen‐coated wells. MAbs secreted by the monoclonal hybridoma cell line JIM 44 recognized epitopes present in the antigen preparations from Mycosphaerella pinodes and Phoma medicaginis var. pinodella, but not those present in preparations from Ascochyta pisi. At high tissue culture supernatant concentration, MAbs produced by the monoclonal line JIM 45 recognized epitopes from all three fungi, however, on dilution of MAb the antigens from A. pisi were recognized preferentially to those from M. pinodes and P. medicaginis var. pinodella. On the basis of heat and periodate treatment of the antigens from the three fungi it can be concluded that the epitope recognized by JIM 44 is carbohydrate in nature, whereas that recognized by JIM 45 is proteinaceous in nature, carried on a glycoprotein antigen. Antigen preparations from other fungi, including other pea pathogens, non‐pathogens associated with pea and other fungi closely related to the ‘Ascochyta complex’, were not detected with either of the two MAbs. Antigen preparations from peas could be used to differentiate healthy and infected seeds in a dot‐blot assay, therefore indicating the potential of using the MAbs in the development of a diagnostic test for infection of Pisum seeds by the ‘Ascochyta complex’ fungi.