Globodera pallida and G. rostochiensis proteins (Gp-5.7 and Gr-5.9, of pl 5.7 and 5.9 respectively) were purified from acrylamide gel bands excised after isoelectric focusing. A panel of monoclonal antibodies (MAbs) and a monospecific polyclonal antibody (PC 320) were produced to Gp-5.7 and Gr-5.9, respectively. The polyclonal antibody reacted equally, but some of the MAbs reacted differentially with the two species of potato cyst nematodes (PCN) MAb IACR Gp-5.7.1 recognises a proteic epitope and preliminary results indicated that the molecule is N-terminally blocked. This MAb bound only to antigens derived from cysts containing live eggs. Proteins re related to Gp-5.7 and Gr-5.9 were identified in all pathotypes of potato cyst nematodes and in other Globodera species, but not in the Heterodera species tested. The antigen has the same molecular weight in all the species tested, but the isoelectric points varied between the different species. The pl values were 5.9 for G. rostochiensis, 5.7 for G. palldia and 5.77 for G. tabacum tabacum, G. t. solanacearum, G. t. virginiae and G. ''mexicana''. This might indicate that the Globodera species from Mexico and the USA are more closely related to each other, than they are to G. pallida or G. rostochiensis. Immunofluorescence studies demonstrated that the MAb bound to the amphids of the Globodera species tested the genus-specificity of this molecule might account for very specialized functions in the amphids of these nematodes. The differences in isoelectric points and antigenicity observed probably indicate that the Globodera species have different isoforms of the same molecule which might be related to specific functions in the nematode amphids.
