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SUMMARY: Purified isoenzymes of α-l-arabinofuranosidase (AF I, pI value 3·0) and polygalacturonase (PG III, pI 5·5; PGIV, pI 9·7) separated from culture filtrates of Sclerotinia fructigena by isoelectric focusing and gel chromatography were used to produce antisera in sheep. The serum produced to AF I was specific as judged by immunodiffusion, immunoadsorbent column chromatography and binding of fluorescein-conjugated serum to the antigen separated by polyacrylamide gel electrophoresis. Fluorescein-labelled anti-AF I serum was bound to mycelium producing this isoenzyme in liquid culture, and binding was decreased when AF production was repressed with glucose; no labelling occurred on mycelium infecting apple fruit tissue.
Data for the anti-PG sera were less conclusive. The antigens gave precipitin lines only with homologous sera, but an anti-PG III immunoadsorbent column bound PG III as well as a smaller proportion of PG IV, while an anti-PG IV column bound neither antigen. Fluorescein isothiocyanate-labelled anti-PG III serum was bound to mycelium of S. fructigena grown in liquid culture and to mycelium-infected apple fruit tissue, but labelled anti-PG IV serum was not bound.