Estimation of amounts of Phytophthora infestans mycelium in leaf tissue by enzyme‐linked immunosorbent assay

A polyclonal antiserum, prepared in a rabbit immunized with a mycelium extract of Phytophthora infestans , reacted in an enzyme‐linked immunosorbent assay (ELISA) with mycelial extracts of two Phytophthora species but not with those of 10 other micro‐organisms found on potato. P. infestans mycelium in leaf tissue was readily detected by ELISA using either the plate‐trapped antigen or F(ab') 2 antibody‐fragment techniques. The amount of mycelium in leaf extracts was estimated by comparing the values obtained in ELISA with those for known concentrations of P. infestans mycelium.