INTERACTION OF PARTIALLY PURIFIED PHYTOTOXINS FROM PHYTOPHTHORA-CACTORUM ON APPLE CELL PLASMA-MEMBRANE

The 'crude' filtrate (CF) of Phytophthora cactorum containing phytotox in(s), having some properties similar to the toxins isolated from othe r Phytophthora species, was processed by three steps (acetone precipit ation, dialysis and gel filtration chromatography). The CF fractions c orresponding to the progressive steps of purification were tested for phytotoxicity on tomato seedlings and for activity on cell trans-membr ane electrical potential (Em) of susceptible and resistant apple roots tocks (Malus domestica). The fractions (F4), obtained from chromatogra phy on Sephadex G50 fine and eluted in the zone corresponding to a mol ecular weight of 15+/-2 kD, induced a specific alteration on susceptib le apple cell membranes. These metabolites, even though incompletely p urified, are able to induce a high and specific activity on susceptibl e apple cell Em only, not on resistant ones. As a consequence, they ma y be of potential use in screening for insensitive cells.