AbstractThe Fusarium graminearum mycotoxin deoxynivalenol was shown to be more phytotoxic to com senotypes susceptible to gibberella ear rot than resistant genotypes. The toxin caused greater damage to the membranes of the susceptible genotypes, as evidenced by the release of Na and K ions into solution. Isolated protoplasts of ear rot‐resistant genotypes were able to bind more radiolabelled deoxynivalenol than those of susceptible genotypes, providing a partial explanation for the membrane tolerance to the toxin. The results are discussed in relation to the role of resistance to this phytotoxin and tolerance to gibberella ear rot. Published 1995 Wiley‐Liss, Inc.