Abstract
SUMMARYPrevious experiments made by the writer showed that scions of tomato varieties that were monogenically resistant to wilt caused by Fusarium oxysporum f. lycopersici were apparently hypersensitive to toxins produced in infected Bonny Best (susceptible) rootstocks on to which they were grafted. The experiments did not prove conclusively, however, that the toxins were generated in the rootstocks, since they might have arisen from an interaction between the invading fungus and the resistant scion or by the generation of toxic materials when non‐toxic metabolites from the invaded root‐stock entered the resistant scion.In the present study it was demonstrated that the symptoms on the resistant scions arose when the fungus was still confined to the susceptible rootstocks. By double grafts, using resistant or susceptible intermediate stem pieces, it was also shown that the translocation of metabolites from invaded susceptible rootstocks through such stem pieces caused no change in their toxicity.It was concluded that resistant scions were highly sensitive to the direct action of toxins formed in invaded susceptible rootstocks, at concentrations which had no apparent effect on susceptible scions.
Published Version
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