Reaction to phytotoxins in a potato population derived from mesophyll protoplasts.

Alternaria solani, the causal agent of early blight disease in potato, produces two host-specific, lipidlike toxins in culture. Both compounds are required in the leaf bioassay for the elicitation of typical early blight symptoms, but the compounds are individually inactive. The procedures for the preparation of both compounds are outlined. These compounds can be used effectively to select for toxin-insensitive and sensitive clones of a Russet Burbank potato cultivar that have been regenerated from single mesophyll protoplasts. Furthermore, both sensitivity and insensitivity to the toxins in these clones is well correlated with susceptibility and resistance to A. solani. Potato clones that have been produced by somatic cell regeneration techniques maintain their reaction type to these fungal toxins for at least two generations of vegetative propagation. The genetic basis for this variation among these potato clones remains to be explained.