A report describing the strong resistance and tolerance of the accession PI128655 of Solanum peruvianum to two BLTVA strains (beet leafhopper transmitted virescence agent; `Candidatus Phytoplasma trifolii') was published almost twenty years ago. This work was revisited using another BLTVA strain and the PI128655 plants. No resistance or tolerance was observed. Instead the plants showed either one of two different sets of symptoms. A genetic control of the response to the phytoplasma isolated by the PI128655 plants was demonstrated using clones of host plants. However we obtained experimental evidence that the BLTVA isolate lacked homogeneity or stability, which could also explain the occurrence of two sets of symptoms. A possible hypothesis is that the PI128655 plants, by interfering with the competition between the 'components' of the BLTVA isolate, can alter the final composition of the phytoplasma population and therefore influence the induced symptoms.