The invention relates to plants of the Compositae family which are resistantto the aphid Nasonovia ribisnigri due to presence inthe genome of the Nr resistance gene, wherein the genetic informationresponsible for the CRA phenotype is absent from the genomeof the plant at least to such an extent that the CRA phenotype is notexpressed. The plants are for example lettuce plants of the genusLactuca, in particular L.sativa. L. and can be obtained by selecting a parentplant which is heterozygous for Nr resistance, manufacturinga segregating population, producing a progeny of substantially each plant ofthe segregating population, testing the progeny for resistanceand CRA phenotype, selecting from a suitable progeny plants which are eitherresistant or which have no CRA phenotype, producing seedfrom these plants by self-pollination and culturing progeny from this seed inorder to obtain a line, and testing the line for resistance andCRA phenotype and selecting lines which are uniformly resistant and whichuniformly have a non-CRA phenotype.
