| 摘要 |
Plants of the Compositae family which are resistant to the aphid Nasonovia ribisnigri due to presence in the genome of the Nr resistance gene, wherein the genetic information responsible for the CRA phenotype is absent from the genome of the plant at least to such an extent that the CRA phenotype is not expressed. The plants are for example lettuce plants of the genus Lactuca, in particular L.sativa. L. and can be obtained by selecting a parent plant which is heterozygous for Nr resistance, manufacturing a segregating population, producing a progeny of substantially each plant of the segregating population, testing the progeny for resistance and CRA phenotype, selecting from a suitable progeny plants which are either resistant or which have no CRA phenotype, producing seed from these plants by self-pollination and culturing progeny from this seed in order to obtain a line, and testing the line for resistance and CRA phenotype and selecting lines which are uniformly resistant and which uniformly have a non-CRA phenotype.
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