A method for the generation of a Euphorbia pulcherrima ( Poinsettia) plant having a white foliage phenotype, comprising the steps of: a. providing a Euphorbia pulcherrima ( Poinsettia) plant without a white foliage phenotype comprising in its genome at least one functional allele of a glutathione S-transferase gene EpGST encoding a protein of SEQ ID No 3 or a functional variant of said protein with at least 90%, preferably 95% amino acid identity, the EpGST gene comprising, in the region encoding amino acids at positions 40 - 50 of the protein of SEQ ID No 3, a stretch of 12 nucleotides consisting of a threefold CTTC repeat, wherein the Euphorbia pulcherrima ( Poinsettia) plant is heterozygous for the EpGST gene, comprising one functional allele as well as one dysfunctional allele comprising the CTTC deletion, said heterozygous Euphorbia pulcherrima ( Poinsettia) plant without a white foliage phenotype being selected by a molecular marker suitable for the detection of the CTTC deletion; b. subjecting the Euphorbia pulcherrima ( Poinsettia) plant of step a. to a mutagenesis treatment to produce a mutant Euphorbia pulcherrima ( Poinsettia) plant; c. selecting a mutant Euphorbia pulcherrima ( Poinsettia) plant of step b., wherein at least two alleles of the EpGST gene comprises a CTTC deletion in the stretch of 12 nucleotides consisting of a threefold CTTC repeat as present in the genome of the Euphorbia pulcherrima ( Poinsettia) plant of step a.; d. optionally repeating steps b. and c. until all alleles of the EpGST gene in the plant genome comprise the said CTTC deletion; e. selecting a Euphorbia pulcherrima ( Poinsettia) plant with white foliage phenotype being homozygous for the EpGST gene comprising the said CTTC deletion, and f. optionally further asexually propagating said Euphorbia pulcherrima ( Poinsettia) plant being homozygous for the EpGST gene comprising the said CTTC deletion. a. providing a Euphorbia pulcherrima ( Poinsettia) plant without a white foliage phenotype comprising in its genome at least one functional allele of a glutathione S-transferase gene EpGST encoding a protein of SEQ ID No 3 or a functional variant of said protein with at least 90%, preferably 95% amino acid identity, the EpGST gene comprising, in the region encoding amino acids at positions 40 - 50 of the protein of SEQ ID No 3, a stretch of 12 nucleotides consisting of a threefold CTTC repeat, wherein the Euphorbia pulcherrima ( Poinsettia) plant is heterozygous for the EpGST gene, comprising one functional allele as well as one dysfunctional allele comprising the CTTC deletion, said heterozygous Euphorbia pulcherrima ( Poinsettia) plant without a white foliage phenotype being selected by a molecular marker suitable for the detection of the CTTC deletion; b. subjecting the Euphorbia pulcherrima ( Poinsettia) plant of step a. to a mutagenesis treatment to produce a mutant Euphorbia pulcherrima ( Poinsettia) plant; c. selecting a mutant Euphorbia pulcherrima ( Poinsettia) plant of step b., wherein at least two alleles of the EpGST gene comprises a CTTC deletion in the stretch of 12 nucleotides consisting of a threefold CTTC repeat as present in the genome of the Euphorbia pulcherrima ( Poinsettia) plant of step a.; d. optionally repeating steps b. and c. until all alleles of the EpGST gene in the plant genome comprise the said CTTC deletion; e. selecting a Euphorbia pulcherrima ( Poinsettia) plant with white foliage phenotype being homozygous for the EpGST gene comprising the said CTTC deletion, and f. optionally further asexually propagating said Euphorbia pulcherrima ( Poinsettia) plant being homozygous for the EpGST gene comprising the said CTTC deletion.