الفهرس 
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Abstract
The aim of the present study was to Induce Milk thistle (Silybum marianum) mutant plants with higher active ingredients and\or useful morphological characters and to prove the role of Leucocyanidin oxygenase (LDOX) gene which is a key enzyme in the taxifolin synthesis (the most important precursor of silymarin biosynthesis). br Five ecotypes -#102;-#114;-#111;-#109; milk thistle (Silybum marianum) were used in this study to improve its morphological characters and\or active ingredients properties. Results of HPLC analysis of (Silybum marianum) Seeds -#102;-#114;-#111;-#109; five different ecotypes and ten of its induced types by two doses of ethylmethanesulfonate (EMS) and Sodium Azide respectively, and irradiated by 4 doses of gamma rays showed that the percentages of silymarin ranged -#102;-#114;-#111;-#109; 0.25 % to 3.3 %, also Accession L.2 can be considered as important source for silymarin. And the lowest percentage was in accession 5 L.5. br Degenerate primers were designed for a given multiple alignment of DNA sequences of Leucocyanidin oxygenase (LDOX) gene using ClustalW algorithm. an insilico approach were used to find a homology between more than one accession number of cDNA sequences, Multiple sequence alignment was performed by ClustalW algorithm to produce a conserved blocks and determine the consensus region which had been used to produce the forward and reverse primer by the primer select module of DNAStar LasergeneV7 and insilco PCR module of FASTPCR program ver.4.0.8 which was performed to detect the melting temperatures (Tm) and predict the PCR product size. The results of designed degenerate primer showed that there was a homology between the designed primers and the DNA templates for the accession numbers with at least 80% identity. The result of sequencing of eluted band of the amplified RT-PCR products of the four accessions was detected at the molecular weight of 250 bp were BLASTed to prove the role of Leucocyanidin oxygenase (LDOX) gene in the taxifolin synthesis and to detect the mutation effect in its DNA sequence.