Impact of Organic Fertilization on Polyphenolic Content in Milk Thistle (Silybum marianum L. Gaertn.) Genotypes from Romania

Silybum marianum (L.) Gaertn. is a major source of active principles, but also a plant that perfectly meets the needs of sustainable agriculture. The present research analyses the efficiency of organic fertilization for the increase of active principles in the fruits of milk thistle cultivated in the area of Măciuca, southern Vâlcea County, Romania. The aim of this work was the spectrophotometric determination of the total polyphenols content (TPC) of five different genotypes of milk thistle (Prahova, a1; Secuieni, a2; Iași, a3; Dacia Plant, a4; Brașov, a5) both unfertilized, and treated with organic fertilizers. Significant quantitative differences were identified between the five populations of Silybum marianum, the genotypes "Dacia Plant" fertilized and "Prahova" unfertilized presenting the highest TPC (18.87 mg GAE/g, 18.15 mg GAE/g, respectively). Fertilization did not necessarily have an impact on the accumulation of polyphenols in the fruits, but the climatic and soil conditions, as well as the genetic background being able to influence the quality of the milk thistle fruits.