Milk Thistle (Silybum Marianum L.) as a Novel Multipurpose Crop for Agriculture in Marginal Environments: A Review

Milk thistle (Silybum marianum (L.) Gaertn.) is a versatile crop that has adapted to the broadly different soil and environmental conditions throughout all continents. To date, the fruits (“seeds”) of the plant are the only reliable source of silymarin, which, given its recognized therapeutic effects and its many present and potential uses, has led to a significant re-discovery and enhancement of the crop in recent years. Overall, although many studies have been carried out globally on the bioactivity, phytochemistry, and genetics of milk thistle, few and discontinuous research activity has been conducted on its basic agronomy as well as on the farm opportunities offered by the cultivation of this species. However, the multiple potential uses of the plant and its reduced need for external inputs suggest that milk thistle can perfectly fit among the most interesting alternative crops, even for marginal environments. The growing interest in natural medicine, the increasing popularity of herbal dietary supplements, and the multiple possibilities for livestock feeding are all arguments supporting the idea that in many rural areas, this crop could represent a significant tool for enhancing and stabilizing farm income. However, several issues still have to be addressed. The species retains some morphological and physiological traits belonging to non-domesticated plants, which make the application of some common agronomic practices challenging. Furthermore, the lack of reliable field data devoted to the definition of suitable cropping protocols represents a major constraint on the spread of this crop among farmers. This review has therefore focused on updating information on the main morphological and phytochemical traits of the crop and its agronomic characteristics and novel uses. Several gaps in technical knowledge have been addressed, and further goals for experimental activity have been outlined in order to guide farmers eager to cope with the cultivation of such a challenging and resource-rich crop.