Drought stress has an adverse effect on crop production and food quality. Milk thistle (Silybum marianum L.) is an oil and medicinal crop known as an alternative oil crop with high level of unsaturated fatty acids, which makes it a favourable edible oil for use in food production. Silymarin (a mixture of flavonolignans) is the main active medicinal component. Biochemical diversity, changes induced by water deficit stress in secondary metabolites, and their relationships with production traits in native germplasm are poorly understood in milk thistle. Twenty-six ecotypes mainly collected from different regions of Iran were evaluated for oil, fatty acid profile, triacylglycerol (TAG) composition, silymarin and agro-morphological traits under non-stress and water stress conditions for 2 years. Water stress increased oil and silymarin content while decreasing fruit yield and related traits. The most abundant fatty acid averaged over all ecotypes under both moisture conditions was linoleic acid (L, 39%), followed by oleic acid (O, 36%), palmitic acid (P, 9%) and stearic acid (E, 6%). Among the 24 detected TAGs, the five major compositions were OOL, OLL + OOLn (linolenic), POL, OOO, LLL + OLLn and EOL. Superior ecotypes rich in monounsaturated and polyunsaturated fatty acids were identified and can be introduced as candidates for food, medicinal and industrial purposes. Associations among different attributes are discussed.

Background: Better understanding of genetic structure of economic traits is crucial for identification and selection of superior genotypes in specific breeding programs. Best linear unbiased prediction (BLUP) is the most efficient method in this regard, which is poorly used in forage plant breeding. The present study aimed to assess genetic variation, estimate genetic parameters, and predict breeding values of five essential traits in full sib families (recognized by EST-SSR markers) of tall fescue using REML/BLUP procedure. Method: Forty-two full-sib families of tall fescue (included of 120 individual genotypes), recognized by EST-SSR markers along with twenty-one their corresponding parental genotypes were assessed for biomass production and agro-morphological traits at three harvests (spring, summer, and autumn) in the field during 4 years (2017–2020). Results: Considerable genotypic variability was observed for all traits. Low narrow-sense heritability (h²_n) for dry forage yield (DFY) at three harvest indicates that non-additive gene actions may play an important role in the inheritance of this trait. Higher h²_n of yield related traits and flowering time and also significant genetic correlation of these traits with forage yield, suggests that selection based on these traits may lead to indirect genetic improvement of DFY. Conclusion: Our results showed the adequacy of REML/BLUP procedure for identification and selection of preferable parental genotypes and progenies with higher breeding values for future breeding programs such as variety development in tall fescue. Parental genotypes 21 M, 1 M, and 20 L were identified as superior and stable genotypes and could also produce the best hybrid combinations when they were mostly used as maternal parent.