Determination of Seed and Oil Yield and Yield Components in Two Variety of Milk Thistle (Silybum marianum Gaetrn.) Based on Path Analysis and Regression

Silybum marianum Gatrn. (Family: Asteraceae) is an annual or biennial plant, native to the Mediterranean area, which has spread in North and South of Iran. The seeds contain high amount of oil (20 - 35%) which exhibits wound-healing, anti-burn, and hepatoprotective properties. Determine the most seed yield components and oil yield in milk thistle. This research was conducted using two genotypes of milk thistle (Ahvaz wild type and Germany) in a randomized complete block design with four replications, to evaluate the most seed yield components and oil yield. Initially, oil and seed yield (dependent variable) separately determined for any variety using stepwise regression analysis. In Ahvas type, seed yield and oil percent for oil yield, and capitulum diameter for seed yield whereas, in Germany type, number of capitulum for seed yield and seed yield for oil yield justified variation related to dependent variable significantly. Regression analysis represented seed yield is affected by capitulum diameter and number, and secondary metabolites of seed (R2=98.16) and oil yield is justified by oil percent and seed active constituents and yield (R2=99.91). The path analysis revealed that direct and positive effect number of capitulum (0.49), diameter of main capitulum (0.41) and oil percent (0.1) and direct and negative effect of active ingredient silymarin, are important components of oil yield. In general, this result showed that for increasing of seed and oil yield can be used from capitulum diameter and number and oil percent in medicinal plant breeding of milk thistle.