ارزیابی اکوتیپ‌های مختلف ماریتیغال از نظر مقاومت به خشکی در محیط کشت هیدروپونیک

This study was conducted to evaluate drought resistance of milk thistle (Silybum marianum L.) at seedling stage. The experiment was designed as a split plot in a randomized complete block design. Treatments were combination of drought stress levels as main plots and different milk thistle ecotypes as subplot layouts replicated 3 times and run in a hydroponic system. Root length, root volume, chlorophyll content, electrolyte leakage and dry weight of root were measured for assessing the ecotypes. Results showed that there were significant differences between the measured traits at 1% level. Significant interaction between stress and ecotypes, indicated that the ecotypes had different trends over stress levels. Mean comparison of ecotypes suggested that decreased chlorophyll, root tolerance index, root volume and dry weight and increased electrolyte leakage were related to the increased stress intensity. Values of root tolerance index and electrolyte leakage suggested Ghaemieh as a drought tolerant ecotype. Correlation among root characteristics and root tolerance index showed that root volume and dry weight are more efficient criteria, compared to root length, for evaluation of drought tolerance in milk thistle genotypes.