In order to investigate the effect of water stress (primary factor) on the amount of seed oil in different lines (secondary factor) of cultivated safflower (Carthamus tinctorius L.), an experiment was performed in the experimental farm of Urmia University. The safflower lines under investigation consisted of four winter types (697, Zarghan 279, LRV51-51 and LRV51-279) and one spring type Esfahan-1. Seeds of the above five lines were planted each in two rows with four replications during spring season. The experimental design used for the winter types was a split plot and a completely randomized design was used for the spring type. Water stress levels were applied in the form of increasing the days between irrigations beginning with plot A towards plot D at flowering time which consisted of four treatments for the four plots A, B, C and D. Data analysis for the amount of oil in winter types indicated that water stress level C had the highest effect on the increase of seed oil. On the other hand the line 697 had the highest overall seed oil among the entries. The highest interaction was recorded for the line 697 in the A plot (check) having 35.55% seed oil. In the one way analysis of variance for the seed oil in the spring type plot B was considered as check. The interaction between winter type × stress resulted in a decrease in oil content, however, in the Spring types, water stress caused an increase in oil content. These contrasting results were due to genetic differences between spring and winter types and the meteorological specificity of the experimental site.
