Effects of foliar application of 6-benzylaminopurine on yield and oil content in two spring safflower (Carthamus tinctorius L.) cultivars

To study the effect of an exogenous cytokinin application on safflower yield, an experiment was conducted in 2012–2013. Two cultivars of safflower (Goldasht and Zendehrood) and five concentrations of 6-benzylaminopurine (BAP) (0, 25, 50, 75, and 100 μM) were applied at the flowering stage. Results indicated that the application of 75 μM of BAP showed increased seed and oil yield by 17.54 and 18.29 % over the control, respectively. The increase in seed yield by application of BAP was attributed to the increase in characters like number of heads per plant, number of seeds per head, and 1,000 seed weight. Applying of BAP increased oil content compared with the control. To determine the concentration of cytokinin which has the highest performance for increasing seed yield, regression analysis were estimated showing that in the Zendehrood cultivar, the application of 43 μM of BAP produced the highest seed yield, and in the Goldasht cultivar the application of 73 μM of BAP during flowering produced the highest seed yield.