Cardinal Temperatures and Germination Responses of Wild Relatives of Safflower

Safflower (Carthamus tinctorius L.) is one of the oldest domesticated crops, mainly grown as oilseed in the arid and semi-arid regions of the world. This study was conducted to investigate the cardinal temperature of some Carthamus species and to identify the effects of drought stress on its seeds germination aspects. For this purpose, seeds of 13 genotypes from five species including C. tinctorius, C. palaestinus, C. oxyacantha, C. glaucus and C. lanatus which were harvested from drought stressed and non-stressed plants were used. Then, they were subjected to 9 fixed temperatures (5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C and 45°C) according to a factorial experiment in a growth chamber during germination. Results showed that the effect of genotype, species, temperature, drought stress pre-treatment and some of their interactions were significant on germination characteristics. Significant reductions occurred in the germination rate of seeds at temperatures less than 10 °C and upper than 30 °C. This experiment showed that cardinal temperatures more likely will not be problematic in the case of inter-specific breeding programs. However, there were significant differences in germination percentage of seeds among species. The results showed that seeds which were harvested from drought stressed plants did not show a significant difference in cardinal temperature but the germination percentage significantly decreased in comparison with the ones harvested from plants at normal moisture condition.