A study on cold resistance in safflower varieties and lines by physiological and biochemical indices

The aim of the present investigation was to study the response of different safflower genotypes to low temperatures in germination and seedling stages and find its relation with field performance. In this study, 16 winter safflower genotypes were evaluated for cold and frost tolerance in germination and seedling stages in controlled condition and field condition. Results showed that the effect of temperature, genotype and temperature × genotype interaction on germination and germination rate was significant. Below 15 °C, temperature reduced maximum germination significantly. The lowest and the highest germination per cent occurred in 5 °C and 15 °C, respectively. Results revealed that cold stress led to increase proline and soluble sugars concentration in leaves significantly and there was high variation among genotypes for this character. Cold stress increased cell membrane injury, electrolyte leakage and electric conductivity (EC) in leaves. There were significant differences between genotypes for cell membrane injury at 1% level of probability. Combined analysis of variance indicated differences among genotypes for thousand kernel weight (TKW), days to heading (DH) and maturity (DM), plant height (PH) and grain yield to be significant (P < 0.01). The results of cluster analysis also showed the genotypes based on physiological traits and mean yield tend to be classified in three groups, where the best genotypes (entries No. 1, 2,15 and 16) with high promptness index (PI), proline content, low injury index and high-yielding performance were classified in the third group.