Evaluation of total soluble protein and antioxidant activities in two spring cultivars of canola (Brassica napus L.) in response to low temperature

ABSTRACT: Canola (Brassica napus L.), as the third oil seed worldwide, is an important resource in providing raw oil in Iran. The expansion of spring annual production is limited by high temperature during the flowering. In Iran where high temperature in summer appears to be premature, canola is cultivated in autumn or winter. However, spring cultivars are perceived to be low resistant to low-temperatures particularly in the early stages. In efficient physiological processes, they are induced in cold-tolerance. The present work aims at assessing the physiological traits of two spring canola cultivars: cold-sensitive (Option 500, cv.1) and cold-resistant (Zarfam, cv. 2). They responded to cold treatment at a four-leaf stage in terms of the amount of total protein and SOD (superoxide dismutase), POX (peroxidase) and CAT (catalase) antioxidant enzymes by a treatment comprising shifts from 22 °C to 10 °C. Variance analyses showed significant differences between sampling times, cultivars and temperature treatments as a result of low temperature (LT) on SOD, CAT, and POX. As a result of LT on protein content, there were significant differences between all sources of variation except between-temperature treatments. In both cultivars, antioxidant activity was changed differently, increasing significantly under low-temperature, in comparison with the controls but in Zarfam cv. cultivar, it was more. In cold-resistant the highest increase in protein content and SOD activity under low-temperature was observed in the second day. It was in the fourth day of POD and CAT activity that the features of cold hardening in Zarfam cv. were found. It shows the importance of cellular antioxidant machinery for protection against low-temperature.