Evaluation of the Effects of Drought Stress and Salicylic Acid on Growth and Physiological Parameters in Four Spring Canola Cultivars

  Oilseed canola plant (Brassica napus L.) is an important agricultural crop grown primarily for its edible oil. It is well known that abiotic stresses especially drought stress are very restrictive factors for agricultural production around the world. Drought stress affects a vast range of morphological, physiological and biochemical characteristics in plants. However, exogenous application of materials such as salicylic acid (SA) has been regarded as a good alternative to counter the adverse effects of various environmental stresses on plant functions. Salicylic acid is a naturally occurring plant hormone that controls plant growth and induces water deficit tolerance in plants.
Material and The experiment was carried out as a split split plot layout with three replications in East Azarbaijan Research Center for Agriculture and Natural Resources. Treatments included three level of drought stress (well-watered, drought stress at flowering and podding stages) (as main plot), two level of SA spraying (0 and 150 ppm) (as sub plot) and four cultivars of spring canola (Zafar, Zarfam, Dalgan and RGS003) (as sub-sub plot). The studied traits were included number of pods, number of seeds per pod, 1000 seed weight, grain yield, chlorophyll a, b and total, carotenoid, H2O2, MDA, proline, total sugar contents and seed oil percentage. The collected data were analyzed using SAS 9.1 software and means were compared with Duncan test at the 5% and 1% level of probability using MSTATC software. Results indicated that withholding irrigation from flowering stage had a more negative effect on yield components and physiological traits compared to withholding irrigation from podding stage. Withholding irrigation in both stages reduced the content of chlorophyll a, b and total and increased the content of H2O2 and MDA. Also, Zarfam and RGS003 cultivars had the highest content of chlorophyll and the lowest content of H2O2 and MDA. Salicylic acid (SA) spraying increased 31.79%, 41.1% and 7.33% of proline content, leaf soluble carbohydrate and seed oil, and decreased the content of MDA and H2O2 by 16.1% and 18.67% respectively. The results also showed that SA spraying led to 31.96% increase in grain yield under drought stress from podding stage. SA may compensate the negative impacts of drought stress on plant yield and other parameters. In general, in this experiment, the use of salicylic acid not only improved the morphological and physiological traits of the plant under drought stress, probably through the effect on the antioxidant system but also increased the yield and quality of the cultivars