Application of Brown Algae (Sargassum angustifolium) Extract for Improvement of Drought Tolerance in Canola (Brassica napus L.)

BACKGROUND: Abiotic environmental stresses, especially drought stress, is one of the most important problems in arid and semi-arid regions. Like other major crops, Brassica napus is vulnerable to drought stress. OBJECTIVE: The present study was conducted to evaluate efficacy of Sargassum angustifolium extract on mitigating adverse effects of drought stress on B. napus seedlings during vegetative growth under greenhouse conditions. MATERIALS AND METHODS: Seedlings were periodically sprayed with the seaweed extract until they reached 7-leaf stage. Then water deficit stress was imposed and measurements were performed at morphological, biochemical and molecular levels on three phases: 80% field capacity for 20 days (Phase I), 60% field capacity for 20 days (Phase II) and 40% field capacity for 20 days (Phase III). Real-Time PCR assay was carried out to monitor the changes in expression of the genes involved in proline biosynthesis. RESULTS: Morphological measurements revealed that seaweed treatment improved shoot height and dry weight compared to control (p<0.05). Biochemical analyses indicated that foliar application of seaweed extract significantly enhanced the photosynthetic pigments’ content, free radical scavenging and superoxide dismutase activity (p<0.05). Moreover, proline content was significantly increased in plant tissues treated with seaweed extract (p<0.05). The results of Real-Time PCR assay showed that the increase in proline content is due to enhanced expression of P5CS which is involved in biosynthesis of proline, and to decreased expression of PRODH which catalyzes proline degradation. CONCLUSIONS: Overall, the results obtained in this research suggest that application of S. angustifolium extract as a biostimulant is able to protect canola seedlings against deteriorating effects of drought stress.