Differential response to physiological drought stress in tolerant and susceptible cultivars of canola

Abstract

In this study, two cultivars of Brassica napus L. viz., Okapi (drought sensitive) and Zarfam (drought tolerant) were evaluated for their response to drought stress at physiological and molecular levels. Physiological drought stress was imposed on 10-day-old seedlings grown in half MS medium containing 200 mM mannitol at 0, 3, 12 and 24 h. At physiological level, water deficit changed ascorbate peroxidase, peroxidase and catalase activities in both the cultivars. However, the magnitude of changes differed in roots and shoots and was also genotype specific. Drought stress caused change in lipid peroxidation in terms of malondialdehyde (MDA) accumulation, soluble sugar and total protein contents in two cultivars with Zarfam responding earlier (3 h) compared to Okapi (12 h). At molecular level, there were significant variations between two cultivars in response to drought stress. Drought stress significantly up-regulated Auxin responsive protein (ARP), MPK3, Protein kinase (PK) and MPK4 genes transcript level in Okapi, while down-regulated expression in Zarfam. It can be concluded that drought stress imposed adverse effects on both cultivars by exertion of different responses.