Effect of Drought Tension Application on the Germination, Physiological and Biochemical Characteristics of Rapeseed Cultivars (Brassica napus L.)

Rapeseed is one of the most important oil crops in the world and Iran and water shortage is one of the most important factors limiting rapeseed growth and development in Iran. Plant growth in the early stages and its proper establishment can be considered as a selection criterion in the plant breeding. Since germination rate and percentage and growth-related traits are directly involved in the plant yielding, direct selection for growth traits under tension conditions is important in the identification of tolerant genotypes. A factorial experiment was conducted with four levels of osmotic tension (zero, -0.3, -0.5 and -1 bar) obtained from different concentrations of polyethylene glycol (zero, 20, 15 and 10 percent) and seeds of three rapeseed cultivars in a completely randomized design with three replications at the laboratory of Kerman Graduate University of Industrial and Advanced Technology for nine months in 2018-2019. After the seed’s disinfection, they were planted in the petri dishes and the drought treatments were applied on them. The interaction of genotype and drought treatments was significant for all evaluated traits except for stem height trait at one percent probability level. Statistical analysis and mean comparisons showed that in the applied moisture tension the amount of germination percentage, seedling growth, root growth, photosynthetic pigments and the amount of protein decreased and the amount of proline and antioxidant enzymes increased. The highest amount of germination percentage (78 percent), root length (5.78 millimeter), proline content (1.33) and polyphenol oxidase enzyme (0.063) were observed in Agamax cultivar, the highest amount of fresh (1.83) and dry (0.927) stem weight, chlorophyll a (9.007), chlorophyll b (2.56), total chlorophyll (10.9), carotenoids (2.64) and soluble sugar (0.65) was evaluated in Traper cultivar and the highest amount of soluble protein (0.714) and catalase enzyme (0.008) in Hayola 61 cultivar. By applying sever osmotic tension, Agamex cultivar showed a 25 percent reduction in germination rate and 63 percent in soluble proteins content, increasing 2.3 times more proline content, 1.54 times more soluble sugar content, 33 percent polyphenol oxidase and 67 percent catalase enzymes in compare to normal moisture conditions and showed better response than Hayola 61 and Trapper cultivars.