Morpho-anatomical, biochemical and molecular genetic responses of canola (Brassica napus L.) to sulphur application

Abstract

Brassica napus (canola), a major economic crop in Egypt, contains much oils and proteins. In the present study, the foliar applications of ammonium sulphate (A.S.) [(NH4)2SO4] (0, 1% 0.2% and 0.3%) to canola plants had distinctive impacts on the morpho-anatomical, biochemical, and molecular genetic responses. Interestingly, there is a positive impact when sulphur (S) is foliarly applied at 0.2% of A.S. as revealed in antioxidants, flavonoids, total carbohydrates, and protein contents which were significantly affected. On the other hand, higher levels of glucosinolates were recorded for 0.3% and 1% A.S. (4.838 and 1.905, respectively). The electrophoretic analysis of proteins displayed 51 bands of molecular weights ranging from 8.555 to 240.6 kDa with 88.24% polymorphism with a mean band frequency of 0.373. Cytotoxicity assay revealed that the lower cell death was detected in treated root tips of canola plants following 0.2% A.S. treatment, as compared to control. With increasing of sulphur treatment, the root cortex thickness, number of conducting elements, and pericycle thickness decreased while root pith area increased. In canola leaves of high S level, the leaf blade thickness, the thickness of abaxial and adaxial epidermis surface, mesophyll thickness, and metaxylem area increased, while the xylem conducting elements number decreased. Moreover, SCoT molecular markers have been used to evaluate the genetic variation among Brassica napus genotypes subjected to different A.S. treatments. Four of the seven SCoT primers were revealed to be polymorphic in both treated and untreated samples. A total of 39 amplicons, ranging in size from 200 to 1080 bp, were amplified, with 9 (23.07%) of them being polymorphic. Clustering dendogram based on SCot markers data divided Brassica genotypes into two main clusters based on similarity coefficients indices. B. napus treated with 0.2% A.S. was separated in a distinct cluster. Furthermore, treatments with sulphur enhanced the activity of antioxidant enzymes as well as the expression level of their encoding genes (CAT, catalase; POD, peroxidase; APX, ascorbate peroxidase; SOD, superoxide dismutase; GR, glutathione reductase), particularly at 1% and 0.2% A.S. treatments. Taken together, this study revealed that foliar application of sulphur treatments, particularly at 0.2%, have a great potential to improve canola crop.