Exogenous Spermine Mitigate Adversities of Salinity Induced Oxidative Stress through Antioxidant Metabolites in Wheat

Change in climatic scenarios due to global warming is characterized by extreme climate variability, land and water degradation which resulted in water scarcity. Accumulation of salts at the surface and sub-surface layers of soils affect crop production of major cereals which is a constraint in sustainable food production. Salinity is a major challenge to tackle wheat cultivation and harness productivity in arid and semi-arid regions of India. In the present investigation, mitigation of salinity induced oxidative stress through exogenous application of spermine (Spm) in four wheat genotypes was studied in relation to antioxidant metabolites. The levels of O2.- increased with increasing levels of salinity in wheat flag leaves. DBW 88 showed the levels of O2.- of 11.75 nmol g-1 FW and 15.74 nmol g-1 FW (at 8 dSm-1 and 12 dSm-1 respectively) at 21 Days After Sowing (DAS) and application of Spm decreased the O2.- content under control and saline stressed conditions at 8 dSm-1 and 12 dSm-1. Hydrogen peroxide content was increased with increasing levels of salinity in all the wheat varieties at 21 DAS. However, the increase was more in the case of DBW 88 when compared with HD 3086. Treatment of Spm decreased the H2O2 content when compared with control and saline stressed wheat varieties. The malondialdehyde (MDA) content was increased with increasing levels of salinity at 21 DAS. The highest increase in MDA content was seen in DBW 88 whereas the lowest increase was found in Kharchia 65. Application of Spm decreased the MDA content under control at both levels of salinity treated wheat varieties. The carotenoid content decreased with increasing levels of salinity in all four wheat varieties. However, the decrease was more in DBW 88 when compared with other varieties viz. HD 3086, Kharchia 65 and KRL 210 at 21 DAS. Exogenous Spm increased the carotenoids content in all four wheat varieties irrespective of the salinity. The leaves of Kharchia 65 and KRL 210 had higher levels of ascorbic acid as compared to that of DBW 88 and HD 3086. Increased content of carotenoid was observed in Spm-treated wheat. Exogenous application of Spm increased the ascorbic acid content in control at both levels of salt stress. The glutathione content increased with an increase in salinity treatment in all the varieties however, a higher increase was observed in Kharchia 65. Exogenous Spm increased the glutathione content in all the varieties irrespective of salinity stress. The results presented in the study indicated that the exogenous application of Spm improved their tolerance levels under salinity.