Possible Association of Metabolites Accumulation with Salt Tolerance of Sugarcane

Abstract

Sugarcane is a moderately salt tolerant glycophyte grown in tropical and sub-tropical regions for its high demand as a source of sugar and for biofuel production. Salinity is one of the major adversities that are affecting crop production all over the world. Vegetative propagated sugarcane is very sensitive to salinity at sprouting/germination stage; later it develops tolerance as it reached to maturity. This research was planned to study the accumulation of various metabolites in shoots and roots of sprouts in simulation as well as natural saline/sodic fields in two planting seasons. The ten sugarcane clones obtained from Ayub Agriculture Research Institute Faisalabad, Pakistan were screened using single buds setts in different levels of EC/SAR in simulation and in selected field plots in two planting seasons (Autumn season 2012 and Spring season 2013). The two screened sugarcane clones, one as tolerant (CPF-246) and other as sensitive (S-2003-US-778) were selected for detailed studies at three selected levels of salinity/sodicity at fore-nightly intervals (Autumn season 2013 and Spring season 2014). Growth of both the sugarcane clones reduced as salinity/sodicity increased in simulation as well as field trials. Metabolites such as Chl-a, Chl-b, and Chl-T were severely damaged by the salts concentrations, Chl a/b ratios were found to be higher under stress as compared to control. Total free amino acid contents were higher in both saline/sodic conditions especially in Autumn season. Reduction in primary metabolites under stress shifted the metabolic processes towards enhanced production of secondary metabolites. Antioxidant pigments such as carotenoids were also damaged by high EC/SAR. Anthocyanins were high in shoot and roots of sprouts, especially CPF-246, at all treatments and harvests. High production of H2O2 induced lipid peroxidation by the production of MDA contents in both parts of sprouts as compared to control. Greater production of osmoprotectants such as glycine betaine, proline, soluble sugars, and reducing power assay as well as phenolics occurred at all harvests in both simulation and field trials. The total alkaloids and total lignins were higher in roots of CPF-246 compared to S-2003-US-778, and resulted in reduction of root size. The greater uptake of toxic ions, Na+, Cl-, SO42-, in both roots and shoots of sprouts showed the antagonistic effect on the concentration of essential nutrients; K+, Ca2+, NO3-, PO43-, and Mg2+ thus justify the effect of salinity/sodicity stress more on S-2003-US-778 as compared to CPF-246 and Autumn season reduced more growth of both sugarcane clones as compared to spring season.