Glutathione and moringa leaf extract improve wheat tolerance to heavy metal-contaminated saline soil by regulation of antioxidant defense system and nutrient balance.

Integrated application of MLE and GSH mitigated salinity and HM stress in wheat via enhancement of antioxidant defense system, nutrient balance, and reduced sodium toxicity, and thereby improved crop performance and grain nutritional quality. Salinity obstructs the uptake of essential minerals by simultaneously increasing heavy metal (HM) concentration to affect the growth, yield, and grain nutritional quality in crop plants. This study evaluated the potential of moringa leaf extract (MLE; 3%) and glutathione (GSH; 1 mM) applied in sequence with H2O as a seed priming (SP) and foliar spray (FS) on antioxidant enzymes activity, GSH, and protein levels, leaf macronutrients as well leaf and grain micronutrients, and HM contents at booting and maturity stages under HM-contaminated saline conditions (9.06 dS m-1) for two growing seasons. Soil salinity induced high Na+ and Cd toxicity, triggered leaf antioxidant enzymes activities (SOD, CAT, GPOX), enhanced GSH levels, and reduced protein content as well as macronutrient (N, P, Ca) and micronutrient (Fe, Mn, Zn) contents. This was associated with increased Na+ (~ 50-52.94%) and HMs (Cu~23.89%, Pb~65.58-86.52%, Cd~36.21-40.5%) as well NO3 and NO2 contents, ultimately reducing the straw (29.92-34.96%) and grain yields (31.59-32.78%) in wheat. Sequenced application of MLE and GSH as SP and FS further enhanced antioxidant enzymes activities (SOD~44.78-49.00%, GPOX~51.4-56.14%), increased total protein (~ 32.16-33.2%) and GSH (~ 60.38-70.4%) contents, macronutrients N (~ 28.01-50.94%), P (~ 47.62-50.0%), K+ (~ 19.6-25.89%), and Ca2+ (~ 33.33-53.34%), and micronutrient contents (Fe~33.33-51.13, Zn~47.72-53.57, Mn~36.18-36.55) in the leaves and grains (Fe~47.1-50.44, Zn~48.57-74.19, Mn~48.57-74.19) of wheat. This increase was with a simultaneous decrease of HM contents (Cu~19.28%, Cd~47.21-50.42, Pb~48.50-49.31) in leaves and grain (Cu~26.47%, Cd~29.00-30.11%, Pb~47.05-53.86%), as well as grain NO3 and NO2 contents under saline HM conditions. This enhanced nutritional crop status, antioxidant defense system, and its homeostasis with reduced leaf Na+ (~ 40.00-45.45%) toxicity, and NO3 (~ 47.32-54.25%) and NO2 (~ 54.10-61.2%) contents, which led to increased wheat straw and grain yields under HM-contaminated saline soil. In conclusion, integrated applications of MLE and GSH can be a promising strategy to reduce the detrimental effects of dual salinity and HM stress with substantial increase in crop performance and grain nutritional quality in wheat.