Soil and foliar applications of silicon and selenium effects on cadmium accumulation and plant growth by modulation of antioxidant system and Cd translocation: Comparison of soft vs. durum wheat varieties.

Minimization of Cd accumulation in wheat is an effective strategy to prevent Cd hazard to human. This study compared and highlighted the roles of soil and foliar applications of Se and Si effects on Cd accumulation and toxicity in soft and durum wheat. Soil Se (0.5-1.0 mg kg) and Si (3-6 mg kg) applications provided an effective strategy to reduce wheat grain Cd concentrations of both wheat varieties by 59-61 % and 16-30 %, but foliar Se (0.125-0.25 mM) and Si (2.5-5 mM) application reduced grain Cd of soft wheat by 20-36 %. Both soil and foliar Se and Si applications significantly alleviated Cd toxicity by regulation of Cd transport genes, as reflected by increased the grain yield and antioxidant enzymes activities, and reduced MDA in wheat tissues. Selenium applications were more effective than Si on the reduction of Cd-induced toxicity and concentrations in soft wheat, but not in durum wheat due to more tolerant to Cd. Downregulation of influx transporter (TaNramp5) and upregulation of efflux transporter (TaTM20 and TaHMA3) in soft wheat may contribute to the Si/Se-dependent Cd mitigation and enhance the tolerance to toxic Cd. Overall, Se/Si applications, especially soil Se, can be efficiently used for reducing grain Cd uptake from Cd-contaminated soils.