Cadmium accumulation in different pakchoi cultivars and screening for pollution-safe cultivars

The selection and breeding of pollution-safe cultivars (PSCs) is a practicable and cost-effective approach to minimize the influx of heavy metal to the human food chain.In this study,both pot-culture and field experiments were conducted to identify and screen out cadmium pollution-safe cultivars (Cd-PSCs) from 50 pakchoi (Brassica rapa L.ssp.chinensis) cultivars for food safety.When treated with 1.0 or 2.5 mg/kg Cd,most of the pakchoi cultivars (>70%) showed greater or similar shoot biomass when compared with the control.This result indicates that pakchoi has a considerable tolerance to soil Cd stress.Cd concentrations in the shoot varied significantly (P<0.05) between cultivars:in two Cd treatments (1.0 and 2.5 mg/kg),the average values were 0.074 and 0.175 mg/kg fresh weight (FW),respectively.Cd concentrations in the shoots of 14 pakchoi cultivars were lower than 0.05 mg/kg FW.In pot-culture experiments,both enrichment factors (EFs) and translocation factors (TFs) of six pakchoi cultivars were lower than 1.0.The field studies further confirmed that the Hangzhouyoudonger,Aijiaoheiye 333,and Zaoshenghuajing cultivars are Cd-PSCs,and are therefore suitable for growth in low Cd-contaminated soils (≤1.2 mg/kg) without any risk to food safety.