Identification of cadmium-excluding welsh onion (Allium fistulosum L.) cultivars and their mechanisms of low cadmium accumulation

Abstract

Screening out cadmium (Cd) excluding cultivars of a crop in agricultural production is an effective way to prohibit Cd entering into food chain. A judging criterion for Cd-excluding cultivars based on food safety was suggested and used in the identification of Cd-excluding welsh onion (Allium fistulosum L.) cultivars. A pot culture experiment was carried out to screen out Cd-excluding cultivars, of which the results were confirmed by plot experiments. The relevant factors of Cd accumulation in the pseudostem were analyzed and used in the correlation analysis aiming to study the low Cd accumulation mechanisms. The concentration of Cd in the pseudostem of welsh onions was 0.08-0.20, 0.18-0.41, and 0.26-0.61 mg/kg fresh weight (FW) under three treatments (1.0, 2.5, and 5.0 mg/kg), respectively. The significant (p < 0.05) difference in the concentration of Cd in the pseudostem was observed among 25 welsh onion cultivars, but Cd contamination in soil had little influence on biomass and the contents of soluble sugar, NO(3)(-)-N, and eight other elements in the tested welsh onion cultivars. Two cultivars were identified as Cd-excluding cultivars, mainly because the accumulation of Cd in their pseudostem was only 0.041 ± 0.003 and 0.046 ± 0.002 mg/kg FW, and 0.054 ± 0.001 and 0.066 ± 0.011 mg/kg FW, when growing in plots with Cd concentration of 0.49 and 0.99 mg/kg, respectively. Ribentiegancongwang and Wuyeqi could be identified as Cd-excluding cultivars. Low bioaccumulation factor of the roots was the main mechanism of Cd-excluding welsh onion cultivars.