Comparison of Cadmium Efflux in Wheat (Triticum aestivum) Cultivars with Contrasting Cadmium Accumulation

Cadmium (Cd) is a highly toxic heavy metal threatening human health. Wheat readily translocates Cd to grains, posing food safety risks in contaminated soils. Screening low-Cd cultivars is therefore critical. In pot experiments with 53 wheat cultivars, Kaimai 21 (KM21) and Lunxuan 6 (LX6) showed the lowest and highest grain Cd, respectively. Under 5-10 µM Cd in hydroponics, KM21 harbored 30.1%-63.6% lower root Cd, 54.7%-69.1% lower shoot Cd, and exhibited superior root growth and Cd tolerance than LX6. Crucially, KM21 showed a 36.9% higher Cd efflux rate and a larger Cd efflux proportion than LX6 (44.3% vs. 15.5%). Real-time Cd²⁺ flux measurements using Non-invasive Micro-test Technology (NMT) further confirmed higher Cd efflux capacity in KM21, which contributed to higher Cd tolerance and lower Cd accumulation. Overall, KM21 is a stably high-Cd efflux and low-Cd accumulation wheat cultivar suitable for safe production in Cd-contaminated soils.