Prospective sustainable production of safe food for growing population based on the soybean (Glycine max L. Merr.) crops under Cd soil contamination stress

Abstract

Sustainable food production for steadily growing world's population under the conditions of increasing environmental stress and soil pollution is a challenge that calls for optimization of farmland resource management. Soybean (Glycine max. L. Merr) as one of the world's most important protein crops can play a leading role in addressing global food security provided it fulfills safety requirements, in particular with respect to Cd level. The aim of this comparative study was elaborating efficient methods for the selection of soybean cultivars assuring safe Cd contents for food/feed purposes. The pot culture experiment was conducted using 15 soybean cultivars grown in soil moderately polluted with Cd (1.98 mg kg−1), and in unpolluted soil (0.15 mg Cd kg−1) as a control. The evaluation was based on the novel Cd concentration/load trend analysis in plant tissues, Seed Accumulation Factors SAFn and Cd load balance. The soybean demonstrated fundamentally different response of the same cultivars to low and moderate Cd concentrations in soil. In cultivars grown in unpolluted soil, besides genetically determined detoxification factors, important seed protective role played Cd accumulation in stem, leaves and root (Seed Accumulation Factor SAFn<0.5, Cd load reduction in bean by 25–82%). In the moderately polluted soil, the most essential effect on Cd accumulation in seed exerted a plant genotype determining Cd flux and translocation from soil to shoot via root (Enrichment Factor EF < 1), while seed protection by accumulating Cd in other plant tissues was weak, declining or none (SAFn >0.5 up to >1, whereas Cd load in bean ranged from −23 to +11% related to mean value in shoot). Root to shoot flux rate was found to be a decisive factor in Cd enrichment in soybean seed at the elevated soil pollution with Cd. The efficient screening for safe Cd content in soybean should be thus based on EF and Cd concentrations in shoot at the actual target soil pollution level.