Selenium Biofortification Enhanced Grain Yield and Alleviated the Risk of Arsenic and Cadmium Toxicity in Rice for Human Consumption

Abstract

Arsenic (As) and Cadmium (Cd) are toxic to rice plants. However, selenium (Se) has the potential to regulate As and Cd toxicity. The present study aimed to evaluate the co-exposure to As⁵⁺ and Se⁶⁺ species in two rice cultivars, BRS Pampa and EPAGRI 108. The plants were divided into six groups and cultivated until complete maturation of the grains, under greenhouse conditions. Regarding total As and inorganic As (i-As) accumulation in grains, the highest concentrations were found for BRS Pampa. For Se, EPAGRI 108 presented the highest concentration of inorganic and organic Se (i-Se and o-Se). The exposure assessments showed that Se biofortification can mitigate the As accumulation in rice and, consequently, the risk of As and Cd toxicity in grains for human consumption. The combined effect of As and Se in rice plants could represent an alternative to biofortify this food in a safe way and with a higher percentage of bioavailable Se. Although Se is able to mitigate As toxicity in rice plants, in the present study we showed that co-exposure in different cultivars under the same growing conditions may present different responses to As and Se exposure.

Keywords: HPLC-ICP-MS; arsenic; cadmium; chemical speciation; co-exposure; human risk assessment; selenium.

Figure 1

Organic and inorganic As and Se accumulated in the grains of the cultivars tested. Bars not shown are under the limit of detection. Treatments: Control, As5, Se5, As2.5 + Se5, As5 + Se5, and As10 + Se5. (A) organic and inorganic As in BRS Pampa cultivar; (B) organic and inorganic As in EPAGRI 108 cultivar; (C) organic and inorganic Se in BRS Pampa cultivar; (D) organic and inorganic Se in EPAGRI 108 cultivar.

Figure 2

As and Se species in the grains of the cultivars tested. Chemical species and treatments that presented values below LOD: BRS Pampa C: SeMet/SeCys in Control; Se⁴⁺/SeCys in As5; Se⁴⁺ in As10 + Se5; EPAGRI 108 D: SeCys/Se⁴⁺ in Control and As5: (A) arsenic species in the grains of BRS Pampa; (B) arsenic species in the grains of EPAGRI 108; (C) Se species in the grains of BRS Pampa; (D) Se species in the grains of EPAGRI 108.