Quantification and Tissue Localization of Selenium in Rice (Oryza sativa L., Poaceae) Grains: A Perspective of Agronomic Biofortification

Abstract

In worldwide production, rice is the second-most-grown crop. It is considered a staple food for many populations and, if naturally enriched in Se, has a huge potential to reduce nutrient deficiencies in foodstuff for human consumption. This study aimed to develop an agronomic itinerary for Se biofortification of Oryza sativa L. (Poaceae) and assess potential physicochemical deviations. Trials were implemented in rice paddy field with known soil and water characteristics and two genotypes resulting from genetic breeding (OP1505 and OP1509) were selected for evaluation. Plants were sprayed at booting, anthesis and milky grain phases with two different foliar fertilizers (sodium selenate and sodium selenite) at different concentrations (25, 50, 75 and 100 g Se·ha−1). After grain harvesting, the application of selenate showed 4.9–7.1 fold increases, whereas selenite increased 5.9–8.4-fold in OP1509 and OP1505, respectively. In brown grain, it was found that in the highest treatment selenate or selenite triggered much higher Se accumulation in OP1505 relatively to OP1509, and that no relevant variation was found with selenate or selenite spraying in each genotype. Total protein increased exponentially in OP1505 genotype when selenite was applied, and higher dosage of Se also increased grain weight and total protein content. It was concluded that, through agronomic biofortification, rice grain can be enriched with Se without impairing its quality, thus highlighting its value in general for the industry and consumers with special needs.

Effect of Rice Grain (Oryza sativa L.) Enrichment with Selenium on Foliar Leaf Gas Exchanges and Accumulation of Nutrients

“…The agronomic management of trials, namely the application of nitrogen fertilizers, control of weeds, insect pests and diseases and the water management (irrigation) were those recommended and typically used for the rice crop in this region. Furthermore, the accurate characterization, regarding soil characteristics and irrigation water, of the studied area was identical to that described in a previous and recently published work [ 42 ], where some climate parameters were also taken into account.…”

“…Two different cultivars of rice were submitted to foliar fertilization by various concentrations of selenite and selenate (25, 50, 75 and 100 g Se.ha −1 ) at different stages of rice development, i.e., booting, anthesis and milky grain phase. After harvest a 4.9–7.1-fold increase in Se content was observed in grain from plants sprayed with selenate, while a 5.9–8.4-fold increase was noted for selenite [ 42 ]. These findings are in agreement with previous reports using four rice genotypes (Ariete, Albatros, OP1105 and OP1109) in field trials with foliar fertilization ranging between 0 and 300 g Se.ha −1 for sodium selenite and sodium selenate [ 14 ].…”

Effects of Selenium Fertilizer Application on Yield and Selenium Accumulation Characteristics of Different Japonica Rice Varieties

“…Many studies have shown that there are two ways to improve the selenium content of rice: one is to improve the content of Se in rice by exogenous application of selenium, the other one is breeding of selenium-rich rice varieties [10,14,32,36,55]. Zhang et al [56] studied 151 rice varieties before finding that brown rice contained selenium ranging from 0.029 mg kg −1 to 0.103 mg kg −1 .…”

“…Many levels of selenium fertilizer were studied to produce Se-rich rice [10,20,37], and the concentrations of foliar fertilizers ranging between 25 and 100 g Se ha −1 did not surpass the threshold of toxicity [10]. Therefore, there was a division of the treatment into three groups: 0 g Se ha −1 (L0), 40 g Se ha −1 (L1), and 80 g Se ha −1 (L2) in this study.…”

“…Rice is also among the main food crops in China. It is reported that more than 80% of selenium in the grain is organic selenium (SeMet and SeCys) [9,10], which was found to be more bioavailable than selenate and selenite in that it was more effective in raising blood Se concentrations (suggesting better absorption and retention). However, all forms were able to increase selenoenzyme (glutathione peroxidase) activity [11].…”