SUMMARYSelenium (Se) is an essential micronutrient for humans, yet its dietary intake is low, mostly due to the low bioavailability in soils and therefore in edible plant tissues. To overcome Se deficiency, the breeding approach (i.e., genetic biofortification), namely in rice, is largely dependent on available Se pools. To ensure the success of genetic biofortification with Se, agronomic biofortification can be accomplished through foliar Se application. Considering this background, the main hypothesis of this work was centered in the foliar application of Se to attain agronomic biofortification of rice crops. This study also aimed to assess the full potential for increasing grain Se concentrations during rice filling, as well as the types of nutrients deposition. An experimental design applying two foliar fertilizers (sodium selenite and sodium selenate) was developed. As test systems, four rice genotypes (Ariete, Albatros, OP1105 and OP1109) were used and the kinetics of micro- and macro-nutrients accumulation and deposition were assessed. Biofortification was performed in field trials for two years with foliar fertilization ranging between 0 and 300 g Se ha−1. At the end of the plant cycle, selenite applications triggered 427- to 884-fold increases in grain Se concentrations among rice genotypes (Albatros > OP1105 > OP1109 > Ariete). The application of selenate also prompted 128- to 347-fold increases in grain Se concentrations in rice crops (Albatros > OP1105 > Ariete > OP1109). Regardless of the foliar fertilizer applied, Se deposition among genotypes occurred throughout the grain without relevant inhibitory effects on yields. In each genotype, micro and macronutrients varied among crop tissues.

No abstract

Durum wheat (Triticum turgidum L. ssp. durum (Desf.) Husnot) was grown under conditions to promote mineral biofortification at the grain level. Along plant development, biomass accumulation and the kinetics of nutrients accumulation were assessed, identifying the nutrient fluxes of roots and shoots, and the timescale constraints of crop biofortification. Plants were grown under environmentally controlled conditions, submitted to four increasing concentrations of nutrient solutions (1-, 2-, 4-and 6-fold) of micro-(Fe, Zn, Cu and Mn) and macronutrients (Ca, K, P and Mg). The threshold of mineral toxicity was not reached as evaluated through plant biomass accumulation, but considering grain yield, the twofold nutrient concentration was the best treatment for biofortification. In the different treatments, the contents and the mineral unrests of roots uptake and shoots translocation varied, at different magnitudes and trends, before the onset of booting and from the physiological maturity onwards. Except for Cu, all mineral nutrients were mainly detected in the bran and embryo of the grains; therefore, the production of biofortified pasta for human consumption requires the use of integral semolina. ARTICLE HISTORY

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.

An agronomic itinerary for Se biofortification of two rice cultivars (Ariete and Ceres) through foliar fertilization with sodium selenate and sodium selenite with different concentrations (25, 50, 75 and 100 g Se.ha−1), was implemented in experimental fields. The selenium toxicity threshold was not exceeded, as shown by the eco-physiological data obtained through leaf gas exchanges. The highest Se enrichment in paddy grains was obtained with selenite for both cultivars, especially at the highest doses, i.e., 75 and 100 g Se.ha−1, with approximately a 5.0-fold increase compared with control values. In paddy grains, Zn was the most affected element by the treatments with Se with decreases up to 54%. When comparing the losses between rough and polished grains regardless of the cultivars, Se species and concentrations, it was observed that only Cu, Mg and Zn exhibited losses <50%. The remaining elements generally had losses >70%. The loss of Se is more pronounced in Ceres cultivar than in Ariete but rarely exceeds 50%. The analysis by µ-EDXRF showed that, in Ariete cultivar, Se is mostly homogeneously distributed in the grain regardless of any treatments, while in Ceres cultivar, the Se distribution seems to favor accumulation in the periphery, perhaps in the bran.

The biofortification, process of nutrients creation for food crops, provides a sustainable strategy for rural populations in developing countries. Crops are created for greater levels of micronutrients, by using conventional and transgenic breeding methods. Recent studies provide evidence that biofortification is a promising strategy to combat nutritional deficits. Being a basic and common food of the population of developing countries, the flour got a significant attention as appropriate matrix for biofortification.

Selenium is an antioxidant trace mineral with important biochemical functions related to the enzymatic activity of selenoproteins. Due to a wide variation in the content of selenium from different plant sources, there is a high risk of deficiency of this nutrient in human nutrition, and particularly in the early childhood. Thus, the use of biofortified staple foods, namely selenium rice flour can be understood as an important trait, namely for food production for infants. This study aims to evaluate the importance of selenium biofortified rice flour, further considering baby foods.

Micronutrient deficiencies, namely those arising from zinc, pose serious human health problems. As a staple food crop, wheat is a major source of dietary energy and protein for the world's growing population, and a main target to reduce malnutrition via integration of agronomic fertilization practices. In this context, agronomic biofortification through fertilizer approaches, namely foliar application of Zn can increase grain Zn above the breeding target set by nutritionists. Nevertheless, zinc uptake and translocation, as well as milling yields and bioassimilation in the human intestinal mucosa must be also considered. This review synthesizes the progress made in the framework of the agronomic biofortification strategies for Zn enrichment of wheat, further considering the flour production and bioassimilation limitations.