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

Ana Coelho Marques,Roberta G Leitão,Maria Fernanda Pessoa,José C Ramalho,Cláudia Campos Pessoa,Maria Manuela Silva,Paula Scotti-Campos,Karliana Oliveira,Cátia Silva,Paula Marques,Carlos Galhano,Paulo Legoinha,Inês Carmo Luís,Isabel P Pais,Ana Sofia Almeida,Fernando C Lidon,David Ferreira,Ana Rita F Coelho,Mauro Guerra ,J N Moreira ,José N Semedo ,María José Silva ,Ana I Ribeiro‐Barros ,A L Rodrigues ,Ana Sofia Bagulho ,Fernando H Reboredo

doi:10.3390/plants9121670

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.

Highlights

Selenium is an essential micronutrient for human growth, acting in the antioxidant defense metabolism [1]
It is fundamental to develop new strategies to increase Se content in cereals, namely by fertilization and to cultivate varieties with higher accumulation potential [28]. In this context, considering that soil and irrigation water properties were adequate for rice production, with the goal of increasing Se content in rice grain, genetic breeding and agronomic biofortification were combined, testing different spray concentrations of Se, from two different chemical sources, with two different genetic backgrounds
O. sativa sprayed with selenate or selenite concentrations ranging between 25–100 g Se·ha−1 did not surpass the threshold of toxicity

Summary

Introduction

Selenium is an essential micronutrient for human growth, acting in the antioxidant defense metabolism [1]. Of the world’s population of six billion, with babies being the most vulnerable [2] This physiological stress increases the risk of male infertility, heart disease, thyroid disorder, weakened immunity, cancer, and various inflammatory disorders [3]. Selenium deficiency is further associated with increased susceptibility to infections such as COVID-19 and HIV [4]. To address this physiological deficiency, the World Health Organization (WHO) recommends a daily intake of 30-40 μg Se for adults (with toxicity limits being reached if 400 μg are exceeded) while the National Academy of Sciences recommends 40–70 μg for male and 45–55 μg for female [5]. Plant roots mobilize Se in the form of selenate (SeO4 2− )

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Discussion

Conclusion