- Title
- Selenium biofortification in chickpea and wheat using innovative materials
- Creator
- Yeasmin, Marjana
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Selenium (Se) is an essential micronutrient for humans that is necessary for both physical and mental well-being. Insufficient dietary intake of Se is associated with selenium deficiency in humans resulting in disruption of thyroid and immune system and reducing cognitive health. Selenium deficiency is also associated with myodegenerative diseases and reduction of important antioxidant selenoproteins. Thus, mitigating Se deficiency that affects about 1 billion people across the world is essential. Typically, Se deficiency occurs due to inadequate dietary intake of selenium due to the lack of Se content in soils in a particular region. Selenium fertilization and application to grain crops is a process of agronomic biofortification that can be efficiently used to improve the Se nutrition in humans. Even though several experiments have been reported on Se biofortification of various crops, Se speciation and translocation in various crops, especially in presence of interfering ions, is not well studied. Similarly, Se uptake in plants from the nanosized Se and its distribution in plants and its potential advantages over the conventional forms have never been explored. Thus, the primary aim of this thesis was to determine the Se uptake, translocation and speciation in grain crops using nanosized forms of metallic Se and its comparison with inorganic salts of Se. Selenium biofortification was thus investigated in chickpea (Cicer arietinum) and wheat (Triticum aestivum). The influence of sulfur (S) on the speciation and accumulation of Se in two chickpea cultivars (Amber and PBA Sheamer) is described in Chapter 3. The crops were grown in Se-deficient soil under glasshouse conditions and fortified with Se in the presence and absence of S. To achieve this, two doses of S (0 and 14 mg kg-1) as sulfate and three doses of Se (0, 1, and 2 mg kg-1) as selenate (SeVI) were used to treat Se deficiency in a randomized factorial design. It was found that the addition of SeVI has a significant effect on the Se content which was found to increase in grain in both cultivars as compared to the control treatment. Evaluation of Se speciation in grain showed that almost 85% of the Se accumulated as organic forms in chickpea grain. PBA Sheamer, a desi type and widely grown chickpea cultivar showed the most significant proportion of organic Se species, SeCys (57%) and SeMeCys (40%). Inorganic Se content was observed to be lower than 15% and was primarily present as SeVI. Selenium dosing also had a significant impact on the yield as 2 mg kg-1 Se addition significantly reduced the biomass and grain yield (P<0.01). In comparison, treatment with S addition tended to increase crop yield. Additionally, S application with Se also increased the proportion with increased SeMeCys in PBA Sheamer grains. These findings suggest that S plays a major role in the accumulation and speciation of Se in chickpea grain. Following these findings, the influence of S on the Se speciation and accumulation in three wheat cultivars was studied. The protocols for plant growth and both S and Se dosing were similar to the study conducted on Chickpea. Similarly to the chickpea, SeVI fortification increased the Se content in grains of all wheat cultivars as compared to the control treatment. It was also observed that the Se accumulation was highest in leaf tissue while stem demonstrated low amounts of Se accumulation. Speciation analysis showed the presence of Se in the form of SeCys and SeMeCys in wheat grains while the inorganic Se, primarily as SeVI, was below 10%. In contrast to chickpea, concurrent fertilization of S with Se resulted in decreased production of organic Se in grain. The findings from this study provide new insights into the influence of S on the Se biofortification and speciation transformation processes in wheat while highlighting the dependence of the biofortification on the type of the crops as well. Foliar application of Se has advantages over traditional soil-applied fertilizer application methods due to the high mobility of Se in soil. In chapter 5, the focus is on Se absorption, translocation, and transformation using isotopically enriched 77SeVI applied to leaves of wheat along with selenoprotein gene expression and distribution of 77SeVI in wheat grain. Treatment of isotopically enriched 77SeVI was applied directly to the leaves at 0, 5, 10 and 20 mg L-1 doses by infiltration. Further, synchrotron-based X-ray fluorescence microscopy (µ-XRF) imaging and µ-XANES (x-ray absorption near-edge spectroscopy) were used to study the Se distribution and Se speciation, respectively, in actively photosynthesising wheat leaves as a function of time. While µ-XRF did not detect noticeable movement of the applied, µ-XANES speciation analysis confirmed that the majority of the accumulated Se remained as inorganic species of Se. In wheat grain, a high-resolution elemental map of wheat grain revealed that Se partitioned primarily on the outer surface of the endosperm. Selenium accumulation increased with concentration of the dose, and the highest Se accumulation in wheat grains was observed in the 10 mg L-1 treatment. Genetic analysis revealed higher expression of two selenium-binding protein (SBP) genes in wheat leaves following SeVI application with SPBb depicting a higher abundance at 10 mg L-1 treatment. High-performance liquid chromatography Inductively coupled with plasma mass spectrometry (HPLC-ICP-MS) analysis for Se speciation confirmed the accumulation of organic Se species (84%), mostly SeCys, in wheat grains. Thus, this study showed that wheat has good potential for Se fortification using foliar application and can be used to produce Se–fortified food. Chapter 6 reports the results of experimental data on the potential of Se nanoparticles (SeNPs) for the biofortification of Se in wheat via foliar application. The foliar application of SeNPs demonstrated a tremendous impact on plant growth facilitated by higher (15 times higher than the control) accumulation of Se in shoots (226 µg kg-1). It was observed that SeNPs infiltrated within the leaves and were mostly located adjacent to chloroplasts. Confocal microscopy revealed that Se addition reduced the accumulation of reactive oxygen species (superoxide anion and hydrogen peroxide) by 50%. Furthermore, SeNPs application at 10 mg L-1 exhibited a significant increase in photochemical efficiency (19%), carboxylation rate (35%) and electron transport rate (30%) relative to control treatments. Interestingly, rapid biotransformation of SeNPs to seleno-amino acids occurred within four days suggesting the superiority of SeNPs addition over SeVI. These results indicate that foliar application of SeNPs to wheat leaves provides tremendous advantages, including reactive oxygen species (ROS) mitigation, higher photosynthesis, and generation of desirable Se forms within a short period of time. Overall, Se biofortification can be achieved by exogenous Se application in field crops. Foliar applied SeVI could become bioavailable in grain and transformed into organic species (> 80%). Selenium nanoparticles could easily be translocated from foliar applied leaves to other parts of plants and rapidly transformed into organic species. Therefore, wheat could be a potential crop for Se translocation and biotransformation of Se in grain and used as Se fortified food for recovering micronutrient malnutrition. Selenium nanoparticles can be used as a novel fertilizer in foliar applications to increase plant photosynthesis, reviving stress and biotransformation of desirable Se species.
- Subject
- selenium; selenium deficiency; agronomic biofortification; chickpea; wheat; Triticum aestivum; Cicer arietinum; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1504751
- Identifier
- uon:55569
- Rights
- Copyright 2022 Marjana Yeasmin
- Language
- eng
- Full Text
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