Grain zinc concentrations differ among Brazilian wheat genotypes and respond to zinc and nitrogen supply

Do agronomic approaches aligned to regenerative agriculture improve the micronutrient concentrations of edible portions of crops? A scoping review of evidence

Regenerative Agriculture (RA) is used to describe nature-based agronomic approaches that aim to build soil health and crop resilience, minimize negative environmental outcomes, and improve farmer livelihoods. A benefit that is increasingly attributed to crops grown under RA practices is improved nutritional content. However, we do not know the extent to which RA influences crop nutritional quality and under what management approaches and context, can such effects be realized. A scoping review of recent literature (Web of Science, 2000-2021) was carried out to assess the evidence that RA approaches improve crop micronutrient quality. Papers included combinations of agronomic approaches that could be defined as Regenerative: "Organic Inputs" including composts and manures, cover crops, crop rotations, crop residues and biochars; "Reduced Tillage", "Intercropping", "Biostimulants" e.g. arbuscular mycorrhizal fungi; plant growth promoting bacteria, and "Irrigation", typically deficit-irrigation and alternate wetting and drying. The crop types reviewed were predetermined covering common sources of food and included: Tomato (Solanum lycopersicum L.), Wheat (Triticum aestivum L.), Rice (Oryza sativa L.), Maize (Zea mays L.), Pulses (Fabaceae), Alliums (Allium spp.), and "other" crop types (30 types). This scoping review supports a potential role for RA approaches in increasing the concentrations of micronutrients in the edible portions of several crop types under specific practices, although this was context specific. For example, rice grown under increased organic inputs showed significant increases in grain zinc (Zn) concentration in 15 out of 16 studies. The vitamin C concentration of tomato fruit increased in ~50% of studies when plants were grown under increased organic inputs, and in 76% of studies when plants were grown under deficit irrigation. Overall, the magnitude and reproducibility of the effects of RA practices on most crop nutritional profiles were difficult to assess due to the diversity of RA approaches, geographical conditions, and the limited number of studies for most crops in each of these categories. Future research with appropriate designs, improved on-farm surveillance and nutritional diagnostics are needed for better understanding the potential role of RA in improving the quality of food, human nutrition, and health.

Agronomic bio-fortification of wheat (Triticum aestivum L.) to alleviate zinc deficiency in human being

Worldwide, 40% population consumes wheat (Triticum aestivum L.) as a staple food that is low in zinc (Zn) content. Zn deficiency is a major micronutrient disorder in crop plants and humans worldwide, adversely impacting agricultural productivity, human health and socio-economic concern. Globally, the entire cycle of increasing the Zn concentration in wheat grains and its ultimate effect on grain yield, quality, human health & nutrition and socio-economic status of livelihood is less compared. So the present studies were planned to compare the worldwide studies for the alleviation of Zn malnutrition. Zn intake is affected by numerous factors from soil to crop, crop to food and food to humans. The post-harvest fortification, diversification in dietary habits, mineral supplementation and biofortification are various possible approaches to enhance the Zn concentration in food. The wheat grains Zn is influenced by the Zn application technique and time concerning crop developmental stages. The use of soil microorganisms mobilize unavailable Zn, and improve Zn assimilation, plant growth, yield and Zn content in wheat. Climate change can have an inverse impact on the efficiency of agronomic biofortification methods due to a reduction in grain-filling stages. Agronomic biofortification can improve Zn content, crop yield as well as quality and ultimately, have a positive impact on human nutrition, health and socioeconomic status of livelihood. Though bio-fortification research has progressed, some crucial areas are still needed to be addressed or improved to achieve the fundamental purpose of agronomic biofortification.

Synchrotron X-ray Fluorescence Technique Identifies Contribution of Node Iron and Zinc Accumulations to the Grain of Wheat

Increasing iron (Fe) and zinc (Zn) concentrations in crop grains with high yield is an effective measure to ensure food supply and alleviate mineral malnutrition in humans. Micronutrient concentrations in grains depend on not only their availability in soils but also their uptake in roots and translocation to shoots and grains. In this three-year field study, we investigated genotypic variation in Fe and Zn uptake and translocation within six wheat cultivars and examined in detail Fe and Zn distributions in various tissues of two cultivars with similar high yield but different grain Fe and Zn concentrations using synchrotron micro-X-ray fluorescence. Results revealed that root Fe and Zn concentrations were 11 and 44% greater in high-nutrient (HN) than in low-nutrient (LN) concentration cultivar. Although both cultivars accumulated similar amounts of Fe in shoots, HN cultivar had greater accumulation of Fe in grain and greater accumulation of Zn in both shoots and grain. Grain Zn concentration was positively correlated with shoot Zn accumulation, and grain Fe concentration was positively correlated with the ability to translocate Fe from leaves/stem to grains. In the first nodes of shoots, HN cultivar had 482% greater Fe and 36% greater Zn concentrations in the enlarged vascular bundle (EVB) than LN cultivar. In top nodes, HN cultivar had 225 and 116% greater Fe and Zn concentrations in the transit vascular bundle and 77 and 71% greater in the EVB when compared to LN cultivar. HN cultivar also had a greater ability to allocate Fe and Zn to the grain than LN cultivar. In conclusion, HN cultivar had greater capacity of Fe and Zn acquirement by roots and translocation and partitioning from shoots into grains. Screening wheat cultivars for larger Fe and Zn concentrations in shoot nodes could be a novel strategy for breeding crops with greater grain Fe and Zn concentrations.

Genetic biofortification of wheat with zinc: Opportunities to fine-tune zinc uptake, transport and grain loading

Zinc (Zn) is an important micronutrient in the human body, and health complications associated with insufficient dietary intake of Zn can be overcome by increasing the bioavailable concentrations in edible parts of crops (biofortification). Wheat (Triticum aestivum L) is the most consumed cereal crop in the world; therefore, it is an excellent target for Zn biofortification programs. Knowledge of the physiological and molecular processes that regulate Zn concentration in the wheat grain is restricted, inhibiting the success of genetic Zn biofortification programs. This review helps break this nexus by advancing understanding of those processes, including speciation regulated uptake, root to shoot transport, remobilisation, grain loading and distribution of Zn in wheat grain. Furthermore, new insights to genetic Zn biofortification of wheat are discussed, and where data are limited, we draw upon information for other cereals and Fe distribution. We identify the loading and distribution of Zn in grain as major bottlenecks for biofortification, recognising anatomical barriers in the vascular region at the base of the grain, and physiological and molecular restrictions localised in the crease region as major limitations. Movement of Zn from the endosperm cavity into the modified aleurone, aleurone and then to the endosperm is mainly regulated by ZIP and YSL transporters. Zn complexation with phytic acid in the aleurone limits Zn mobility into the endosperm. These insights, together with synchrotron-X-ray-fluorescence microscopy, support the hypothesis that a focus on the mechanisms of Zn loading into the grain will provide new opportunities for Zn biofortification of wheat.

Zinc Accumulates in the Nodes of Wheat Following the Foliar Application of 65Zn Oxide Nano- and Microparticles

Using zinc (Zn) foliar fertilizers to enhance the grain quality of wheat (Triticum aestivum) can be an effective alternative or supplement to Zn soil fertilizers. However, knowledge about the mechanisms of Zn absorption and translocation following foliar application is scarce. Here, autoradiography and γ-spectrometry were used to investigate the behavior of ⁶⁵Zn applied to wheat leaves as soluble ⁶⁵Zn chloride (⁶⁵ZnCl₂), chelated ⁶⁵Zn (⁶⁵ZnEDTA), ⁶⁵Zn oxide nanoparticle (⁶⁵ZnO-NP) suspensions, and ⁶⁵ZnO microparticle (⁶⁵ZnO-MP) suspensions. The largest amount of ⁶⁵Zn absorption occurred in ⁶⁵ZnCl₂ treated leaves. However, this treatment (⁶⁵ZnCl₂) also had the lowest proportion of absorbed ⁶⁵Zn translocated away from the treated leaf after 15 d due to leaf scorching (p = 0.0007). Foliar-applied ⁶⁵ZnO-NPs and ⁶⁵ZnO-MPs had the lowest absorption, but ⁶⁵ZnO-NPs had the highest relative translocation. ⁶⁵Zinc EDTA was intermediate, with higher ⁶⁵Zn absorption than ⁶⁵ZnO treatments but similar translocation. Regardless, the majority of the foliar-applied ⁶⁵Zn remained in the treated leaf for all treatments. Furthermore, ⁶⁵ZnO-NPs and ⁶⁵ZnO-MPs accumulated in plant nodes, suggesting that Zn was absorbed as dissolved ⁶⁵Zn and particulate ⁶⁵ZnO. Overall, the form and amount of absorbed ⁶⁵Zn affected translocation.

Do New-Generation Recycled Phosphorus Fertilizers Increase the Content of Potentially Toxic Elements in Soil and Plants?

Phosphorus (P)-rich secondary raw materials can provide a valuable base for modern mineral fertilizers, provided that the new formulations do not load the soil–plant system with potentially toxic elements. Fertilizers from sewage sludge ash (SSA) and/or animal bones, activated by phosphorus-solubilizing bacteria (Bacillus megaterium or Acidithiobacillus ferrooxidans), were tested in field experiments in north-eastern Poland. The reference provided treatments with superphosphate and treatment without phosphorus fertilization. In one experiment, all P-fertilizers were applied at a P dose of 21 kg·ha−1, and in the other three experiments, three P doses were adopted: 17.6, 26.4, and 35.2 kg·ha−1. The effect of recycled fertilizers on the content of arsenic (As), chromium (Cr), nickel (Ni), copper (Cu), and zinc (Zn) in the soil, in wheat grain and straw (test plant), weeds, and post-harvest residues was investigated. The application of recycled fertilizers in P amounts up to 35.2 kg·ha−1 did not change the As, Cr, Ni, Cu, or Zn contents in the soil and plant biomass. The contents of these elements in soil were below the permissible levels for arable land in Poland. Their concentrations in wheat grain and straw did not exceed the permissible or suggested limits for plant material to be used for food and feed, while in the weed and post-harvest residue biomass, they usually fell within the biological plant variability ranges.