Agronomic Biofortification with Se, Zn, and Fe: An Effective Strategy to Enhance Crop Nutritional Quality and Stress Defense—A Review

Human micronutrient deficiencies are a widespread problem worldwide and mainly concern people whose diet (mainly of plant origin) consists of insufficient amounts of critical vitamins and minerals. Low levels of micronutrients in plants are linked to, i.e., their decreasing concentration in soils and/or low bioavailability and presence of abiotic stresses which disturb the proper growth and development of plants. Agronomic biofortification of crops is a very promising way to improve the concentration of micronutrients in edible parts of crops without compromising yield and is recognized as the cheapest strategy to alleviate hidden hunger worldwide. The review is focused on the factors influencing the effectiveness of biofortified crops (a type of application, form, and a dose of applied microelement, biofertilizers, and nanofertilizers). Also, the accumulation of zinc, selenium, and iron in edible parts of crops, their effects on metabolism, morphological and yield parameters, and an impact on plants’ defense mechanisms against abiotic stress like salt, high/low temperature, heavy metal, and drought was discussed. Finally, the directions of future agronomic biofortification studies are proposed.

Agronomic Biofortification through Integrated Nutrient Management on Maize (Zea mays L.) Hybrids

Background: Supplement of balanced nutrition is required for the growth and development of crops and humans, particularly essential amino acids, vitamins and minerals. The application of mineral micronutrient fertilizers to soil or plant leaves to increase micronutrient content in edible parts of crop. Therefore, this study is focused to evaluate the effect of agronomic biofortification with different nutrient levels on maize. Methods: A field experiment was conducted on sandy clayey loam soil during the Rabi season of 2020-21 Perambalur, Tamil Nadu to study the effect of agronomic biofortification through integrated nutrient management for improving maize (Zea mays L.) yield and quality under Cauvery delta condition. Two hybrids in main-plots both, QPM and non-QPM were sown by direct method on ridges at a spacing of 60 x 20 cm under split plot design (SPD) with 6 treatments of nutrient management in sub-plot combination under three replications. Result: The results revealed that the nutrient level treatments containing 50% RDF through NPK + 50% RDF through FYM with Fe and Zn as foliar application @0.5% conc led to highest growth and yield attributes, grain yield (8.52 tha-1) and stover yield (10.35 tha-1) and also resulted in maximum crude protein content (14.93%), starch content (63.85 mg g-1), Fe (36.25 mg kg-1) and Zn (29.35 mg kg-1) in maize grain. It was observed that Agronomic biofortification through integrated nutrient management enhanced the vegetative growth and yield components of non-QPM hybrid, whereas it improved the grain quality content of the QPM hybrid.

Agronomic Biofortification of Cayenne Pepper Cultivars with Plant Growth-Promoting Rhizobacteria and Chili Residue in a Chinese Solar Greenhouse

Agronomic biofortification of horticultural crops using plant growth-promoting rhizobacteria (PGPR) under crop residue incorporation systems remains largely underexploited. Bacillus subtilis (B1), Bacillus laterosporus (B2), or Bacillus amyloliquefaciens (B3) was inoculated on soil containing chili residue, while chili residue without PGPR (NP) served as the control. Two hybrid long cayenne peppers, succeeding a leaf mustard crop were used in the intensive cultivation study. Net photosynthesis, leaf stomatal conductance, transpiration rate, photosynthetic water use efficiency, shoot and root biomass, and fruit yield were evaluated. Derivatives of folate, minerals, and nitrate contents in the pepper fruits were also assessed. B1 elicited higher net photosynthesis and photosynthetic water use efficiency, while B2 and B3 had higher transpiration rates than B1 and NP. B1 and B3 resulted in 27–36% increase in pepper fruit yield compared to other treatments, whereas B3 produced 24–27.5% and 21.9–27.2% higher 5-methyltetrahydrofolate and total folate contents, respectively, compared to B1 and NP. However, chili residue without PGPR inoculation improved fruit calcium, magnesium, and potassium contents than the inoculated treatments. ‘Xin Xian La 8 F1’ cultivar had higher yield and plant biomass, fruit potassium, total soluble solids, and total folate contents compared to ‘La Gao F1.’ Agronomic biofortification through the synergy of Bacillus amyloliquefaciens and chili residue produced better yield and folate contents with a trade-off in the mineral contents of the greenhouse-grown long cayenne pepper.

Wheat Leaf Antioxidative Status—Variety-Specific Mechanisms of Zinc Tolerance during Biofortification

In this study, we evaluated the leaf antioxidative responses of three wheat varieties (Srpanjka, Divana, and Simonida) treated with two different forms of zinc (Zn), Zn-sulfate and Zn-EDTA, in concentrations commonly used in agronomic biofortification. Zn concentration was significantly higher in the flag leaves of all three wheat varieties treated with Zn-EDTA compared to control and leaves treated with Zn-sulfate. Both forms of Zn increased malondialdehyde level and total phenolics content in varieties Srpanjka and Divana. Total glutathione content was not affected after the Zn treatment. Zn-sulfate increased the activities of glutathione reductase (GR) and guaiacol peroxidase (GPOD) in both Srpanjka and Divana, while glutathione S-transferase (GST) was only induced in var. Srpanjka. Chelate form of Zn increased the activities of GST and GPOD in both Simonida and Divana. Catalase activity was shown to be less sensitive to Zn treatment and was only induced in var. Srpanjka treated with Zn-EDTA where GPOD activity was not induced. Concentrations of Zn used for agronomic biofortification can induce oxidative stress in wheat leaves. The antioxidative status of wheat leaves could be a good indicator of Zn tolerance, whereas wheat genotype and chemical form of Zn are the most critical factors influencing Zn toxicity.

Agronomic Biofortification of Zinc in Chickpea Varieties in Calcareous Soil

Background: Pulses are wonderful gift of the nature to agriculture. They provide nutrition to human beings and animals as food and feed respectively. Among the pulses, chickpea is an important rabi season crop with high acceptability and wider use in nutritional food basket. A field experiment was carried out on medium black calcareous soil at Junagadh Agricultural University, Junagadh, Gujarat during rabi season 2017-18 under saurastra condition to evaluate agronomic biofortification of zinc in chickpea (Cicer arietinum L.) varieties through seed, soil and foliar application. Methods: The experiment was laid out in factorial randomized block design with three replications. The treatment combinations comprised two varieties viz., GG 1 (V1) and GJG 3 (V2) and six zinc fortification treatments viz., control, seed treatment ZnSO4 @ 3 g kg-1 seed, 0.5% ZnSO4 foliar spray, seed treatment ZnSO4 @ 3g kg-1 seed + 0.5% ZnSO4 foliar spray, soil application ZnSO4 @ 25 kg ha-1 and soil application ZnSO4 @ 25 kg ha-1 + 0.5% ZnSO4 foliar spray. The chickpea was grown with standard package of practices. Result: The results revealed that a significant improvement in 100-seed weight, seed yield, stover yield and biological yield were observed with chickpea variety GJG 3 over GG 1. Significantly higher numbers of pods per plant (45.83) was recorded with variety GG 1. Significantly, chickpea variety GJG 3 was found superior in zinc content and uptake in seed and stover. Under agronomic strategy, zinc fortification through soil application ZnSO4 @ 25 kg ha-1 + 0.5% ZnSO4 foliar spray at flowering and pod filling stages significantly improved yield attribute and yield viz., pods per plant (55.17), seed yield (2288 kg ha-1) and stover yield (3553 kg ha-1) and quality parameters viz., protein content in seed (22.89%) and protein yield (523 kg ha-1), zinc content and uptake in seed and stover (45.98 and 37.51 ppm and 104.87 and 133.35 g ha-1, respectively) over all other zinc biofortification treatments.

Economic Feasibility of Iodine Agronomic Biofortification: A Projective Analysis with Ugandan Vegetable Farmers

Cost–benefit analysis of (iodine) biofortification at farm level is limited in the literature. This study aimed to analyze the economic feasibility of applying iodine-rich fertilizers (agronomic biofortification) to cabbage and cowpea in Northern Uganda. Data on costs and revenues were obtained from a survey of 100 farmers, and benefits that would accrue from using iodine fertilizers were elicited using consumers’ willingness to pay (WTP) for the iodine-biofortified vegetables. The cost–benefit analysis demonstrated iodine agronomic biofortification as a highly profitable effort, generating average benefit–cost ratios (BCRs) of 3.13 and 5.69 for cabbage and cowpea production, respectively, higher than the conventional production practice. However, the projective analysis showed substantive variations of economic gains from iodine biofortification among farmers, possibly due to differences in farming practices and managerial capabilities. For instance, only 74% of cabbage farmers would produce at a BCR above 1 if they were to apply iodine fertilizer. Furthermore, a sensitivity analysis to estimate the effect of subsidizing the cost of iodine fertilizer showed that a higher proportion of farmers would benefit from iodine biofortification. Therefore, as biofortification is considered a health policy intervention targeting the poor and vulnerable, farmers could be supported through fertilizer subsidies to lower the production cost of iodine-biofortified foods and to avoid passing on the price burden to vulnerable consumers.

Agronomic biofortification with zinc on yield, nutritional quality, nutrient uptake and economics of babycorn

The aim of the present study was to investigate the effect of agronomic biofortification with zinc on yield, nutritional quality, nutrient uptake and economics of babycorn under irrigated condition. The observations on yield viz., green cob yield, babycorn yield and green fodder yield and quality parameters (crude protein, total soluble sugars, starch and Zn content) were recorded at harvest stage. The nutrient uptake was analysed at different growth stages and economic indices viz., the total cost of cultivation, gross return, net return and benefit cost ratio were worked out for various zinc fertilization treatments. Increased green cob yield and babycorn yield was recorded higher in soil application of zinc sulphate @ 37.5 kg ha-1 along with a foliar spray of 1.0 % on 20 and 40 DAS. Quality parameters of babycorn viz., crude protein, total soluble sugars, starch and Zn content in corn were significantly increased with soil application of ZnSO4 @ 37.5 kg ha -1 along with a foliar spray of 0.5% at 20 and 40 DAS that recorded higher values of these quality characters. Plant nutrient uptake of N, K and Zn in babycorn was significantly increased with the application of ZnSO4 @ 37.5 kg ha -1 in soil with foliar spray of 0.5% at 20 and 40 DAS. Higher net monetary returns and B: C ratio were obtained with application of ZnSO4@ 37.5 kg ha -1in soil with foliar spray @ 0.5% on 20 and 40 DAS.

Combined Selenium and Zinc Biofortification of Bread-Making Wheat under Mediterranean Conditions

Millions of people worldwide have an inadequate intake of selenium (Se) and zinc (Zn), and agronomic biofortification may minimise these problems. To evaluate the efficacy of combined foliar Se and Zn fertilisation in bread making wheat (Triticum aestivum L.), a two-year field experiment was established in southern Spain under semi-arid Mediterranean conditions, by following a split-split-plot design. The study year (2017/2018, 2018/2019) was considered as the main-plot factor, soil Zn application (50 kg Zn ha−1, nor Zn) as a subplot factor and foliar application (nor Se, 10 g Se ha−1, 8 kg Zn ha−1, 10 g Se ha−1 + 8 kg Zn ha−1) as a sub-subplot factor. The best treatment to increase both Zn and Se concentration in both straw, 12.3- and 2.7-fold respectively, and grain, 1.3- and 4.3-fold respectively, was the combined foliar application of Zn and Se. This combined Zn and Se application also increased on average the yield of grain, main product of this crop, by almost 7%. Therefore, bread-making wheat seems to be a very suitable crop to be used in biofortification programs with Zn and Se to alleviate their deficiency in both, people when using its grain and livestock when using its straw.

Agronomic biofortification of rice and wheat with zinc: A metanalytical study

A diet based on cereals may lack essential mineral elements, among them zinc. The provision of this element in diets can be via supplements, food fortifiers or agronomic biofortification (AB), a practice adopted on a farmer scale. It was carried out different studies in countries with specific local conditions. The meta-analysis allows combining quantitative results from different studies, providing a synthesis of results with high reliability. The objective of this work was to analyze the response of rice (Oryza spp.) and wheat (Triticum spp.) to fertilization with zinc in terms of grain yield and accumulation of this nutrient in the grain. We carried out a systematic review where 16 scientific articles from the last five years were selected, and 179 studies fitted the established criteria. The effect size for Zn application via leaf or soil in rice and wheat compared to the control was calculated using the natural logarithm (lnR) between the ratio of the treatment group and the control group for both variables. Agronomic biofortification with Zn increases grain yield (7%) and zinc content in grains (53%). These results depend on plant species and the fertilization way (via the soil or foliar spray). Agronomic Biofortification may be a valuable strategy to combat malnutrition and guarantee food sovereignty.

Agronomic Biofortification of Significant Cereal Crops with Selenium—A Review

Selenium (Se) is an important micronutrient which is essential for most living organisms and occurs in both organic and inorganic forms in the water system, soils, biomass, and the atmosphere. In addition to being essential for humans and animals, Se is beneficial for plants and is mostly involved in antioxidant activity/response, as well as a growth promoter. Se deficiency in the diet is a global problem, and Se levels in soils generally reflect its presence in food and, thus, availability to humans. Se participates in the antioxidant response mechanisms of the organism, heavy-metal detoxification, and regulation of the reproductive and immune system, as well as ensures the proper function of the thyroid gland. Plants are the main dietary source of Se for humans. Biofortification is a key strategy to increase Se in edible parts of plants. Agronomic biofortification provides an effective route to increase Se content in edible crop products via application of Se-enriched fertilizers to soil or by foliar application. The most common cereals in the human diet are wheat, rice, maize, and barley, making them the most suitable targets for agronomic biofortification. This review focuses on summarizing the most efficient form and method of Se application via agronomic biofortification corroborated by a meta-analysis of the literature reports. In the assessed literature, foliar application showed better results compared to application in soil. The selenate form appears to be the more efficient form of Se for biofortification than selenite in the most common cereals in human diet: wheat, rice, maize, and barley.