Next Generation Nutrition: Genomic and Molecular Breeding Innovations for Iron and Zinc Biofortification in Rice

Global efforts to address malnutrition and hidden hunger, particularly prevalent in low- and middle-income countries, have intensified, with a focus on enhancing the nutritional content of staple crops like rice. Despite serving as a staple for over half of the world's population, rice falls short in meeting daily nutritional requirements, especially for iron(Fe) and zinc(Zn). Genetic resources, such as wild rice species and specific rice varieties, offer promising avenues for enhancing Fe and Zn content. Additionally, molecular breeding approaches have identified key genes and loci associated with Fe and Zn accumulation in rice grains. This review explores the genetic resources and molecular mechanisms underlying Fe and Zn accumulation in rice grains. The functional genomics involved in Fe uptake, transport, and distribution in rice plants have revealed key genes such as OsFRO1, OsIRT1, and OsNAS3. Similarly, genes associated with Zn uptake and translocation, including OsZIP11 and OsNRAMP1, have been identified. Transgenic approaches, leveraging transporter gene families and genome editing technologies, offer promising avenues for enhancing Fe and Zn content in rice grains. Moreover, strategies for reducing phytic acid(PA) content, a known inhibitor of mineral bioavailability, have been explored, including the identification of low-PA mutants and natural variants. The integration of genomic information, including whole-genome resequencing and pan-genome analyses, provides valuable insights into the genetic basis of micronutrient traits and facilitates targeted breeding efforts. Functional genomics studies have elucidated the molecular mechanisms underlying Fe uptake and translocation in rice. Furthermore, transgenic and genome editing techniques have shown promise in enhancing Fe and Zn content in rice grains through the manipulation of key transporter genes. Overall, the integration of multi-omics approaches holds significant promise for addressing global malnutrition and hidden hunger by enhancing the nutritional quality of rice, thereby contributing to improved food and nutritional security worldwide.

Application of Zinc, Iron and Boron Enhances Productivity and Grain Biofortification of Mungbean

Deficiencies of essential vitamins,iron(Fe),and zinc(Zn)affect over one-half of the world’s population.A significant progress has been made to control micronutrient deficiencies through supplementation,but new approaches are needed,especially to reach the rural poor.Agronomic biofortification of pulses with Zn,Fe,and boron(B)offers a pragmatic solution to combat hidden hunger instead of food fortification and supplementation.Moreover,it also has positive effects on crop production as well.Therefore,we conducted three separate field experiments for two consecutive years to evaluate the impact of soil and foliar application of the aforementioned nutrients on the yield and seed biofortification of mungbean.Soil application of Zn at 0,4.125,8.25,Fe at 0,2.5,5.0 and B at 0,0.55,1.1 kg ha−1 was done in the first,second and third experiment,respectively.Foliar application in these experiments was done at 0.3%Zn,0.2%Fe and 0.1%B respectively one week after flowering initiation.Data revealed that soil-applied Zn,Fe and B at 8.25,5.0 and 1.1 kg ha−1,respectively,enhanced the grain yield of mungbean;however,this increase in yield was statistically similar to that recorded with Zn,Fe and B at 4.125,2.5 and 0.55 kg ha−1,respectively.Foliar application of these nutrients at flower initiation significantly enhanced the Zn contents by 28%and 31%,Fe contents by 80%and 78%,while B contents by 98%and 116%over control during 2019 and 2020,respectively.It was concluded from the results that soil application of Zn,Fe,and B enhanced the yield performance of mungbean;while significant improvements in seed Zn,Fe,and B contents were recorded with foliar application of these nutrients.

Foliar application of micronutrients enhances crop stand, yield and the biofortification essential for human health of different wheat cultivars

Globally about half of the world’s population is under micronutrient malnutrition due to poor quality food intake.To overcome this problem,fortification and biofortification techniques are often used.Biofortification is considered a better option than fortification due to the easy control of nutrient deficiencies present in daily food.This field experiment was conducted to evaluate the effects of foliar application of a micronutrient mixture(MNM)consisting of zinc(Zn),iron(Fe),copper(Cu),manganese(Mn)and boron(B)on yield and flour quality of wheat.The results show the effectiveness of foliar feeding for growth and yield parameters,in addition to the enriching of wheat grains with Zn,Cu,Fe,Mn and B.Compared to the control without foliar feeding,foliar application on wheat crop increased tillering ability,spike length,grain yield and the contents of Zn,Cu,Mn,Fe and B by 21,47,22,22 and 25%in wheat flour,respectively.Therefore,foliar feeding of micronutrients could be an effective approach to enrich wheat grains with essential nutrients for correcting malnutrition.

Performance of common buckwheat(Fagopyrum esculentum M.) supplied with selenite or selenate for selenium biofortification in northeastern China

Selenium(Se)deficiency commonly occurs in soils of northeastern China and leads to insufficient Se intake by humans.A two-year field study of Se biofortification of common buckwheat supplied with 40 g Se ha^(-1)as selenite(Se(IV)),selenate(Se(VI)),or a combination(1/2 Se(IV+VI))was performed to investigate Se accumulation and translocation in plants and determine the effects of different forms of Se on the grain yield,biomass production,and Se use efficiency of plants and seeds.Se application increased seed Se concentrations to 47.1–265.1μg kg^(-1).Seed Se concentrations following Se(VI)or 1/2 Se(IV+VI)treatment exceeded 100μg kg^(-1),an amount suitable for crop Se biofortification.Se concentration in shoots and roots decreased with plant development,and Se translocation from root to shoot in Se(IV)-treated plants was lower than that in plants treated with 1/2 Se(IV+VI)and Se(VI).Both grain yield and biomass production increased under 1/2 Se(IV+VI)treatment,with grain yields reaching 1663.8 and 1558.5 kg ha^(-1)in 2015 and 2016,respectively,reflecting increases of 11.0% and 10.3% over those without Se application.The Se use efficiency of seeds and plants under Se(VI)treatment was significantly higher than those under 1/2 Se(IV+VI)and Se(IV)treatments.Thus,application of selenate could result in higher Se accumulation in buckwheat seeds than application of the other Se sources,but the combined application of selenate and selenite might be an alternative approach for improving buckwheat grain yield by Se biofortification in northeastern China.

Effects of Different Selenium Application Methods on Wheat (Triticum aestivum L.) Biofortification and Nutritional Quality

Mineral nutrient malnutrition,especially deficiency in selenium(Se),affects the health of approximately 1 billion people worldwide.Wheat,a staple food crop,plays an important role in producing Se-enriched foodstuffs to increase the Se intake of humans.This study aimed to evaluate the effects of different Se application methods on grain yield and nutritional quality,grain Se absorption and accumulation,as well as 14 other trace elements concentrations in wheat grains.A sand culture experiment was conducted via a completely randomized 3×2×1 factorial scheme(three Se levels×two methods of Se application,foliar or soil×one Se sources,selenite),with two wheat cultivars(Guizi No.1,Chinese Spring).The results showed that both foliar Se and soil Se application methods had effects on wheat pollination.Foliar Se application resulted in early flowering of wheat,while soil Se application caused early flowering of wheat at low Se levels(5 mg kg^(−1))and delayed wheat flowering at high selenium levels(10 mg kg^(−1)),respectively.For trace elements,human essential trace elements(Fe,Zn,Mn,Cu,Cr,Mo,Co and Ni)concentrations in wheat grains were dependent of Se applica-tion methods and wheat cultivars.However,toxic trace elements(Cd,Pb,Hg,As,Li and Al)concentrations can be decreased by both methods,indicating a possible antagonistic effect.Moreover,both methods increased Se concentrations,and improved grain yield and nutritional quality,while the foliar application was better than soil.Accordingly,this study provided useful information concerning nutritional biofortification of wheat,indicating that it is feasible to apply Se to conduct Se biofortification,inhibit the heavy metal elements concentrations and improve yield and quality in crops,which caused human health benefits.

Inaccuracies in Phytic Acid Measurement: Implications for Mineral Biofortification and Bioavailability

Biofortification of commonly eaten staple food crops with essential mineral micronutrients is a potential sustainable solution to global micronutrient malnutrition. Because phytic acid (PA;1,2,3,4,5,6-hexakis myo-inositol) reduces mineral micronutrient bioavailability, reduction of PA levels could increase the bioavailability of biofortified iron (Fe), zinc (Zn), calcium (Ca), and magnesium (Mg). PA is viewed as an anti-nutrient, yet PA and other inositol phosphates have also demonstrated positive health benefits. Phytic acid analysis in the agricultural, food, and nutritional sciences is typically carried out by colorimetry and chromatographic techniques. In addition, advanced techniques such as nuclear magnetic resonance and synchrotron X-ray absorption spectroscopy have also been used in phytic acid analysis. The colorimetric analysis may overestimate PA levels and synchrotron X-ray absorption techniques may not detect very low levels of inositol phosphates. This short communication discusses the advantages and disadvantages of each widely used phytic acid analysis method, and suggests high performance anion exchange (HPAE) chromatography with conductivity detection (CD) based analysis can achieve greater accuracy for the identification and quantification of inositol phosphates. Accurate characterization and quantification of PA and inositol phosphates will inform PA reduction and biofortification efforts, allowing retention of the benefits of non-phytic inositol phosphates for both plants and humans.

Can Improve Iron Biofortification Antioxidant Response,Yield and Nutritional Quality in Green Bean?

The aim of this study was to evaluate the effect of iron biofortification on antioxidant response, yield and nutritional qualityof green bean (Phaseolus vulgaris L.) under greenhouse conditions. Fe was applied using two forms (FeSO4 and Fe-EDDHA) at four doses of application (0, 25, 50 and 100 μm) added under a hydroponic system, and were tested over a period of 40 days. The Fe content was assessed in seeds, as well as the activity of antioxidant enzymes, production of H2O2, yield and nutritional quality. The results being obtained indicated that the accumulation of Fe in bean seeds enhanced with the application of Fe-EDDHA at the dose of 25 μm. This demonstrated that low Fe application dose was enough to increase Fe levels in seeds of common bean. In addition, Fe-EDDHA application form at 50 μmol was the best treatment to improve crop yield. Respect to antioxidant system, chelated form of Fe (Fe-EDDHA) was more effective in the activation of antioxidant enzymes (CAT, SOD and GSH-PX), and a lower content of H2O2 in green bean seeds. Finally, to raise the Fe concentration in bean under biofortification program was a promising strategy in cropping systems in order to increase the ingestion of iron and antioxidant capacity in the general population and provided the benefits that this element offered in human health.

Genetics of carotenoids for provitamin A biofortification in tropical-adapted maize

Yellow maize contains high levels of β-carotene(βC), making it an important crop for combating vitamin A deficiency through biofortification. In this study, nine maize inbred lines were selected at random from 31 provitamin A(PVA) maize inbred lines and crossed in a partial diallel mating design to develop 36 crosses. The crosses were evaluated in the field in two locations(Samaru and Kerawa) and their seed carotenoid content were determined by high-performance liquid chromatography. The modes of gene action, heritability, and correlations between agronomic traits and carotenoid content were estimated. Additive genetic variances(σ~2a) were lower than non-additive genetic variances(σ~2d) for all the carotenoids, plant height(PH), and grain yield(GY), suggesting a preponderance of non-additive gene action. Broad-sense heritability(H^2) was high(H^2> 60%) for zeaxanthin,days to anthesis, and PH, moderate(30% < H^2< 60%) for lutein and GY, and low(H^2< 30%)for alpha carotene, beta cryptoxanthin, βC, and PVA. Genetic advance as a percentage of mean, considered with H^2, also suggests a preponderance of non-additive gene action for PVA carotenoids. Hybrid variety development is thus an appropriate approach to improving grain yield and PVA. GY showed no significant genotypic correlations with carotenoid content, suggesting that these traits can be improved concurrently. Thus, there is ample scope for improvement of PVA and GY in the sample of tropical-adapted maize.

Advocacy and Use of Advocates as a Quick Win in Scaling Up Biofortification in Nigeria: The Case of Building Nutritious Food Basket (BNFB) Project

The Building Nutritious Food Baskets (BNFB) Project explored advocacy and the use of advocates as a model strategy for scaling up biofortification in Nigeria during its three-year implementation. In addition to its direct advocacy efforts, the BNFB project identified and selected key personnel across disciplines, gender and sectors, based on some selected criteria, as Advocates to support the scaling up of biofortification by raise of investments, resource mobilization, the inclusion of biofortification in relevant policy documents, strategies and plans of action. To realize these, the selected 32 Advocates were empowered to mainstream biofortification into their existing and/or potential programs/projects, as well as create awareness and demand for biofortified crops within their spheres of influence. Training and retreats were organized for the Advocates to strengthen their capacities in advocacy and promotion of biofortification and biofortified crops, while a social platform was launched to share opportunities, experiences and address issues around biofortification within the Advocates. As a result of these efforts, biofortification was included in three key national policies, strategies/plans of actions with resource allocation, and investments, over USD3 million were raised for biofortification. The Federal Government of Nigeria and some external governments became committed to biofortification programs while biofortified crops were mainstreamed in at least two national programs in Nigeria. Biofortified crops were included in the Home-Grown School Feeding Program of two states. The use of Advocates proved to be a resultful strategy in the biofortification scaling up model of BNFB as the advocates, upon being trained, looked out within their sectors and disciplines to mainstream biofortification into their programs. They gave timely information on potential opportunities to follow up with in influencing favorable policies;they mobilized resources nationally, regionally and locally;they facilitated wider coverage of biofortification within a short time. However, the influence of the Advocates was limited to their number and locations;thus, for a quick win in Nigeria, there is a need to raise advocates in all the 36 states of the country while giving equal priority to national and state level advocacy. As a lesson, to engender adoption of biofortification, participation/leveraging on existing programs in advocacy works faster and easier than starting afresh in Nigeria.

Linking Agriculture with Health through Genetic and Agronomic Biofortification

Malnutrition and associated health problems are partly related to minerals and vitamins deficiencies where anemia and stunting are the major diseases affecting nearly half of pregnant women and about 20% children under age of five, respectively in developing countries. Despite the significant progress made in recent decades, prevalence of stunting in Ethiopia remains high (44%, among children) that necessitate the country yet to make significant investment in nutrition and health. Strategies designed to overcome the problem range from micronutrient rich foods supplement to complementing foods with vegetables and fruits. However, such strategies are expensive as well as not sustainable to reach the poor households of developing countries. The persistence of the problem calls for agriculture based alternative solutions such as agronomic biofortification and micronutrients biofortification through plant breeding. Utilization of crop wild relatives, local landraces and old cultivars are proved to contain sufficient grain micronutrients and their utilization in breeding programs can solve the deficiency of micronutrients such as zinc and iron. Similarly, agronomic biofortification could improve grain Zn and Fe contents in several folds. Application methods and crop developmental stages during which fortification applied significantly determine the efficiency of fortification. Foliar application at heading and milking stages could accumulate very high Zn and Fe in cereal grains. The synergistic effect of genetic and agronomic fortification could also be utilized to produce Zn and Fe rich food crops. Hence, linking agriculture with nutrition and health could offer equitable, effective, sustainable and cheap solutions to micronutrients malnutrition and their deficiency related health problems.

Open avenues for carotenoid biofortification of plant tissues

Plant carotenoids are plastidial isoprenoids that function as photoprotectants,pigments,and precursors of apocarotenoids such as the hormones abscisic acid and strigolactones.Humans do not produce carotenoids but need to obtain them from their diet as precursors of retinoids,including vitamin A.Carotenoids also provide numerous other health benefits.Multiple attempts to improve the carotenoid profile of different crops have been carried out by manipulating carotenoid biosynthesis,degradation,and/or storage.Here,we will focus on open questions and emerging subjects related to the use of biotechnology for carotenoid biofortification.After impressive achievements,new efforts should be directed to extend the use of genome-editing technologies to overcome regulatory constraints and improve consumer acceptance of the carotenoid-enriched products.Another challenge is to prevent off-target effects like those resulting from altered hormone levels and metabolic homeostasis.Research on biofortification of green tissues should also look for new ways to deal with the negative impact that altered carotenoid contents may have on photosynthesis.Once a carotenoid-enriched product has been obtained,additional effort should be devoted to confirming that carotenoid intake from the engineered food is also improved.Thiswork involves ensuring post-harvest stability and assessing bioaccessibility of the biofortified product to confirm that release of carotenoids from the food matrix has not been negatively affected.Successfully addressing these challenges will ensure new milestones in carotenoid biotechnology and biofortification.

Enhanced protective effect of selenium-biofortified peptide RYNA(Se)MNDYT compared with its native peptide RYNAMNDYT in lipopolysaccharide-injured murine gut microbiota

Selenopeptides may be a valuable bioactive compound to promote gut microbiota-targeted therapeutic methods for intestinal disease and hepatopathy.However,limited information is available on the utilization of selenopeptides by gut microbiota,especially Selenium(Se)function.For this purpose,the present study aimed to investigate the protective effect of selenopeptide(RYNA(Se)MNDYT,Se-P2,purity of≥95%)and its original peptide(RYNAMNDYT,P2,purity of≥95%)in vivo by the microbiota-metabolite axis and further analyze the potential contribution of Se biofortification to Se-P2 bioactivity.The results showed that Se-P2 exhibits a higher protective effect on lipopolysaccharide(LPS)-induced inflammation than P2,including pathology of the colon and liver,which suggested that the bioactivity of P2 was promoted by the organic combination of Se.Notably,gut microbiota composition tended to be a healthy structure by Se-P2 pretreatment in LPS-injured mice,which had a positive effect on LPS-induced gut microbiota dysbacteriosis.Additionally,only Se-P2 promoted an increase in the relative abundance of Lactobacillus,Alistipes,and Roseburia and a decrease in the relative abundance of Akkermansia,Erysipelatoclostridium,and Bacteroides in LPS-injured mice.The changes in gut microbiota were obviously correlated with the changes in metabolites and affected the metabolic pathways of valine,leucine,isoleucine,phenylalanine,tyrosine,and tryptophan biosynthesis and phenylalanine metabolism.This may be one of the key reasons for Se-P2 to exert bioactivity through the microbiota-metabolite axis.Furthermore,Se-biofortification in Se-enriched Cordyceps militaris affected the parental proteins of Se-P2 to modulate mitogen-activated protein kinase,GPI anchored protein,and carbohydrate metabolism,translation,folding,sorting and degradation,which may contribute to the bioactivity of Se-P2.Our study provides information on the effect of Se on selenopeptides in vivo,which further promotes the prospective applications of selenopeptides as dietary supplements.

Synthesis of betanin by expression of the core betalain biosynthetic pathway in carrot

Betalain has received increased attention because of its high nutritional value and crucial physiological functions.Based on the elucidation of its core biosynthetic pathway,betalain can be produced in additional plants by metabolic engineering.Synthesis of betalain in carrot(Daucus carota L.)can improve its nutritional quality and economic value by extracting betalain from the fleshy root,non-edible part,and processing residue of carrot.In this study,two different constructs,namely,pYB:mCD(AomelOS,BvCYP76AD1S,and BvDODA1S)and p YB:CDD(BvCYP76AD1S,BvDODA1S,and MjcDOPA5GTS),were introduced into carrot for betanin synthesis by Agrobacterium-mediated transformation.Betanin can be synthetized in both transgenic calli,and p YB:m CD-transgenic callus can be used to produce betacyanin by suspension culture.However,pYB:mCD-transgenic seedlings can synthetize betanin only by tyrosine feeding.The p YB:CDD-transgenic lines can synthetize betanin in whole plants.The betanin content in fleshy root of pYB:CDD-transgenic carrot was(63.4±9)μg·g^(-1)fresh weight according to quantitative analysis.These betanin-producing carrot plant materials can be used to synthesize betanin for industrial application or consumption as dietary sources.

Effect of Biostimulants Based on Natural Products on the Growth and Nutritional Value of Bean (Phaseolus vulgaris L.)

Beans (Phaseolus vulgaris L.) are widely grown in Cameroon and play a key role in the fight against food insecurity, malnutrition and poverty. However, its cultivation encounters problems due to abiotic and biotic stresses, which leads to the use of synthetic fertilizers and pesticides, which cause significant damage to the environment and human health due to the presence of synthetics residues in the seeds, pods and in the leaves that are eaten. Promoting the use of natural products is becoming a necessity for organic and eco-responsible agriculture that limits contamination problems and improves people’s purchasing power. This study aims to assess the effect of biostimulants based on natural products on the growth and nutritional value of common bean (Phaseolus vulgaris L.). Bean seedlings from white variety (MEX-142) and red variety (DOR-701) were treated every seven days in the field from their pre-emergence, emergence and growth to their maturation under a randomized block experimental design. Six treatments and three repetitions with the biostimulants based on natural products and controls were thus performed and the agromorphological parameters were measured. After 120 days, the contents of growth biomarkers and defense-related enzymes were evaluated in leaves, while the contents of macromolecules, minerals and antinutrients were evaluated in seeds. These biostimulants significantly increased (P P < 0.0001) of antinutrients including oxalates, phytates, tannins and saponins in seeds compared to controls (T+ and T−). Treatment with biostimulants, in particular BS4, improves the performance of bean plants in the field as well as the biofortification of seeds regardless of the variety.

Folate Biofortification of Potato by Tuber-Specific Expression of Four Folate Biosynthesis Genes

Insufficient dietary intake of micronutHents, known as ＂hidden hunger＂, is a devastating global burden, affecting two billion people. Deficiency of folates （vitamin B9）, which are known to play a central role in Cl metabolism, causes birth defects in at least a quarter million people annually. Biofortification to enhance the level of naturally occurring folates in crop plants, proves to be an efficient and cost-effective tool in fighting folate deficiency. Previously, introduction of folate biosynthesis genes GTPCHI andADCS, proven to be a successful biofortification strategy in rice and tomato, turned out to be insufficient to adequately increase folate levels in potato tubers. Here, we provide a proof of concept that additional introduction of HPPK/DHPS and/or FPGS, downstream genes in mitochonddal folate biosynthesis, enables augmenta- tion of folates to satisfactory levels （12-fold） and ensures folate stability upon long-term storage of tubers. In conclusion, this engineering strategy can serve as a model in the creation of folate-accumulating potato cultivars, readily applicable in potato-consuming populations suffedng from folate deficiency.

Zinc in plants:Integrating homeostasis and biofortification

Zinc plays many essential roles in life.As a strong Lewis acid that lacks redox activity under environ-mental and cellular conditions,the Zn2+cation is central in determining protein structure and catalytic function of nearly 10%of most eukaryotic proteomes.While specific functions of zinc have been elucidated at a molecular level in a number of plant proteins,wider issues abound with respect to the acquisition and distribution of zinc by plants.An important challenge is to understand how plants balance between Zn supply in soil and their own nutritional requirement for zinc,particularly where edaphic factors lead to a lack of bioavailable zinc or,conversely,an excess of zinc that bears a major risk of phyto-toxicity.Plants are the ultimate source of zinc in the human diet,and human Zn deficiency accounts for over 400000 deaths annually.Here,we review the current understanding of zinc homeostasis in plants from the molecular and physiological perspectives.We provide an overview of approaches pursued so far in Zn biofortification of crops.Finally,we outline a"push-pull"model of zinc nutrition in plants as a simplifying concept.In summary,this review discusses avenues that can potentially deliver wider bene-fits for both plant and human Zn nutrition.

Regulation of Plant Vitamin Metabolism:Backbone of Biofortification for the Alleviation of Hidden Hunger

Micronutrient deficiencies include shortages of vitamins and minerals.They affect billions of people and are associated with long-range effects on health,learning ability,and huge economic losses.Biofortification of multiple micronutrients can play an important role in combating malnutrition.The challenge,however,is to balance plant growth with nutrient requirements for humans.Here,we summarize the major progress about vitamin biosynthesis and its response to the changing environment.We discuss the interactions among vitamins as well as possible strategies for vitamin biofortification.Finally,we propose to integrate new breeding technologies with metabolic pathway modification to facilitate the biofortification of crops,thereby alleviating the hidden hunger of target populations.

Biofortification of iron and zinc in rice and wheat

Iron and zinc are critical micronutrients for human health.Approximately two billion people suffer from iron and zinc deficiencies worldwide,most of whom rely on rice(Oryza sativa)and wheat(Triticum aestivum)as staple foods.Therefore,biofortifying rice and wheat with iron and zinc is an important and economical approach to ameliorate these nutritional deficiencies.In this review,we provide a brief introduction to iron and zinc uptake,translocation,storage,and signaling pathways in rice and wheat.We then discuss current progress in efforts to biofortify rice and wheat with iron and zinc.Finally,we provide future perspectives for the biofortification of rice and wheat with iron and zinc.

Molecular processes in iron and zinc homeostasis and their modulation for biofortification in rice

More than a billion people suffer from iron or zinc deficiencies globally. Rice(Oryza sativa L.) iron and zinc biofortification; i.e., intrinsic iron and zinc enrichment of rice grains, is considered the most effective way to tackle these deficiencies. However, rice iron biofortification, by means of conventional breeding, proves difficult due to lack of sufficient genetic variation. Meanwhile,genetic engineering has led to a significant increase in the iron concentration along with zinc concentration in rice grains. The design of impactful genetic engineering biofortification strategies relies upon vast scientific knowledge of precise functions of different genes involved in iron and zinc uptake, translocation and storage. In this review, we present an overview of molecular processes controlling iron and zinc homeostasis in rice. Further,the genetic engineering approaches adopted so far to increase the iron and zinc concentrations in polished rice grains are discussed in detail, highlighting the limitations and/or success of individual strategies. Recent insight suggests that a few genetic engineering strategies are commonly utilized for elevating iron and zinc concentrations in different genetic backgrounds, and thus, it is of great importance to accumulate scientific evidence for diverse genetic engineering strategies to expand the pool of options for biofortifying farmer-preferred cultivars.

Mechanisms underlying cereal/legume intercropping as nature-based biofortification: A review

The deficiencies of micronutrients known as hidden hunger are severely affecting more than one-half of the world’s population, which is highly related to low bioavailability of micronutrients, poor quality diets, and consumption of cereal-based foods in developing countries. Although numerous experiments proved biofortification as a paramount approach for improving hidden hunger around the world, its effectiveness is highly related to various soil factors, climate conditions, and the adoption rates of biofortified crops. Furthermore, agronomic biofortification may result in the sedimentation of heavy metals in the soil that pose another detrimental effect on plants and human health. In response to these challenges, several studies suggested intercropping as one of the feasible, eco-friendly, low-cost, and short-term approaches for improving the nutritional quality and yield of crops sustainable way. Besides, it is the cornerstone of climate-smart agriculture and the holistic solution for the most vulnerable area to solve malnutrition that disturbs human healthy catastrophically. Nevertheless, there is meager information on mechanisms and processes related to soil-plant interspecific interactions that lead to an increment of nutrients bioavailability to tackle the crisis of micronutrient deficiency in a nature-based solution. In this regard, this review tempted to (1) explore mechanisms and processes that can favor the bioavailability of Zn, Fe, P, etc. in soil and edible parts of crops, (2) synthesize available information on the benefits and synergic role of the intercropping system in food and nutritional security, and (3) outline the bottlenecks influencing the effectiveness of biofortification for promoting sustainable agriculture in sub-Saharan Africa (SSA). Based on this review SSA countries are malnourished due to limited access to diverse diets, supplementation, and commercially fortified food;hence, I suggest integrated research by agronomists, plant nutritionists, and agroecologist to intensify and utilize intercropping systems as biofortification sustainably alleviating micronutrient deficiencies.