Molecular Breeding for Nutritionally Enriched Maize: Status and Prospects

Germination-induced modifications of starch structure, flour-processing characteristics, and in vitro digestive properties in maize

Current research on maize germination suffers from long sampling intervals, and the relationship between the starch structure and the processing properties of flour in maize is still unclear. This study observed the effect of germination on the structure and composition of maize starch and the processing properties of maize flour over a 72 h period using a short interval sampling method. At 36 h, the short-range ordered structure, crystallinity, and enthalpy of starch reached the highest values of 1.02, 34.30%, and 9.90 J/g, respectively. At 72 h, the ratios of rapidly-digested starch (RDS) and slowly-digested starch (SDS) enhanced to 29.37% and 28.97%; the RS content reduced to 35.37%; and the flow properties of the starch were improved. This study enhances the understanding of the effects of germination on the processing properties of maize starch and flour, determines the appropriate application, and recommends the use of germination in the food industry.

Biofortification as a solution for addressing nutrient deficiencies and malnutrition

Malnutrition, defined as both undernutrition and overnutrition, is a major global health concern affecting millions of people. One possible way to address nutrient deficiency and combat malnutrition is through biofortification. A comprehensive review of the literature was conducted to explore the current state of biofortification research, including techniques, applications, effectiveness and challenges. Biofortification is a promising strategy for enhancing the nutritional condition of at-risk populations. Biofortified varieties of basic crops, including rice, wheat, maize and beans, with elevated amounts of vital micronutrients, such as iron, zinc, vitamin A and vitamin C, have been successfully developed using conventional and advanced technologies. Additionally, the ability to specifically modify crop genomes to improve their nutritional profiles has been made possible by recent developments in genetic engineering, such as CRISPR-Cas9 technology. The health conditions of people have been shown to improve and nutrient deficiencies were reduced when biofortified crops were grown. Particularly in environments with limited resources, biofortification showed considerable promise as a long-term and economical solution to nutrient shortages and malnutrition. To fully exploit the potential of biofortified crops to enhance public health and global nutrition, issues such as consumer acceptance, regulatory permitting and production and distribution scaling up need to be resolved. Collaboration among governments, researchers, non-governmental organizations and the private sector is essential to overcome these challenges and promote the widespread adoption of biofortification as a key part of global food security and nutrition strategies.

Analysis of nutritional composition in opaque2- and crtRB1-based single- and double-biofortified super sweet corn

Sweet corn has emerged as a favorite food item worldwide owing to its kernel sweetness. However, traditional sweet corn cultivars are poor in provitamin-A (proA) and essential amino acids, viz., lysine and tryptophan. So far, no sweet corn hybrid with high nutritional qualities has been commercialized elsewhere. Here, we analyzed accumulation of provitamin-A (proA), lysine, and tryptophan in a set of mutant versions of (i) crtRB1-, (ii) o2-, and (iii) crtRB1 + o2-based sweet corn inbreds and hybrids with (iv) traditional sweet corn (wild-type: O2 + CrtRB1). The crtRB1- and crtRB1 + o2-based genotypes possessed significantly higher proA (17.31 ppm) over traditional sweet corn (2.83 ppm), while o2- and crtRB1 + o2-based genotypes possessed significantly higher lysine (0.345%) and tryptophan (0.080%) over traditional sweet corn (lysine 0.169%, tryptophan 0.036%). Late sowing favored high kernel lysine, proA, and green cob yield among hybrids. Sweetness (17.87%) among the improved inbreds and hybrids was comparable to the original sweetcorn genotypes (17.84%). Among the four genotypic classes, crtRB1 + o2-based improved genotypes showed stronger association among traits over genotypes with o2 and crtRB1 genes alone. Significant association was observed among (i) proA and BC (r = 0.99), (ii) proA and BCX (r = 0.93), (iii) lysine and tryptophan (r = 0.99), and (iv) green cob yield with fodder yield (r = 0.73) in sweet corn hybrids. The study demonstrated that combining crtRB1 and o2 genes did not pose any negative impact on nutritional, yield, and agronomic performance. Sweet corn with crtRB1 + o2 assumes significance for alleviating malnutrition through sustainable and cost-effective approach.

Investigating genomic prediction strategies for grain carotenoid traits in a tropical/subtropical maize panel

Vitamin A deficiency remains prevalent on a global scale, including in regions where maize constitutes a high percentage of human diets. One solution for alleviating this deficiency has been to increase grain concentrations of provitamin A carotenoids in maize (Zea mays ssp. mays L.)-an example of biofortification. The International Maize and Wheat Improvement Center (CIMMYT) developed a Carotenoid Association Mapping panel of 380 inbred lines adapted to tropical and subtropical environments that have varying grain concentrations of provitamin A and other health-beneficial carotenoids. Several major genes have been identified for these traits, 2 of which have particularly been leveraged in marker-assisted selection. This project assesses the predictive ability of several genomic prediction strategies for maize grain carotenoid traits within and between 4 environments in Mexico. Ridge Regression-Best Linear Unbiased Prediction, Elastic Net, and Reproducing Kernel Hilbert Spaces had high predictive abilities for all tested traits (β-carotene, β-cryptoxanthin, provitamin A, lutein, and zeaxanthin) and outperformed Least Absolute Shrinkage and Selection Operator. Furthermore, predictive abilities were higher when using genome-wide markers rather than only the markers proximal to 2 or 13 genes. These findings suggest that genomic prediction models using genome-wide markers (and assuming equal variance of marker effects) are worthwhile for these traits even though key genes have already been identified, especially if breeding for additional grain carotenoid traits alongside β-carotene. Predictive ability was maintained for all traits except lutein in between-environment prediction. The TASSEL (Trait Analysis by aSSociation, Evolution, and Linkage) Genomic Selection plugin performed as well as other more computationally intensive methods for within-environment prediction. The findings observed herein indicate the utility of genomic prediction methods for these traits and could inform their resource-efficient implementation in biofortification breeding programs.

In vitro regeneration of triploid from mature endosperm culture of Passiflora edulis "Mantianxing"

The regeneration of shoots from endosperm tissue is a highly effective method to obtain triploid plants. In this study, we elucidated the establishment of an in vitro regeneration system from endosperm culture for the production of Passiflora edulis "Mantianxing." The highest callus induction rate (83.33%) was obtained on the media supplemented with 1.0 mg/L TDZ. Meanwhile, the MS medium containing 1.0 mg/L 6-BA and 0.4 mg/L IBA gave the optimum 75% shoot bud induction. Chromosome analysis revealed that the chromosomal count of P. edulis "Mantianxing" regenerated from endosperm tissues was 27 (2n = 3x = 27), which indicated that shoots regenerated from endosperm tissues were triploids. Triploid P. edulis had more drought resistance than diploid plants. Our study provided a method for breeding of passion fruit by means of a stable and reproducible regeneration system from endosperm culture, leading to the generation of triploid plants.

Multilocus functional characterization of indigenous and exotic inbreds for dgat1-2, fatb, ge2 and wri1a genes affecting kernel oil and fatty acid profile in maize

Demand for maize oil is progressively increasing due to its diverse industrial applications, aside from its primary role in human nutrition and animal feed. Oil content and composition are two crucial determinants of maize oil in the international market. As kernel oil in maize is a complex quantitative trait, improving this trait presents a challenge for plant breeders and biotechnologists. Here, we characterized a set of 292 diverse maize inbreds of both indigenous and exotic origin by exploiting functional polymorphism of the dgat1-2, fatb, ge2, and wri1a genes governing kernel oil in maize. Genotyping using gene-based functional markers revealed a lower frequencies of dgat1-2 (0.15) and fatb (0.12) mutant alleles and a higher frequencies of wild-type alleles (Dgat1-2: 0.85; fatB: 0.88). The favorable wri1a allele was conserved across genotypes, while its wild-type allele (WRI1a) was not detected. In contrast, none of the genotypes possessed the ge2 favorable allele. The frequency of favorable alleles of both dgat1-2 and fatb decreased to 0.03 when considered together. Furthermore, pairwise protein-protein interactions among target gene products were conducted to understand the effect of one protein on another and their responses to kernel oil through functional enrichments. Thus, the identified maize genotypes with dgat1-2, fatb, and wri1a favourable alleles, along with insights gained through the protein-protein association network, serve as prominent and unique genetic resources for high-oil maize breeding programs. This is the first comprehensive report on the functional characterization of diverse genotypes at the molecular and protein levels.

Maize hydroxycinnamic acids: unveiling their role in stress resilience and human health

Maize production is pivotal in ensuring food security, particularly in developing countries. However, the crop encounters multiple challenges stemming from climatic changes that adversely affect its yield, including biotic and abiotic stresses during production and storage. A promising strategy for enhancing maize resilience to these challenges involves modulating its hydroxycinnamic acid amides (HCAAs) content. HCAAs are secondary metabolites present in plants that are essential in developmental processes, substantially contributing to defense mechanisms against environmental stressors, pests, and pathogens, and exhibiting beneficial effects on human health. This mini-review aims to provide a comprehensive overview of HCAAs in maize, including their biosynthesis, functions, distribution, and health potential applications.

Mutant crtRB1 gene negates the unfavourable effects of opaque2 gene on germination and seed vigour among shrunken2-based biofortified sweet corn genotypes

Sweet corn is one of the most popular vegetables worldwide. However, traditional shrunken2 (sh2 )-based sweet corn varieties are poor in nutritional quality. Here, we analysed the effect of (1) β-carotene hydroxylase1 (crtRB1 ), (2) opaque2 (o2 ) and (3) o2+crtRB1 genes on nutritional quality, germination, seed vigour and physico-biochemical traits in a set of 27 biofortified sh2 -based sweet corn inbreds. The biofortified sweet corn inbreds recorded significantly higher concentrations of proA (16.47μg g-1 ), lysine (0.36%) and tryptophan (0.09%) over original inbreds (proA: 3.14μg g-1 , lysine: 0.18%, tryptophan: 0.04%). The crtRB1 -based inbreds had the lowest electrical conductivity (EC), whereas o2 -based inbreds possessed the highest EC. The o2 +crtRB1 -based inbreds showed similar EC to the original inbreds. Interestingly, o2 -based inbreds also had the lowest germination and seed vigour compared to original inbreds, whereas crtRB1 and o2 +crtRB1 introgressed sweet corn inbreds showed similar germination and seed vigour traits to their original versions. This suggested that the negative effect of o2 on germination, seed vigour and EC is nullified by crtRB1 in the double mutant sweet corn. Overall, o2 +crtRB1 -based sweet corn inbreds were found the most desirable over crtRB1 - and o2 -based inbreds alone.

Genetic control of grain amino acid composition in a UK soft wheat mapping population

Wheat (Triticum aestivum L.) is a major source of nutrients for populations across the globe, but the amino acid composition of wheat grain does not provide optimal nutrition. The nutritional value of wheat grain is limited by low concentrations of lysine (the most limiting essential amino acid) and high concentrations of free asparagine (precursor to the processing contaminant acrylamide). There are currently few available solutions for asparagine reduction and lysine biofortification through breeding. In this study, we investigated the genetic architecture controlling grain free amino acid composition and its relationship to other traits in a Robigus × Claire doubled haploid population. Multivariate analysis of amino acids and other traits showed that the two groups are largely independent of one another, with the largest effect on amino acids being from the environment. Linkage analysis of the population allowed identification of quantitative trait loci (QTL) controlling free amino acids and other traits, and this was compared against genomic prediction methods. Following identification of a QTL controlling free lysine content, wheat pangenome resources facilitated analysis of candidate genes in this region of the genome. These findings can be used to select appropriate strategies for lysine biofortification and free asparagine reduction in wheat breeding programs.

Effects of planting date, environments and their interaction on grain yield and quality traits of maize hybrids

Maize is one of the most important staple food crops for most low-income households in the Southern African region. Erratic and inconsistent rainfall distribution across maize-growing areas is a major threat to maize production. Late rains in recent years have forced farmers to plant later than the optimal planting dates, leading to poor maize quality being reported by industry, which raised the question of the influence of later planting dates on grain yield and quality traits of maize. Three yellow and three white maize hybrids were evaluated at three planting dates in three different production environments for three consecutive seasons using a randomized complete block design with three replications. The second and third planting dates caused a significant yield decrease of 23.37 % and 53.73 % from the first planting date across environments, respectively. Planting date three was associated with decreased grain yield, starch content, and increased protein but no significant change in fat and fiber content. Some hybrids yielded relatively well at all planting dates. In conclusion, the early planting date was the most suitable for maize grain yield and starch production in the maize-growing areas of the country. However, planting in January should be avoided at all costs, as it leads to very low yield and poor grain quality.

Low expression of lipoxygenase 3 (LOX3) enhances the retention of kernel tocopherols in maize during storage

BACKGROUND

Deficiency of vitamin E results in several neurological and age-related disorders in humans. Utilization of maize mutants with favourable vte4-allele led to the development of several α-tocopherol (vitamin E) rich (16-19 µg/g) maize hybrids worldwide. However, the degradation of tocopherols during post-harvest storage substantially affects the efficacy of these genotypes.

METHODS AND RESULTS

We studied the role of lipoxygenase enzyme and Lipoxygenase 3 (LOX3) gene on the degradation of tocopherols at monthly intervals under traditional storage up to six months in two vte4-based contrasting-tocopherol retention maize inbreds viz. HKI323-PVE and HKI193-1-PVE. The analysis revealed significant degradation of tocopherols across storage intervals in both the inbreds. Lower retention of α-tocopherol was noticed in HKI193-1-PVE. HKI323-PVE with the higher retention of α-tocopherol showed lower lipoxygenase activity throughout the storage intervals. LOX3 gene expression was higher (~ 1.5-fold) in HKI193-1-PVE compared to HKI323-PVE across the storage intervals. Both lipoxygenase activity and LOX3 expression peaked at 120 days after storage (DAS) in both genotypes. Further, a similar trend was observed for LOX3 expression and lipoxygenase activity. The α-tocopherol exhibited a significantly negative correlation with lipoxygenase enzyme and expression of LOX3 across the storage intervals.

CONCLUSIONS

HKI323-PVE with high tocopherol retention, low -lipoxygenase activity, and -LOX3 gene expression can act as a potential donor in the vitamin E biofortification program. Protein-protein association network analysis also indicated the independent effect of vte4 and LOX genes. This is the first comprehensive report analyzing the expression of the LOX3 gene and deciphering its vital role in the retention of α-tocopherol in biofortified maize varieties under traditional storage.

Enhancement of nutritional quality in maize kernel through marker-assisted breeding for vte4, crtRB1, and opaque2 genes

Traditional maize is poor in vitamin-E [α-tocopherol (α-T): 6-8 ppm], vitamin-A [provitamin-A (proA): 1-2ppm], lysine (0.150-0.2-50%), and tryptophan (0.030-0.040%). Here, we combined favourable alleles of vte4, crtRB1, and opaque2 (o2) genes in the parents of maize hybrids, viz., APQH-10 (PMI-PV-9 × PMI-PV-14) and APQH-11 (PMI-PV-9 × PMI-PV-15) using molecular breeding. Gene-specific markers were successfully used to select vte4, crtRB1, and o2 in BC1F1, BC2F1, and BC2F2 generations. Simple sequence repeats (104-109) were used for background selection, leading to an average recovery of 94% recurrent parent genome. The introgressed inbreds possessed significantly higher α-T: 18.38 ppm, α-/γ-tocopherol (α-/γ-T: 52%), and α-/total tocopherol (α-/TT: 32%) compared to original inbreds (α-T: 8.17 ppm, α-/γ-T: 25%, α-/TT: 18%). These newly derived inbreds also possessed higher β-carotene (BC: 8.91 ppm), β-cryptoxanthin (BCX: 1.27 ppm), proA (9.54 ppm), lysine (0.348%), and tryptophan (0.082%) compared to traditional maize inbreds. The reconstituted hybrids recorded higher α-T (2.1-fold), α-/γ-T (1.9-fold), and α-/TT (1.6-fold) over the original hybrids. These reconstituted hybrids were also rich in BC (5.7-fold), BCX (3.3-fold), proA (5.3-fold), lysine (1.9-fold), and tryptophan (2.0-fold) over the traditional hybrids. The reconstituted hybrids had similar grain yield and phenotypic characteristics to original versions. These multinutrient-rich maize hybrids hold great potential to alleviate malnutrition in sustainable and cost-effective manner.

5'-UTR allelic variants and expression of the lycopene-ɛ-cyclase LCYE gene in maize (Zea mays L.) inbred lines of Russian selection

In breeding, biofortification is aimed at enriching the edible parts of the plant with micronutrients. Within the framework of this strategy, molecular screening of collections of various crops makes it possible to determine allelic variants of genes, new alleles, and the linkage of allelic variants with morphophysiological traits. The maize (Zea mays L.) is an important cereal and silage crop, as well as a source of the main precursor of vitamin A - β-carotene, a derivative of the β,β-branch of the carotenoid biosynthesis pathway. The parallel β,ε-branch is triggered by lycopene-ε-cyclase LCYE, a low expression of which leads to an increase in provitamin A content and is associated with the variability of the 5'-UTR gene regulatory sequence. In this study, we screened a collection of 165 maize inbred lines of Russian selection for 5'- UTR LCYE allelic variants, as well as searched for the dependence of LCYE expression levels on the 5'-UTR allelic variant in the leaves of 14 collection lines. 165 lines analyzed were divided into three groups carrying alleles A2 (64 lines), A5 (31) and A6 (70), respectively. Compared to A2, allele A5 contained two deletions (at positions -267- 260 and -296-290 from the ATG codon) and a G251→T substitution, while allele A6 contained one deletion (-290-296) and two SNPs (G251→T, G265→T). Analysis of LCYE expression in the leaf tissue of seedlings from accessions of 14 lines differing in allelic variants showed no associations of the 5'-UTR LCYE allele type with the level of gene expression. Four lines carrying alleles A2 (6178-1, 6709-2, 2289-3) and A5 (5677) had a significantly higher level of LCYE gene expression (~0.018-0.037) than the other 10 analyzed lines (~0.0001-0.004), among which all three allelic variants were present.

Unravelling the genetic framework associated with grain quality and yield-related traits in maize (Zea mays L.)

Maize serves as a crucial nutrient reservoir for a significant portion of the global population. However, to effectively address the growing world population's hidden hunger, it is essential to focus on two key aspects: biofortification of maize and improving its yield potential through advanced breeding techniques. Moreover, the coordination of multiple targets within a single breeding program poses a complex challenge. This study compiled mapping studies conducted over the past decade, identifying quantitative trait loci associated with grain quality and yield related traits in maize. Meta-QTL analysis of 2,974 QTLs for 169 component traits (associated with quality and yield related traits) revealed 68 MQTLs across different genetic backgrounds and environments. Most of these MQTLs were further validated using the data from genome-wide association studies (GWAS). Further, ten MQTLs, referred to as breeding-friendly MQTLs (BF-MQTLs), with a significant phenotypic variation explained over 10% and confidence interval less than 2 Mb, were shortlisted. BF-MQTLs were further used to identify potential candidate genes, including 59 genes encoding important proteins/products involved in essential metabolic pathways. Five BF-MQTLs associated with both quality and yield traits were also recommended to be utilized in future breeding programs. Synteny analysis with wheat and rice genomes revealed conserved regions across the genomes, indicating these hotspot regions as validated targets for developing biofortified, high-yielding maize varieties in future breeding programs. After validation, the identified candidate genes can also be utilized to effectively model the plant architecture and enhance desirable quality traits through various approaches such as marker-assisted breeding, genetic engineering, and genome editing.

Whole-genome resequencing of common bean elite breeding lines

The expansion of bean genome technologies has prompted new perspectives on generating resources and knowledge essential to research and implementing biotechnological tools for the practical operations of plant breeding programs. This study aimed to resequence the entire genome (whole genome sequencing-WGS) of 40 bean genotypes selected based on their significance in breeding programs worldwide, with the objective of generating an extensive database for the identification of single nucleotide polymorphisms (SNPs). Over 6 million SNPs were identified, distributed across the 11 bean chromosomes. After quality variant filtering, 420,509 high-quality SNPs were established, with an average of 38,228 SNPs per chromosome. These variants were categorized based on their predicted effects, revealing that the majority exerted a modifier impact on non-coding genome regions (94.68%). Notably, a significant proportion of SNPs occurred in intergenic regions (62.89%) and at least one SNP was identified in 58.63% of the genes annotated in the bean genome. Of particular interest, 7841 SNPs were identified in 85% of the putative plant disease defense-related genes, presenting a valuable resource for crop breeding efforts. These findings provide a foundation for the development of innovative and broadly applicable technologies for the routine selection of superior genotypes in global bean improvement and germplasm characterization programs.

Transcriptome Analysis Revealed the Potential Molecular Mechanism of Anthocyanidins' Improved Salt Tolerance in Maize Seedlings

Anthocyanin, a kind of flavonoid, plays a crucial role in plant resistance to abiotic stress. Salt stress is a kind of abiotic stress that can damage the growth and development of plant seedlings. However, limited research has been conducted on the involvement of maize seedlings in salt stress resistance via anthocyanin accumulation, and its potential molecular mechanism is still unclear. Therefore, it is of great significance for the normal growth and development of maize seedlings to explore the potential molecular mechanism of anthocyanin improving salt tolerance of seedlings via transcriptome analysis. In this study, we identified two W22 inbred lines (tolerant line pur-W22 and sensitive line bro-W22) exhibiting differential tolerance to salt stress during seedling growth and development but showing no significant differences in seedling characteristics under non-treatment conditions. In order to identify the specific genes involved in seedlings' salt stress response, we generated two recombinant inbred lines (RILpur-W22 and RILbro-W22) by crossing pur-W22 and bro-W22, and then performed transcriptome analysis on seedlings grown under both non-treatment and salt treatment conditions. A total of 6100 and 5710 differentially expressed genes (DEGs) were identified in RILpur-W22 and RILbro-W22 seedlings, respectively, under salt-stressed conditions when compared to the non-treated groups. Among these DEGs, 3160 were identified as being present in both RILpur-W22 and RILbro-W22, and these served as commonly stressed EDGs that were mainly enriched in the redox process, the monomer metabolic process, catalytic activity, the plasma membrane, and metabolic process regulation. Furthermore, we detected 1728 specific DEGs in the salt-tolerant RILpur-W22 line that were not detected in the salt-sensitive RILbro-W22 line, of which 887 were upregulated and 841 were downregulated. These DEGs are primarily associated with redox processes, biological regulation, and the plasma membrane. Notably, the anthocyanin synthesis related genes in RILpur-W22 were strongly induced under salt treatment conditions, which was consistented with the salt tolerance phenotype of its seedlings. In summary, the results of the transcriptome analysis not only expanded our understanding of the complex molecular mechanism of anthocyanin in improving the salt tolerance of maize seedlings, but also, the DEGs specifically expressed in the salt-tolerant line (RILpur-W22) provided candidate genes for further genetic analysis.

Fresh/High-Zinc Maize: A Promising Solution for Alleviating Zinc Deficiency through Significant Micronutrient Accumulation

Zinc deficiency poses a significant health challenge worldwide, particularly in regions where access to and the affordability of dietary diversity are limited. This research article presents a time course analysis of kernel development on the zinc content in maize kernels with different genetic backgrounds, including normal maize, quality protein maize, and high-zinc maize, grown at two locations. Zn concentrations during stage I were high, decreasing between stages II and IV and increasing during stages V to VII. High-zinc kernel genotypes, including those ones with high-quality protein genetic backgrounds, have higher contents of zinc and iron during the milky stage (fresh/green maize). The zinc and iron content in fresh maize differed depending on the genotype. By consuming fresh maize biofortified with zinc, up to 89% and 100% of EAR needs can be fulfilled for pregnant women and children. The results demonstrate that fresh high-zinc maize accumulates a substantial amount of this micronutrient, highlighting its potential as a valuable source for addressing zinc deficiency.

Revisiting maize Brittle endosperm-2 reveals new insights in BETL development and starchy endosperm filling

Rerouting the starch biosynthesis pathway in maize can generate specialty types, like sweet corn and waxy corn, with a drastically increasing global demand. Hence, a fine-tuning of starch metabolism is relevant to create diverse maize cultivars for end-use applications. Here, we characterized a new maize brittle endosperm mutant, referred to as bt1774, which exhibited decreased starch content but a dramatic increase of soluble sugars at maturity. Both endosperm and embryo development was impaired in bt1774 relative to the wild-type (WT), with a prominently arrested basal endosperm transfer layer (BETL). Map-based cloning revealed that BRITTLE ENDOSPERM2 (Bt2), which encodes a small subunit of ADP-glucose pyrophosphorylase (AGPase), is the causal gene for bt1774. A MuA2 element was found to be inserted into intron 2 of Bt2, leading to a severe decrease of its expression, in bt1774. This is in line with the irregular and loosely packed starch granules in the mutant. Transcriptome of endosperm at grain filling stage identified 1, 013 differentially expressed genes in bt1774, which were notably enriched in the BETL compartment, including ZmMRP1, Miniature1, MEG1, and BETLs. Gene expression of the canonical starch biosynthesis pathway was marginally disturbed in Bt1774. Combined with the residual 60% of starch in this nearly null mutant of Bt2, this data strongly suggests that an AGPase-independent pathway compensates for starch synthesis in the endosperm. Consistent with the BETL defects, zein accumulation was impaired in bt1774. Co-expression network analysis revealed that Bt2 probably has a role in intracellular signal transduction, besides starch synthesis. Altogether, we propose that Bt2 is likely involved in carbohydrate flux and balance, thus regulating both the BETL development and the starchy endosperm filling.

Expression Dynamics of lpa1 Gene and Accumulation Pattern of Phytate in Maize Genotypes Possessing opaque2 and crtRB1 Genes at Different Stages of Kernel Development

Phytic acid (PA) acts as a storehouse for the majority of the mineral phosphorous (P) in maize; ~80% of the total P stored as phytate P is not available to monogastric animals and thereby causes eutrophication. In addition, phytic acid chelates positively charged minerals making them unavailable in the diet. The mutant lpa1-1 allele reduces PA more than the wild-type LPA1 allele. Further, mutant gene opaque2 (o2) enhances lysine and tryptophan and crtRB1 enhances provitamin-A (proA) more than wild-type O2 and CRTRB1 alleles, respectively. So far, the expression pattern of the mutant lpa1-1 allele has not been analysed in maize genotypes rich in lysine, tryptophan and proA. Here, we analysed the expression pattern of wild and mutant alleles of LPA1, O2 and CRTRB1 genes in inbreds with (i) mutant lpa1-1, o2 and crtRB1 alleles, (ii) wild-type LPA1 allele and mutant o2 and crtRB1 alleles and (iii) wild-type LPA1, O2 and CRTRB1 alleles at 15, 30 and 45 days after pollination (DAP). The average reduction of PA/total phosphorous (TP) in lpa1-1 mutant inbreds was 29.30% over wild-type LPA1 allele. The o2 and crtRB1-based inbreds possessed ~two-fold higher amounts of lysine and tryptophan, and four-fold higher amounts of proA compared to wild-type alleles. The transcript levels of lpa1-1, o2 and crtRB1 genes in lpa1-1-based inbreds were significantly lower than their wild-type versions across kernel development. The lpa1-1, o2 and crtRB1 genes reached their highest peak at 15 DAP. The correlation of transcript levels of lpa1-1 was positive for PA/TP (r = 0.980), whereas it was negative with inorganic phosphorous (iP) (r = -0.950). The o2 and crtRB1 transcripts showed negative correlations with lysine (r = -0.887) and tryptophan (r = -0.893), and proA (r = -0.940), respectively. This is the first comprehensive study on lpa1-1 expression in the maize inbreds during different kernel development stages. The information generated here offers great potential for comprehending the dynamics of phytic acid regulation in maize.

Combining ability, heterosis and performance of grain yield and content of Fe, Zn and protein in bread wheat under normal and late sowing conditions

Wheat (Triticum aestivum L.) is inherently low in protein content, Zn and Fe. Boost yield gains have unwittingly reduced grain Zn and Fe, which has had negative impacts on human health. The aim of this study was to understand the inheritance of grain yield per plant and grain Fe, Zn, and protein concentrations in bread wheat (Triticum aestivum L.) under normal and late sown conditions. Half diallel crosses were performed using 10 parents. The crosses and parents were evaluated in replicated trials for the two conditions, to assess the possibility of exploiting heterosis to improve micronutrient contents. The per se performance, heterosis, combining ability, and genetic components were estimated for different characters in both environments. The results revealed that hybrid GW 451 × GW 173 exhibited better parent heterosis (BPH) and standard heterotic effects (SH) in all environments. In both sowing conditions, the general combining ability (GCA) effects of poor × poor parents also showed high specific combining ability (SCA) effects of hybrids for both the micronutrients and protein contents. However, σ2A/σ2D greater than unity confirmed the preponderance of additive gene action for protein content, and GW 173 was identified as a good general combiner for these characteristics under both environments. SCA had positive significant (P < 0.001) correlations with BPH, SH1, SH2, and the phenotype for yield component traits and grain protein, Fe, and Zn concentrations in both conditions. A supplementary approach for biofortifying wheat grainis required to prevent malnutrition.

Combining ability and testcross performance of multi-nutrient maize under stress and non-stress environments

While significant progress has been made by several international breeding institutions in improving maize nutritional quality, stacking of nutritional traits like zinc (Zn), quality protein, and provitamin A has not received much attention. In this study, 11 newly introduced Zn-enhanced inbred lines were inter-mated with seven testers from normal, provitamin A and quality protein maize (QPM) nutritional backgrounds in order to estimate the general combining ability (GCA) and specific combining ability (SCA) for grain yield (GY) and secondary traits under stress conditions [(combined heat and drought stress (HMDS) and managed low nitrogen (LN)] and non-stress conditions [(summer rainfed; OPT) and well-watered (irrigated winter; WW)] in Zimbabwe. Lines L6 and L7 had positive GCA effects for GY and secondary traits under OPT and LN conditions, and L8 and L9 were good general combiners for GY under HMDS conditions. Superior hybrids with high GY and desirable secondary traits were identified as L10/T7 and L9/T7 (Zn x normal), L2/T4, L4/T4, L3/T5 (Zn x provitamin A), and L8/T6 and L11/T3 (Zn x QPM), suggesting the possibility of developing Zn-enhanced hybrids with high yield potential using different nutritional backgrounds. Both additive and dominance gene effects were important in controlling most of the measured traits. This suggests that selecting for desirable traits during inbred line development followed by hybridization and testing of specific crosses under different management conditions could optimize the breeding strategy for stacked nutritionally-enhanced maize genotypes.

Impact of CGIAR maize germplasm in Sub-Saharan Africa

This study reports on the adoption and impacts of CGIAR-related maize varieties in 18 major maize-producing countries in sub-Saharan Africa (SSA) during 1995-2015. Of the 1345 maize varieties released during this timeframe, approximately 60% had a known CGIAR parentage. About 34% (9.5 million ha) of the total maize area in 2015 was cultivated with 'new' CGIAR-related maize varieties released between 1995 and 2015. In the same year, an additional 13% of the maize area was cultivated with 'old' CGIAR-related maize varieties released before 1995. The aggregate annual economic benefit of using new CGIAR-related maize germplasm for yield increase in SSA was estimated at US$1.1-1.6 billion in 2015, which we attributed equally to co-investments by CGIAR funders, public-sector national research and extension programs, and private sector partners. Given that the annual global investment in CGIAR maize breeding at its maximum was US$30 million, the benefit-cost ratios for the CGIAR investment and CGIAR-attributable portion of economic benefits varied from 12:1-17:1, under the assumption of a 5-year lag in the research investment to yield returns. The study also discusses the methodological challenges involved in large-scale impact assessments. Post-2015 CGIAR tropical maize breeding efforts have had a strong emphasis on stress tolerance.

Zinc and Provitamin A Biofortified Maize Genotypes Exhibited Potent to Reduce Hidden-Hunger in Nepal

Zinc deficiency affects one third of the population worldwide, and vitamin A deficiency is a prevalent public health issue in Sub-Saharan Africa and South-Asia, including Nepal. Crop biofortification is the sustainable solution to these health-related problems, thus we conducted two different field trials in an alpha lattice design to identify zinc and provitamin A biofortified maize genotypes consistent and competitive in performance over the contrasting seasons (Season 1: 18 February to 6 July 2020 and Season 2: 31 August to 1 February, 2020/21). In our study, the performance of introduced maize genotypes (zinc-15 and provitamin A biofortified-24) were compared with that of the local check, focusing on the overall agro-morphology, yield attributes, yield, and kernel zinc and total carotenoid content. Zinc and total carotenoid in the tested genotypes were found in the range between 14.2 and 24.8 mg kg^-1 and between 1.8 and 3.6 mg 100 g^-1. Genotypes A1831-8 from zinc and EEPVAH-46 from provitamin A biofortified maize trial recorded kernel zinc and total carotenoid as high as 52.3, and 79.5%, respectively, compared to the local check (DMH849). The provitamin A genotypes EEPVAH-46 and EEPVAH-51 (total carotenoid: 3.6 and 3.3 mg 100 g^-1), and zinc biofortified genotypes A1847-10 and A1803-42 (20.4 and 22.4 mg kg^-1 zinc) were identified as superior genotypes based on their yield consistency over the environments and higher provitamin A and zinc content compared to the check. In addition, farmers can explore August sowing to harvest green cobs during December-January to boost up the emerging green cob business.

Allelic variation in shrunken2 gene affecting kernel sweetness in exotic-and indigenous-maize inbreds

Sweet corn has become a popular food worldwide. It possesses six-times more sugar than field corn due to the presence of recessive shrunken2 (sh2) gene. Despite availability of diverse sweet corn germplasm, comprehensive characterization of sh2 has not been undertaken so far. Here, entire Sh2 gene (7320 bp) among five field corn-(Sh2Sh2) and six sweet corn-(sh2sh2) inbreds was sequenced. A total of 686 SNPs and 372 InDels were identified, of which three SNPs differentiated the wild-(Sh2) and mutant-(sh2) allele. Ten InDel markers were developed to assess sh2 gene-based diversity among 23 sweet corn and 25 field corn lines. Twenty-five alleles and 47 haplotypes of sh2 were identified among 48 inbreds. Among markers, MGU-InDel-2, MGU-InDel-3, MGU-InDel-5 and MGU-InDel-8 had PIC>0.5. Major allele frequency varied from 0.458–0.958. The gene sequence of these maize inbreds was compared with 25 orthologues of monocots. Sh2 gene possessed 15–18 exons with 6-225bp among maize, while it was 6–21 exons with 30-441bp among orthologues. While intron length across maize genotypes varied between 67-2069bp, the same among orthologues was 57–2713 bp. Sh2-encoded AGPase domain was more conserved than NTP transferase domain. Nucleotide and protein sequences of sh2 in maize and orthologues revealed that rice orthologue was closer to maize than other monocots. The study also provided details of motifs and domains present in sh2 gene, physicochemical properties and secondary structure of SH2 protein in maize inbreds and orthologues. This study reports detailed characterization and diversity analysis in sh2 gene of maize and related orthologues in various monocots.

Wheat Biofortification: Utilizing Natural Genetic Diversity, Genome-Wide Association Mapping, Genomic Selection, and Genome Editing Technologies

Alleviating micronutrients associated problems in children below five years and women of childbearing age, remains a significant challenge, especially in resource-poor nations. One of the most important staple food crops, wheat attracts the highest global research priority for micronutrient (Fe, Zn, Se, and Ca) biofortification. Wild relatives and cultivated species of wheat possess significant natural genetic variability for these micronutrients, which has successfully been utilized for breeding micronutrient dense wheat varieties. This has enabled the release of 40 biofortified wheat cultivars for commercial cultivation in different countries, including India, Bangladesh, Pakistan, Bolivia, Mexico and Nepal. In this review, we have systematically analyzed the current understanding of availability and utilization of natural genetic variations for grain micronutrients among cultivated and wild relatives, QTLs/genes and different genomic regions regulating the accumulation of micronutrients, and the status of micronutrient biofortified wheat varieties released for commercial cultivation across the globe. In addition, we have also discussed the potential implications of emerging technologies such as genome editing to improve the micronutrient content and their bioavailability in wheat.

Marker-assisted pyramiding of γ-tocopherol methyltransferase and glutamate formiminotransferase genes for development of biofortified sweet corn hybrids

Micronutrients, including vitamins, minerals, and other bioactive compounds, have tremendous impacts on human health. Much progress has been made in improving the micronutrient content of inbred lines in various crops through biofortified breeding. However, biofortified breeding still falls short for the rapid generation of high-yielding hybrids rich in multiple micronutrients. Here, we bred multi-biofortified sweet corn hybrids efficiently through marker-assisted selection. Screening by molecular markers for vitamin E and folic acid, we obtained 15 inbred lines carrying favorable alleles (six for vitamin E, nine for folic acid, and three for both). Multiple biofortified corn hybrids were developed through crossing and genetic diversity analysis.

Global maize production, consumption and trade: trends and R&D implications

Since its domestication some 9,000 years ago, maize (Zea mays L.; corn) has played an increasing and diverse role in global agri-food systems. Global maize production has surged in the past few decades, propelled by rising demand and a combination of technological advances, yield increases and area expansion. Maize is already the leading cereal in terms of production volume and is set to become the most widely grown and traded crop in the coming decade. It is a versatile multi-purpose crop, primarily used as a feed globally, but also is important as a food crop, especially in sub-Saharan Africa and Latin America, besides other non-food uses. This paper reviews maize production, consumption, and international trade to examine the changing trends in global supply and demand conditions over the past quarter century and the implications for research and development (R&D), particularly in the Global South. The inclusiveness and sustainability of the ongoing transformation of agri-food systems in the Global South merit particular attention. There is a need for further investments in R&D, particularly to enhance maize’s food and livelihood security roles and to sustainably intensify maize production while staying within the planetary boundaries.

Allelic Variation in Zmfatb Gene Defines Variability for Fatty Acids Composition Among Diverse Maize Genotypes

Edible oil with lower saturated fatty acids is desired for perceived quality and health benefits to humans and livestock. fatb gene encoding acyl-ACP thioesterase is a key player in the conversion of palmitic acid to oleic acid, thereby modifying the ratio of saturated to unsaturated fatty acids in maize kernels. The present investigation characterised the full-length sequence of the Zmfatb gene (4.63 kb) in two mutants (Zmfatb) and eight wild-types (ZmfatB) inbreds to study allelic variation, gene-based diversity, phylogenetic-relationship, protein-modelling, and molecular-docking to identify novel candidates for modification of fatty acid profile. Sequence alignment revealed wide genomic variability for Zmfatb among the inbreds; identified five novel SNPs and two InDels that clearly differentiated the wild-type and mutant genotypes. Gene-based diversity using 11-InDel markers categorised 48-diverse maize-inbreds into two-clusters. The majority of mutant and wild-type inbreds were grouped in separate clusters and led to the generation of 41 haplotypes. Genetic relationship of maize fatb gene with orthologues among 40 accessions of 12 oilseed-crops using both nucleotide and protein sequence clustered maize, soybean, sunflower, opium-poppy, Citrulus lanata, quinoa, and prunus species into one cluster; and brassica, camelina, and arabidopsis into the different cluster. The clustering pattern revealed that the plant oil with higher unsaturated fatty acids, particularly oleic, linoleic, and linolenic acids grouped together in one cluster and higher proportions of other fractions like arachidic, eicosenoic, and erucic acids grouped in another cluster. Physico-chemical properties highlighted more similarity between maize and 29 orthologue proteins, but orthologues were found to have better thermostability. Homology models have been developed for maize mutant and wild-type inbreds using Umbellularia californica (PDB ID: 5x04) as a template. Predicted protein models possessed optimum confidence-score and RMSD values and validated stability via., Ramachandran plots. Molecular docking indicated most of the interactions of protein-ligand were having similar binding-affinity due to the broader specificity of fatty acyl-ACP thioesterases and the presence of conserved-domains across crops. This is the first report on the comprehensive molecular characterisation of the fatb gene in maize and various orthologues. The information generated here provided new insights into the genetic diversity of fatb gene which can be utilised for the enhanced nutritive value of oil in the breeding programme.

Deciphering Pleiotropic Signatures of Regulatory SNPs in Zea mays L. Using Multi-Omics Data and Machine Learning Algorithms

Maize is one of the most widely grown cereals in the world. However, to address the challenges in maize breeding arising from climatic anomalies, there is a need for developing novel strategies to harness the power of multi-omics technologies. In this regard, pleiotropy is an important genetic phenomenon that can be utilized to simultaneously enhance multiple agronomic phenotypes in maize. In addition to pleiotropy, another aspect is the consideration of the regulatory SNPs (rSNPs) that are likely to have causal effects in phenotypic development. By incorporating both aspects in our study, we performed a systematic analysis based on multi-omics data to reveal the novel pleiotropic signatures of rSNPs in a global maize population. For this purpose, we first applied Random Forests and then Markov clustering algorithms to decipher the pleiotropic signatures of rSNPs, based on which hierarchical network models are constructed to elucidate the complex interplay among transcription factors, rSNPs, and phenotypes. The results obtained in our study could help to understand the genetic programs orchestrating multiple phenotypes and thus could provide novel breeding targets for the simultaneous improvement of several agronomic traits.

Identification and fine mapping of a major QTL (qRtsc8-1) conferring resistance to maize tar spot complex and validation of production markers in breeding lines

A major QTL of qRtsc8-1 conferring TSC resistance was identified and fine mapped to a 721 kb region on chromosome 8 at 81 Mb, and production markers were validated in breeding lines. Tar spot complex (TSC) is a major foliar disease of maize in many Central and Latin American countries and leads to severe yield loss. To dissect the genetic architecture of TSC resistance, a genome-wide association study (GWAS) panel and a bi-parental doubled haploid population were used for GWAS and selective genotyping analysis, respectively. A total of 115 SNPs in bin 8.03 were detected by GWAS and three QTL in bins 6.05, 6.07, and 8.03 were detected by selective genotyping. The major QTL qRtsc8-1 located in bin 8.03 was detected by both analyses, and it explained 14.97% of the phenotypic variance. To fine map qRtsc8-1, the recombinant-derived progeny test was implemented. Recombinations in each generation were backcrossed, and the backcross progenies were genotyped with Kompetitive Allele Specific PCR (KASP) markers and phenotyped for TSC resistance individually. The significant tests for comparing the TSC resistance between the two classes of progenies with and without resistant alleles were used for fine mapping. In BC₅ generation, qRtsc8-1 was fine mapped in an interval of  ~ 721 kb flanked by markers of KASP81160138 and KASP81881276. In this interval, the candidate genes GRMZM2G063511 and GRMZM2G073884 were identified, which encode an integral membrane protein-like and a leucine-rich repeat receptor-like protein kinase, respectively. Both genes are involved in maize disease resistance responses. Two production markers KASP81160138 and KASP81160155 were verified in 471 breeding lines. This study provides valuable information for cloning the resistance gene, and it will also facilitate the routine implementation of marker-assisted selection in the breeding pipeline for improving TSC resistance.

Optimization of Protein Quality Assay in Normal, opaque-2, and Quality Protein Maize

The development of quality protein maize (QPM) was considered a significant leap toward improvement in the nutritional status of rural masses in developing countries. The nutritional quality of QPM is attributed to the higher concentration of essential amino acids, particularly lysine and tryptophan, in its kernel endosperm. However, the similarity in the grains of QPM and normal maize necessitates the development of a standard protocol to assess the protein quality of maize. The present study aimed at improving the protocol of protein quality assessment in QPM. For this purpose, endosperm defatting and protein estimation procedures were restandardized and optimized with respect to the protocol duration and its amenability for high-throughput analysis. Unlike normal maize, QPM and opaque-2 mutants were completely defatted within a 48 h period. It was observed that the tryptophan content, calculated at each defatting interval, increased in the samples defatted for a longer duration. No significant differences were observed in the tryptophan content analyzed in the samples defatted for 48 and 72 h. Moreover, the endosperm protein estimated by using the Bradford method with certain modifications strongly correlated with the micro-Kjeldahl method (r = 0.9). Relative to the micro-Kjeldahl method, the Bradford method was found to be precise, rapid, and hazard-free. The present findings enable a testing protocol of reduced time duration that can be used in resource-poor settings for the determination of a protein quality assay in QPM. Overall, the present study effectively helped in reducing the defatting time by 24 h and protein estimation by 3 h as compared to the already established International Maize and Wheat Improvement Center protocol. This is expected to enable the aggregation of high-protein-quality maize to facilitate its commercialization.

Applications of Genomic Tools in Plant Breeding: Crop Biofortification

Crop breeding has mainly been focused on increasing productivity, either directly or by decreasing the losses caused by biotic and abiotic stresses (that is, incorporating resistance to diseases and enhancing tolerance to adverse conditions, respectively). Quite the opposite, little attention has been paid to improve the nutritional value of crops. It has not been until recently that crop biofortification has become an objective within breeding programs, through either conventional methods or genetic engineering. There are many steps along this long path, from the initial evaluation of germplasm for the content of nutrients and health-promoting compounds to the development of biofortified varieties, with the available and future genomic tools assisting scientists and breeders in reaching their objectives as well as speeding up the process. This review offers a compendium of the genomic technologies used to explore and create biodiversity, to associate the traits of interest to the genome, and to transfer the genomic regions responsible for the desirable characteristics into potential new varieties. Finally, a glimpse of future perspectives and challenges in this emerging area is offered by taking the present scenario and the slow progress of the regulatory framework as the starting point.

Simultaneous dissection of grain carotenoid levels and kernel color in biparental maize populations with yellow-to-orange grain

Maize enriched in provitamin A carotenoids could be key in combatting vitamin A deficiency in human populations relying on maize as a food staple. Consumer studies indicate that orange maize may be regarded as novel and preferred. This study identifies genes of relevance for grain carotenoid concentrations and kernel color, through simultaneous dissection of these traits in 10 families of the US maize nested association mapping panel that have yellow to orange grain. Quantitative trait loci were identified via joint-linkage analysis, with phenotypic variation explained for individual kernel color quantitative trait loci ranging from 2.4% to 17.5%. These quantitative trait loci were cross-analyzed with significant marker-trait associations in a genome-wide association study that utilized ∼27 million variants. Nine genes were identified: four encoding activities upstream of the core carotenoid pathway, one at the pathway branchpoint, three within the α- or β-pathway branches, and one encoding a carotenoid cleavage dioxygenase. Of these, three exhibited significant pleiotropy between kernel color and one or more carotenoid traits. Kernel color exhibited moderate positive correlations with β-branch and total carotenoids and negligible correlations with α-branch carotenoids. These findings can be leveraged to simultaneously achieve desirable kernel color phenotypes and increase concentrations of provitamin A and other priority carotenoids.

Conservation Agriculture Affects Grain and Nutrient Yields of Maize (Zea Mays L.) and Can Impact Food and Nutrition Security in Sub-Saharan Africa

Maize is a major staple and plays an essential role in food and nutrition security in Sub-Saharan Africa (SSA). Conservation agriculture (CA), a climate-smart agriculture practise based on minimum soil disturbance, crop residue retention, and crop diversification, has been widely advocated but without extensive research on the impact it may have on maize nutrient composition, and food and nutrition security. This study assessed the grain yield, macro- and micronutrient mineral content, and nutrient yield of eight maize varieties grown in Malawi, and how these are affected by CA practises over two seasons. The minerals were analysed by inductively coupled plasma (ICP) coupled to optical emission spectroscopy (OES) and to mass spectroscopy (MS). Grain yield and Se content differed among the varieties, while C, N, Fe, K, Mg, Mn, P, and Zn were similar. The local variety Kanjerenjere showed lowest grain and nutrient yields. The open-pollinated varieties (OPVs) concentrated more minerals than the F1 hybrids, but the latter showed higher yields for both grain and nutrients. Typical consumption of the eight maize varieties could fully meet the protein and Mg dietary reference intake (DRIs) of Malawian children (1–3 years), as well as Mg and Mn needs of adult women (19–50 years), but their contribution to dietary requirements was low for Fe (39–41%) and K (13–21%). The trials showed that CA increased grain yield (1.2- to 1.8-fold) and Se content (1.1- to 1.7-fold), but that it had no effect on C, K, Mg, P, and Zn, and that N (1.1- to 1.2-fold), Mn (1.1- to 1.8-fold), and Fe (1.3- to 3.4-fold) were reduced. The high increase in grain yield under CA treatments resulted in increased yields of protein and Se, no effect on the yields of K, Mg, Mn, P, Zn, and reduced Fe yield. Conservation agriculture could contribute in reducing the risk of Se deficiency in Malawian women and children but exacerbates the risk of Fe deficiency. A combination of strategies will be needed to mitigate some of the foreseen effects of climate change on agriculture, and food and nutrition security, and improve nutrient intake.

Biological Properties of Vitamins of the B-Complex, Part 1: Vitamins B1, B2, B3, and B5

This review summarizes the current knowledge on essential vitamins B₁, B₂, B₃, and B₅. These B-complex vitamins must be taken from diet, with the exception of vitamin B₃, that can also be synthetized from amino acid tryptophan. All of these vitamins are water soluble, which determines their main properties, namely: they are partly lost when food is washed or boiled since they migrate to the water; the requirement of membrane transporters for their permeation into the cells; and their safety since any excess is rapidly eliminated via the kidney. The therapeutic use of B-complex vitamins is mostly limited to hypovitaminoses or similar conditions, but, as they are generally very safe, they have also been examined in other pathological conditions. Nicotinic acid, a form of vitamin B₃, is the only exception because it is a known hypolipidemic agent in gram doses. The article also sums up: (i) the current methods for detection of the vitamins of the B-complex in biological fluids; (ii) the food and other sources of these vitamins including the effect of common processing and storage methods on their content; and (iii) their physiological function.

Combining higher accumulation of amylopectin, lysine and tryptophan in maize hybrids through genomics-assisted stacking of waxy1 and opaque2 genes

Waxy maize rich in amylopectin has emerged as a preferred food. However, waxy maize is poor in lysine and tryptophan, deficiency of which cause severe health problems. So far, no waxy hybrid with high lysine and tryptophan has been developed and commercialized. Here, we combined recessive waxy1 (wx1) and opaque2 (o2) genes in the parental lines of four popular hybrids (HQPM1, HQPM4, HQPM5, and HQPM7) using genomics-assisted breeding. The gene-based markers, wx-2507F/RG and phi057 specific for wx1 and o2, respectively were successfully used to genotype BC₁F₁, BC₂F₁ and BC₂F₂ populations. Background selection with > 100 SSRs resulted in recovering > 94% of the recurrent parent genome. The reconstituted hybrids showed 1.4-fold increase in amylopectin (mean: 98.84%) compared to the original hybrids (mean: 72.45%). The reconstituted hybrids also showed 14.3% and 14.6% increase in lysine (mean: 0.384%) and tryptophan (mean: 0.102%), respectively over the original hybrids (lysine: 0.336%, tryptophan: 0.089%). Reconstituted hybrids also possessed similar grain yield (mean: 6248 kg/ha) with their original versions (mean: 6111 kg/ha). The waxy hybrids with high lysine and tryptophan assume great significance in alleviating malnutrition through sustainable and cost-effective means. This is the first report of development of lysine and tryptophan rich waxy hybrids using genomics-assisted selection.

Capacities of local maize seed enterprises in Mexico: Implications for seed systems development

Where maize plays a critical role in food security, governments and donors have invested heavily in support of local, privately owned, often small and medium sized, maize seed enterprises (maize SMEs). Underpinning these investments are strong assumptions about maize SMEs’ capacity to produce and distribute seed to smallholders. This study assesses the capacities of 22 maize SMEs in Mexico that engaged with MasAgro—a large-scale development program initiated in 2011 that has provided maize SMEs with improved genetic material and technical assistance. Data were collected onsite from in-depth interviews with enterprise owners and managers and complemented with other primary and secondary sources. Overall, maize SMEs showed high levels of absorptive capacity for seed production, but limited signs of learning and innovation in terms of business organization and strategic seed marketing. Asset endowments varied widely among the SMEs, but generally they were lowest among the smaller enterprises, and access to business development services beyond MasAgro was practically nonexistent. Results highlighted the critical role of MasAgro in reinvigorating the portfolios of seeds produced by maize SMEs, as well as the challenges ahead for maize SMEs to scale the new technologies in a competitive market that has long been dominated by multinational seed enterprises. Among these challenges were limited investment in seed marketing, weak infrastructure for seed production, and limited experience in business management. Achieving the food security goals through maize SMEs will require making national maize seed industry development a strategic imperative.

Biofortification of Cereals and Pulses Using New Breeding Techniques: Current and Future Perspectives

Cereals and pulses are consumed as a staple food in low-income countries for the fulfillment of daily dietary requirements and as a source of micronutrients. However, they are failing to offer balanced nutrition due to deficiencies of some essential compounds, macronutrients, and micronutrients, i.e., cereals are deficient in iron, zinc, some essential amino acids, and quality proteins. Meanwhile, the pulses are rich in anti-nutrient compounds that restrict the bioavailability of micronutrients. As a result, the population is suffering from malnutrition and resultantly different diseases, i.e., anemia, beriberi, pellagra, night blindness, rickets, and scurvy are common in the society. These facts highlight the need for the biofortification of cereals and pulses for the provision of balanced diets to masses and reduction of malnutrition. Biofortification of crops may be achieved through conventional approaches or new breeding techniques (NBTs). Conventional approaches for biofortification cover mineral fertilization through foliar or soil application, microbe-mediated enhanced uptake of nutrients, and conventional crossing of plants to obtain the desired combination of genes for balanced nutrient uptake and bioavailability. Whereas, NBTs rely on gene silencing, gene editing, overexpression, and gene transfer from other species for the acquisition of balanced nutritional profiles in mutant plants. Thus, we have highlighted the significance of conventional and NBTs for the biofortification of cereals and pulses. Current and future perspectives and opportunities are also discussed. Further, the regulatory aspects of newly developed biofortified transgenic and/or non-transgenic crop varieties via NBTs are also presented.

Sustainable intensification of maize and wheat cropping system through pulse intercropping

The intercropping of legumes with cereals help to achieve sustainable intensification by their mutual complementarity at efficiently using radiation, nutrients, etc. Several studies indicated such beneficial effects on the other component crop however, little research has been conducted to quantify their effects on the subsequent crop in a cropping system. In this study, the effect of the legume intercropping on the entire cropping system, particularly the maize + legume-wheat system was studied. Four legumes intercropped to maize followed by wheat crop were studied for intensification measures such as wheat equivalent yield (WEY), land equivalent ratio (LER), sustainable value index (SVI), and economic returns. N saving effect of legumes on the subsequent wheat crop was quantified with two N levels. Maize + cowpea-wheat combination was the most productive and economic intercrop combination (LER = 1.71, SVI = 0.96) with an increase in net economic return (43.63%) with a B:C ratio of 1.94. An additional 25% N (37.5 kg ha^-1) was saved in the wheat crop when the legume intercropping was undertaken with maize. The results suggest that intercropping is the key to diversification and reduces the risk of crop failures by enhancing land-use efficiency, soil fertility, and economic returns under weather vagaries. This will be beneficial to small and marginal farmers of many countries.

Transition From Targeted Breeding to Mainstreaming of Biofortification Traits in Crop Improvement Programs

Biofortification breeding for three important micronutrients for human health, namely, iron (Fe), zinc (Zn), and provitamin A (PVA), has gained momentum in recent years. HarvestPlus, along with its global consortium partners, enhances Fe, Zn, and PVA in staple crops. The strategic and applied research by HarvestPlus is driven by product-based impact pathway that integrates crop breeding, nutrition research, impact assessment, advocacy, and communication to implement country-specific crop delivery plans. Targeted breeding has resulted in 393 biofortified crop varieties by the end of 2020, which have been released or are in testing in 63 countries, potentially benefitting more than 48 million people. Nevertheless, to reach more than a billion people by 2030, future breeding lines that are being distributed by Consultative Group on International Agricultural Research (CGIAR) centers and submitted by National Agricultural Research System (NARS) to varietal release committees should be biofortified. It is envisaged that the mainstreaming of biofortification traits will be driven by high-throughput micronutrient phenotyping, genomic selection coupled with speed breeding for accelerating genetic gains. It is noteworthy that targeted breeding gradually leads to mainstreaming, as the latter capitalizes on the progress made in the former. Efficacy studies have revealed the nutritional significance of Fe, Zn, and PVA biofortified varieties over non-biofortified ones. Mainstreaming will ensure the integration of biofortified traits into competitive varieties and hybrids developed by private and public sectors. The mainstreaming strategy has just been initiated in select CGIAR centers, namely, International Maize and Wheat Improvement Center (CIMMYT), International Rice Research Institute (IRRI), International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), International Institute of Tropical Agriculture (IITA), and International Center for Tropical Agriculture (CIAT). This review will present the key successes of targeted breeding and its relevance to the mainstreaming approaches to achieve scaling of biofortification to billions sustainably.

Unravelling the Effect of Provitamin A Enrichment on Agronomic Performance of Tropical Maize Hybrids

Maize is consumed in different traditional diets as a source of macro- and micro-nutrients across Africa. Significant investment has thus been made to develop maize with high provitamin A content to complement other interventions for alleviating vitamin A deficiencies. The current breeding focus on increasing β-carotene levels to develop biofortified maize may affect the synthesis of other beneficial carotenoids. The changes in carotenoid profiles, which are commonly affected by environmental factors, may also lead to a trade-off with agronomic performance. The present study was therefore conducted to evaluate provitamin A biofortified maize hybrids across diverse field environments. The results showed that the difference in accumulating provitamin A and other beneficial carotenoids across variable growing environments was mainly regulated by the genetic backgrounds of the hybrids. Many hybrids, accumulating more than 10 µg/g of provitamin A, produced higher grain yields (>3600 kg/ha) than the orange commercial maize hybrid (3051 kg/ha). These hybrids were also competitive, compared to the orange commercial maize hybrid, in accumulating lutein and zeaxanthins. Our study showed that breeding for enhanced provitamin A content had no adverse effect on grain yield in the biofortified hybrids evaluated in the regional trials. Furthermore, the results highlighted the possibility of developing broadly adapted hybrids containing high levels of beneficial carotenoids for commercialization in areas with variable maize growing conditions in Africa.

Development of Maize Hybrids With Enhanced Vitamin-E, Vitamin-A, Lysine, and Tryptophan Through Molecular Breeding

Malnutrition is a widespread problem that affects human health, society, and the economy. Traditional maize that serves as an important source of human nutrition is deficient in vitamin-E, vitamin-A, lysine, and tryptophan. Here, favorable alleles of vte4 (α-tocopherol methyl transferase), crtRB1 (β-carotene hydroxylase), lcyE (lycopene ε-cyclase), and o2 (opaque2) genes were combined in parental lines of four popular hybrids using marker-assisted selection (MAS). BC₁F₁, BC₂F₁, and BC₂F₂ populations were genotyped using gene-based markers of vte4, crtRB1, lcyE, and o2. Background selection using 81-103 simple sequence repeats (SSRs) markers led to the recovery of recurrent parent genome (RPG) up to 95.45%. Alpha (α)-tocopherol was significantly enhanced among introgressed progenies (16.13 μg/g) as compared to original inbreds (7.90 μg/g). Provitamin-A (proA) (10.42 μg/g), lysine (0.352%), and tryptophan (0.086%) were also high in the introgressed progenies. The reconstituted hybrids showed a 2-fold enhancement in α-tocopherol (16.83 μg/g) over original hybrids (8.06 μg/g). Improved hybrids also possessed high proA (11.48 μg/g), lysine (0.367%), and tryptophan (0.084%) when compared with traditional hybrids. The reconstituted hybrids recorded the mean grain yield of 8,066 kg/ha, which was at par with original hybrids (mean: 7,846 kg/ha). The MAS-derived genotypes resembled their corresponding original hybrids for the majority of agronomic and yield-related traits, besides characteristics related to distinctness, uniformity, and stability (DUS). This is the first report for the development of maize with enhanced vitamin-E, vitamin-A, lysine, and tryptophan.