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SUMMARY: Enhancing maize kernel oil is vital for improving the bioavailability of fat‐soluble vitamins. Here, we combined favourable alleles of dgat1‐2 and fatb into parental lines of four multi‐nutrient‐rich maize hybrids (APTQH1, APTQH4, APTQH5 and APTQH7) using marker‐assisted selection (MAS). Parental lines possessed favourable alleles of crtRB1, lcyE, vte4 and opaque2 genes. Gene‐specific markers enabled successful foreground selection in BC1F1, BC2F1 and BC2F2, while background selection using genome‐wide microsatellite markers (127–132) achieved 93% recurrent parent genome recovery. Resulting inbreds exhibited significantly higher oil (6.93%) and oleic acid (OA, 40.49%) and lower palmitic acid (PA, 14.23%) compared to original inbreds with elevated provitamin A (11.77 ppm), vitamin E (16.01 ppm), lysine (0.331%) and tryptophan (0.085%). Oil content significantly increased from 4.80% in original hybrids to 6.73% in reconstituted hybrids, making them high‐oil maize hybrids. These hybrids displayed 35.70% increment in oil content and 51.56% increase in OA with 36.32% reduction in PA compared to original hybrids, while maintaining higher provitamin A (two‐fold), vitamin E (nine‐fold), lysine (two‐fold) and tryptophan (two‐fold) compared to normal hybrids. Lipid health indices showed improved atherogenicity, thrombogenicity, cholesterolaemic, oxidability, peroxidizability and nutritive values in MAS‐derived genotypes over original versions. Besides, the MAS‐derived inbreds and hybrids exhibited comparable grain yield and phenotypic characteristics to the original versions. The maize hybrids developed in the study possessed high‐yielding ability with high kernel oil and OA, low PA, better fatty acid health and nutritional properties, higher multi‐vitamins and balanced amino acids, which hold immense significance to address malnutrition and rising demand for oil sustainably in a fast‐track manner. [ABSTRACT FROM AUTHOR]

Corn is one of the most important cereal crops in the world with highest yield potential. Nevertheless, its potential productivity is constrained by the occurrences of drought stress worldwide. Besides, in the era of climate change, frequent occurrences of severe droughts are predicted. The present investigation was carried out at Main Agricultural Research Station, University of Agricultural Sciences, Dharwad in split plot design to study response of twenty-eight new corn inbreds under drought free (well-watered) conditions and drought simulated by withholding irrigation from 40 to 75 DAS to create water stress. Significant differences among the corn inbreds, moisture treatments and interaction between inbreds were observed for morpho-physiological, yield and yield components indicating differential response of corn inbreds. The inbreds CAL 1426-2 (higher RWC, SLW& wax and lower ASI), PDM 4641(higher SLW, proline, & wax, and lower ASI) and GPM 114 (higher proline & wax, and lower ASI) were drought tolerant. These inbreds are having higher production potential (>5.0 t/ha) under moisture stress condition with less per cent reduction (

Multi-location experiments on maize were conducted from 2016 to 2019 at ten locations distributed across two agro-climatic zones (ACZ) i.e., ACZ-3 and ACZ-8 of Karnataka, India. Individual analysis of variance for each location-year combination showed significant differences among the hybrids; similarly, combined analysis showed a higher proportion of GE interaction variance than due to genotype. Mega-environments were identified using biplot approaches such as AMMI, GGE, and WAASB methodologies for the years 2016 to 2019. The BLUP method revealed a high correlation between grain yield and stability indices ranging from 0.67 to 1.0. Considering all three methods together, the three location pairs Arabhavi-Belavatagi, Bailhongal-Belavatagi, and Hagari-Sirguppa had three occurrences in the same mega-environment with a value of 0.67, and these location combinations consistently produced winning genotypes. Among the common winning genotypes identified, it was G7 during 2016 and 2017 and G10 during 2018 and 2019, based on WAASBY. The likelihood of Arabhavi-Nippani, Hagari-Mudhol, and Dharwad-Hagari occurring in the same mega-environment is minimal because they did not share the same winning genotype, with the exception of a small number of events. Despite being in the same agro-climatic zone, Arabhavi, Hagari, and Mudhol rarely had a winning genotype in common. An agro-climatic zone is grouped based on climatic and soil conditions which doesn't consider GE interaction of cultivars thus, releasing the cultivars for commercial cultivation considering mega environments pattern would enhance the yield for the given target region. [ABSTRACT FROM AUTHOR]

Background: Kernel row number (KRN) is an important yield component trait with a direct impact on the productivity of maize. The variability in KRN is influenced by the inflorescence meristem size, which is determined by the CLAVATA-WUSCHEL pathway. A CLAVATA receptor-like protein, encoded by the FASCIATED EAR2 (fea2gene), enhances the growth of inflorescence meristem and is thus involved in the determination of KRN. The amplicon sequencing-based method was employed to dissect the allelic variation of the fea2 gene in tropical field corn. Methodology/Principal finding: Amplicon-based sequencing of AI 535 (Low KRN) and AI 536 (High KRN) was undertaken for the gene fea 2 gene that codes for KRN in maize. Upon multiple sequence alignment of both sequences, A to T transversion at the 1311 position was noticed between Low KRN and High KRN genotypes resulting in different allelic forms of a fea2 gene in tropical maize. An allele-specific primer 1311 fea2.1 was designed and validated that can differentiate High and Low KRN genotypes. Conclusion/Significance: Maize has high variability for KRN and is exemplified by the wide values ranging from 8–26 KRN in the maize germpalsm. The sequence-based approach of SNP detection through the use of a specific primer facilitated the detection of variation present in the target trait. This makes it possible to capture these variations in the early generation. In the study, the PCR-based differentiation method described for the identification of desirable high KRN genotypes would augment the breeding programs for improving the productivity of field corn. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

'Sikkim Primitive' is a prolific maize landrace with five to nine ears per plant. Though the landrace was discovered in 1960s, loci governing the prolificacy was not identified. Here, a prolific inbred 'MGUSP101' developed from 'Sikkim Primitive' was crossed with two nonprolific inbreds, namely, HKI1128 and UMI1200. Two F2:3 populations (MGUSP101 × HKI1128 and MGUSP101 × UMI1200) were evaluated at three locations. Across locations, number of ears per plant varied from 1.35 to 5.38 in MGUSP101 × HKI1128 population. Bulked‐segregant analysis coupled with targeted QTL mapping identified a major QTL (bin: 8.05) explaining 31.7% phenotypic variation amongst 145 F2:3 individuals. The QTL was further validated in 138 F2:3 individuals of MGUSP101 × UMI1200 (range: 1.10–4.88). The identified QTL explained 29.2% of phenotypic variance at the same interval. We designated this novel QTL as 'qProl‐SP‐8.05' which has not been reported earlier. Six candidate genes responsible for prolificacy were also identified. This novel QTL can be introgressed through marker‐assisted selection for induction of prolificacy in elite maize. This is the first report of identification of locus governing prolificacy in 'Sikkim Primitive'. [ABSTRACT FROM AUTHOR]

Malnutrition has emerged as one of the major health problems worldwide. Traditional yellow maize has low provitamin-A (proA) content and its genetic base in proA biofortification breeding program of subtropics is extremely narrow. To diversify the proA rich germplasm, 10 elite low proA inbreds were crossed with a proA rich donor (HP702-22) having mutant crtRB1 gene. The F2 populations derived from these crosses were genotyped using InDel marker specific to crtRB1. Severe marker segregation distortion was observed. Seventeen crtRB1 inbreds developed through marker-assisted pedigree breeding and seven inbreds generated using marker-assisted backcross breeding were characterized using 77 SSRs. Wide variation in gene diversity (0.08 to 0.79) and dissimilarity coefficient (0.28 to 0.84) was observed. The inbreds were grouped into three major clusters depicting the existing genetic diversity. The crtRB1-based inbreds possessed high β-carotene (BC: 8.72μg/g), β-cryptoxanthin (BCX: 4.58μg/g) and proA (11.01μg/g), while it was 2.35μg/g, 1.24μg/g and 2.97μg/g in checks, respectively. Based on their genetic relationships, 15 newly developed crtRB1-based inbreds were crossed with five testers (having crtRB1 gene) using line × tester mating design. 75 experimental hybrids with crtRB1 gene were evaluated over three locations. These experimental hybrids possessed higher BC (8.02μg/g), BCX (4.69μg/g), proA (10.37μg/g) compared to traditional hybrids used as check (BC: 2.36 μg/g, BCX: 1.53μg/g, proA: 3.13μg/g). Environment and genotypes × environment interaction had minor effects on proA content. Both additive and dominance gene action were significant for proA. The mean proportion of proA to total carotenoids (TC) was 44% among crtRB1-based hybrids, while 11% in traditional hybrids. BC was found to be positively correlated with BCX (r = 0.68) and proA (r = 0.98). However, no correlation was observed between proA and grain yield. Several hybrids with >10.0 t/ha grain yield with proA content >10.0 μg/g were identified. This is the first comprehensive study on development of diverse proA rich maize hybrids through marker-assisted pedigree breeding approach. The findings provides sustainable and cost-effective solution to alleviate vitamin-A deficiency. [ABSTRACT FROM AUTHOR]

Traditional yellow maize though contains high kernel carotenoids, the concentration of provitamin A (proA) is quite low (<2µg/g), compared to recommended level (15µg/g). It also possesses poor endosperm protein quality due to low concentration of lysine and tryptophan. Natural variant of crtRB1 (β-carotene hydroxylase) and lcyE (lycopene-ε-cyclase) cause significant enhancement of proA concentration, while recessive allele, opaque2 (o2) enhances the level of these amino acids. Development of biofortified maize enriched in proA, lysine and tryptophan thus holds significance in alleviation of micronutrient malnutrition. In the present study, marker-assisted stacking of crtRB1, lcyE and o2 was undertaken in the genetic background of four maize hybrids (HQPM1, HQPM4, HQPM5, and HQPM7) popularly grown in India. HP704-22 and HP704-23 were used as donors, while four elite QPM parents viz., HKI161, HKI163, HKI193-1, and HKI193-2 were used as recipients. CrtRB1 showed severe segregation distortion, while lcyE segregated as per the expectation. Recovery of recurrent parent genome (RPG) among selected backcross progenies ranged from 89 to 93%. Introgressed progenies possessed high concentration of proA (7.38-13.59µg/g), compared to 1.65-2.04µg/g in the recurrent parents. The reconstituted hybrids showed an average of 4.5-fold increase in proA with a range of 9.25-12.88µg/g, compared to original hybrids (2.14-2.48µg/g). Similar plant-, ear-, and grain- characteristics of improved versions of both inbreds and hybrids were observed when evaluated with their respective original versions. Mean lysine (0.334%) and tryptophan (0.080%) of the improved hybrids were at par with the original versions (lysine: 0.340%, tryptophan: 0.083%). Improved hybrids also possessed similar grain yield potential (6,301-8,545 kg/ha) with their original versions (6,135-8,479 kg/ha) evaluated at two locations. This is the first study of staking crtRB1-, lcyE-, and o2-, favorable alleles in single genetic background. The improved inbreds can be effectively used as potential donor for independent and/or simultaneous introgression of crtRB1, lcyE, and o2 in the future breeding programme. These biofortified maize hybrids, rich in proA, lysine and tryptophan will hold great promise for nutritional security. [ABSTRACT FROM AUTHOR]

Deficiency of iron and zinc causes micronutrient malnutrition or hidden hunger, which severely affects ~25% of global population. Genetic biofortification of maize has emerged as cost effective and sustainable approach in addressing malnourishment of iron and zinc deficiency. Therefore, understanding the genetic variation and stability of kernel micronutrients and grain yield of the maize inbreds is a prerequisite in breeding micronutrient-rich high yielding hybrids to alleviate micronutrient malnutrition. We report here, the genetic variability and stability of the kernel micronutrients concentration and grain yield in a set of 50 maize inbred panel selected from the national and the international centres that were raised at six different maize growing regions of India. Phenotyping of kernels using inductively coupled plasma mass spectrometry (ICP-MS) revealed considerable variability for kernel minerals concentration (iron: 18.88 to 47.65 mg kg–1; zinc: 5.41 to 30.85 mg kg–1; manganese: 3.30 to17.73 mg kg–1; copper: 0.53 to 5.48 mg kg–1) and grain yield (826.6 to 5413 kg ha–1). Significant positive correlation was observed between kernel iron and zinc within (r = 0.37 to r = 0.52, p < 0.05) and across locations (r = 0.44, p < 0.01). Variance components of the additive main effects and multiplicative interactions (AMMI) model showed significant genotype and genotype × environment interaction for kernel minerals concentration and grain yield. Most of the variation was contributed by genotype main effect for kernel iron (39.6%), manganese (41.34%) and copper (41.12%), and environment main effects for both kernel zinc (40.5%) and grain yield (37.0%). Genotype main effect plus genotype-by-environment interaction (GGE) biplot identified several mega environments for kernel minerals and grain yield. Comparison of stability parameters revealed AMMI stability value (ASV) as the better representative of the AMMI stability parameters. Dynamic stability parameter GGE distance (GGED) showed strong and positive correlation with both mean kernel concentrations and grain yield. Inbreds (CM-501, SKV-775, HUZM-185) identified from the present investigation will be useful in developing micronutrient-rich as well as stable maize hybrids without compromising grain yield. [ABSTRACT FROM AUTHOR]

Development of vitamin A-rich cereals can help in alleviating the widespread problem of vitamin A deficiency. We report here significant enhancement of kernel β-carotene in elite maize genotypes through accelerated marker-assisted backcross breeding. A favourable allele (543 bp) of the β-carotene hydroxylase (crtRB1) gene was introgressed in the seven elite inbred parents, which were low (1.4 µg/g) in kernel β-carotene, by using a crtRB1-specific DNA marker for foreground selection. About 90% of the recurrent parent genome was recovered in the selected progenies within two backcross generations. Concentration of β-carotene among the crtRB1-introgressed inbreds varied from 8.6 to 17.5 µg/g - a maximum increase up to 12.6-fold over recurrent parent. The reconstituted hybrids developed from improved parental inbreds also showed enhanced kernel β-carotene as high as 21.7 µg/g, compared to 2.6 µg/g in the original hybrid. The reconstituted hybrids evaluated at two locations possessed similar grain yield to that of original hybrids. These β-carotene enriched high yielding hybrids can be effectively utilized in the maize biofortification programs across the globe. [ABSTRACT FROM AUTHOR]

Globally, one-third of the population is affected by iron (Fe) and zinc (Zn) deficiency, which is severe in developing and underdeveloped countries where cereal-based diets predominate. The genetic biofortification approach is the most sustainable and one of the cost-effective ways to address Fe and Zn malnutrition. Maize is a major source of nutrition in sub-Saharan Africa, South Asia and Latin America. Understanding systems' biology and the identification of genes involved in Fe and Zn homeostasis facilitate the development of Fe- and Zn-enriched maize. We conducted a genome-wide transcriptome assay in maize inbred SKV616, under –Zn, –Fe and –Fe–Zn stresses. The results revealed the differential expression of several genes related to the mugineic acid pathway, metal transporters, photosynthesis, phytohormone and carbohydrate metabolism. We report here Fe and Zn deficiency-mediated changes in the transcriptome, root length, stomatal conductance, transpiration rate and reduced rate of photosynthesis. Furthermore, the presence of multiple regulatory elements and/or the co-factor nature of Fe and Zn in enzymes indicate their association with the differential expression and opposite regulation of several key gene(s). The differentially expressed candidate genes in the present investigation would help in breeding for Fe and Zn efficient and kernel Fe- and Zn-rich maize cultivars through gene editing, transgenics and molecular breeding. [ABSTRACT FROM AUTHOR]

Abstract Deficiency of vitamin-E or tocopherol causes neurological disorders in humans. α-tocopherol possessing the highest vitamin-E activity is present in low concentration in maize kernel. Nine lines and four testers possessing favourable allele of ZmVTE4 that significantly enhances vitamin-E activity were used to generate 36 hybrid combinations. Significant variation was observed for α- (5.95–39.03 μg/g), γ- (11.69–50.82 μg/g), δ- (4.09–10.76 μg/g) and total-tocopherol (33.18–90.53 μg/g). α-, γ- and δ-tocopherol constituted 36%, 53% and 11% of the total tocopherol, respectively. Majority of the experimental hybrids possessed significantly higher α-tocopherol (mean: 21.37 μg/g) than the check hybrids (mean: 11.16 μg/g). AMMI analysis revealed that across tocopherols, genotype and interaction effect accounted 35–77% and 23–45% of variation, respectively. The environmental effects were of minor magnitude. Non-additive gene action was predominant for α-, γ-, and total-tocopherol, while δ-tocopherol was conditioned predominantly by additive gene action. The information generated here assumes great significance in biofortification programme. This is the first report of variability, G × E interactions and combining ability for kernel tocopherol using maize hybrids possessing novel allele of ZmVTE4. Highlights • In maize, the level of α-tocopherol (efficient form of vitamin-E) is very low. • The novel and the favourable allele of γ-tocopherol methyl transferase (ZmVTE4) enhance α-tocopherol in maize grain by 2–3 folds. • Here, maize inbreds with favourable allele of ZmVTE4 were used to generate single cross hybrids. • These hybrids were evaluated at multi-locations to study the variability of different tocopherol components, their G × E interactions and nature of gene action. • The results obtained holds immense significance in maize biofortification programme for the development of vitamin-E rich maize. [ABSTRACT FROM AUTHOR]

The improvement of protein quality in maize so far has been based on recessive opaque2 ( o2 ) mutant that along with endosperm-modifiers led to development of quality protein maize (QPM). Recent discovery of nutritional benefits of recessive opaque16 ( o16 ) mutant was of immense significance for further improvement of protein quality. In the present study, o16 was introgressed into o2 -based parental inbreds (HKI161, HKI193-1, HKI193-2 and HKI163) of four commercial QPM hybrids (HQPM-1, HQPM-4, HQPM-5 and HQPM-7) released in India, using marker-assisted backcross breeding. Background selection led to high recovery of recurrent parent genome (RPG) to maximum of 95%, and introgressed progenies showed considerable phenotypic resemblance for plant-, ear- and grain- characteristics to their respective recurrent parents. Selection of markers for o2 and o16 led to development of pyramided lines ( o2o2/o16o16 ) that possessed as high as 76% and 91% more lysine and tryptophan over the recurrent parents, respectively. Reconstituted hybrids showed an average enhancement of 49% and 60% in lysine and tryptophan over the original hybrids, with highest enhancement amounting 64% and 86%, respectively. This is first report of enhancement of both lysine and tryptophan by o16 in maize genotypes adaptable to sub-tropics. Moderate variation in lysine and tryptophan was also observed in pyramided lines. Multi-location evaluation of reconstituted hybrids revealed similar grain yield and attributing traits to their original versions. This study signified the role of o16 as supplementary to o2 for nutritional quality enhancement in maize, and improved elite inbreds and hybrids developed here hold great significance in maize biofortification programme. [ABSTRACT FROM AUTHOR]