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.

Traditional yellow maize though contains high kernel carotenoids, the concentration of provitamin A (proA) is quite low (<2 μg/g), compared to recommended level (15 μg/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 (7.38–13.59 μg/g), compared to 1.65–2.04 μg/g in the recurrent parents. The reconstituted hybrids showed an average of 4.5-fold increase in proA with a range of 9.25–12.88 μg/g, compared to original hybrids (2.14–2.48 μg/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.

A pot experiment with 17 diverse genotypes of cucumber with four levels of salt stress viz., 0, 2, 4 and 6 dS m -1 was carried out during 2006. ANOVA revealed significant differences amongst genotypes and genotype 9 salt stress interaction indicating the genetic variability and differential response of the genotypes to different salt stress levels. The salt stress adversely affected the biochemical parameters; effects were severe under 4 dS m -1 . No genotype could survive at 6 dS m -1 . Sodium content, Na ? -K ? ratio, proline, reducing sugars, phenol and yield reduction (%) increased significantly as the salt stress increased. Potassium, chlorophyll, membrane stability index and fruit yield decreased significantly under salt stress in all genotypes. However, the genotypes CRC-8, CHC-2 and G-338 showed lower accumulation of sodium, lesser depletion of potassium, lower Na ? -K ? ratio and higher accumulation of proline, reducing sugars, phenols, better membrane stability and lower yield reduction (%) under salt stress, while CH-20 and DC-1 were sensitive to salt stress. Thus, a combination of traits such as higher membrane stability, lower Na ? -K ? ratio, higher osmotic concentration and selective uptake of useful ions and prevention of over accumulation of toxic ions contribute to salt stress tolerance in cucumber. These traits would be useful selection criteria during salt stress breeding in cucumber.

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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.

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.

Prolificacy assumes significance for development of high‐yielding baby corn hybrids. “Sikkim Primitive” is a native landrace of North‐Eastern Himalaya, and is the highest prolific maize germplasm. So far, the genetics of prolificacy in “Sikkim Primitive” has not been deciphered. Here, a prolific inbred (MGU‐SP‐101) developed from “Sikkim Primitive” was crossed with four non‐prolific inbreds viz., LM13, BML7, HKI161 and HKI1128. Six generations (P1, P2, F1, F2, BC1P1 and BC1P2) of the crosses were evaluated at two locations during rainy season 2018. MGU‐SP‐101 possessed 2.50–3.78 ears per plant compared to 1.06–1.86 among non‐prolific inbreds. The variation for ears was the highest in F2s (1–8), followed by BC1P1 (1–7) and BC1P2 (1–5). The quantitative inheritance pattern of prolificacy with prevalence of non‐allelic interactions of duplicate epistasis type has been observed. Dominance × dominance effect was predominant over additive × additive and additive × dominance effects. Total number of major gene blocks ranged from 0.41 to 2.86, thereby suggesting the involvement of at least one major gene/QTL governing the prolificacy. This is the first report of genetic dissection of prolificacy in “Sikkim Primitive”.

Assessment of the differential expression of antioxidative enzymes and their isozymes, was done in 30 day-old ex vitro raised plants of three highly resistant (DP-25, Jhankri and Duradim) and one highly susceptible (N-118) genotypes of taro [Colocasia esculenta (L.) Schott]. Antioxidative enzymes were assayed in the ex vitro plants, 7 days after inoculation with the spores (15,000 spores ml(-1) water) of Phytophthora colocasiae Raciborski to induce taro leaf blight disease. Uninoculated ex vitro plants in each genotype were used as control. The activity of superoxide dismutase (SOD) and guaiacol peroxidase (GPX) increased under induced blight condition when compared with control. Increase in antioxidative enzymes was more (67-92%) in the resistant genotypes than that (21-29%) of the susceptible genotype. The zymograms of SOD and GPX in the resistant genotypes, with pathogenic infection, showed increased activity for anodal isoform of SOD and increased expression and/or induction of either POX 1 or POX 2 isoforms of GPX. In susceptible genotype, expression of the above isoforms was faint for SOD and nearly absent for GPX under both blight free and induced blight conditions. Induction and/or increased activity of particular isoform of SOD and GPX against infection of Phytophthora colocasiae in the resistant genotypes studied led to the apparent conclusion of linkage of isozyme expression with blight resistance in taro. This might be an important criterion in breeding of taro for Phytophthora leaf blight resistance.