Breeding Drought-Tolerant Pearl Millet Using Conventional and Genomic Approaches: Achievements and Prospects.

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a C4 crop cultivated for its grain and stover in crop-livestock-based rain-fed farming systems of tropics and subtropics in the Indian subcontinent and sub-Saharan Africa. The intensity of drought is predicted to further exacerbate because of looming climate change, necessitating greater focus on pearl millet breeding for drought tolerance. The nature of drought in different target populations of pearl millet-growing environments (TPEs) is highly variable in its timing, intensity, and duration. Pearl millet response to drought in various growth stages has been studied comprehensively. Dissection of drought tolerance physiology and phenology has helped in understanding the yield formation process under drought conditions. The overall understanding of TPEs and differential sensitivity of various growth stages to water stress helped to identify target traits for manipulation through breeding for drought tolerance. Recent advancement in high-throughput phenotyping platforms has made it more realistic to screen large populations/germplasm for drought-adaptive traits. The role of adapted germplasm has been emphasized for drought breeding, as the measured performance under drought stress is largely an outcome of adaptation to stress environments. Hybridization of adapted landraces with selected elite genetic material has been stated to amalgamate adaptation and productivity. Substantial progress has been made in the development of genomic resources that have been used to explore genetic diversity, linkage mapping (QTLs), marker-trait association (MTA), and genomic selection (GS) in pearl millet. High-throughput genotyping (HTPG) platforms are now available at a low cost, offering enormous opportunities to apply markers assisted selection (MAS) in conventional breeding programs targeting drought tolerance. Next-generation sequencing (NGS) technology, micro-environmental modeling, and pearl millet whole genome re-sequence information covering circa 1,000 wild and cultivated accessions have helped to greater understand germplasm, genomes, candidate genes, and markers. Their application in molecular breeding would lead to the development of high-yielding and drought-tolerant pearl millet cultivars. This review examines how the strategic use of genetic resources, modern genomics, molecular biology, and shuttle breeding can further enhance the development and delivery of drought-tolerant cultivars.

Identification of heterotic groups in South-Asian-bred hybrid parents of pearl millet.

KEY MESSAGE: Pearl millet breeding programs can use this heterotic group information on seed and restorer parents to generate new series of pearl millet hybrids having higher yields than the existing hybrids. Five hundred and eighty hybrid parents, 320 R- and 260 B-lines, derived from 6 pearl millet breeding programs in India, genotyped following RAD-GBS (about 0.9 million SNPs) clustered into 12 R- and 7 B-line groups. With few exceptions, hybrid parents of all the breeding programs were found distributed across all the marker-based groups suggesting good diversity in these programs. Three hundred and twenty hybrids generated using 37 (22 R and 15 B) representative parents, evaluated for grain yield at four locations in India, showed significant differences in yield, heterosis, and combining ability. Across all the hybrids, mean mid- and better-parent heterosis for grain yield was 84.0% and 60.5%, respectively. Groups G12 B × G12 R and G10 B × G12 R had highest heterosis of about 10% over best check hybrid Pioneer 86M86. The parents involved in heterotic hybrids were mainly from the groups G4R, G10B, G12B, G12R, and G13B. Based on the heterotic performance and combining ability of groups, 2 B-line (HGB-1 and HGB-2) and 2 R-line (HGR-1 and HGR-2) heterotic groups were identified. Hybrids from HGB-1 × HGR-1 and HGB-2 × HGR-1 showed grain yield heterosis of 10.6 and 9.3%, respectively, over best hybrid check. Results indicated that parental groups can be formed first by molecular markers, which may not predict the best hybrid combination, but it can reveal a practical value of assigning existing and new hybrid pearl millet parental lines into heterotic groups to develop high-yielding hybrids from the different heterotic groups.

Removal of 4-Nitrophenol from Water Using Ag-N-P-Tridoped TiO2 by Photocatalytic Oxidation Technique.

Photocatalytic oxidation using semiconductor nanoparticles is an efficient, eco-friendly, and cost-effective process for the removal of organic pollutants, such as dyes, pesticides, phenols, and their derivatives in water. In the present study, nanosize Ag-N-P-tridoped titanium(IV) oxide (TiO2) was prepared by using sol-gel-synthesized Ag-doped TiO2 and soybean (Glycine max) or chickpea (Cicer arietinum) seeds as nonmetallic bioprecursors. As-synthesized photocatalysts were characterized using X-ray diffraction, Fourier transform infrared, and ultra violet (UV)-visible spectroscopic techniques. Average crystallite size of the studied photocatalysts was within 39-46 nm. Whereas doped Ag in TiO2 minimized the photogenerated electron-hole recombination, doped N and P extended its photoabsorption edge to visible region. Tridoping of Ag, N, and P in TiO2 exhibited synergetic effect toward enhancing its photocatalytic degradation of 4-nitrophenol (4-NP), separately, under UV and visible irradiations. At three hours, degradations of 4-NP over Ag-N-P-tridoped TiO2 under UV and visible radiations were 73.8 and 98.1%, respectively.

Induced defence responses of contrasting bread wheat genotypes under differential salt stress imposition.

Plants, being sessile in nature, have developed mechanisms to cope with high salt concentrations in the soil. In this study, the effects of NaCl (50-200 mM) on expression of high-affinity potassium transporters (HKTs), antioxidant enzymes and their isozyme profiles were investigated in two contrasting bread wheat (Triticum aestivum L.) genotypes viz., HD2329 (salt-sensitive) and Kharchia65 (salt-tolerant). Kharchia65 can successfully grow in salt affected soils, while HD2329 cannot tolerate salt stress. Differential expression studies of two HKT genes (TaHKT2;1.1 and TaHKT2;3.1) revealed their up-regulated expression (-1.5-fold) in the salt-sensitive HD2329 and down-regulated (-5-fold) inducible expression in the salt-tolerant genotype (Kharchia65). Specific activity of antioxidant enzymes, viz. superoxide dismutase (SOD), peroxidase (POX), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) was found to be higher in the salt-tolerant genotype. Isozyme profile of two (POX and GR) antioxidant enzymes showed polymorphism between salt-tolerant and salt-sensitive genotypes. A new gene TaHKT2;3.1 was also identified and its expression profile and role in salt stress tolerance in wheat was also studied. Partial sequences of the TaHKT2;1.1 and TaHKT2;3.1 genes from bread wheat were submitted to the EMBL GenBank database. Our findings indicated that defence responses to salt stress were induced differentially in contrasting bread wheat genotypes which provide evidences for functional correlation between salt stress tolerance and differential biochemical and molecular expression patterns in bread wheat.

Ribonuclease, deoxyribonuclease, and antiviral activity of Escherichia coli-expressed Bougainvillea xbuttiana antiviral protein 1.

A full-length cDNA encoding ribosome-inactivating/antiviral protein from the leaves of Bougainvillea xbuttiana was recently isolated. The coding region of cDNA was cloned and expressed in Escherichia coli, and the protein product was designated as BBAP1 (Bougainvillea xbuttiana antiviral protein 1). BBAP1 showed ribonuclease activity against Torula yeast RNA. It also exhibited depurination activity against supercoiled pBlueScript SK+ plasmid DNA in a concentration dependent manner, and was found to convert nicked circular DNA into linear form only at higher concentration. On bioassay, BBAP1 exhibited antiviral activity against sunnhemp rosette virus infecting Cyamopsis tetragonoloba leaves in which 95% inhibition of local lesion formation was observed.

Possible mechanism of action of antiviral proteins from the leaves of Chenopodium album L.

Antiviral proteins (AVPs) named CAP-I and CAP-II purified from the leaves of Chenopodium album cv Pusa Bathua-1 induced systemic resistance against tobacco mosaic virus (TMV) and sunnhemp rosette virus (SRV) in both hypersensitive as well as systemic hosts. An increased accumulation of two polypeptides (approximately 17 kDa and approximately 26 kDa) was observed in untreated upper leaves of Cyamopsis tetragonoloba plants whose basal leaves were treated with CAP-I/CAP-II. Both AVPs exhibited ribosomal RNA N-glycosidase activity on 28S rRNA of tobacco leaves and also caused in vitro degradation of TMV RNA. It is suggested that the CAP-I and -II are multi-functional and may be acting at multiple levels to ensure maximum possible inhibition of viral infection.

Mapping and characterisation of QTL x E interactions for traits determining grain and stover yield in pearl millet.

A mapping population of 104 F(3) lines of pearl millet, derived from a cross between two inbred lines H 77/833-2 x PRLT 2/89-33, was evaluated, as testcrosses on a common tester, for traits determining grain and stover yield in seven different field trials, distributed over 3 years and two seasons. The total genetic variation was partitioned into effects due to season (S), genotype (G), genotype x season interaction (G x S), and genotype x environment-within-season interaction [G x E(S)]. QTLs were determined for traits for their G, G x S, and G x E(S) effects, to assess the magnitude and the nature (cross over/non-crossover) of environmental interaction effects on individual QTLs. QTLs for some traits were associated with G effects only, while others were associated with the effects of both G and G x S and/or G, G x S and G x E(S) effects. The major G x S QTLs detected were for flowering time (on LG 4 and LG 6), and mapped to the same intervals as G x S QTLs for several other traits (including stover yield, harvest index, biomass yield and panicle number m(-2)). All three QTLs detected for grain yield were unaffected by G x S interaction however. All three QTLs for stover yield (mapping on LG 2, LG 4 and LG 6) and one of the three QTLs for grain yield (mapping on LG 4) were also free of QTL x E(S) interactions. The grain yield QTLs that were affected by QTL x E(S) interactions (mapping on LG 2 and LG 6), appeared to be linked to parallel QTL x E(S) interactions of the QTLs for panicle number m(-2) on (LG 2) and of QTLs for both panicle number m(-2) and harvest index (LG 6). In general, QTL x E(S) interactions were more frequently observed for component traits of grain and stover yield, than for grain or stover yield per se.

A study on plasma selenium level among pregnant women at Rohtak, Haryana.

Selenium is an important trace element for human health. Selenium levels in mothers may have significant effects on fetal and neonatal nutrition. In a cross-sectional study undertaken in Rohtak, Haryana, plasma selenium level in mothers was investigated at the time of delivery. The mean plasma selenium level in full term mothers (n=82) was 70.63 +/- 1.62 ppb and in preterm mothers (n = 58), it was 63.28 +/- 2.31 ppb. The difference was statistically significant (p < 0.05). These levels were, however, below the reported normal level of 75-120 ppb in adults. Rura/urban stay, parity, maternal age, socio-economic and literacy status etc. did not influence the selenium level of mothers in either of the groups.

Selenium in the neonate.

Selenium is a trace element of tremendous importance in human health. It is a constituent of the antioxidant enzyme. Glutathione peroxidase and therefore is vital to antioxidant defense. Several diseases of the neonate have been shown to be caused at least in part by oxygen free radicals. These include bronchopulmonary dysplasia retinopathy of prematurity necrotising enterocolitis patient ductus arteriosus and neuronal injury of hypoxic ischemic encephalopathy. Good selenium nutrition is therefore of key importance to antioxidant defense in the neonate. The communique reviews the important role that selenium might play in neonatal health & disease.

Maternal and cord plasma selenium levels in full-term neonates.

Selenium is a part of the enzyme glutathione peroxidase and has an important role in the prevention of oxygen free radical injury. Hence good selenium nutrition is of special relevance to the neonate. The present study evaluated plasma selenium levels in cord plasma of 82 full term, appropriate for gestational age babies and their mothers at delivery. The plasma selenium levels in babies were 54.17 +/- 1.34 ppb which was significantly lower than 70.63 +/- 1.62 ppb seen in their mothers. Anemic mothers with a Hb < 8 g/dl had a plasma selenium level (60.74 +/- 4.57 ppb) which was lower than those with a Hb > 8 g/dl i.e. 74.19 +/- 2.17 ppb. Maternal age, parity, literacy and socio-economic status did not affect the plasma selenium levels.

Downy mildew incidence of pearl millet hybrids with different male-sterility inducing cytoplasms.

The use of different sources of cytoplasmic male sterility (CMS) in hybrid seed production of pearl millet [Pennisetum glaucum (L.) R. Br.] is advocated to avoid possible disease epidemics occurring due to cytoplasmic uniformity. The effects of commercially unexploited, but potentially exploitable, sources of CMS, like A2, A3 and A4, on downy mildew [Sclerospora graminicola (Sacc.) Schroet] incidence were studied by using the disease incidence of isonuclear hybrids with male-sterile and fertile cytoplasm. The mean downy mildew incidence of hybrids carrying different male-sterile cytoplasm was similar to that of hybrids retaining the fertile cytoplasm. The cytoplasm accounted for only 0.6% of the total variation and its effect was non-significant; pollinators could explain most of the variation in determining the disease incidence of hybrids. This suggested that these male-sterile cytoplasms are not linked to downy mildew susceptibility and thus can be exploited commercially to broaden the cytoplasmic base of the male-sterile lines and, ultimately, of hybrids.

Effect of A1 cytoplasm on the combining ability for smut severity in pearl millet.

Among the various available sources of male-sterile cytoplasm in pearl millet [Pennisetum glaucum (L.) R.Br.], the A1 source has been exploited the most for the breeding of commercial F1 hybrids. The effect of this source on the combining ability (CA) for smut severity was studied since it is the CA that determines the performance of hybrids. The effect was estimated by comparing the CA estimates of 5 pairs of lines and 35 pairs of crosses with and without A1 cytoplasm. The cytoplasm showed either a significantly desirable or at least no adverse effect on the CA of 4 out of the 5 line pairs and 56 out of 70 pairs of comparison of crosses in two environments. The differential effect of cytoplasm in some pairs might be due to its interaction with nuclear genes. These results further substantiated that the A1 cytoplasm is not linked with increased smut severity in pearl millet hybrids.

Influence of A1 cytoplasmic substitution on the downy-mildew incidence of pearl millet.

Large-scale cultivation of pearl millet [Pennisetum glaucum (L.) R. Br. F1 hybrids in India has led to increased incidence of downy-mildew (Sclerospora graminicola). There is concern that the A1 male-sterile cytoplasm used in all the hybrids released so far is responsible for this increase. The influence of A1 malesterile cytoplasm on downy-mildew incidence in pearl millet was studied by comparing the disease reaction of 40 pairs of F1 hybrids, each pair carrying respectively a1 male-sterile and normal B cytoplasm. Mean downy-mildew incidence was similar in the hybrids carrying either A1 male-sterile or B cytoplasm. The general combining ability of lines with and without A1 cytoplasm was found to be similar for downy-mildew incidence. These results indicated that in pearl millet A1 cytoplasm is not associated with increased downymildew incidence. The possible danger of using only one source of cytoplasm has been briefly discussed.

Malnutrition among children in an urban Indian slum and its associations.

PIP: In a cross-sectional study in Bhopal, India, mothers and other family members were surveyed by questionnaire, then 1000 randomly selected slum children were clinically examined, to detect nutritional deficiency diseases. Anthropometric measurements were also taken. Malnutrition classification followed the Harvard classification (weight in relation to the age of the child) modified by the Indian Academy of Pediatrics. The weight of the children was recorded using the Avery personal weighing machine. Of the 1000 children, 520 were males and 480 were females almost matched in age and birth order. The prevalence of various nutritional deficiency diseases comprised: protein calorie malnutrition (63.4%), vitamin A deficiency (23.4%), vitamin B deficiency (16.2%), vitamin C deficiency (2.6%), vitamin D deficiency (9.4%), fluorine deficiency (2.9%), and anemia (7.2%). The prevalence of malnutrition was 65.0% among females compared to 61.9% in males (p 0.05). However, higher grades of malnutrition (III+IV) were 13.12% among females in comparison to 7.87% among males (p 0.05); whereas lower grades of malnutrition (I+II) were 54.04% among males and 51.87% among females (p0.05). The birth order of the children was positively associated with their grades of malnutrition (p 0.05). On the other hand, an inverse relationship was observed between birth interval and grades of malnutrition (p 0.05). The prevalence of malnutrition was significantly higher among those children whose fathers were illiterate (p 0.05). In general, as the literacy status of father increased, the prevalence of malnutrition among children decreased. The prevalence of malnutrition had a positive association (p 0.05) with children's family size: 3 members (47.0%), 4-6 members (63.9%), and 7 members and above (70.6%). On the other hand, an inverse correlation was observed between socioeconomic status and the prevalence of malnutrition (p 0.05). The prevalence of malnutrition was significantly (p 0.05) higher among the children with a history of infection (81.8%) and worm infestation (77.0%) in comparison to those without history of infection (13.1%) and worm infestation (61.9%), respectively. Similarly, nonimmunized children experienced more malnutrition (66.4%) in comparison to immunized children (57.0%).^ieng