•Marker-assisted backcross improvement of mega varieties of rice.•QTLs for drought, submergence and salt tolerance.•Foreground and recombinant selection.•Background selection using high density 50K ...SNP chip.
Rice is a staple cereal of India cultivated in about 43.5Mha area but with relatively low average productivity. Abiotic factors like drought, flood and salinity affect rice production adversely in more than 50% of this area. Breeding rice varieties with inbuilt tolerance to these stresses offers an economically viable and sustainable option to improve rice productivity. Availability of high quality reference genome sequence of rice, knowledge of exact position of genes/QTLs governing tolerance to abiotic stresses and availability of DNA markers linked to these traits has opened up opportunities for breeders to transfer the favorable alleles into widely grown rice varieties through marker-assisted backcross breeding (MABB). A large multi-institutional project, “From QTL to variety: marker-assisted breeding of abiotic stress tolerant rice varieties with major QTLs for drought, submergence and salt tolerance” was initiated in 2010 with funding support from Department of Biotechnology, Government of India, in collaboration with International Rice Research Institute, Philippines. The main focus of this project is to improve rice productivity in the fragile ecosystems of eastern, northeastern and southern part of the country, which bear the brunt of one or the other abiotic stresses frequently. Seven consistent QTLs for grain yield under drought, namely, qDTY1.1, qDTY2.1, qDTY2.2, qDTY3.1, qDTY3.2, qDTY9.1 and qDTY12.1 are being transferred into submergence tolerant versions of three high yielding mega rice varieties, Swarna-Sub1, Samba Mahsuri-Sub1 and IR 64-Sub1. To address the problem of complete submergence due to flash floods in the major river basins, the Sub1 gene is being transferred into ten highly popular locally adapted rice varieties namely, ADT 39, ADT 46, Bahadur, HUR 105, MTU 1075, Pooja, Pratikshya, Rajendra Mahsuri, Ranjit, and Sarjoo 52. Further, to address the problem of soil salinity, Saltol, a major QTL for salt tolerance is being transferred into seven popular locally adapted rice varieties, namely, ADT 45, CR 1009, Gayatri, MTU 1010, PR 114, Pusa 44 and Sarjoo 52. Genotypic background selection is being done after BC2F2 stage using an in-house designed 50K SNP chip on a set of twenty lines for each combination, identified with phenotypic similarity in the field to the recipient parent. Near-isogenic lines with more than 90% similarity to the recipient parent are now in advanced generation field trials. These climate smart varieties are expected to improve rice productivity in the adverse ecologies and contribute to the farmer’s livelihood.
Leaf rust (Puccinia triticina Eriks.) is a fungal disease of wheat (Triticum spp.), which causes considerable yield loss. Adult plant resistance (APR) is one of the most sustainable approaches to ...control leaf rust. In this study, field-testing was carried out across ten different locations, followed by molecular screening, to detect the presence of APR genes, Lr34+, Lr46+, Lr67+ and Lr68 in Indian wheat germplasm. In field screening, 190 wheat accessions were selected from 6,319 accessions based on leaf tip necrosis (LTN), disease severity and the average coefficient of infection. Molecular screening revealed that 73% of the accessions possessed known APR genes either as single or as a combination of two or three genes. The occurrence of increased LTN intensity, decreased leaf rust severity and greater expression of APR genes were more in relatively cooler locations. In 52 lines, although the presence of the APR genes was not detected, it still displayed high levels of resistance. Furthermore, 49 accessions possessing either two or three APR genes were evaluated for stability across locations for grain yield. It emerged that eight accessions had wider adaptability. Resistance based on APR genes, in the background of high yielding cultivars, is expected to provide a high level of race non-specific resistance, which is durable.
Relativistic millicharged particles (χq) have been proposed in various extensions to the standard model of particle physics. We consider the scenarios where they are produced at nuclear reactor core ...and via interactions of cosmic rays with the Earth’s atmosphere. Millicharged particles could also be candidates for dark matter and become relativistic through acceleration by supernova explosion shock waves. The atomic ionization cross section of χq with matter are derived with the equivalent photon approximation. Smoking-gun signatures with significant enhancement in the differential cross section are identified. New limits on the mass and charge of χq are derived, using data taken with a point-contact germanium detector with 500 g mass functioning at an energy threshold of 300 eV at the Kuo-Sheng Reactor Neutrino Laboratory.
This minireview explores the environmental bioremediation mediated by genetically engineered (GE) bacteria and it also highlights the limitations and challenges associated with the release of ...engineered bacteria in field conditions. Application of GE bacteria based remediation of various heavy metal pollutants is in the forefront due to eco-friendly and lesser health hazards compared to physico-chemical based strategies, which are less eco-friendly and hazardous to human health. A combination of microbiological and ecological knowledge, biochemical mechanisms and field engineering designs would be an essential element for successful in situ bioremediation of heavy metal contaminated sites using engineered bacteria. Critical research questions pertaining to the development and implementation of GE bacteria for enhanced bioremediation have been identified and poised for possible future research. Genetic engineering of indigenous microflora, well adapted to local environmental conditions, may offer more efficient bioremediation of contaminated sites and making the bioremediation more viable and eco-friendly technology. However, many challenges are to be addressed concerning the release of genetically engineered bacteria in field conditions. There are possible risks associated with the use of GE bacteria in field condition, with particular emphasis on ways in which molecular genetics could contribute to the risk mitigation. Both environmental as well as public health concerns need to be addressed by the molecular biologists. Although bioremediation of heavy metals by using the genetically engineered bacteria has been extensively reviewed in the past also, but the bio-safety assessment and factors of genetic pollution have been never the less ignored.
A matter-dominated model with gravitationally induced matter creation is proposed in the framework of Brans-Dicke theory. We obtain the main cosmological functions such as the scale factor of the ...Universe, the Hubble expansion rate, and the deceleration parameter analytically. We explore the viability of the model to explain the present accelerated expansion of the Universe. In this scenario, the present cosmic acceleration is supposed to be driven only by the negative creation pressure associated with the matter component. The evolution of such a model is tested by statistical analysis of the latest SNe, OHD, and BAO probes. We study and plot the trajectories of the evolution of the Universe with the best estimated values of the model parameters. It is observed that the expanding Universe begins with a big bang followed by a smooth transition from the decelerated phase to the accelerated phase. The ages of the Universe obtained by SNe+OHD and SNe+OHD+BAO in this model are in good agreement with the age predicted by the ΛCDM model. We analyze the model with a statefinder diagnostic and find that the model is different from the ΛCDM model but approaches ΛCDM in the future. The model shows quintessence behavior.
Recent work has underscored the importance of the microbiome in human health, and has largely attributed differences in phenotype to differences in the species present among individuals. However, ...mobile genes can confer profoundly different phenotypes on different strains of the same species. Little is known about the function and distribution of mobile genes in the human microbiome, and in particular whether the gene pool is globally homogenous or constrained by human population structure. Here, we investigate this question by comparing the mobile genes found in the microbiomes of 81 metropolitan North Americans with those of 172 agrarian Fiji islanders using a combination of single-cell genomics and metagenomics. We find large differences in mobile gene content between the Fijian and North American microbiomes, with functional variation that mirrors known dietary differences such as the excess of plant-based starch degradation genes found in Fijian individuals. Notably, we also observed differences between the mobile gene pools of neighbouring Fijian villages, even though microbiome composition across villages is similar. Finally, we observe high rates of recombination leading to individual-specific mobile elements, suggesting that the abundance of some genes may reflect environmental selection rather than dispersal limitation. Together, these data support the hypothesis that human activities and behaviours provide selective pressures that shape mobile gene pools, and that acquisition of mobile genes is important for colonizing specific human populations.
We study the matter creation cosmology as an alternative theory to explain the dark energy phenomena. We discuss the matter-dominated Universe in a flat Friedmann-Robertson-Walker line element by ...adopting the thermodynamics of open systems, in which the matter creation irreversible processes may take place at a cosmological scale. We propose a new form of the matter creation rate,
Γ
=
3
α
H
0
+
3
β
H
+
3
γ
a
¨
a
˙
, which generalizes some of the previous models in the literature. Exact solutions of the field equations are found and discussed the evolution of the Universe. Constraints on the model parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the Supernova distance modulus data, observational measurements of Hubble parameter, Baryon acoustic oscillation data. The trajectories of the evolution of the scale factor, deceleration parameter and equation of state parameter are plotted by using best-fit values of the parameters. It is observed that the model shows accelerating behavior and behaves quintessence like (
ω
>
-
1
). The age of the Universe is obtained which is in good agreement with
Λ
CDM model. We examine the model using two independent diagnostic parameters, namely statefinder and
Om
. We apply Akaike information criterion (
AIC
) and Bayesian information criterion (
BIC
) to discriminate the model based on the penalization associated to the number of parameters. The analysis shows that the model has close resemblance to the
Λ
C
D
M
cosmology. We also discuss the thermodynamics of the model and find that the model satisfies the generalized second law of thermodynamics with certain constraints.
In this work, we study a flat Friedmann–Robertson–Walker universe filled with dark matter and viscous new holographic dark energy. We present four possible solutions of the model depending on the ...choice of the viscous term. We obtain the evolution of the cosmological quantities such as scale factor, deceleration parameter and transition redshift to observe the effect of viscosity in the evolution. We also emphasis upon the two independent geometrical diagnostics for our model, namely the statefinder and the
Om
diagnostics. In the first case we study new holographic dark energy model without viscous and obtain power-law expansion of the universe which gives constant deceleration parameter and statefinder parameters. In the limit of the parameter, the model approaches to
Λ
C
D
M
model. In new holographic dark energy model with viscous, the bulk viscous coefficient is assumed as
ζ
=
ζ
0
+
ζ
1
H
, where
ζ
0
and
ζ
1
are constants, and
H
is the Hubble parameter. In this model, we obtain all possible solutions with viscous term and analyze the expansion history of the universe. We draw the evolution graphs of the scale factor and deceleration parameter. It is observed that the universe transits from deceleration to acceleration for small values of
ζ
in late time. However, it accelerates very fast from the beginning for large values of
ζ
. By illustrating the evolutionary trajectories in
r
-
s
and
r
-
q
planes, we find that our model behaves as an quintessence like for small values of viscous coefficient and a Chaplygin gas like for large values of bulk viscous coefficient at early stage. However, model has close resemblance to that of the
Λ
C
D
M
cosmology in late time. The
Om
has positive and negative curvatures for phantom and quintessence models, respectively depending on
ζ
. Our study shows that the bulk viscosity plays very important role in the expansion history of the universe.
In this paper, we study Friedmann cosmology with time-varying vacuum energy density in the context of Brans–Dicke theory. We consider an isotropic and homogeneous flat space, filled with a ...matter-dominated perfect fluid and a dynamical cosmological term
Λ
(
t
)
, obeying the equation of state of the vacuum. As the exact nature of a possible time-varying vacuum is yet to be found, we explore
Λ
(
t
)
given by the phenomenological law
Λ
(
t
)
=
λ
+
σ
H
, where
λ
and
σ
are positive constants. We solve the model and then focus on two different cases
Λ
H
1
and
Λ
H
2
by assuming
Λ
=
λ
and
Λ
=
σ
H
, respectively. Notice that
Λ
H
1
is the analog of the standard
Λ
CDM, but within the Brans–Dicke cosmology. We find the analytical solution of the main cosmological functions such as the Hubble parameter, the scale factor, deceleration and equation of state parameters for these models. In order to test the viability of the cosmological scenarios, we perform two sets of joint observational analyses of the recent Type Ia supernova data (Pantheon), observational measurements of Hubble parameter data, Baryon acoustic oscillation/Cosmic microwave background data and Local Hubble constant for each model. For the sake of comparison, the same data analysis is performed for the
Λ
CDM model. Each model shows a transition from decelerated phase to accelerated phase and can be viewed as an effective quintessence behavior. Using the model selection criteria AIC and BIC to distinguish from existing dark energy models, we find that the Brans–Dicke analog of the
Λ
-cosmology (i.e. our model
Λ
H
1
) performs at a level comparable to the standard
Λ
CDM, whereas
Λ
H
2
is less favoured.
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