Genomic Approaches to Enhance Stress Tolerance for Productivity Improvements in Pearl Millet

Pearl millet [Pennisetum glaucum (L.) R. Br.], the sixth most important cereal crop (after rice, wheat, maize, barley, and sorghum), is grown as a grain and stover crop by the small holder farmers in the harshest cropping environments of the arid and semiarid tropical regions of sub-Saharan Africa and South Asia. Millet is grown on ~31 million hectares globally with India in South Asia; Nigeria, Niger, Burkina Faso, and Mali in western and central Africa; and Sudan, Uganda, and Tanzania in Eastern Africa as the major producers. Pearl millet provides food and nutritional security to more than 500 million of the world’s poorest and most nutritionally insecure people. Global pearl millet production has increased over the past 15 years, primarily due to availability of improved genetics and adoption of hybrids in India and expanding area under pearl millet production in West Africa. Pearl millet production is challenged by various biotic and abiotic stresses resulting in a significant reduction in yields. The genomics research in pearl millet lagged behind because of multiple reasons in the past. However, in the recent past, several efforts were initiated in genomic research resulting into a generation of large amounts of genomic resources and information including recently published sequence of the reference genome and re-sequencing of almost 1000 lines representing the global diversity. This chapter reviews the advances made in generating the genetic and genomics resources in pearl millet and their interventions in improving the stress tolerance to improve the productivity of this very important climate-smart nutri-cereal

Size Dependent Magnetic Properties of Nd0.7Ca0.3MnO3 Nanomanganite

Nanoscale materials show different properties compared to bulk materials. Due to the size dependent properties the nanoscale materials have potential applications in industry. In this paper the size dependent magnetic properties of Nd0.7Ca0.3MnO3 nanomanganite have been investigated. Nd0.7Ca0.3MnO3 nanoparticles were prepared by low temperature sol-gel method. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and EDAX techniques were used to understand the structure, grain size and composition. Nanoparticles prepared were of the sizes 15 nm, 19 nm and 25 nm respectively. SQUID magnetometer was used to study the magnetic behavior of the nanoparticles. Field cooled (FC) and zero field cooled (ZFC) magnetization of all the nanosamples with respect to temperature was studied and compared. We have observed drastic changes in magnetic properties of 15 nm particles compared to the other nanoparticles. The `charge order peak' was seen to have disappeared in 15 nm particles while it was present in the other nanoparticles. All the nano particles exhibit superparamagnetism whose blocking temperature decreases as a function of decreasing particle size. The possible reasons for the influence of the particle size on the magnetic properties are discussed

EPR Evidence for Premonitory Charge-Ordering Fluctuations in Hydrothermally Grown Pr0.57Ca0.41Ba0.02MnO3 Nanowires

Electron paramagnetic resonance (EPR) and magnetic properties of nanowires of Pr0.57Ca0.41Ba0.02MnO3 (PCBMO) are studied and compared with those of the bulk material. PCBMO nanowires with diameter of 80-90 nm and length of similar to 3.5 mu m were synthesized by a low reaction temperature hydrothermal method and the bulk sample was prepared following a solid-state reaction route. The samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The bulk PCBMO manganite exhibits charge order at 230 K along with a ferromagnetic transition at 110 K. However, superconducting quantum interference device measurements on the PCBMO nanowires show a complete `melting' of charge ordering and a ferromagnetic transition at 115 K. This result is confirmed by the EPR intensity behavior as well. However, the EPR line width, which is reflective of the spin dynamics, shows a shallow minimum for nanowires at the temperature corresponding to the charge-ordering transition, i.e., 230 K. We interpret this result as an indication of the presence of charge-ordering fluctuations in the nanowires even though the static charge order is absent, thus heralding the occurrence of charge order in the bulk sample

Complete 'melting' of charge order in hydrothermally grown Pr0.57Ca0.41Ba0.02MnO3 nanowires

Nanowires of Pr0.57Ca0.41Ba0.02MnO3 (PCBM) (diameter similar to 80-90 nm and length similar to 3.5 mu m) were synthesized by a low reaction temperature hydrothermal method. Single-phase nature of the sample was confirmed by XRD experiments. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the morphology and microstructures of the nanowires. While the bulk PCBM is known to exhibit charge order (CO) below 230 K along with a ferromagnetic transition at 110 K, SQUID measurements on the nanowires of PCBM show that the charge order is completely absent and a ferromagnetic transition occurs at 115 K. However, the magnetization in the nanowires is observed to be less compared to that in the bulk. This observation of the complete 'melting' of the charge order in the PCBM nanowires is particularly significant in view of the observation of only a weakening of the CO in the nanowires of Pr0.5Ca0.5MnO3. Electron paramagnetic resonance experiments were also carried out on the PCBM nanowires using an X-band EPR spectrometer. Characteristic differences were observed in the line width of nanowires when compared with that of the bulk

Complete 'melting' of charge order in hydrothermally grown Pr0.57Ca0.41Ba0.02MnO3Pr_{0.57}Ca_{0.41}Ba_{0.02}MnO_3 nanowires

Nanowires of $Pr_{0.57}Ca_{0.41}Ba_{0.02}MnO_3$ (PCBM) (diameter similar to 80-90 nm and length similar to 3.5 mu m) were synthesized by a low reaction temperature hydrothermal method. Single-phase nature of the sample was confirmed by XRD experiments. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the morphology and microstructures of the nanowires. While the bulk PCBM is known to exhibit charge order (CO) below 230 K along with a ferromagnetic transition at 110 K, SQUID measurements on the nanowires of PCBM show that the charge order is completely absent and a ferromagnetic transition occurs at 115 K. However, the magnetization in the nanowires is observed to be less compared to that in the bulk. This observation of the complete 'melting' of the charge order in the PCBM nanowires is particularly significant in view of the observation of only a weakening of the CO in the nanowires of $Pr_{0.5}Ca_{0.5}MnO_3$. Electron paramagnetic resonance experiments were also carried out on the PCBM nanowires using an X-band EPR spectrometer. Characteristic differences were observed in the line width of nanowires when compared with that of the bulk

Zinc doping effects on the magnetic properties of Nd0.65Ca0.35Mn0.9Zn0.1O3 nanomanganite

In this paper, we report the synthesis and magnetic properties of Nd0.65Ca0.35Mn0.9Zn0.1O3 manganite. Bulk (NZOB) and nanoparticles (NZON) of hole-doped Nd0.65Ca0.35Mn0.9Zn0.1O3 were prepared by sol gel method. These particles were characterised by XRD, TEM and EDAX. Magnetisation measurements were carried out in temperature range 10 K <= T <= 300 K by a SQUID magnetometer. The parent bulk Nd0.65Ca0.35MnO3 (NCMO) manganite exhibits charge order (CO) around the temperature 210 K followed by an antiferromagnetic (AFM) transition at the Neel temperature (T-N = 120 K). With the doping of nonmagnetic Zn2+ cation, the valency balance is maintained by the creation of Mn4+ ions, which leads to ferromagnetism owing to the double exchange interaction between Mn3+ and Mn4+. Magnetisation measurements show that the ferromagnetic component enhances in nanoparticles (NZON) as compared to its bulk counterpart at low temperature, along with some amount of residual antiferromagnetism owing to the uncompensated surface spins. Further the temperature dependence of magnetisation (M*T vs. T) shows the melting of CO in both the samples. The ferromagnetic transition temperature (Tc) is found to be higher (similar to 53 K) in nanosample (size about 20 nm) when compared with its bulk counterpart (similar to 41 K)

Weakening of charge order and antiferromagnetic to ferromagnetic switch over in Pr0.5Ca0.5MnO3Pr_{0.5}Ca_{0.5}MnO_{3} nanowires

We have prepared crystalline nanowires (diameter similar to 50 nm,length similar to a few microns) of the charge-ordering manganite $Pr_{0.5}Ca_{0.5}MnO_{3}$ using a low reaction temperature hydrothermal method and characterized them using x-ray diffraction, transmission electron microscopy, superconducting quantum interference device (SQUID) magnetometry and electron magnetic resonance measurements. While the bulk sample shows a charge ordering transition at 245 K and an antiferromagnetic transition at 175 K, SQUID magnetometry and electronmagnetic resonance experiments reveal that in the nanowires phase, a ferromagnetic transition occurs at similar to 105 K. Further, the antiferromagnetic transition disappears and the charge ordering transition is suppressed. This result is particularly significant since the charge order in $Pr_{0.5}Ca_{0.5}MnO_{3}$ is known to be very robust, magnetic fields as high as 27 T being needed to melt it

EPR Evidence for Premonitory Charge-Ordering Fluctuations in Nanomanganite Pr0.57Ca0.41Ba0.02MnO3Pr_{0.57}Ca_{0.41}Ba_{0.02}MnO_3

Electron paramagnetic resonance (EPR) and magnetic properties of nanocrystalline $Pr_{0.57}Ca_{0.41}Ba_{0.02}MnO_3$ are studied and compared with those of the bulk material. The nanoscale samples prepared by the sol–gel method were annealed at different temperatures to obtain particles of different sizes. The crystallite and particle sizes were estimated by X-ray diffraction and transmission electron microscopy and found to be approximately equal to 30, 60 and 100 nm. Magnetization studies on the 60 and 100 nm particles show charge-ordering at 230 K similar to the bulk sample prepared by solid-state reaction, while in the 30 nm particles the charge-ordering signature is absent. At low temperatures all the three nanosamples show ferromagnetic transitions. This result is confirmed by the EPR intensity behavior as well. However, the EPR line width, which is reflective of the spin dynamics, shows a shallow minimum for the 30 nm particles at the temperature of 230 K, corresponding to the charge-ordering transition. We interpret this result as an indication of the presence of charge-ordering fluctuations in the nanoparticles of 30 nm size even though the static charge order is absent, thus heralding the occurrence of charge order in the larger particles

Weakening of charge order and antiferromagnetic to ferromagnetic switch over in Pr0.5Ca0.5MnO3 nanowires

We have prepared crystalline nanowires (diameter ∼ 50 nm, length ∼ a few microns) of the charge-ordering manganite Pr0.5Ca0.5MnO3 using a low reaction temperature hydrothermal method and characterized them using x-ray diffraction, transmission electron microscopy, superconducting quantum interference device (SQUID) magnetometry and electron magnetic resonance measurements. While the bulk sample shows a charge ordering transition at 245 K and an antiferromagnetic transition at 175 K, SQUID magnetometry and electron magnetic resonance experiments reveal that in the nanowires phase, a ferromagnetic transition occurs at ∼ 105 K. Further, the antiferromagnetic transition disappears and the charge ordering transition is suppressed. This result is particularly significant since the charge order in Pr0.5Ca0.5MnO3 is known to be very robust, magnetic fields as high as 27 T being needed to melt it