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Stripe rust disease of wheat, caused by Puccinia striiformis f. sp. tritici , ( Pst ) is one of the most serious diseases of wheat worldwide. In India, virulent stripe rust races have been constantly evolving in the North-Western Plains Zone leading to the failure of some of the most widely grown resistant varieties in the region. With the goal of studying the recent evolution of virulent races in this region, we conducted whole-genome re-sequencing of three prevalent Indian Pst pathotypes Pst46S119, Pst78S84 and Pst110S119. We assembled 58.62, 58.33 and 55.78 Mb of Pst110S119, Pst46S119 and Pst78S84 genome, respectively and found that pathotypes were highly heterozygous. Comparative phylogenetic analysis indicated the recent evolution of pathotypes Pst110S119 and Pst78S84 from Pst46S119. Pathogenicity-related genes classes (CAZyme, proteases, effectors, and secretome proteins) were identified and found to be under positive selection. Higher rate of gene families expansion were also observed in the three pathotypes. A strong association between the effector genes and transposable elements may be the source of the rapid evolution of these strains. Phylogenetic analysis differentiated the Indian races in this study from other known United States, European, African, and Asian races. Diagnostic markers developed for the identification of three Pst pathotypes will help tracking of yellow rust at farmers field and strategizing resistance gene deployment.

Leaf rust caused by Puccinia triticina is the most common and widely distributed of the three wheat rusts. Losses from leaf rust are usually less damaging than those from stem rust and stripe rust, but leaf rust causes greater annual losses due to its more frequent and widespread occurrence. Yield losses from leaf rust are mostly due to reductions in kernel weight. Many laboratories worldwide conduct leaf rust surveys and virulence analyses. Most currently important races (pathotypes) have either evolved through mutations in existing populations or migrated from other, often unknown, areas. Several leaf rust resistance genes are cataloged, and high levels of slow rusting adult plant resistance are available in high yielding CIMMYT wheats. This paper summarizes the importance of leaf rust in the main wheat production areas as reflected by yield losses, the complexity of virulence variation in pathogen populations, the role cultivars with race-specific resistance play in pathogen evolution, and the control measures currently practiced in various regions of the world.

The phenomenon of stimulated Raman scattering (SRS) of elliptical q -Gaussian laser beams interacting nonlinearly with underdense plasmas has been investigated theoretically. When an intense laser beam with frequency ω 0 propagates through plasma, due to the nonuniform irradiance over its cross-section d.c component of ponderomotive force becomes active. Due to this ponderomotive nonlinearity of plasma, the laser beam gets coupled with a preexisting electron plasma wave (EPW) at frequency ω ep . The nonlinear interaction of pump beam with EPW produces a back scattered wave at frequency ω s = ω 0 - ω ep . Using variational theory semi-analytical solution of the set of coupled nonlinear wave equations for the three waves (pump, EPW and scattered) has been obtained under W.K.B approximation technique. It has been observed that power of the scattered wave is significantly affected by the self-focusing effect of pump beam.

Rusts also called as moving targets, are very devastating diseases of wheat. Epidemics of wheat rusts have been recorded since times immemorial. The landmark contribution of Dr. E. C. Stakman at Cereal Rust Laboratory, Minnesota, USA opened a new area that races occur in Puccinia graminis tritici . In India wheat rust research started in 1923 under the leadership of Dr. K. C. Mehta. His basic work on the identification of races in three wheat rust pathogens and epidemiology of wheat rusts have led to the foundation of a strong rust research programme in India. He proved it beyond doubt that alternate hosts are not functional under Indian situation. Dr. K. C. Mehta was working at the Agra College, Agra, Dr. R. Prasada provided a sound background support. Since then a number of Scientists have led the programme and made significant contributions. Now we identify the pathotypes on Near Isogenic Lines (NILs) using a binomial system of nomenclature and have a collection of more than 150 pathotypes of different rust pathogens. Information on the rust resistance of Indian wheat and barley material till today is available. Based on the gene matching technique and molecular markers, we are able to characterize rust resistance genes in all the wheat materials. To achieve durable rust resistance, we deploy a mosaic of wheat varieties carrying all time, adult and slow rusting resistance. The recommendation of wheat varieties is made based on the multi-location testing for field resistance to the region-specific rust diseases and pathotype distribution. There is a narrow diversity for stripe rust resistance in wheat and efforts are on to build it. Pyramiding of rust resistance genes has led to the registration of 63 genetic stocks of wheat and barley with NBPGR, New Delhi. The genomes of 21 pathotypes of three rust pathogens have been sequenced. Two new rust resistance genes in wheat; Lr80 and Sr65 (two of the eleven rust resistance genes designated by Indian researchers among the 235 designated internationally in the last 88 years), were designated from Flowerdale centre. Studies on doubled haploid production, epidemiology in changed situation, effectors, and molecular basis of pathogenesis were conducted. For the last 52 years, we had no rust epidemic on wheat. The system is now in place to combat any threat of wheat and barley rusts in India.

Leaf rust is one of the important diseases limiting global wheat production and productivity. To identify quantitative trait nucleotides (QTNs) or genomic regions associated with seedling and adult plant leaf rust resistance, multilocus genome-wide association studies (ML-GWAS) were performed on a panel of 400 diverse wheat genotypes using 35 K single-nucleotide polymorphism (SNP) genotyping assays and trait data of leaf rust resistance. Association analyses using six multi-locus GWAS models revealed a set of 201 significantly associated QTNs for seedling and 65 QTNs for adult plant resistance (APR), explaining 1.98–31.72% of the phenotypic variation for leaf rust. Among these QTNs, 51 reliable QTNs for seedling and 15 QTNs for APR were consistently detected in at least two GWAS models and were considered reliable QTNs. Three genomic regions were pleiotropic, each controlling two to three pathotype-specific seedling resistances to leaf rust. We also identified candidate genes, such as leucine-rich repeat receptor-like (LRR) protein kinases, P-loop containing nucleoside triphosphate hydrolase and serine-threonine/tyrosine-protein kinases (STPK), which have a role in pathogen recognition and disease resistance linked to the significantly associated genomic regions. The QTNs identified in this study can prove useful in wheat molecular breeding programs aimed at enhancing resistance to leaf rust and developing next-generation leaf rust-resistant varieties.

An algorithm for characterizing attosecond extreme ultraviolet pulses that is not bandwidth-limited, requires no interpolation of the experimental data, and makes no approximations beyond the strong-field approximation is introduced. This approach fully incorporates the dipole transition matrix element into the retrieval process. Unlike attosecond retrieval methods such as phase retrieval by omega oscillation filtering (PROOF), or improved PROOF, it simultaneously retrieves both the attosecond and infrared (IR) pulses, without placing fundamental restrictions on the IR pulse duration, intensity or bandwidth. The new algorithm is validated both numerically and experimentally, and is also found to have practical advantages. These include an increased robustness to noise, and relaxed requirements for the size of the experimental dataset and the intensity of the streaking pulse.

Wheat is the second most important food crop of the world after rice. Rust pathogens, one of the major biotic stresses in wheat production, are capable of threatening the world food security. Understanding the molecular basis of plant–pathogen interactions is essential for devising novel strategies for resistance breeding and disease management. Now, it has been established that effectors, the proteins secreted by pathogens, play a key role in plant–pathogen interactions. Therefore, effector biology has emerged as one of the most important research fields in plant biology. Recent advances in genomics and bioinformatics have allowed identification of a large repertoire of candidate effectors, while the evolving high-throughput tools have continued to assist in their functional characterization. The repertoires of effectors have become an important resource for better understanding of effector biology of pathosystems and resistance breeding of crop plants. In recent years, a significant progress has been made in the field of rust effector biology. This review describes the recent advances in effector biology of obligate fungal pathogens, identification and functional analysis of wheat rust pathogens effectors and the potential applications of effectors in molecular plant biology and rust resistance breeding in wheat.

Theoretical study on the generation of superthermal electrons by intense laser beams in hot dense plasmas during inertial confinement fusion has been presented. In order to obtain uniform heating of the fuel pellet the irradiance over the beam cross section has been modeled by Cosh Gaussian profile. The effect of self-focusing of the laser beam on energy gained by the electrons has been investigated in detail. Following moment theory and hydrodynamic fluid model of plasma coupled differential equations governing the evolution of beam width of the laser beam and energy of the superthermal electrons have been obtained. It has been observed that the uniformity of the irradiance over the beam cross section enhances the energy of superthermal electrons considerably.

In the present work, optical absorption coefficients and refractive index changes of a GaAs spherical quantum dot are investigated within the framework of the Coulomb plus linear harmonic potential. To this effect, analytical expressions for energy eigenvalues and corresponding eigen functions are obtained by solving the radial Schrödinger equation by applying the parametric Nikiforov–Uvarov method. Thereafter, using the density matrix formalism, expressions for linear and third-order nonlinear absorption coefficients along with refractive index changes are computed and plotted. Effect of the radius of quantum dot, the potential height and the incident light intensity on these quantities are further investigated and found in good agreement with literature results. The effect of external magnetic field on the energy spectra of the quantum dot is also presented. Graphic Abstract

Theoretical investigation on stimulated Brillouin scattering of intense q-Gaussian laser beams interacting with axially nonuniform plasmas has been presented. A ramp-shaped density profile has modelled the axial inhomogeneity of the plasma and the optical nonlinearity of the plasma has been considered to be originating owing to the dependence of the relativistic mass of the plasma electrons on laser intensity. An intense laser beam with frequency ω 0 propagating through plasma gets coupled with a preexisting ion acoustic wave (IAW) at frequency ω ia and produces a backscattered wave at frequency ω s = ω 0 – ω ia . Using variational theory semi-analytical solution of the set of coupled wave equations for the pump, an IAW and a scattered wave have been obtained under W.K.B. approximation. It has been noted that the power of the scattered wave is significantly affected by the self-focusing effect of the pump beam.