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The energy dissipation in collisionless plasmas as the solar wind is not yet fully understood. The intermittent nature of magnetic structures appears to be a fundamental part of the energy cascade. Understanding energy transfer and dissipation in the solar wind requires an accurate description of its intermittency. Upcoming multi-spacecraft missions will provide new insight on this matter. However, the use of multi-point data requires developing new data analysis techniques as wellas cross-validating these techniques. In this study, we address the latter and explore the intermittency in a 3D simulation of anisotropic plasma turbulence using two approaches. We implement the standard single-spacecraft partial variance increments technique as well as a multi-point partial variance increments technique. We contrast these two techniques and explore their dependence on the angle between the spacecraft-configuration travel direction and the background magnetic field. [ABSTRACT FROM AUTHOR]

The distribution of turbulence in the heliosphere remains a mystery, due to the complexity in not only modeling the turbulence transport equations but also identifying the drivers of turbulence that vary with time and spatial location. Beyond the ionization cavity (a few astronomical units (AU) from the Sun), the turbulence is driven predominantly by freshly created pickup ions (PUIs), in contrast to the driving by stream shear and compression. Understanding the source characteristics is necessary to refine turbulence transport models and interpret measurements of turbulence and solar wind temperature in the outer heliosphere. Using a recent latitude-dependent solar wind speed model and the ionization rate of neutral interstellar hydrogen (H), we investigate the temporal and spatial variation in the strength of low-frequency turbulence driven by PUIs from 1998 to 2020. We find that the driving rate is stronger during periods of high solar activity and at lower latitudes in the outer heliosphere. The driving rates for parallel and anti-parallel propagating (relative to the background magnetic field) slab turbulence have different spatial and latitude dependences. The calculated generation rate of turbulence by PUIs is an essential ingredient to investigate the latitude dependence of turbulence in the outer heliosphere, which is important to understand the heating of the distant solar wind and the modulation of cosmic rays. [ABSTRACT FROM AUTHOR]

Genetic diversity found in crop wild relatives is critical to preserve and utilize for crop improvement to achieve sustainable food production amid climate change and increased demand. We genetically characterized a large collection of 1,041 Aegilops accessions distributed among 23 different species using more than 45K single nucleotide polymorphisms identified by genotyping-by-sequencing. The Wheat Genetics Resource Center (WGRC) Aegilops germplasm collection was curated through the identification of misclassified and redundant accessions. There were 49 misclassified and 28 sets of redundant accessions within the four diploid species. The curated germplasm sets now have improved utility for genetic studies and wheat improvement. We constructed a phylogenetic tree and principal component analysis cluster for all Aegilops species together, giving one of the most comprehensive views of Aegilops. The Sitopsis section and the U genome Aegilops clade were further scrutinized with in-depth population analysis. The genetic relatedness among the pair of Aegilops species provided strong evidence for the species evolution, speciation, and diversification. We inferred genome symbols for two species Ae. neglecta and Ae. columnaris based on the sequence read mapping and the presence of segregating loci on the pertinent genomes as well as genetic clustering. The high genetic diversity observed among Aegilops species indicated that the genus could play an even greater role in providing the critical need for untapped genetic diversity for future wheat breeding and improvement. To fully characterize these Aegilops species, there is an urgent need to generate reference assemblies for these wild wheats, especially for the polyploid Aegilops. [ABSTRACT FROM AUTHOR]

The solar wind (SW) and local interstellar medium (LISM) are turbulent media. Their interaction is governed by complex physical processes and creates heliospheric regions with significantly different properties in terms of particle populations, bulk flow and turbulence. Our knowledge of the solar wind turbulence nature and dynamics mostly relies on near-Earth and near-Sun observations, and has been increasingly improving in recent years due to the availability of a wealth of space missions, including multi-spacecraft missions. In contrast, the properties of turbulence in the outer heliosphere are still not completely understood. In situ observations by Voyager and New Horizons, and remote neutral atom measurements by IBEX strongly suggest that turbulence is one of the critical processes acting at the heliospheric interface. It is intimately connected to charge exchange processes responsible for the production of suprathermal ions and energetic neutral atoms. This paper reviews the observational evidence of turbulence in the distant SW and in the LISM, advances in modeling efforts, and open challenges. [ABSTRACT FROM AUTHOR]

A-genome diploid wheats represent the earliest domesticated and cultivated wheat species in the Fertile Crescent and include the donor of the wheat A sub-genome. The A-genome species encompass the cultivated einkorn (Triticum monococcum L. subsp. monococcum), wild einkorn (T. monococcum L. subsp. aegilopoides (Link) Thell.), and Triticum urartu. We evaluated the collection of 930 accessions in the Wheat Genetics Resource Center (WGRC) using genotyping by sequencing and identified 13,860 curated single-nucleotide polymorphisms. Genomic analysis detected misclassified and genetically identical (>99%) accessions, with most of the identical accessions originating from the same or nearby locations. About 56% (n = 520) of the WGRC A-genome species collections were genetically identical, supporting the need for genomic characterization for effective curation and maintenance of these collections. Population structure analysis confirmed the morphology-based classifications of the accessions and reflected the species geographic distributions. We also showed that T. urartu is the closest A-genome diploid to the A-subgenome in common wheat (Triticum aestivum L.) through phylogenetic analysis. Population analysis within the wild einkorn group showed three genetically distinct clusters, which corresponded with wild einkorn races α, β, and γ described previously. The T. monococcum genome-wide FST scan identified candidate genomic regions harboring a domestication selection signature at the Non-brittle rachis 1 (Btr1) locus on the short arm of chromosome 3Am at ~70 Mb. We established an A-genome core set (79 accessions) based on allelic diversity, geographical distribution, and available phenotypic data. The individual species core set maintained at least 79% of allelic variants in the A-genome collection and constituted a valuable genetic resource to improve wheat and domesticated einkorn in breeding programs. [ABSTRACT FROM AUTHOR]

A detailed study of solar wind turbulence throughout the heliosphere in both the upwind and downwind directions is presented. We use an incompressible magnetohydrodynamic (MHD) turbulence model that includes the effects of electrons, the separation of turbulence energy into proton and electron heating, the electron heat flux, and Coulomb collisions between protons and electrons. We derive expressions for the turbulence cascade rate corresponding to the energy in forward and backward propagating modes, the fluctuating kinetic and magnetic energy, the normalized crosshelicity, and the normalized residual energy, and calculate the turbulence cascade rate from 0.17 to 75 au in the upwind and downwind directions. Finally, we use the turbulence transport models to derive cosmic ray (CR) parallel and perpendicular mean free paths (mfps) in the upwind and downwind heliocentric directions. We find that turbulence in the upwind and downwind directions is different, in part because of the asymmetric distribution of new born pickup ions in the two directions, which results in the CR mfps being different in the two directions. This is important for models that describe the modulation of cosmic rays by the solar wind. [ABSTRACT FROM AUTHOR]

Alfalfa leaf rust caused by the fungal pathogen Uromyces striatus compromises forage yield and quality. We investigated the genetic basis of leaf rust resistance in alfalfa using an F1 mapping population segregating for resistance to the disease in addition to segregation for fall dormancy (FD) and winter hardiness (WH). The objective of this work was to map quantitative trait loci (QTL) associated with alfalfa leaf rust resistance using genotyping-by-sequencing (GBS) SNP markers in the biparental F1 mapping population. The female parent 3010 displayed susceptibility to rust while the male parent CW 1010 was moderately resistant. The mapping population consisted of 184 F1 progenies that were planted with the parents in a randomized complete block (RCBD) design with three replications at Watkinsville and Blairsville, GA. Four clones generated from stem cuttings of each genotype were planted in each replication. Phenotyping rust severity (RS) was based on the NAAIC visual rating scores of 1–5. RS and FD exhibited a negative phenotypic correlation (r = −0.26). RS and WH also exhibited a negative correlation (r = −0.27) suggesting that the dormant and winter hardy genotypes were more susceptible to leaf rust than the non-dormant and cold sensitive. Four QTL for alfalfa leaf rust resistance and one QTL for rust susceptibility were identified in the CW 1010 genetic map while three QTL for rust susceptibility were identified in the 3010 parent. The most important QTL Us-RustR1 explained 13% (R2 = 0.13) of the phenotypic variance. This study suggests that leaf rust resistance in alfalfa is most likely incomplete and has polygenic inheritance. Comparative genome analysis of QTL regions using sequences of significant SNPs revealed homology to M. truncatula sequences that were previously reported for their role in plant defense mechanisms. Validation of the QTLs in different genetic backgrounds as well as fine mapping of the QTL regions would be the next step of this research. The markers presented in this study would be valuable resources for alfalfa genetic improvement via marker-assisted selection (MAS). • Eight QTLs associated with alfalfa rust resistance were detected using GBS of a pseudo-testcross mapping population. • In this population, the inheritance of rust resistance caused by Uromyces striatus was polygenic and incomplete. • The sequences of QTL SNPs exhibited homology with genes associated with fungal diseases defense in M. truncatula. • Alfalfa rust severity correlated with FD and WH, but the relationship might be specific to the population. [ABSTRACT FROM AUTHOR]

Understanding key adaptation traits is crucial to developing new cultivars with broad adaptations. The main objective of this research is to understand the genetic basis of winter hardiness (WH) and fall dormancy (FD) in alfalfa and the association between the two traits. QTL analysis was conducted in a pseudo-testcross F1 population developed from two cultivars contrasting in FD (3010 with FD = 2 and CW 1010 with FD = 10). The mapping population was evaluated in three replications at two locations (Watkinsville and Blairsville, GA). FD levels showed low to moderate correlations with WH (0.22–0.57). Assessing dormancy in winter is more reliable than in the fall in southern regions with warm winters. The mapping population was genotyped using Genotyping-by-sequencing (GBS). Single dose allele SNPs (SDA) were used for constructing linkage maps. The parental map (CW 1010) consisted of 32 linkage groups spanning 2127.5 cM with 1377 markers and an average marker density of 1.5 cM/SNP. The maternal map (3010) had 32 linkage groups spanning 2788.4 cM with 1837 SDA SNPs with an average marker density of 1.5 cM/SNP. Forty-five significant (P < 0.05) QTLs for FD and 35 QTLs for WH were detected on both male and female linkage maps. More than 75% (22/28) of the dormancy QTL detected from the 3010 parent did not share genomic regions with WH QTLs and more than 70% (12/17) dormancy QTLs detected from CW 1010 parent were localized in different genomic regions than WH QTLs. These results suggest that the two traits have independent inheritance and therefore can be improved separately in breeding programs. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is a critical micronutrient for nitrogen (N) fixation in legumes. Low pH limits the availability of Mo, thereby reducing nodulation and N fixation. This study investigates the effect of Mo supplementation on alfalfa nodulation and its correlation with root and shoot biomass in low-pH soil. Three experiments were conducted in the greenhouse, involving 14 genotypes of alfalfa subjected to four different treatments, unlimed low-pH soil (5.2) with Mo applied (lithium (Li)−Mo+), low-pH soil (5.2) without Mo (Li−Mo−), limed soil (pH 7.3) with Mo applied (Li+Mo+), and limed soil (pH 7.3) without Mo (Li+Mo−). Foliar application of Mo resulted in a significant increase in nodule counts in the 14 alfalfa cultivars grown in low-pH soil (5.2) even though to a lesser extent than in limed soil with neutral pH (7.3). The increase in number of nodules correlated positively with plant root weight and upper plant biomass. [ABSTRACT FROM PUBLISHER]