Search

The causes of the intrinsic elastic anisotropy of shales are very complicated, and clay mineralogy and crack properties are critical for rock-physics models and geomechanics applications in shales, but they are still poorly understood. Further, it is difficult to directly measure the elastic properties of single-crystal clays due to their small particle size. To reduce the multiparametric influence factors caused by complex components in natural shales, two sets of artificial rocks with different clay minerals are fabricated, and their porosity, permeability, and ultrasonic velocities are measured under different pressure conditions. The results suggest that clay mineralogy can significantly affect physical and elastic properties and their pressure sensitivity, and the permeabilities of the sample composed of kaolinite are much higher than those of the sample composed of smectite due to the larger particle size of kaolinite compared with smectite. Further, the type of clay can cause a difference in “intrinsic” velocity and anisotropy. The microcrack can enhance the velocity anisotropy on the basis of intrinsic anisotropy, and crack properties such as maximum dip angle and normal-to-tangential compliance ratio are obtained by a theoretical model, which is also affected by clay type, causing the difference in the pressure sensitivity of elastic properties. Water has a significant influence on the elastic properties and anisotropy of artificial clay samples, which can reduce the S-wave velocity and increase the P-wave velocity driven by multiple competing factors. Water reduces the velocity anisotropy because the presence of water narrows the difference between the velocity parallel and perpendicular to the axis of symmetry. The normal-to-tangential compliance ratio of cracks is also affected by water as a stiffer fluid can reduce the normal compliance of cracks at the grain scale.

There are various lithofacies with complex spatial patterns in shale oil reservoirs. The seismic reflections usually reveal the combination of sets of thin mud shales with various lithofacies. The seismic response characteristics of the lithofacies and the differences in seismic response of different lithofacies are still unclear, making the reservoir description difficult. The complex tectonic structures, diverse lithofacies, thin interlayers, fractures with various length scales, and various fracture development zones in the shale oil reservoir have placed very high demands on the design and construction method during the physical modeling of the shale oil reservoir. Facing preceding challenges, a physical modeling study on shale oil reservoir with complex lithofacies and meter-scale structures was carried out. The target is the shale oil reservoir of the ES4 s subsegment in the Jiyang depression. The complex physical model of a shale oil reservoir, with the thin stratigraphic layers and the complicated lithofacies and fracture patterns to date, was designed and constructed in a laboratory. In total, 25 combinations of materials were developed to simulate various lithofacies with different elastic parameters, and the error of the wave velocity simulation is less than 2.35%. The simulation of 1 m thick interlayers and the construction method for seismic physical models with meter-scale geologic structures was realized. The quality control analysis finds that the simulation accuracy of small-scale geologic structure, complex lithofacies, and fractures is relatively reliable. Based on the physical model of the shale oil reservoir, high-density and wide-azimuth seismic data are acquired. Preliminary data processing and analysis find that the model layers have clear reflection characteristics, providing reliable data for the next step of seismic characteristics analysis of complex lithofacies shale oil reservoir. The methodology has improved the capacity of seismic physical modeling to simulate complex oil and gas reservoirs, enabling the seismic physical simulation method to be applied in analyzing the commonly observed complex lithofacies, fractures, and meter-scale structures in unconventional oil and gas reservoirs.

Soil testing and formulated fertilization technology can effectively solve the problem of the excessive and inefficient use of chemical fertilizers. Previous studies have found that the use of the Internet can increase the adoption of soil testing and formulated fertilization technology among farmers. However, they do not distinguish between the effects of the different uses of the Internet (with or without productive use) on the adoption of soil testing and formulated fertilization technology. This study investigates the Internet use of 5341 professional farmers in rural China in 2019, finding that 18.97% of them still use the Internet for only communication and entertainment and do not use any agricultural productive services on the Internet. The adoption rate of soil testing and fertilization technology among these farmers is only 23.77%, which is approximately 10 percentage points lower than that of farmers who use the Internet for productive purposes. The double robust model shows that the probability of the adoption of soil testing and formulated fertilization technology by farmers with productive use of the Internet increases by six percentage points, which is both statistically and economically significant. In the future, China should train more farmers to use the Internet for productive purposes; this will help more farmers, particularly those with low skills and low educational attainment, to use the Internet and play a positive role in promoting the Internet for green agricultural production techniques.

Key message Salt tolerance at germination and seedling growth stages was investigated. GWAS revealed nine genomic regions with pleiotropic effects on salt tolerance. Salt tolerant genotypes were identified for future breeding program. Abstract With 20% of the irrigated land worldwide affected by it, salinity is a serious threat to plant development and crop production. While wheat is the most stable food source worldwide, it has been classified as moderately tolerant to salinity. In several crop plants; such as barley, maize and rice, it has been shown that salinity tolerance at seed germination and seedling establishment is under polygenic control. As yield was the ultimate goal of breeders and geneticists, less attention has been paid to understanding the genetic architecture of salt tolerance at early stages. Thus, the genetic control of salt tolerance at these stages is poorly understood relative to the late stages. In the current study, 176 genotypes of spring wheat were tested for salinity tolerance at seed germination and seedling establishment. Genome-Wide Association Study (GWAS) has been used to identify the genomic regions/genes conferring salt tolerance at seed germination and seedling establishment. Salinity stress negatively impacted all germination and seedling development parameters. A set of 137 SNPs showed significant association with the traits of interest. Across the whole genome, 33 regions showed high linkage disequilibrium (LD). These high LD regions harbored 15 SNPs with pleiotropic effect (i.e. SNPs that control more than one trait). Nine genes belonging to different functional groups were found to be associated with the pleiotropic SNPs. Noteworthy, chromosome 2B harbored the gene TraesCS2B02G135900 that acts as a potassium transporter. Remarkably, one SNP marker, reported in an early study, associated with salt tolerance was validated in this study. Our findings represent potential targets of genetic manipulation to understand and improve salinity tolerance in wheat.

Central to the diversity of wheat products was the origin of hexaploid bread wheat, which added the D-genome of Aegilops tauschii to tetraploid wheat giving rise to superior dough properties in leavened breads. The polyploidization, however, imposed a genetic bottleneck, with only limited diversity introduced in the wheat D-subgenome. To understand genetic variants for quality, we sequenced 273 accessions spanning the known diversity of Ae. tauschii. We discovered 45 haplotypes in Glu-D1, a major determinant of quality, relative to the two predominant haplotypes in wheat. The wheat allele 2 + 12 was found in Ae. tauschii Lineage 2, the donor of the wheat D-subgenome. Conversely, the superior quality wheat allele 5 + 10 allele originated in Lineage 3, a recently characterized lineage of Ae. tauschii, showing a unique origin of this important allele. These two wheat alleles were also quite similar relative to the total observed molecular diversity in Ae. tauschii at Glu-D1. Ae. tauschii is thus a reservoir for unique Glu-D1 alleles and provides the genomic resource to begin utilizing new alleles for end-use quality improvement in wheat breeding programs., Delorean et al., along with colleagues from the Open Wild Wheat Consortium, present an analysis of Aegilops tauschii genomes to investigate the origins of the Glu-D1 gene in modern wheats. They discover an abundance of novel Glu-D1 gene alleles that could serve as a reservoir for generating higher quality wheat varieties. This is a companion to the Consortium paper which is available in Nature Biotechnology.

The multi-objective evolutionary algorithm based on decomposition (MOEA/D) has achieved remarkable success in regular optimizing multi-objective problems. In practice, there are lots of irregular problems. The projection of their Pareto fronts (PF) may not cover the whole triangle on the first octant. There is an empty PF (EPF) or complex PF area. These problems significantly reduce the performance of MOEA/D. In this paper, an improved algorithm is proposed to deal with such complex problems. The basic idea is: (1) the PBI method is used to ensure the convergence and simultaneously keep diversity over the triangle; (2) a non-dominated and maximum distance based selection is used to replace the dominated objective individuals selected by the PBI method. It is referred to selection based on the PBI and Non-dominated Maximum distance (MOEAD-PNM). First, the mathematical foundation between the penalty factor and contour line is deduced. Based on the foundation, the penalty factor setting method is proposed and the PBI-based method is used to select an individual for each reference vector. The reference vectors directing to the EPF induce “bad” solutions. Then, these solutions are gradually replaced by better individuals selected according to the non-dominated and maximum distance-based selection strategy. The proposed two-step selection method can guarantee the wideness and uniformity of the “good” solution set. Finally, the performance of the MOEAD-PNM algorithm and five classic algorithms on more than ten test problems are compared. The experimental results show the competitiveness and effectiveness of the proposed algorithm on these challenging problems.

Advances in genomics have expedited the improvement of several agriculturally important crops but similar efforts in wheat (Triticum spp.) have been more challenging. This is largely owing to the size and complexity of the wheat genome1, and the lack of genome-assembly data for multiple wheat lines2,3. Here we generated ten chromosome pseudomolecule and five scaffold assemblies of hexaploid wheat to explore the genomic diversity among wheat lines from global breeding programs. Comparative analysis revealed extensive structural rearrangements, introgressions from wild relatives and differences in gene content resulting from complex breeding histories aimed at improving adaptation to diverse environments, grain yield and quality, and resistance to stresses4,5. We provide examples outlining the utility of these genomes, including a detailed multi-genome-derived nucleotide-binding leucine-rich repeat protein repertoire involved in disease resistance and the characterization of Sm16, a gene associated with insect resistance. These genome assemblies will provide a basis for functional gene discovery and breeding to deliver the next generation of modern wheat cultivars., Comparison of multiple genome assemblies from wheat reveals extensive diversity that results from the complex breeding history of wheat and provides a basis for further potential improvements to this important food crop.

Key message The first cytological characterization of the 2NvS segment in hexaploid wheat; complete de novo assembly and annotation of 2NvS segment; 2NvS frequency is increasing 2NvS and is associated with higher yield. Abstract The Aegilops ventricosa 2NvS translocation segment has been utilized in breeding disease-resistant wheat crops since the early 1990s. This segment is known to possess several important resistance genes against multiple wheat diseases including root knot nematode, stripe rust, leaf rust and stem rust. More recently, this segment has been associated with resistance to wheat blast, an emerging and devastating wheat disease in South America and Asia. To date, full characterization of the segment including its size, gene content and its association with grain yield is lacking. Here, we present a complete cytological and physical characterization of this agronomically important translocation in bread wheat. We de novo assembled the 2NvS segment in two wheat varieties, ‘Jagger’ and ‘CDC Stanley,’ and delineated the segment to be approximately 33 Mb. A total of 535 high-confidence genes were annotated within the 2NvS region, with > 10% belonging to the nucleotide-binding leucine-rich repeat (NLR) gene families. Identification of groups of NLR genes that are potentially N genome-specific and expressed in specific tissues can fast-track testing of candidate genes playing roles in various disease resistances. We also show the increasing frequency of 2NvS among spring and winter wheat breeding programs over two and a half decades, and the positive impact of 2NvS on wheat grain yield based on historical datasets. The significance of the 2NvS segment in wheat breeding due to resistance to multiple diseases and a positive impact on yield highlights the importance of understanding and characterizing the wheat pan-genome for better insights into molecular breeding for wheat improvement.

Aegilops tauschii, the diploid wild progenitor of the D subgenome of bread wheat, is a reservoir of genetic diversity for improving bread wheat performance and environmental resilience. Here we sequenced 242 Ae. tauschii accessions and compared them to the wheat D subgenome to characterize genomic diversity. We found that a rare lineage of Ae. tauschii geographically restricted to present-day Georgia contributed to the wheat D subgenome in the independent hybridizations that gave rise to modern bread wheat. Through k-mer-based association mapping, we identified discrete genomic regions with candidate genes for disease and pest resistance and demonstrated their functional transfer into wheat by transgenesis and wide crossing, including the generation of a library of hexaploids incorporating diverse Ae. tauschii genomes. Exploiting the genomic diversity of the Ae. tauschii ancestral diploid genome permits rapid trait discovery and functional genetic validation in a hexaploid background amenable to breeding.

Bacterial leaf streak (BLS) of wheat and barley has been a disease of increasing concern in the Upper Midwest over the past decade. In this study, intra- and interfield genetic and pathogenic diversity of bacteria causing BLS in Minnesota was evaluated. In 2015, 89 strains were isolated from 100 leaf samples collected from two wheat and two barley fields naturally infected with BLS. Virulence assays and multilocus sequence alignments of four housekeeping genes supported pathovar identifications. All wheat strains were pathogenic on wheat and barley and belonged to the same lineage as the Xanthomonas translucens pv. undulosa-type strain. All barley strains were pathogenic on barley but not on wheat. Three lineages of barley strains were detected. The frequency and number of sequence types of each pathovar varied within and between fields. A significant population variance was detected between populations of X. translucens pv. undulosa collected from different wheat fields. Population stratification of X. translucens pv. translucens was not detected. Significant differences in virulence were detected among three dominant sequence types of X. translucens pv. undulosa but not those of X. translucens pv. translucens. Field trials with wheat and barley plants inoculated with strains of known sequence type and virulence did not detect significant race structures within either pathovar. Knowledge of virulence, sequence types, and population structures of X. translucens on wheat and barley can support studies on plant–bacterial interactions and breeding for BLS disease resistance.

The development of next generation sequencing (NGS) enabled a shift from array-based genotyping to high-throughput genotyping by directly sequencing genomic libraries. Even though whole genome sequencing was initially too costly for routine analysis in large populations, such as those utilized for breeding or genetic studies, continued advancements in genome sequencing and bioinformatics have provided the opportunity to utilize whole-genome information. As new sequencing platforms can routinely provide high-quality sequencing data for sufficient genome coverage, a limitation comes in the time and high cost of library construction when multiplexing a large number of samples. Here we describe a high-throughput whole-genome skim-sequencing (skim-seq) approach that can be utilized for a broad range of genotyping and genomic characterization. Using optimized low-volume Illumina Nextera chemistry, we developed a skim-seq method and combined up to 960 samples in one multiplex library using dual index barcoding. With the dual-index barcoding, the number of samples for multiplexing can be adjusted depending on amount of data required and extended to 3,072 samples or more. Panels of double haploid wheat lines (Triticum aestivum, CDC Stanley x CDC Landmark), wheat-barley (T. aestivum x Hordeum vulgare) and wheat-wheatgrass (Triticum durum x Thinopyrum intermedium) introgression lines as well as known monosomic wheat stocks were genotyped using the skim-seq approach. Bioinformatics pipelines were developed for various applications where sequencing coverage ranged from 1x down to 0.01x per sample. Using reference genomes, we detected chromosome dosage, identified aneuploidy, and karyotyped introgression lines from the low coverage skim-seq data. Leveraging the recent advancements in genome sequencing, skim-seq provides an effective and low-cost tool for routine genotyping and genetic analysis, which can track and identify introgressions and genomic regions of interest in genetics research and applied breeding programs.

There is growing concern that farmland transfers lead to less agricultural investment, which may adversely affect agricultural productivity growth in China. Prior research has primarily focused on the differences between owned cultivated land and rented plots, but little is known about how farmland transfers between relatives, which are popular in rural China, specifically affect agricultural investment. In this paper, we present a conceptual framework of transaction cost economics to compare different contracting strategies in China's farmland rental markets. As farmland rental markets in China are immature, land transfer between relatives establishes bilateral governance, which has the advantage of addressing the opportunistic activities of both parties and can ultimately increase investment by tenants. Based on data from two waves of household surveys, we empirically examine the impact of bilateral governance on the application of organic fertilizer, an indicator for agricultural investment. Our findings show that apart from economic factors, kinship is important to the functioning of farmland rental markets in rural areas.

The Mullins effect during uniaxial compression tests, together with its reversibility, of ethylene-vinyl acetate copolymer (EVA)/nitrile-butadiene rubber (NBR)/zinc dimethacrylate (ZDMA) thermoplastic vulcanizates (TPVs) were investigated systematically. The experimental results indicated that the Mullins effect could be observed during the cyclic uniaxial compression tests and was accompanied with stress softening, residual deformation accumulation and hysteresis. The reversibility of the Mullins effect showed a temperature-dependent feature and was enhanced with increasing temperature.

Objective. Clopidogrel and Xuesaitong dispersible tablet (XST) have been clinically proven to be effective for treating cardiocerebrovascular disease. The present study was to investigate the herb-drug interaction of Clopidogrel and XST by modulation of the pharmacodynamics and liver Carboxylesterase 1A(CES1A) metabolism. Methods. 30 male SD rats were randomly divided into a control group (equal volumes of saline, 6 rats for mRNA analysis), a clopidogrel group (clopidogrel with dose 30 mg/kg), and a combination group (clopidogrel and XST, with dose 30 and 50 mg/kg respectively, each group continuous administration once daily for 30 days). The clopidogrel and combination group comprised 12 rats, with 6 designated for mRNA analysis and 6 for the pharmacokinetic study. The 2-bromo-3’-methoxyacetophenone- (MPB-) derivatized clopidogrel active thiol metabolite (CAMD) was measured by UHPLC-MS/MS for pharmacokinetics (n=6). The expression of CES1A mRNA was examined with real-time RT-PCR (n=6). Molecular simulation was used to investigate the inhibition effect of XST on the CES1A protein. The CAMD pharmacodynamics and CES1A metabolism were investigated to evaluated the herb-drug interaction. Results. Clopidogrel and XST coadministration appreciably increased the Cmax, AUC, and MRT of CAMD. However, the expression of CES1A mRNA was decreased accordingly. It also indicated that the bioactive components in XST had good interaction with the CES1A metabolism target by molecular simulation. The animal study indicated that clopidogrel and XST coadministration produced significant herb-drug interactions at active CAMD pharmacokinetic and CES1A metabolic enzyme aspect. Conclusion. 30-days dose of coadministration altered hepatic CES1A protein and resulted in reduced plasma levels of active CAMD. both the decreased CES1A mRNA expression and the inhibition on the protein were due to the combination of XST, which accordingly upregulated the pharmacokinetics of plasma active CAMD.

The wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt), race TTKSK and related races pose a serious threat to world wheat production. Knowing the effectiveness of wheat stem rust resistance (Sr) genes against Pgt race TTKSK is fundamental in mitigating this threat through resistance breeding. Sr15 was previously identified as being ineffective against Pgt race TTKSK. Here, multirace disease phenotyping data, linkage analyses, allelism testing and haplotype analyses are presented to support the conclusion that Sr15 is effective against Pgt race TTKSK. Resistance to race TTKSK was mapped to Sr15 in a biparental population. Thirty‐two accessions with Sr15 displayed seedling resistance phenotypes against race TTKSK. However, these accessions were susceptible as seedlings at high temperatures (22–25 °C), consistent with previous reports that the interaction between avirulent Pgt isolates and Sr15 is temperature‐sensitive. Markers STS638, wri4 and KASP_IWB30995 were found to predict the presence of Sr15, suggesting the utility of these assays for marker‐assisted selection in breeding programmes. The effectiveness of Sr15 to specific Pgt races and temperatures makes it a less‐desirable TTKSK‐effective gene. Wheat lines assayed as resistant to race TTKSK at the seedling stage may possess Sr15 and breeders should be aware of the limitations of Sr15 for conferring stem rust resistance.

Patients with breast cancer are often afflicted by bone metastases, while the establishment and growth of bone metastases depend on interaction between cancer cells and the host environment. Moreover, osteoblasts, which play a vital role in cancer cells survival and colonization, can form an osteogenic niche in early stage of bone metastases. Also, it is widely accepted that there is a genetic determinant during bone metastases. Nephronectin (NPNT) is an extracellular matrix protein which has shown biological activities in breast cancer metastases and osteoblasts differentiation. But the role of NPNT in mediating breast cancer bone metastases remains elusive. In the present study, we revealed that up regulation of NPNT is associated with incidence of bone metastases. What's more, NPNT could significantly enhance the tumor cell clone formation but not proliferation and migration. We further demonstrated that NPNT significantly enhance osteoblast differentiation and tumor adhesion. Thus, we proposed that cancer secreted NPNT may be a novel marker with potential value of prediction and diagnosis of breast cancer bone metastases. Keyword: NPNT, Breast cancer, Bone metastases, Osteoblast

With the widespread use of new information systems such as social networks, recommendation systems as well as location-based services, graph data has become a very common and important data type. It has been shown that, from these collected graph data, some special substructures can be found through clustering analysis, and can further support the intelligent decision. However, directly publishing or using clustering results on these graph data would disclose the privacy information of system users. To this end, based a classical structural clustering algorithm for networks (SCAN) and the technology of differential privacy, we propose a differentially private graph clustering algorithm named DP-SCAN. Specifically, we first reasonably calibrate the global sensitivity of the function of computing structure similarity between nodes in the graph, and thus specify parameters of the Laplace mechanism for capturing differential privacy. Then, we provide details of the DP-SCAN algorithm. The theoretical analysis indicates that DPSCAN algorithm satisfies e-differential privacy, without trading off the clustering efficiency. The experimental results show that, when compared with the original SCAN clustering algorithm, DP-SCAN clustering algorithm can maintain the validity of clustering under the premise of satisfying differential privacy.

Bacterial leaf streak (BLS) of wheat and barley, caused by Xanthomonas translucens pv. undulosa and X. translucens pv. translucens, has been of growing concern in small grains production in the Upper Midwestern United States. To optimize disease resistance breeding, a greater awareness is needed of the pathovars and genetic diversity within the pathogens causing BLS in the region. Multilocus sequencing typing (MLST) and analysis (MLSA) of four common housekeeping genes (rpoD, dnaK, fyuA, and gyrB) was used to evaluate the genetic diversity of 82 strains of X. translucens isolated between 2006 and 2013 from wheat, barley, rye, and intermediate wheatgrass. In addition, in planta disease assays were conducted on 75 strains to measure relative virulence in wheat and barley. All strains were determined by MLSA to be related to X. translucens pv. undulosa and X. translucens pv. translucens. Clustering of strains based on Bayesian, network, and minimum spanning trees correlated with relative virulence levels in inoculated wheat and barley. Thus, phylogeny based on rpoD, dnaK, fyuA, and gyrB correlated with host of isolation and was an effective means for predicting virulence of strains belonging to X. translucens pv. translucens and X. translucens pv. undulosa.

The method of fabricating nonprecious metal electrocatalysts with high activity and durability through a facile and eco-friendly procedure is of great significance to the development of low-cost fuel cells and metal–air batteries. Herein, we present that an ancient chemical reaction of “Pharaoh’s snakes” can be a fast and convenient technique to prepare Fe-/N-doped carbon (Fe/N–C) nanosheet/nanotube electrocatalysts with sugar, soda, melamine, and iron nitrate as precursors. The resultant Fe/N–C catalyst has a hierarchically porous structure, a large surface area, and uniformly distributed active sites. The catalyst shows high electrocatalytic activities toward both the oxygen reduction reaction with a half-wave potential of 0.90 V (vs reversible hydrogen electrode) better than that of Pt/C and the oxygen evolution reaction with an overpotential of 0.46 V at the current density of 10 mA cm–2 comparable to that of RuO2. The activity and stability of the catalyst are also evaluated in primary and rechargeab...

The urban and rural dual structure is a defining characteristic of the social and economic development process in China. With rapid urbanization, remarkable development of agriculture and rural modernization, the relationship between urban and rural areas is undergoing significant changes in China. Using macro data, we find that the relationship between urban and rural areas started to change in 2010. The transition has mainly been reflected in three dimensions: agriculture, rural areas and farmers. First, agricultural versatility has gradually increased, and the number of participants in leisure agriculture and rural tourism has grown rapidly since 2010. Second, the rural employment rate has risen gradually, and the share of rural employees in the tertiary sector has grown markedly. Third, the urban–rural income ratio and consumption ratio have begun to decrease, and the levels of consumption of domestic tourism by urban and rural residents are becoming small.

The goal of this paper is to examine the impact of changes in China's rural land policy on agricultural investments. Dramatic changes occurred in China's rural land policies after 2000, including the extension of rural land contractual period, restriction of land reallocation among villages and villagers groups, elimination of agricultural taxes for responsibility land, and rapid development of rural land rental markets. These changes have given farmers more secure tenure on collectively controlled responsibility land and have strengthened farmers' income rights for responsibility lands, incentivizing them to increase their investments on responsibility lands. A panel data method was used to quantitatively investigate the impact of land policy changes on agricultural investment. We considered the application of organic fertilizer as an indicator for long-term agricultural investment, and compared the use of organic fertilizer between private plots and responsibility lands operated by the same household. The results showed that the difference in organic fertilizer use between private plots and responsibility land for the same household has become smaller from 2000 to 2008. Our findings suggest that recent changes in rural land policies have provided farmers incentives to increase land quality investment on their responsibility lands.

Stem rust, caused by the fungus Puccinia graminis Pers. f. sp. tritici Ericks, is one of the most damaging diseases of wheat (Triticum aestivum L.). The recent emergence of the stem rust Ug99 race group poses a serious threat to world wheat production. Utilization of genetic resistance in cultivar development is the optimal way to control stem rust. Here, we report association mapping of stem rust resistance in a global spring wheat germplasm collection (2152 accessions) genotyped with the wheat iSelect 9K single-nucleotide polymorphism array. Using a unified mixed model method (or QK method), we identified a total of 47 loci that were significantly associated with various stem rust resistance traits including field disease resistance and seedling resistance against multiple stem rust pathogen races including BCCBC, TRTTF, TTKSK (Ug99), and TTTTF. The 47 loci could be further condensed into 11 quantitative trait locus (QTL) regions according to linkage disequilibrium information among adjacent markers. We postulate that these QTLs represent known stem rust resistance genes including Sr2, Sr6, Sr7a, Sr8a, Sr9h, Sr13, Sr28, and Sr36. We further employed a multilocus mixed model to explore marker-trait associations and identified two additional QTLs (one potentially represents Sr31) that were significantly associated with stem rust resistance against various races. Combinations of the most significant loci for each trait explained up to 38.6% of the phenotypic variance. Markers identified through this study could be used to track the genes or QTLs. Accessions with high numbers of resistance-associated alleles may serve as important breeding materials for stem rust resistance.

Staphylococcus aureus, a commensal and a pathogenic bacterium, causes a wide variety of diseases in humans and animals with a high impact on public health and the livestock industry. The risk of zoonotic transmission to humans highlights the need to understand the molecular ecology of S. aureus in foods. In this study, we obtained 25 S. aureus isolates from 39 crayfish samples in Hubei, China. PCR was applied for detection of presence of virulence and methicillin resistance genes in the pathogen genome. The result revealed that all of the 25 S. aureus isolates harbored at least four virulence genes, and 64 % of them were positive for five or more virulence genes. The most predominant virulence genes were coa, α-HL and β-HL genes (100 %), followed by sea (68 %), fnbA (60 %), tsst-1 (36 %), while none of the examined isolates presented positive for mecA gene conferring methicillin resistance. Subsequently, all of the isolates were assessed for phenotypic biofilm formation with the microtiter plate assay. The results showed 92 % isolates could produce biofilm with different forming capacity. Multilocus sequence typing divided the isolates into five sequence types (STs), three of which (ST1920, ST188 and ST398) were the same with the isolates from livestock and clinic in China. This study provides preliminary insights into the genetic diversity and virulence gene profiles of S. aureus from crayfish, suggesting that S. aureus isolates from crayfish is a potential hazard for consumers and deserves further attention.

Bacterial leaf streak (BLS) of wheat and barley has been a disease of increasing concern in the Upper Midwest over the past decade. In this study, intra- and interfield genetic and pathogenic diversity of bacteria causing BLS in Minnesota was evaluated. In 2015, 89 strains were isolated from 100 leaf samples collected from two wheat and two barley fields naturally infected with BLS. Virulence assays and multilocus sequence alignments of four housekeeping genes supported pathovar identifications. All wheat strains were pathogenic on wheat and barley and belonged to the same lineage as the