High-throughput sequencing data revealed genotype-specific changes evoked by heat stress in crown tissue of barley sdw1 near-isogenic lines.

BACKGROUND: High temperature shock is becoming increasingly common in our climate, affecting plant growth and productivity. The ability of a plant to survive stress is a complex phenomenon. One of the essential tissues for plant performance under various environmental stimuli is the crown. However, the molecular characterization of this region remains poorly investigated. Gibberellins play a fundamental role in whole-plant stature formation. This study identified plant stature modifications and crown-specific transcriptome re-modeling in gibberellin-deficient barley sdw1.a (BW827) and sdw1.d (BW828) mutants exposed to increased temperature. RESULTS: The deletion around the sdw1 gene in BW827 was found to encompass at least 13 genes with primarily regulatory functions. A bigger genetic polymorphism of BW828 than of BW827 in relation to wild type was revealed. Transcriptome-wide sequencing (RNA-seq) revealed several differentially expressed genes involved in gibberellin metabolism and heat response located outside of introgression regions. It was found that HvGA20ox4, a paralogue of the HvGA20ox2 gene, was upregulated in BW828 relative to other genotypes, which manifested as basal internode elongation. The transcriptome response to elevated temperature differed in the crown of sdw1.a and sdw1.d mutants; it was most contrasting for HvHsf genes upregulated under elevated temperature in BW828, whereas those specific to BW827 were downregulated. In-depth examination of sdw1 mutants revealed also some differences in their phenotypes and physiology. CONCLUSIONS: We concluded that despite the studied sdw1 mutants being genetically related, their heat response seemed to be genotype-specific and observed differences resulted from genetic background diversity rather than single gene mutation, multiple gene deletion, or allele-specific expression of the HvGA20ox2 gene. Differences in the expressional reaction of genes to heat in different sdw1 mutants, found to be independent of the polymorphism, could be further explained by in-depth studies of the regulatory factors acting in the studied system. Our findings are particularly important in genetic research area since molecular response of crown tissue has been marginally investigated, and can be useful for wide genetic research of crops since barley has become a model plant for them.

Predictors of Acute Encephalopathy in Patients with COVID-19.

INTRODUCTION: The majority of patients with severe COVID-19 suffer from delirium as the main sign of encephalopathy associated with this viral infection. The aim of this study was to identify early markers of the development of this condition. MATERIALS: The prospective cohort-based study included patients with community-acquired pneumonia and confirmed pulmonary tissue infiltration based on CT data, with a lesion consisting of at least 25% of one lung. The main group included patients who have developed acute encephalopathy (10 patients, 3 (30%) women; average age, 47.9 ± 7.3 years). The control group included patients who at discharge did not have acute encephalopathy (20 patients, 11 (55%) women; average age, 51.0 ± 10.5 years). The study collected clinical examination data, comprehensive laboratory data, neurophysiological data, pulse oximetry and CT data to identify the predictors of acute encephalopathy (study ClinicalTrials.gov identifier NCT04405544). RESULTS: Data analysis showed a significant relationship between encephalopathy with the degree of lung tissue damage, arterial hypertension, and type 2 diabetes mellitus, as well as with D-dimer, LDH, and lymphopenia. CONCLUSIONS: The development of encephalopathy is secondary to the severity of the patient's condition since a more severe course of the coronavirus infection leads to hypoxic brain damage.

Image Phenotyping of Spring Barley (Hordeum vulgare L.) RIL Population Under Drought: Selection of Traits and Biological Interpretation.

Image-based phenotyping is a non-invasive method that permits the dynamic evaluation of plant features during growth, which is especially important for understanding plant adaptation and temporal dynamics of responses to environmental cues such as water deficit or drought. The aim of the present study was to use high-throughput imaging in order to assess the variation and dynamics of growth and development during drought in a spring barley population and to investigate associations between traits measured in time and yield-related traits measured after harvesting. Plant material covered recombinant inbred line population derived from a cross between European and Syrian cultivars. After placing the plants on the platform (28th day after sowing), drought stress was applied for 2 weeks. Top and side cameras were used to capture images daily that covered the visible range of the light spectrum, fluorescence signals, and the near infrared spectrum. The image processing provided 376 traits that were subjected to analysis. After 32 days of image phenotyping, the plants were cultivated in the greenhouse under optimal watering conditions until ripening, when several architecture and yield-related traits were measured. The applied data analysis approach, based on the clustering of image-derived traits into groups according to time profiles of statistical and genetic parameters, permitted to select traits representative for inference from the experiment. In particular, drought effects for 27 traits related to convex hull geometry, texture, proportion of brown pixels and chlorophyll intensity were found to be highly correlated with drought effects for spike traits and thousand grain weight.

Mapping of quantitative trait loci for traits linked to fusarium head blight in barley.

Fusarium head blight (FHB) is a devastating disease occurring in small grain cereals worldwide. The disease results in the reduction of grain yield, and mycotoxins accumulated in grain are also harmful to both humans and animals. It has been reported that response to pathogen infection may be associated with the morphological and developmental traits of the host plant, e.g. earliness and plant height. Despite many studies, effective markers for selection of barley genotypes with increased resistance to FHB have not been developed. In the present study, we investigated 100 recombinant inbred lines (RIL) of spring barley. Plants were examined in field conditions (three locations) in a completely randomized design with three replications. Barley genotypes were artificially infected with spores of Fusarium culmorum before heading. Apart from the main phenotypic traits (plant height, spike characteristic, grain yield), infected kernels were visually scored and the content of deoxynivalenol (DON) mycotoxin was investigated. A set of 70 Quantitative Trait Loci (QTLs) were detected through phenotyping of the mapping population in field conditions and genotyping using a barley Ilumina 9K iSelect platform. Six loci were detected for the FHB index on chromosomes 2H, 3H, 5H, and 7H. A region on the short arm of chromosome 2H was detected in which many QTLs associated with FHB- and yield-related traits were found. This study confirms that agromorphological traits are tightly related to FHB and should be taken into consideration when breeding barley plants for FHB resistance.

Production of wheat-doubled haploids resistant to eyespot supported by marker-assisted selection

BACKGROUND: Wheat is one of the most important crops cultivated all over the world. New high-yielding cultivars that are more resistant to fungal diseases have been permanently developed. The present study aimed at the possibility of accelerating the process of breeding new cultivars, resistant to eyespot, by using doubled haploids (DH) system supported by marker-assisted selection. RESULTS: Two highly resistant breeding lines (KBP 0916 and KBH 4942/05) carrying Pch1 gene were crossed with the elite wheat genotypes. Hybrid plants of early generations were analyzed using endopeptidase EpD1 and two SSR markers linked to the Pch1 locus. Selected homozygous and heterozygous genotypes for the Pch1-linked EpD1b allele were used to produce haploid plants. Molecular analyses were performed on haploids to identify plants possessing Pch1 gene. Chromosome doubling was performed only on haploid plants with Pch1 gene. Finally, 65 DH lines carrying eyespot resistance gene Pch1 and 30 lines without this gene were chosen for the eyespot resistance phenotyping in a field experiment. CONCLUSIONS: Results of the experiment confirmed higher resistance to eyespot of the genotypes with Pch1 in comparison to those without this gene. This indicates the efficiency of selection at the haploid level.

Chlorophyll a Fluorescence Parameters of Hulled and Hull-less Barley (Hordeum vulgare L.) DH Lines Inoculated with Fusarium culmorum.

Barley worldwide is affected seriously by Fusarium seedling blight (FSB) and Fusarium head blight (FHB) diseases caused by the Fusarium species. The objective of this study was to facilitate the resistance of hulled and hull-less barley at different growth stages to F. culmorum according to direct parameters: disease rating (DR), fresh weight of leaves and roots, kernel weight per spike, kernel number per spike, plump kernels, and indirect parameters - chlorophyll a fluorescence (CF). Plate assay, greenhouse and field tests were performed on 30 spring barley doubled haploid (DH) lines and their parents infected with Fusarium culmorum. Direct parameters proved that hulled genotypes show less symptoms. Most studied chlorophyll a fluorescence (CF) parameters (apart from DIo/CS - amount of energy dissipated from PSII for laboratory test, TRo/CS - amount of excitation energy trapped in PSII reaction centers, ETo/CS - amount of energy used for electron transport and RC/CS - number of active reaction centres in the state of fully reduced PSII reaction center in field experiment) were significantly affected by F. culmorum infection. In all experiments, hulled genotypes had higher values of CF parameters compared to hull-less ones. Significant correlations were detected between direct and indirect parameters and also between various environments. It was revealed that ABS/CS, TRo/CS, and RC/CS have significant positive correlation in greenhouse test and field experiment. Significant correlations suggest the possibility of applying the CF parameters in selection of barley DH lines resistant to F. culmorum infection.

The influence of Glu-1 and Glu-3 loci on dough rheology and bread-making properties in wheat (Triticum aestivum L.) doubled haploid lines.

BACKGROUND: The major determinants of wheat quality are Glu-1 and Glu-3 glutenin loci and environmental factors. Additive effects of alleles at the Glu-1 and Glu-3 loci, as well as their interactions, were evaluated for dough rheology and baking properties in four groups of wheat doubled haploid lines differing in high- and low-molecular-weight glutenin composition. RESULTS: Flour quality, Reomixer (Reologica Instruments, Lund, Sweden), dough extension, Farinograph (Brabender GmbH, Duisburg, Germany) and baking parameters were determined. Groups of lines with the alleles Glu-A3b and Glu-B3d were characterized by higher values of dough and baking parameters compared to those with the Glu-A3e and Glu-B3a alleles. Effects of interactions between allelic variants at the Glu-1 and Glu-3 loci on Reomixer parameters, dough extension tests and baking parameters were significant, although additive effects of individual alleles were not always significant. CONCLUSION: The allelic variants at Glu-B3 had a much greater effect on dough rheological parameters than the variants at Glu-A3 or Glu-D3 loci. The effect of allelic variations at the Glu-D3 loci on rheological parameters and bread-making quality was non-significant, whereas their interactions with a majority of alleles at the other Glu-1 × Glu-3 loci were significant. © 2017 Society of Chemical Industry.

Quantitative trait loci for plant height in Maresi × CamB barley population and their associations with yield-related traits under different water regimes.

High-yielding capacity of the modern barley varieties is mostly dependent on the sources of semi-dwarfness associated with the sdw1/denso locus. The objective of the study was to identify quantitative trait loci (QTLs) associated with the plant height and yield potential of barley recombinant inbred lines (RILs) grown under various soil moisture regimes. The plant material was developed from a hybrid between the Maresi (European cv.) and CamB (Syrian cv.). A total of 103 QTLs affecting analysed traits were detected and 36 of them showed stable effects over environments. In total, ten QTLs were found to be significant only under water shortage conditions. Nine QTLs affecting the length of main stem were detected on 2H-6H chromosomes. In four of the detected QTLs, alleles contributed by Maresi had negative effects on that trait, the most significant being the QLSt-3H.1-1 in the 3H.1 linkage group. The close linkage between QTLs identified around the sdw1/denso locus, with positive alleles contributed by Maresi, indicates that the semi-dwarf cv. Maresi could serve as a donor of favourable traits resulting in grain yield improvement, also under water scarcity. Molecular analyses revealed that the Syrian cv. also contributed alleles which increased the yield potential. Available barley resources of genomic annotations were employed to the biological interpretation of detected QTLs. This approach revealed 26 over-represented Gene Ontology terms. In the projected support intervals of QGWSl-5H.3-2 and QLSt-5H.3 on the chromosome 5H, four genes annotated to 'response to stress' were found. It suggests that these QTL-regions may be involved in a response of plant to a wide range of environmental disturbances.

Interactions between Glu-1 and Glu-3 loci and associations of selected molecular markers with quality traits in winter wheat (Triticum aestivum L.) DH lines.

The quality of wheat depends on a large complex of genes and environmental factors. The objective of this study was to identify quantitative trait loci controlling technological quality traits and their stability across environments, and to assess the impact of interaction between alleles at loci Glu-1 and Glu-3 on grain quality. DH lines were evaluated in field experiments over a period of 4 years, and genotyped using simple sequence repeat markers. Lines were analysed for grain yield (GY), thousand grain weight (TGW), protein content (PC), starch content (SC), wet gluten content (WG), Zeleny sedimentation value (ZS), alveograph parameter W (APW), hectolitre weight (HW), and grain hardness (GH). A number of QTLs for these traits were identified in all chromosome groups. The Glu-D1 locus influenced TGW, PC, SC, WG, ZS, APW, GH, while locus Glu-B1 affected only PC, ZS, and WG. Most important marker-trait associations were found on chromosomes 1D and 5D. Significant effects of interaction between Glu-1 and Glu-3 loci on technological properties were recorded, and in all types of this interaction positive effects of Glu-D1 locus on grain quality were observed, whereas effects of Glu-B1 locus depended on alleles at Glu-3 loci. Effects of Glu-A3 and Glu-D3 loci per se were not significant, while their interaction with alleles present at other loci encoding HMW and LMW were important. These results indicate that selection of wheat genotypes with predicted good bread-making properties should be based on the allelic composition both in Glu-1 and Glu-3 loci, and confirm the predominant effect of Glu-D1d allele on technological properties of wheat grains.

QTLs for earliness and yield-forming traits in the Lubuski × CamB barley RIL population under various water regimes.

Drought has become more frequent in Central Europe causing large losses in cereal yields, especially of spring crops. The development of new varieties with increased tolerance to drought is a key tool for improvement of agricultural productivity. Material for the study consisted of 100 barley recombinant inbred lines (RILs) (LCam) derived from the cross between Syrian and European parents. The RILs and parental genotypes were examined in greenhouse experiments under well-watered and water-deficit conditions. During vegetation the date of heading, yield and yield-related traits were measured. RIL population was genotyped with microsatellite and single nucleotide polymorphism markers. This population, together with two other populations, was the basis for the consensus map construction, which was used for identification of quantitative trait loci (QTLs) affecting the traits. The studied lines showed a large variability in heading date. It was noted that drought-treatment negatively affected the yield and its components, especially when applied at the flag leaf stage. In total, 60 QTLs were detected on all the barley chromosomes. The largest number of QTLs was found on chromosome 2H. The main QTL associated with heading, located on chromosome 2H (Q.HD.LC-2H), was identified at SNP marker 5880-2547, in the vicinity of Ppd-H1 gene. SNP 5880-2547 was also the closest marker to QTLs associated with plant architecture, spike morphology and grain yield. The present study showed that the earliness allele from the Syrian parent, as introduced into the genome of an European variety could result in an improvement of barley yield performance under drought conditions.

Introgression of LTP2 gene through marker assisted backcross in barley (Hordeum vulgare L. )

Background: Marker-assisted introgression currently represents the most widely spread application of DNA markers as an aid to selection in plant breeding. New barley germplasm should be supplemented by genes that facilitate growth and development under stressful conditions. The homology search against known genes is a fundamental approach to identify genes among the generated sequences. This procedure can be utilized for SNP search in genes of predicted function of interest and associated gene ontology (GO). Results: Backcross breeding enhanced by marker selection may become a powerful method to transfer one or a few genes controlling a specific trait. In the study, the integrated approach of combining phenotypic selection with marker assisted backcross breeding for introgression of LTP2 gene, in the background of semi-dwarf spring barley cultivar, was employed. This study discusses the efficiency of molecular marker application in backcrossing targeted on the selected gene. Conclusions: BC6 lines developed in this study can serve as a unique and adequate plant material to dissect the role of LTP2 gene. Due to its role in lipid transfer, the LTP2 may be crucial in lipidome modification in response to abiotic stress.

Analysis of Drought-Induced Proteomic and Metabolomic Changes in Barley (Hordeum vulgare L.) Leaves and Roots Unravels Some Aspects of Biochemical Mechanisms Involved in Drought Tolerance.

In this study, proteomic and metabolomic changes in leaves and roots of two barley (Hordeum vulgare L.) genotypes, with contrasting drought tolerance, subjected to water deficit were investigated. Our two-dimensional electrophoresis (2D-PAGE) combined with matrix-assisted laser desorption time of flight mass spectrometry (MALDI-TOF and MALDI-TOF/TOF) analyses revealed 121 drought-responsive proteins in leaves and 182 in roots of both genotypes. Many of the identified drought-responsive proteins were associated with processes that are typically severely affected during water deficit, including photosynthesis and carbon metabolism. However, the highest number of identified leaf and root proteins represented general defense mechanisms. In addition, changes in the accumulation of proteins that represent processes formerly unassociated with drought response, e.g., phenylpropanoid metabolism, were also identified. Our tandem gas chromatography - time of flight mass spectrometry (GC/MS TOF) analyses revealed approximately 100 drought-affected low molecular weight compounds representing various metabolite types with amino acids being the most affected metabolite class. We compared the results from proteomic and metabolomic analyses to search for existing relationship between these two levels of molecular organization. We also uncovered organ specificity of the observed changes and revealed differences in the response to water deficit of drought susceptible and tolerant barley lines. Particularly, our results indicated that several of identified proteins and metabolites whose accumulation levels were increased with drought in the analyzed susceptible barley variety revealed elevated constitutive accumulation levels in the drought-resistant line. This may suggest that constitutive biochemical predisposition represents a better drought tolerance mechanism than inducible responses.

Simultaneous selection for yield-related traits and susceptibility to Fusarium head blight in spring wheat RIL population.

Fusarium head blight (FHB), caused by the fungal plant pathogen Fusarium, is a fungal disease that occurs in wheat and can cause significant yield and grain quality losses. The present paper examines variation in the resistance of spring wheat lines derived from a cross between Zebra and Saar cultivars. Experiments covering 198 lines and parental cultivars were conducted in three years, in which inoculation with Fusarium culmorum was applied. Resistance levels were estimated by scoring disease symptoms on kernels. In spite of a similar reaction of parents to F. culmorum infection, significant differentiation between lines was found in all the analyzed traits. Seven molecular markers selected as linked to FHB resistance QTLs gave polymorphic products for Zebra and Saar: Xgwm566, Xgwm46, Xgwm389, Xgwm533, Xgwm156, Xwmc238, and Xgwm341. Markers Xgwm389 and Xgwm533 were associated with the rate of Fusarium-damaged kernels (FDK) as well as with kernel weight per spike and thousand kernel weight in control plants. Zebra allele of marker Xwmc238 increased kernel weight per spike and thousand kernel weight both in control and infected plants, whereas Zebra allele of marker Xgwm566 reduced the percentage of FDK and simultaneously reduced the thousand kernel weight in control and infected plants.

Quantitative Trait Loci for Yield and Yield-Related Traits in Spring Barley Populations Derived from Crosses between European and Syrian Cultivars.

In response to climatic changes, breeding programmes should be aimed at creating new cultivars with improved resistance to water scarcity. The objective of this study was to examine the yield potential of barley recombinant inbred lines (RILs) derived from three cross-combinations of European and Syrian spring cultivars, and to identify quantitative trait loci (QTLs) for yield-related traits in these populations. RILs were evaluated in field experiments over a period of three years (2011 to 2013) and genotyped with simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers; a genetic map for each population was constructed and then one consensus map was developed. Biological interpretation of identified QTLs was achieved by reference to Ensembl Plants barley gene space. Twelve regions in the genomes of studied RILs were distinguished after QTL analysis. Most of the QTLs were identified on the 2H chromosome, which was the hotspot region in all three populations. Syrian parental cultivars contributed alleles decreasing traits' values at majority of QTLs for grain weight, grain number, spike length and time to heading, and numerous alleles increasing stem length. The phenomic and molecular approaches distinguished the lines with an acceptable grain yield potential combining desirable features or alleles from their parents, that is, early heading from the Syrian breeding line (Cam/B1/CI08887//CI05761) and short plant stature from the European semidwarf cultivar (Maresi).

Segregation distortion in homozygous lines obtained via anther culture and maize doubled haploid methods in comparison to single seed descent in wheat (Triticum aestivum L. )

Background The quality of wheat grain depends on several characteristics, among which the composition of high molecular weight glutenin subunits, encoded by Glu-1 loci, are the most important. Application of biotechnological tools to accelerate the attainment of homozygous lines may influence the proportion of segregated genotypes. The objective was to determine, whether the selection pressure generated by the methods based on in vitro cultures, may cause a loss of genotypes with desirable Glu-1 alleles. Results Homozygous lines were derived from six winter wheat crosses by pollination with maize (DH-MP), anther culture (DH-AC) and single seed descent (SSD) technique. Androgenetically-derived plants that originated from the same callus were examined before chromosome doubling using allele-specific and microsatellite markers. It was found that segregation distortion in SSD and DH-MP populations occurred only in one case, whereas in anther-derived lines they were observed in five out of six analyzed combinations. Conclusions Segregation distortion in DH-AC populations was caused by the development of more than one plant of the same genotype from one callus. This distortion was minimized if only one plant per callus was included in the population. Selection of haploid wheat plants before chromosome doubling based on allele-specific markers allows us to choose genotypes that possess desirable Glu-1 alleles and to reduce the number of plants in the next steps of DH production. The SSD technique appeared to be the most advantageous in terms of Mendelian segregation, thus the occurrence of residual heterozygosity can be minimized by continuous selfing beyond the F6 generation.

Effects of the semi-dwarfing sdw1/denso gene in barley.

Recent advances in cereal genomics have made it possible to analyse the architecture of cereal genomes and their expressed components, leading to an increase in our knowledge of those genes that are associated with the key agronomical traits. Presently, use of a dwarfing gene in breeding process is crucial for the development of modern cultivars. In barley, more than 30 types of dwarfs or semi-dwarfs have been hitherto described. However, only a few of them have been successfully used in barley breeding programs. Both breeding and molecular mapping experiments were undertaken to enhance and evaluate the performance of semi-dwarf barley lines. The semi-dwarfing cultivars had improved lodging resistance and a higher harvest index. There have been a lot of investigations that have contributed new information to our basic understanding of the mechanisms underlying growth regulations in barley. This paper reviews semi-dwarfing genes in barley in general and special attention is paid to mapping of the sdw1/denso locus, changes in protein abundance and associations of the semi-dwarfness with gibberellins.

Identification of tillering node proteins differentially accumulated in barley recombinant inbred lines with different juvenile growth habits.

Barley (Hordeum vulgare L.) is an important cereal crop grown for both the feed and malting industries. The allelic dwarfing gene sdw1/denso has been used throughout the world to develop commercial barley varieties. Proteomic analysis offers a new approach to identify a broad spectrum of genes that are expressed in the living system. Two-dimensional electrophoresis and mass spectrometry were applied to investigate changes in protein abundance associated with different juvenile growth habit as effect of the denso locus in barley homozygous lines derived from a Maresi × Pomo cross combination. A total of 31 protein spots were revealed that demonstrate quantitative differences in protein abundance between the analyzed plants with different juvenile growth habit, and these protein spots were selected to be identified by mass spectrometry. Identification was successful for 27 spots, and functional annotations of proteins revealed that most of them are involved in metabolism and disease/defense-related processes. Functions of the identified proteins and their probable influence on the growth habit in barley are discussed.

The relationship between grain hardness, dough mixing parameters and bread-making quality in winter wheat.

The influence of grain hardness, determined by using molecular markers and physical methods (near-infrared (NIR) technique and particle size index-PSI) on dough characteristics, which in turn were determined with the use of a farinograph and reomixer, as well as bread-making properties were studied. The material covered 24 winter wheat genotypes differing in grain hardness. The field experiment was conducted at standard and increased levels of nitrogen fertilization. Results of molecular analyses were in agreement with those obtained by the use of physical methods for soft-grained lines. Some lines classified as hard (by physical methods) appeared to have the wild-type Pina and Pinb alleles, similar to soft lines. Differences in dough and bread-making properties between lines classified as hard and soft on the basis of molecular data appeared to be of less significance than the differences between lines classified as hard and soft on the basis of physical analyses of grain texture. Values of relative grain hardness at the increased nitrogen fertilization level were significantly higher. At both fertilization levels the NIR parameter determining grain hardness was significantly positively correlated with the wet gluten and sedimentation values, with most of the rheological parameters and bread yield. Values of this parameter correlated with quality characteristics in a higher degree than values of particle size index.

Methods to predict transgressive segregation in barley and other self-pollinated crops.

Most of agronomically important characters are biometric traits. An improvement of these traits in cultivated plants by deriving segregants superior to parents, which could be developed as cultivars, is a main goal in breeding of self-pollinated crops. Two problems need to be solved: when will the progeny be better than its parents and how can a genetic potential of a given pair of parental genotypes be predicted? In this paper, transgressive segregation in homozygous barley populations is shortly reviewed. Various approaches to choosing parental forms are shown, and a theoretical method for predicting the frequency of transgressive segregants in a homozygous population is presented. Additionally, relationships between parental diversity estimated with molecular markers and the progeny performance are discussed. Although the prediction of transgressive segregation is still a problem, it seems promising to apply an approach measuring the performance of the parental genotypes and estimating their genetic distance by molecular markers.

Numerical method for detection of linkage between genes for two metrical traits.

A homozygous population derived from hybrids between two homozygous parents may be used for genetic analysis of metrical traits. The paper describes the use of doubled haploids (DH) and single seed descent (SSD) lines for detection of linkage between genes conditioning two quantitative traits. A computational algorithm is presented, which facilitates matching various variants of relations between variances, covariances and means of DH and SSD populations so as to make it possible to conclude on the presence/absence of linkage. The suggested methodology is illustrated with an example concerning three quantitative traits of barley: length of the third internode, stem wall thickness, and 1000-grain weight.