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Race-specific and race-non-specific interactions with barley have been previously reported for Bipolaris sorokiniana. The aims of the study were to characterize a Uruguayan population of B. sorokiniana, to determine the nature of the interactions, and to identify a set of the most informative barley genotypes to characterize the pathogen. Infection responses of 322 single-spore isolates of B. sorokiniana collected from 2001 to 2010 were assessed for their interaction with 35 barley genotypes after inoculation at the two-leaf stage under controlled conditions on a 1–9 scale. After removal of the most redundant isolates, the interactions of 147 isolates were analyzed with Hierarchical Clustering on Principal Components, resulting in eight clusters of barley genotypes and seven clusters of B. sorokiniana isolates. A set of 12 potential differential barley genotypes grouped into 11 clusters that interacted in a partially specific but also in a quantitatively variable manner with the 147 isolates. Despite some clear isolate-specific interactions, the predominately quantitative interactions found make it unlikely that a universal differential set could be used to monitor diversity worldwide. [ABSTRACT FROM AUTHOR]

Key message: The Bt9 resistance locus was mapped and shown to be distinct from the Bt10 locus. New markers linked to Bt9 have been identified and may be used to breed for resistance towards the seed-borne disease. Abstract: Increasing organic wheat production in Denmark, and in other wheat-producing areas, in conjunction with legal requirements for organic seed production, may potentially lead to a rise in common bunt occurrence. As systemic pesticides are not used in organic farming, organic wheat production systems may benefit from genetic resistances. However, little is known about the underlying genetic mechanisms and locations of the resistance factors for common bunt resistance in wheat. A double haploid (DH) population segregating for common bunt resistance was used to identify the chromosomal location of common bunt resistance gene Bt9. DH lines were phenotyped in three environments and genotyped with DArTseq and SSR markers. The total length of the resulting linkage map was 2882 cM distributed across all 21 wheat chromosomes. Bt9 was mapped to the distal end of chromosome 6DL. Since wheat common bunt resistance gene Bt10 is also located on chromosome 6D, the possibility of their co-location was investigated. A comparison of marker sequences linked to Bt9 and Bt10 on physical maps of chromosome 6D confirmed that Bt9 and Bt10 are two distinct resistance factors located at the distal (6DL) and proximal (6DS) end, respectively, of chromosome 6D. Five new SSR markers Xgpw4005-1, Xgpw7433, Xwmc773, Xgpw7303 and Xgpw362 and many SNP and PAV markers flanking the Bt9 resistance locus were identified and they may be used in the future for marker-assisted selection. [ABSTRACT FROM AUTHOR]

Generation of doubled haploid plants is a powerful tool in breeding, as homozygous individuals will be obtained directly from hybrids. However, genotype variability in regeneration efficiency of most European wheat ( Triticum aestivum L.) varieties has limited its use in wheat. This study intended to identify quantitative trait loci ( QTLs) for green plantlet regeneration from wheat microspore cultures. A QTL analysis using DAr T markers was conducted based on a bi-parental F3 population, derived from a cross between the varieties Svilena and Jensen, which displayed markedly different capacity for plantlet regeneration. Two QTLs on chromosome 1B and 7B explained 53% of the variation in green plantlet regeneration. Furthermore, a collection of 94 European wheat varieties was genotyped and phenotyped. The microspore response level was low among western and northern European wheat varieties, and the positive QTLs found in the bi-parental population were rare in the variety collection. Identification of the two QTLs enables introduction of high regeneration efficiency into wheat germplasm. Moreover, our results proved that the efficient regeneration observed for one variety could be crossed into modern winter wheat. [ABSTRACT FROM AUTHOR]

A collection of 189 bread wheat landraces and cultivars, primarily of European origin, released between 1886 and 2009, was analyzed using two DNA marker systems. A set of 76 SSR markers and ~7,000 DArT markers distributed across the wheat genome were employed in these analyses. All of the SSR markers were found to be polymorphic, whereas only 2,532 of the ~7,000 DArT markers were polymorphic. A Mantel test between the genetic distances calculated based on the SSR and DArT data showed a strong positive correlation between the two marker types, with a Pearson's value (r) of 0.66. We assessed the genetic diversity and allelic frequencies among the accessions based on spring- versus winter-wheat type as well as between landraces and cultivars. We also analyzed the changes in genetic diversity and allelic frequencies in these samples over time. We observed separation based on both vernalization type and release date. Interestingly, we detected a decrease in genetic diversity in wheat accessions released over the period from 1960 to 1980. However, our results also showed that modern plant breeding have succeeded in maintaining genetic diversity in modern wheat cultivars. Studying allelic frequencies using SSR and DArT markers over time revealed changes in allelic frequencies for a number of markers that are known to be linked to important traits, which should be useful for genomic screening efforts. Monitoring changes in the frequency of molecular DNA markers over time in wheat cultivars may yield insight into alleles linked to important traits that have been the subject of positive or negative selection in the past and that may be useful for marker-assisted breeding programs in the future. [ABSTRACT FROM AUTHOR]

Genetic diversity and structure plays a key role in the selection of parents for crosses in plant breeding programmes. The aim of the present study was to analyse the genetic diversity and structure of Eritrean bread wheat accessions. We analysed 284 wheat accessions from Eritrea using 30 simple sequence repeat markers. A total of 539 alleles were detected. The allele number per locus ranged from 2 to 21, with a mean allele number of 9.2. The average genetic diversity index was 0.66, with values ranging from 0.01 to 0.89. Comparing the three genomes of wheat, the B genome had the highest genetic diversity (0.66) and the D genome the lowest diversity (0.61). A STRUCTURE analysis based on the Bayesian model-based cluster analysis followed by a graphical representation of the distances by non-parametric multidimensional scaling revealed a distinct partition of the Eritrean wheat accessions into two major groups. This is the first report of the genetic diversity and structure of Eritrean bread wheat. [ABSTRACT FROM AUTHOR]

Progress in plant breeding is facilitated by accurate information about genetic structure and diversity. Here, Diversity Array Technology (DArT) was used to characterize a population of 94 bread wheat (Triticum aestivum L.) varieties of mainly European origin. In total, 1,849 of 7,000 tested markers were polymorphic and could be used for population structure analysis. Two major subgroups of wheat varieties, GrI and GrII, were identified using the program STRUCTURE, and confirmed by principal component analysis (PCA). These subgroups were largely separated according to origin; GrI comprised varieties from Southern and Eastern Europe, whereas GrII contained mostly modern varieties from Western and Northern Europe. A large proportion of the markers contributing most to the genetic separation of the subgroups were located on chromosome 2D near the Reduced height 8 (Rht8) locus, and PCR-based genotyping suggested that breeding for the Rht8 allele had a major impact on subgroup separation. Consistently, analysis of linkage disequilibrium (LD) suggested that different selective pressures had acted on chromosome 2D in the two subgroups. Our data provides an overview of the allele composition of bread wheat varieties anchored to DArT markers, which will facilitate targeted combination of alleles following DArT-based QTL studies. In addition, the genetic diversity and distance data combined with specific Rht8 genotypes can now be used by breeders to guide selection of crossing parents. [ABSTRACT FROM AUTHOR]

Common bunt is a seed borne disease of wheat whose importance is likely to increase due to the growing organic seed market, which, in addition to seed phytosanitary measures, relies on genetic resistances towards the disease. Genome wide association studies in wheat have been proven to be a useful tool in the detection of genetic polymorphisms underlying phenotypic trait variation in wheat. Here 248 wheat landraces and cultivars representing 130 years of breeding history were screened for two years in the field for their resistance reactions towards common bunt. The majority of lines exhibited high levels of susceptibility towards common bunt, while 25 accessions had less than 10% infection. Using Diversity Array Technology (DArT) markers for genotyping and correcting for population stratification by using a compressed mixed linear model, we identified two significant marker trait associations (MTA) for common bunt resistance, designated QCbt.cph-2B and QCbt.cph-7A, located on wheat chromosomes 2B and 7A, respectively. This shows that genome wide association studies (GWAS) are applicable in the search for genetic polymorphisms for resistance towards less studied plant diseases such as common bunt in the context of an under representation of resistant lines. [ABSTRACT FROM AUTHOR]

Two-dimensional gel electrophoresis was used to screen spring barley cultivars for differences in seed protein profiles. In parallel, 72 microsatellite (simple sequence repeat (SSR)) markers and 11 malting quality parameters were analysed for each cultivar. Over 60 protein spots displayed cultivar variation, including peroxidases, serpins and proteins with unknown functions. Cultivars were clustered based on the spot variation matrix. Cultivars with superior malting quality grouped together, indicating malting quality to be more closely correlated with seed proteomes than with SSR profiles. Mass spectrometry showed that some spot variations were caused by amino acid differences encoded by single nucleotide polymorphisms (SNPs). Coding SNPs were validated by mass spectrometry, expressed sequence tag and 2D gel data. Coding SNPs can alter function of affected proteins and may thus represent a link between cultivar traits, proteome and genome. Proteome analysis of doubled haploid lines derived from a cross between a malting (Scarlett) and a feed cultivar (Meltan) enabled genetic localisation of protein phenotypes represented by 48 spot variations, involving e.g. peroxidases, serpins, α-amylase/trypsin inhibitors, peroxiredoxin and a small heat shock protein, in relation to markers on the chromosome map. [ABSTRACT FROM AUTHOR]

One of the substantial differences between conventional and organic growing systems is the degree to which the farmer can control biotic and abiotic stresses; for organic growing systems varieties are needed with a broad adaptation to annually varying factors, while at the same time a good specific adaptation is necessary with respect to more constant climate and soil conditions. This combination of requirements implies that varieties for organic farming need to be better characterised with respect to genotype × environment interactions than varieties for conventional farming. Such interactions, which often are found for quantitatively expressed traits, are in general difficult to deal with in phenotypic selection. New approaches for QTL analyses (e.g. using physiological models) facilitate estimation of effects of genes on a trait (the phenotype) as a response to environmental influences. From such analyses, markers can be identified which may help to predict the trait expression of a plant genotype in relation to defined environmental factors. The application of markers to select for loci with specific interactions with the environment could, therefore, be especially important for plant breeders targeting organic farming systems. [ABSTRACT FROM AUTHOR]

According to a widely accepted theory on barley domestication, wild barley ( Hordeum vulgare ssp. spontaneum) from the Fertile Crescent is the progenitor of all cultivated barley ( H. vulgare ssp. vulgare). To determine whether barley has undergone one or more domestication events, barley accessions from three continents have been studied (a) using 38 nuclear SSR (nuSSRs) markers, (b) using five chloroplast SSR (cpSSR) markers yielding 5 polymorphic loci and (c) by detecting the differences in a 468 bp fragment from the non-coding region of chloroplast DNA. A clear separation was found between Eritrean/Ethiopian barley and barley from West Asia and North Africa (WANA) as well as from Europe. The data from chloroplast DNA clearly indicate that the wild barley ( H. vulgare ssp. spontaneum) as it is found today in the “Fertile Crescent” might not be the progenitor of the barley cultivated in Eritrea (and Ethiopia). Consequently, an independent domestication might have taken place at the Horn of Africa . [ABSTRACT FROM AUTHOR]

A partial genetic linkage map was constructed on 71 doubled-haploid lines derived from a cross between the barley lines Tadmor and WI2291 with 181 molecular markers. The segregating population was used to detect markers linked to the geneMlg conferring resistance to powdery mildew (Erysiphe graminis f. sp. hordei) and to genes for quantitative resistance to scald (Rhynchosporium secalis). The gene Mlg on chromosome 4H was flanked by two AFLP markers at a distance of 2.0 and 2.4 cM, respectively. QTLs for resistance to scald were detected on chromosomes 2H and 3H. This association of molecular markers with qualitative and quantitative disease resistance loci represents a valuable starting-point for marker-assisted selection. [ABSTRACT FROM AUTHOR]

This study investigated the effect of ultraviolet (UV-C) radiation on the germination percentage, germination rate, radicle length, and plumule length of maize and sugar beet seeds. The experiment was implemented in six replicates of 30 seeds per replicate and in sterilized petri dishes under laboratory conditions. Treatments included UV-C (254 nm) radiation exposure durations of 0 min (control), 30 min, 2 h, 4 h, 8 h, and 12 h. The UV-C radiation treatments did not significantly affect the germination percentage of the seeds (p < 0.05). However, the seeds germination rate was significantly affected by the UV-C radiation treatments. The treatments of 8 h and 12 h exposure duration led to the highest seed germination rates in maize and sugar beet, respectively. Lowest seed germination rates belonged to the controls. The radicle length of maize seeds was significantly affected by the UV-C radiation treatments, but the treatments did not significantly affect the radicle length of sugar beet seeds. The 12 h exposure to UV-C radiation treatment resulted in the largest radicle in maize, which was 2.08 cm larger than the radicle of the control seeds. The UV-C radiation treatments had a statistically significant effect on the plumule length of maize and sugar beet seeds. The treatment 8 h UV-C exposure duration led to the largest plumule in maize and sugar beet, which were 0.32 cm and 0.83 cm larger than the plumule of the control seeds, respectively. Breaking down the seed coat and increasing the temperature by UV-C radiation are potential reasons for the observed positive effects. [ABSTRACT FROM AUTHOR]