Search

Leaf stripe, caused by the fungus Pyrenophora graminea Ito et Kuribayashi [anamorph Drechslera graminea (Rabenh. ex. Schlech.) Shoemaker], is an important seed-borne disease of barley (Hordeum vulgare L.). The objective of this study was to verify the reliability of a PCR-based marker (MWG2018) associated with the resistance gene Rdg2a and to assess the leaf stripe resistant phenotype in barley breeding programs. A large number of barley cultivars and accessions were thus evaluated for their reaction to a highly virulent monoconidial isolate (Dg2) of the pathogen and genotyped for the allele of the molecular marker. Several resistant genotypes were identified and four were shown to possess the same allele as the cultivar Thibaut (the resistant parent of the original mapping population in which Rdg2a was identified) at the marker locus. One of them, cv. Rebelle, is being used as a source of leaf stripe resistance in winter barley breeding programs. The allelic composition at the MWG2018 locus was verified in several resistant lines bred from five crosses, in which Rebelle acted directly or indirectly as donor of the resistance. The results showed that the resistant phenotype of the lines was always associated with the resistance allele of the molecular marker, thereby demonstrating its reliability for selecting leaf stripe resistance. The MWG2018 PCR-based marker can therefore be proposed as a tool to assess the resistant phenotype., LEAF STRIPE is a common disease in barley districts characterized by a cold climate during the sowing season, such as Scandinavia, Canada (spring sowing), and the Mediterranean (winter sowing). In [...]

Breeding for resistance is the most effective tool for controlling the corky root disease of tomato caused by the fungus Pyrenochaeta lycopersici. However, little is known about the molecular bases of tomato-P. lycopersici interaction. In order to identify genes involved in the basal defence response activated in a susceptible cultivar and in disease symptom development, a set of cDNA-AFLP fragments derived from a profiling experiment was analysed. A total of 247 differentially expressed TDFs (transcript-derived fragments), identified as putative tomato genes, were characterized by similarity searches, and classified into 11 broad functional classes. Timings ranging between the early [48, 72 and 96 h post-infection (hpi)] and the late infection stages (20 and 27 dpi) were used. The changes of tomato root transcriptional profiles showed large differences in quantity and quality between the early and late stages of infection. Mechanisms of basal defence were most likely activated at early stages, when a gene coding for a receptor-like serine-threonine protein kinase and other genes of the signalling class were upregulated. At 20 dpi some of the mechanisms involved in defence were still activated, while at 27 dpi a general repression of gene expression was observed. [ABSTRACT FROM AUTHOR]

The interspecific relationships among 51 worldwide collected accessions of Salvia have been investigated using the amplified fragment length polymorphism (AFLP) technique. The assessed genetic similarities allowed us to group the genotypes into two main clusters according to their geographical origin. Our results are encouraging for further characterization of the genus with the aim to clarify Salvia taxonomy. [ABSTRACT FROM AUTHOR]

Iodine is an essential microelement for human health, and the recommended daily allowance (RDA) of such element should range from 40 to 200 μg day-1. Because of the low iodine contents in vegetables, cereals, and many other foods, iodine deficiency disorder (IDD) is one of the most widespread nutrient-deficiency diseases in the world. Therefore, investigations of I uptake in plants with the aim of fortifying them can help reach the important health and social objective of IDD elimination. This study was conducted to determine the effects of the absorption of iodine from two different chemical forms-potassium iodide (I-) and potassium iodate (IO-3)-in a wide range of wild and cultivated plant species. Pot plants were irrigated with different concentrations of I- or IO-3, namely 0.05% and 0.1% (w/v) I- and 0.05%, 0.1%, 0.2%, and 0.5% (w/v) IO-3. Inhibiting effects on plant growth were observed after adding these amounts of iodine to the irrigation water. Plants were able to tolerate high levels of iodine as IO-3 better than I- in the root environment. Among cultivated species, barley (Hordeum vulgare L.) showed the lowest biomass reductions due to iodine toxicity and maize (Zea mays L.) together with tobacco (Nicotiana tabacum L.) showed the greatest. After the screening, cultivated tomato and potato were shown to be good targets for a fortification-rate study among the species screened. When fed with 0.05% iodine salts, potato (Solanum tuberosum L.) tubers and tomato (Solanum lycopersicum L.) fruits absorbed iodine up to 272 and 527 μg/100 g fresh weight (FW) from IO-3 and 1,875 and 3,900 μg/100 g FW from I-. These uptake levels were well more than the RDA of 150 μg day-1 for adults. Moreover, the agronomic efficiency of iodine accumulation of potato tubers and tomato fruits was calculated. Both plant organs showed greater accumulation efficiency for given units of iodine from iodide than from iodate. This accumulation efficiency decreased in both potato tubers and tomato fruits at iodine concentrations greater than 0.05% for iodide and at respectively 0.2% and 0.1% for iodate. On the basis of the uptake curve, it was finally possible to calculate the doses of supply in the irrigation water of iodine as iodate (0.028% for potato and 0.014% for tomato) as well as of iodide (0.004% for potato and 0.002% for tomato) to reach the 150 μg day-1 RDA for adults in 100 g of such vegetables, to efficiently control IDD, although these results still need to be validated. [ABSTRACT FROM AUTHOR]

Mapping quantitative trait loci (QTLs) responsible for malting quality traits in barley populations has been the main genetic approach to malting quality breeding. A ‘winter × spring’ doubled haploid barley population ‘Nure’ × ‘Tremois’, where such traits were segregating, has been recently developed. Our objective was to map QTLs for malting quality from 2 years of trials in two contrasting locations. QTLs were found on six chromosomes, with a main cluster on chromosome 1H. For wort viscosity and malt extract, favourable alleles at two loci on chromosome 5H were carried by the winter feeding parent ‘Nure’. Doubled-haploids with higher quality than the spring malting cultivar ‘Tremois’ showed either a facultative or a winter growth habit and a level of frost tolerance comparable with that of the winter tolerant parent ‘Nure’. Markers and QTLs of quality traits were further validated on a separate set of DH lines, coming from the same cross, by means of marker-assisted selection. This showed that, at least in the present cross combination, positive contributions to malting quality can be found in winter feed barley. [ABSTRACT FROM AUTHOR]

Five molecular markers associated to two frost tolerance QTLs ( Fr-H1 and Fr-H2) were tested both on nine Turkish accessions, classified by breeders as highly frost-tolerant, and on a previously described sample of 26 barleys, winter, facultative and spring. Accessions were characterized in terms of frost tolerance under both field conditions and artificial freezing test at −12°C. The Turkish lines resulted to be equal or superior to the most tolerant European genotypes tested, showing that they can be used to improve the frost tolerance of the EU barley germplasm. The marker Hv BM5A ( Vrn-H1 and Fr-H1) resulted to be the best predictor for assisted selection within this germplasm, because of its high correlation between allelic variation and phenotypic traits. Only Hv CBF4 of the three Hv CBF markers tested at Fr-H2 was associated to the trait, but at lower significance than HvBM5A. The PCR-based molecular marker of Vrn-H1 can thus be used in barley breeding not only for selection of facultative and winter types, but also for fast routine selection of frost tolerant genotypes. [ABSTRACT FROM AUTHOR]

To study barley adaptation and improvement in the Mediterranean basin, a collection of 188 entries comprising landraces and old genotypes and current modern varieties from the Mediterranean basin and elsewhere was tested on moisture-contrasted environments in seven Mediterranean countries, during 2004 and 2005 harvest seasons. The experimental design consisted of an unreplicated trial for all entries, augmented by four repeated checks to which a partial replicate containing a quarter of the entries was added. Best Linear Unbiased Predictions (BLUPs) representing adjusted genotypic means were generated for individual trials using a mixed model. BLUPs were used for genotype by environment interaction analysis using main effect plus genotype by environment interaction (GGE) biplots of yield ranked data and for comparisons of landraces, old and modern genotypes using analysis of variance. Mean yields ranged from near crop failure to 6 t/ha. Local landraces were better adapted to environments yielding below 2 t/ha, thus breeding has mostly benefited environments yielding above 2 t/ha where modern genotypes out yielded landraces and old cultivars by 15%. Current barley selection is leading to specifically adapted genotypes. [ABSTRACT FROM AUTHOR]

Barley is an economically important model for the Triticeae tribe. We recently developed a new resource: the ‘Nure’ × ‘Tremois’ mapping population. Two low temperature QTLs were found to segregate on the long arm of chromosome 5H ( Fr-H1, distal; Fr-H2, proximal). With the final aim of positional cloning of the genetic determinants of Fr-H1 and Fr-H2, a large segregating population of 1,849 F2 plants between parents ‘Nure’ and ‘Tremois’ was prepared. These two QT loci were first validated by using a set of F3 families, marker-selected to harbor pairs of reciprocal haplotypes, with one QTL fixed at homozygosity and the alternate one in heterozygous phase. The study was then focused towards the isolation of the determinant of Fr-H2. Subsequent recombinant screens and phenotypic evaluation of F4 segregants allowed us to estimate ( P ≤ 0.01) a refined genomic interval of Fr-H2 (4.6 cM). Several barley genes with the CBF transcription factor signature had been already roughly mapped in cluster at Fr-H2, and they represent likely candidate genes underlying this QTL. Using the large segregating population (3,698 gametes) a high-resolution genetic map of the Hv CBF gene cluster was then constructed, and after fine mapping, six recombinations between the Hv CBFs were observed. It was therefore possible to genetically divide seven Hv CBF subclusters in barley, in a region spanning 0.81 cM, with distances among them varying from 0.03 to 0.32 cM. The few recombinants between the different Hv CBF subclusters are being marker-selected and taken to homozygosity, to phenotypically separate the effects of the single Hv CBF genes. [ABSTRACT FROM AUTHOR]

The naked/hulled kernel trait is controlled in barley by a single gene called nud, on chromosome 7H. The first aim of this work was use bulked segregant analysis to find, new PCR-based markers linked to nud for marker-assisted selection (MAS). A new SCAR marker (sJ14) was developed, which is useful for introgressing the naked trait. This, and three other SCARs, were placed on the ‘Proctor’ × ‘Nudinka’ map to detail a 0.9-cM fragment tagging nud. In order to evaluate the haplotypes around the nud locus, a phenotypically differentiated collection of naked/hulled genotypes was characterized by means of the above markers. Eight different marker haplotypes were found in the breeding germplasm, and a new allele for the marker sKT7 was found. The same barley collection has been surveyed for resistance/susceptibility to leaf stripe ( Pyrenophora graminea), in order to investigate any possible association between this and other traits. The naked/hulled seed trait was not associated with resistance/susceptibility to the fungus. [ABSTRACT FROM AUTHOR]

Abstract: In Mediterranean environments, forage production for livestock is both difficult and costly due to erratic rainfall. As an alternative, barley, oat and triticale can be used as dual-purpose autumn-sown cereals, thus serving as winter grazing and grain for feed. The present study was aimed at estimating the influence of different management systems (dual-purpose with one and two grazings, soft-dough harvest for silage, full maturity grain only) on grain yield, forage and whole plant production, and on quality-related traits of barley (Hordeum vulgare L.) and oat (Avena sativa L.). The trials were conducted over 2 years (1998/1999 and 1999/2000) in a Southern Italy Mediterranean environment using a flock of sheep for grazing and mechanically clipping the plots, thus simulating the dual-purpose, to obtain forage samples for analyses. Effect of the years was not significant, whereas both crops underwent significant reductions of grain yield, harvest index, thousand kernel weight and seeds/m2 in the dual-purpose plots but not in the grain only plots. The most drastic yield reduction was recorded in oat after two grazings by comparison to the ungrazed treatment (2.4t/ha versus 3.9t/ha). Grain protein content was not affected by dual-purpose in oat, and it was independent of the number of grazings in barley. Barley had a higher production of total biomass and milk feed units than oat in the dual-purpose management systems, except for the soft-dough and grain only treatments. In addition, barley reacted positively to both the dual-purpose systems (one and two grazings). More specifically, whole plant biomass increased from 9.6t/ha when grown for grain only to 13.6t/ha in the single grazing system, and milk feed units similarly increased, from 7680 to 9216MFU/ha. Green forage quality was comparable between the two cereals, even though barley whole plants showed lower fibre content, especially after two grazings. The soft-dough stage of both crops had better forage quality parameters, nevertheless, the lower biomass yields and total milk feed units (in the case of barley) rendered this system non-profitable for the environment studied. Barley demonstrated a clear superiority for the dual-purpose systems in Mediterranean Italy and should thus be preferred to oat, except when using oat to interrupt barley monocropping. [Copyright &y& Elsevier]

Expressed sequence tags (ESTs) databases are being created for several plant species. ESTs have the potential to analyse the expressed part of the genome, and to be used in a wide range of applications from the theoretical aspect of plant biology to the breeding process. The present study is based on a cold-stressed cDNA library as a source of ESTs in barley: partial cDNA sequencing of randomly isolated clones yielded 960 ESTs. The strategy of random sequencing cDNA clones at their 5′ ends allows one to obtain information on the steady-state level of the transcripts in a cold-stressed green leaf of barley. Repetitive sequencing of nearly identical ESTs provides, in addition, useful information on the existence of multigene families. The results of a BLAST search performed on this set of ESTs showed that 18.5% of the tags exhibited no significant homology to known genes, 10% had significant levels of homology with known cold or other stress-related genes, about 26% proved homologous to enzymes involved in several metabolic pathways and about 15% encoded for ribosomal proteins, cytoskeleton proteins, histones, ubiquitin, elongation factors and others. Redundancy was found for some classes of tag: RuBisCo, cab proteins, carbonic anhydrase, glutamate decarboxylase and stress related proteins. [ABSTRACT FROM AUTHOR]

A collection of 39 Osteospermum clones and cultivated varieties of different origin were evaluated by random amplified polymorphic DNA (RAPD) analysis. All the clones were identified by 23 decamers selected from a set of 30. This is the first characterization by molecular markers of the genetic material of Osteospermum. The level of genetic diversity among genotypes was assayed and all the accessions tested were then classified into six groups by UPGMA cluster analysis; the clustering of genotypes using the RAPD data proved to be in accordance with their breeding group origin. RAPD analysis can therefore be a useful tool for evaluating genetic variability in other Osteospermum germplasm collections for breeding purposes and for protecting intellectual property rights of improved varieties. [ABSTRACT FROM AUTHOR]

AbstractRandom amplified polymorphic DNA (RAPD) markers were used to verify interspecific hybridization in Alstroemeria. Five putative interspecific hybrids and their parents were analysed by means of four preselected RAPD primers. The putative parentage was confirmed in four hybrids and was excluded in one that showed completely different RAPD patterns from its putative parents and a different phenotype. Our results demonstrated that this molecular technique is a powerful tool for verifying hybridity rapidly if the putative parents are given. This tool will allow screening of small immature seedlings for verification of hybridity and should improve the efficiency of breeding programmes. [ABSTRACT FROM AUTHOR]

Pyrenophora graminea is a seed-borne pathogen and is the causal agent of the barley leaf stripe disease. Our aim is to study the genetic basis of barley resistance to leaf stripe. A qualitatively acting resistance factor has been identified in the cultivar ‘Vada’ and the partial resistance of the cultivar ‘Proctor’ to a P. graminea isolate has been demonstrated to be dominated by a major quantitative trait locus (QTL), mapped on barley chromosome 1. Map colinearity between the leaf stripe ‘Proctor’ resistance QTLs, ‘Vada’ resistance to leaf stripe, and other disease resistance loci have been investigated in this work using molecular markers. Moreover, since inoculation of barley rootlets by the fungus had been shown to induce the accumulation of several PR (pathogen-related) mRNA families, seven barley PR genes have been mapped as RFLPs, and one assigned to a chromosome arm via ditelosomic analysis to verify possible map associations with resistance QTLs. This work discusses the genetic relationships between the known leaf stripe resistance loci, resistance loci towards other seed-borne pathogens and defence gene loci. [ABSTRACT FROM AUTHOR]