Session 7 Disease and Pest Resistance I Generally, Leaf Diseases

Oral Presentation

Optimizing Breeding Strategies Based on the Evolutionary
Potential of Barley Pathogens

B. A. McDonald and C. C. Linde

Institute of Plant Sciences, Swiss Federal Institute of Technology (ETH) Zurich, CH-8092 Switzerland, E-mail: bruce.mcdonald@ipw.agrl.ethz.ch

Pathogen populations evolve in response to the deployment of resistance genes (R-genes) in agroecosystems. One consequence of this evolution is the familiar boom-and-bust cycle whereby major R-genes lose their effectiveness after being grown over a wide area. The evolutionary response of the pathogen population is affected by the mutation rate, mating/reproduction system, gene flow, effective population size, type of resistance gene, and R-gene deployment strategy. Population genetic structure may prove useful for predicting the evolutionary potential of pathogen populations. We will present a strategy that may prove useful for deciding whether to focus on major R-gene or quantitative R-gene resistance and for extending the life expectancy of R-genes in breeding programs. Examples of proposed breeding strategies will be presented for major barley pathogens.

Importance of Secondary and Tertiary Genepools in Barley Genetics and Breeding. I. Cytogenetics and Molecular Analysis

R. Pickering1, P. A. Johnston1 and B. Ruge2

1New Zealand Institute for Crop and Food Research Limited, Christchurch, New Zealand,
E-mail: pickeringr@crop.cri.nz; 2Institute of Agricultural Crops, Federal Centre for Breeding Research
on Cultivated Plants, D-18190 Gross Lüsewitz, Germany

We describe progress in introgressing chromatin from wild Hordeum species into cultivated barley since IBGS 2000. Several new recombinant lines (RLs) have been produced from hybrids between H. vulgare and H. bulbosum, the sole species in the secondary genepool. Production of disease-resistant RLs has been accomplished first by backcrossing triploid H. vulgare (2n = 2x = 14) × H. bulbosum (2n = 4x = 28) hybrids to cultivated barley and second by screening selfed progeny from tetraploid hybrids between the two species. We present data on the early infection mechanisms in leaf rust resistant RLs and results from a yield trial involving leaf rust and powdery mildew resistant RLs. RLs resistant to scald, stem rust, BaYMV/BaMMV and speckled leaf blotch are also being evaluated. Current methods for characterisation include cytogenetic analyses of hybrids and RLs, PCR assays using repetitive sequences, RFLP, AFLP, cDNA-AFLP, STS and SSCP detection of PCR markers derived from EST contigs. We are pyramiding resistance loci at different chromosomal sites to study the effects on agronomic performance and fertility.

Importance of Secondary and Tertiary Genepools in Barley
Genetics and Breeding. II. Disease Resistance, Agronomic Performance and Quality

R. Pickering1, R. E. Niks2, P. A. Johnston1 and R. C. Butler1

1New Zealand Institute for Crop and Food Research Limited, Christchurch, New Zealand,
E-mail: pickeringr@crop.cri.nz;
2Laboratory of Plant Breeding, Wageningen University, 6700 AJ Wageningen, The Netherlands

In this paper on the use of secondary and tertiary genepools in barley improvement, we describe the characterisation of leaf rust resistant recombinant lines (RLs) derived from Hordeum vulgare × H. bulbosum crosses. Twelve RLs were inoculated with leaf rust and the early stages of disease development were observed. Several RLs showed complete resistance to the pathogen, but others had a high level of partial resistance, which may be durable. Some of these RLs and others were tested in yield trials to determine the effects of introgressed chromatin from H. bulbosum on yield and quality. We conclude that there are no major adverse effects that cannot be overcome through normal breeding techniques.

Adaptation of Biotrophic Barley Pathogens to Genetic Resistance
in Central Europe

A. Dreiseitl

Department of Plant Protection, Agricultural Research Institute Kromeriz, Ltd., 767 01 Kromeriz,
Czech Republic, E-mail: dreiseitl@vukrom.cz

The contribution is based on earlier studies aiming at postulation of resistance genes to powdery mildew and leaf rust in barley varieties, multiyear data on resistance evaluations of these varieties in the official variety trials in the Czech Republic, and investigations of pathogen populations of powdery mildew on barley (Blumeria graminis f.sp. hordei) and leaf rust (Puccinia hordei). The examples of some barley varieties demonstrate the role of individual evolutionary forces (in particular, direct selection, indirect selection, migration, and recombination) for the population adaptation of the causal agents of these diseases to individual resistance genes and increasing population virulence complexity. Considering some aspects of breeding and evolutionary potential of the pathogens, it seems that a combination of at least two original and fully effective resistance genes in a variety could be a good way to prolong the durability of resistances to both powdery mildew and leaf rust. However, the progress in barley breeding for disease resistance will depend not only on the resistance sources and extending the diversity of this character in commercial varieties, but also on the critical selection of varieties that combine different effective resistance genes. The use of molecular markers is essential to achieve these aims.

Linkage Disequilibrium Mapping for Yield and Leaf Rust Resistance in Barley

R. E. Niks, A. T. W. Kraakman, P. Stam and F. A. van Eeuwijk

Laboratory of Plant Breeding, Wageningen University and Research Center,
6700 AJ Wageningen, The Netherlands,
E-mail: rients.niks@wur.nl

The recent development of linkage disequilibrium (LD) mapping methodology has widened the scope for the search of quantitative trait loci (QTL). Whereas the applicability of classical QTL studies was restricted to populations of offspring from biparental crosses, LD approaches allow the screening of arbitrary collections of genotypes. We used LD methodology to detect marker-trait associations in a collection of 146 modern European two-row spring barley cultivars. The traits were yield, yield stability, and resistance to barley leaf rust. The marker system consisted of 236 AFLP-markers. Linkage disequilibrium existed up to more than 10 cM distance. A number of markers were found associated with the traits by our LD methodology. These markers were often located in regions where earlier QTLs have been found in standard QTL experiments. Thus, we were able to verify existing QTLs and detect new ones. LD mapping appears a promising technology for studying the genetical basis of qualitative and quantitative traits in barley.

Genetic Mapping of a Novel Scald Resistance
Gene Rrs15CI8288 in Barley

G. Schweizer1,, M. Herz1, S. Mikolajewski1, M. Brenner1, L. Hartl2 and M. Baumer2

1Genome Analysis and 2Barley Breeding, Institute for Crop Production and Plant Breeding,
Bavarian State Research Centre for Agriculture, D-85354 Freising-Weihenstephan, Germany,
E-mail: guenther.schweizer@LfL.bayern.de

Scald caused by Rhynchosporium secalis is one of the major leaf diseases of barley (Hordeum vulgare L.) in Europe. A number of resistance genes against the fungus were published up to now, but most genes for resistance to barley leaf scald map either to the Rh-locus near the Centromer of chromosome 3H, or to the Rh2 locus on the short arm of chromosome 7H. The objective of the present study was to map a single dominant resistance gene from the line CIho8288. No other scald resistance genes have been mapped to this chromosome arm so far. We identified the new resistance gene in a mapping population of 145 DH lines with AFLP- and MS-techniques. The phenotypic evaluation of the population was carried out in the greenhouse with a single spore isolate of R. secalis. In a first test, the developed STS marker will be diagnostic to European barley cultivars. For an efficient marker based selection, a SNP marker will be established by Pyrosequencing.

Suitability of a Selected Barley Differential Set
for Pyrenophora teres f. teres Virulence Screening

M. J. Jalli

Boreal Plant Breeding Ltd, FIN-31600 Jokioinen, Finland,
E-mail: marja.jalli@boreal.fi

Net blotch (Pyrenophora teres Drechs. f. teres Smedeg.) is an economically important disease of barley (Hordeum vulgare L.). Breeding barley for improved resistance to net blotch is a priority in many plant breeding programmes around the world. For such breeding strategies to be successful, it is essential to have reliable information both on the pathogen population and on possible resistance sources. The virulence structure of P. teres populations have been studied at several sites around the world. However, the results are not entirely comparable because of the absence of a commonly used differential set. In response to this fact, barley breeders and researchers have constructed a new barley differential set which includes several P. teres resistance genes available separately or in combination in different genetic backgrounds. This new barley differential set has been assessed and its suitability for P. teres virulence screening will be discussed. Principal results from the virulence study and new resistance sources will be outlined.

Ramularia collo-cygni, Worldwide Evaluation

E. Sachs

Institute for Plant Protection in Field Crops and Grassland, Federal Biological Research Centre
for Agriculture and Forestry, D-14532 Kleinmachnow, Germany,
E-mail: e.sachs@bba.de

Ramularia leaf spot disease has occurred in many European countries and in New Zealand since the 1980s, and later in South America. Ramularia counts among the fungi imperfecti. The species name collo-cygni describes the particular shape of conidiophores, which resemble a swans neck. The fungus mainly parasitises barley, but also other cereal species, grasses and maize. Brown leaf spots 12 mm in size surrounded by a yellow halo appear on leaf blades from the end of May. Later, the spots also appear on stems, leaf sheaths and awns. Ramularia leaf spots turn red when placed on sour water agar (pH 4). Colour response serves as a diagnostic means as Ramularia spots may easily be confused with a number of other leaf spots. They are particularly similar to PLS, but these do not turn red. The main period of attack in Germany lies between end of May to post-maturity of barley. The fungus overwinters on infected young plants and gradually grows from the lowest leaf level to the ear in the following growing season. It has extremely small conidia (511 ) which are easily spread by wind but need high moisture to germinate. Strongly infested plants die off up to 14 days early, which may cause yield losses of up to 20%. Azoles and strobilurin combination products have turned out efficient in controlling the disease. But no fungicides have been specially authorised for Ramularia control yet.

Winter Barley Cultivar Mixtures: Why Isnt Everybody
Growing Them?

A. C. Newton and J. S. Swanston

Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, UK,
E-mail: a.newton@scri.sari.ac.uk

There are many advantages to be gained from growing cultivars in mixtures from reduced disease and improved yield and quality, through to yield and quality stability. Disadvantages lie in the physical requirement to mix components and the perceived quality constraints. For spring barley grown for malting, quality concerns can be not only overcome, but turned to benefits. For winter barley, where yield benefits are already larger, there may be opportunity for spring barley quality performance. Furthermore, specific weights and lodging resistance are significant factors that can be substantially improved in mixtures, while differences in maturity and height are less problematic than expected due to convergence. The benefits to winter barley are probably greater due to a longer growth period exposed to biotic and abiotic stress when the competition and compensation interaction between components is maximised. To maximise disease reduction, we can manipulate not only specific resistance but also plant height, leaf habit and general plant morphology, particularly affecting splash-dispersed pathogens such as Rhynchosporium secalis. Greater reduction of most diseases is correlated with mixture complexity, i.e. the number of component genotypes. The spatial distribution of component genotypes, particularly with respect to connectivity characteristics of individual components, can have an impact on mixture efficacy, and balancing selection for complexity with that of different components of the mixture can be enhanced in stratified spatial deployment patterns.

Detection of Independent Gene Pools of Barley
with the Application of DNA Markers

A. Jahoor1, J. Orabi1, 2, B. Nigusse3, A. Yahyaoui2 and G. Backes1

1Plant Research Department, Risoe National Laboratory, DK-4000 Roskilde, Denmark,
E-mail: a.jahoor@risoe.dk;
2International Center for Agricultural Research in the Dry Areas (ICARDA), Aleppo, Syria;
3Department of Agricultural Research and Human Resource Development (DARHRD), Asmara, Eritrea

Large number of barley accession including cultivars from Europe, land races and wild barley, Hordeum vulgare ssp. spontaneum from the Near East and North Africa were analysed with DNA markers. In addition, 10 single plants per fields that belong to small farmers in Eritrea were collected to study the structure of genetic diversity in this material. In total 240 spikes were randomly sampled. A total of 48 genomic microsatellites distributed randomly over the whole genome of barley and 5 chloroplast microsatellites were employed. The complete germplasm consisting of 550 different barley accessions was screened with the above-mentioned microsatellites. Interestingly, all 240 spikes are genetically different except two spikes collected from two different fields belonging to two different regions in Eritrea. Comparisons of barley accessions from different geographical regions clearly indicate that two independent gene pools have been developed during the evolution of barley. These two different gene pools have been verified with the genomic as well as chloroplast microsatellites.

Trends in Biological and Molecular Variation of Barley Driven
by Long-Term Breeding

J. Kraic and M. Benkova

Division of Applied Genetics and Breeding, Research Institute of Plant Production, 921 68 Piestany, Slovakia, E-mail: kraic@vurv.sk

Variation in morphological, agronomical, phytopathological, biochemical, and molecular traits and characteristics has been studied in assembled and maintained collection of original barley landraces and cultivars. All landraces originated from or have been registered and cultivated in territory of the Czech and Slovak Republic. Most of them have beed created by breeding stations located there. Analyzed set of barleys contains more than one hundred genotypes. Several tens of traits and characteristics have been analyzed in the field surveys and by laboratory methods. The aim of this work is: to study and document temporal flux in diversity of above mentioned traits; to evaluate development in this variation; to survey trends of development of these traits to the future. Preliminary results, at this stage of study, reflect differences between barley genotypes.

Poster Presentation

Evolutionary Potential of Rhynchosporium secalis Populations
and Resistance Breeding Strategies

M. M. Abang1,2, S. M. Udupa1, M. Baum1, B. A. McDonald2, S. Ceccarelli1, S. Grando1
and C. C. Linde2

1International Center for Agricultural Research in the Dry Areas (ICARDA), Germplasm Program, Aleppo, Syria, E-mail: m.abang@cgiar.org; 2Phytopathology Group, Institute of Plant Sciences,
Swiss Federal Institute of Technology (ETH), CH-8092 Zurich, Switzerland

Scald, caused by the fungal pathogen Rhynchosporium secalis, is a damaging disease of barley. Breeding efforts have focused on incorporating major resistance genes to control this disease. Population genetic analyses suggest that a sexual stage exists and may in part explain the rapid evolution of pathogen virulence that leads to loss of resistance following widespread deployment. While knowledge of genetic structure may provide useful insights into the evolutionary processes that affect pathogen population genetics, experimental approaches are needed to provide a sound basis for the prediction of pathogen evolutionary potential. A collaborative project between the ETH Phytopathology Group and ICARDA is utilizing a replicated mark-release-recapture field experiment to quantify the relative impacts of sexual reproduction, asexual propagation, immigration and selection on the genetic structure of an experimental population of R. secalis. The importance of asexual and sexual sources of carryover inoculum in initiating scald epidemics on barley will be evaluated. Analytical methods for estimating the proportion of recombinants and immigrants have been established. Selection coefficients will be calculated based on changes in frequencies of marked inoculated isolates over time. If sexual recombinants constitute a significant source of inoculum for scald epidemics, then breeders should adjust their breeding strategies to focus on quantitative resistance and increasing diversity in host populations.

Genetic Resources of Barley Resistance to Net Blotch

O. Afanasenko1, I. Terentieva2, O. Manninen3, D. Kopahnke4, O. Filatova1
and N. Mironenko1

1Laboratory of Plant Resistance to Diseases, All-Russian Research Institute of Plant Protection, Saint Petersburg, 196608, Russia, E-mail: o_afanasenko@land.ru; 2All Russian Plant Industry Institute named
by N. I. Vavilov, Saint Petersburg, 190000, Russia; 3Plant Breeding Biotechnology, MTT Agrifood Research Finland, Plant Production Research Unit, FIN-31600 Jokioinen, Finland; 4Institute for Epidemiology and Resistance, Federal Centre for Breeding Research on Cultivated Plants (BAZ), D-06449 Aschersleben, Germany

Resistance of more than 6,000 barley accessions were investigated in field and laboratory conditions. Most of resistant barley genotypes were found among the landraces from centres of barley evolution. Effectiveness of known and novel sources and donors of barley resistance to different Pyrenophora teres populations was studied by inoculation with 200 isolates from Russia, Finland and Germany. The genetic diversity of 5 novel sources of resistance was determine by hybridological analysis and phytopathological test. F2 and F3 hybrid populations (resistant × susceptible; resistant × resistant crosses) were studied by using P. teres isolates from Russia, Finland and Germany. Also sources of resistance were inoculated with 60 isolates of fungus hybrid population (phytopathological test). Comparative data of hybridological analysis and phytopathological test will be demonstrated. Genetic collection of donors of resistance, including 30 barley accessions with named genes of resistance to P. teres will be presented.

Genetic Variation in Barley Germplasm for Resistance
to Snow Mold

T. Akar1, F. Duesuenceli 1, S. Ceccarelli2, L. Cetin1, I. Sayim 1 and H. Sipahi 1

1Central Research Institute for Field Crops, 06042 Ulus/Ankara, Turkey, 2International Center
for Agricultural Research in the Dry Areas (ICARDA), Aleppo, Syria,
E-mail: taner_akar@ankara.tagem.gov.tr

The aim of this study was to determine genetic variation among barley cultivars and lines against the snow mold caused by Fusarium nivale under the natural condition. Out of 811 entries used in the trial, 280 entries including some cultivars have been found resistant to snow mold together wheat desirable yield level. Only winter and facultative type of barley lines/cultivars have dealt with the disease and reached the highest yield level. According to correlation analysis, there were significant relationship between snow mold and cold tolerance and growth habit, 0.965 and 0.909 respectively. It is possible to increase snow mold resistance when selecting cold tolerance winter and facultative lines. In spite of the fact that snow mold does not often make epidemic in the Central Higlands of Turkey in general, some part of the areas especially above 1,000 m altitude are the risk of the disease in particular. So, in order to overcome the problem, genetically resistant cultivars should be grown in the areas in the short term and in the long term, resistant lines and cultivars should be used more in crossing program.

Detection of Differences in New Alleles at the Mla-Locus of Barley
(Hordeum vulgare L.) by Various Molecular Techniques

G. Backes1, Z. Kyjovska1,2, I. Araja1, 3 and A. Jahoor1

1Plant Research Department, Risoe National Laboratory, DK-4000 Roskilde, Denmark,
E-mail: gunter.backes@risoe.dk;
2Faculty of Science, Masaryk University, 600 00 Brno, Czech Republic;
3Plant Genetics Laboratory, Institute of Biology, University of Latvia, Salaspils, LV-2169, Latvia

For the effective genetic protection of cultivated barley against powdery mildew a continuing demand of new sources of resistance against this disease is necessary. Wild barley (Hordeum vulgare ssp. spontaneum), the progenitor of cultivated barley, has shown to be a rich and valuable source of resistance genes. Especially for the powdery mildew resistance locus Mla on the short arm of the barley chromosome 1H, more than 20 new and highly effective alleles were detected by infection experiments. These classical analyses reach their limit with the complexity of the increasing amount of alleles at this locus, the risks of the use of isolates not present in the respective geographical regions and the necessity to pyramidize resistance genes in order to build up more durable resistance. Molecular techniques can and will assist in the rapid and secure identification of these alleles. The effectiveness of different techniques to perform this task is shown and compared: marker based techniques (microsatellites, STS) and techniques based on differences in the gene itself. The latter include SNPs with the prerequisite of the knowledge of the complete sequence of the respective allele and Eco-TILLING.

Identification of Molecular Markers Linked to a Pyrenophora teres Avirulence Gene

A. D. Beattie, G. J. Scoles and B. G. Rossnagel

Department of Plant Sciences/Crop Development Center, University of Saskatchewan,
Saskatoon, S7N 5A8, Canada,
E-mail: adb164@mail.usask.ca

Single dominant resistance (R) genes are commonly used by plant breeders to achieve disease resistance. However, rapid changes in pathogen populations often cause the breakdown of such resistance. Because of the effort involved in deploying resistance genes, predicting their durability before introduction into cultivars would be useful. This could be accomplished by assessing the fitness penalty on the pathogen to overcome a particular R gene. R proteins are known to interact directly with pathogen avirulence (avr) gene products, or with avr factors complexed to a host virulence target. Avirulence factors are thought to have arisen during evolution when some of the many virulence factors produced by pathogens became functionally recognized as avirulence determinants by plant R gene products. Subsequent mutation of these avr genes allows pathogens to avoid detection by R genes. However, if the loss of an avr gene incurs a high fitness penalty it may be less likely to occur and R genes targeted against such avr factors would be expected to be more durable. The goal of this research project is to clone and characterize an avr gene from the net blotch pathogen Pyrenophora teres. Identification of molecular markers linked to an avr gene is being conducted using a bulked segregant analysis approach with AFLP markers. Over the next two years we hope to clone this gene.

Inheritance of Resistance to Pyrenophora graminea in Barley

A. Benbelkacem

Techniques des Grandes Cultures (ITGC), Plant Breeding Station, El-Khroub Institute,
El-Khroub, 25100 Algeria,
E-mail: benbelkacem@mail.com

An inheritance study of resistance to Pyrenophora graminea was undertaken in a diallel cross of 4 barley genotypes (two suceptible local genotypes (Saida & Tichedrett) and two resistant varieties (Alpha & M23). A large variability in the disease incidence was found among parents and their progenies. In the crosses between a susceptible and a resistant parent, an intermediate reaction of the plant to barley stripe was observed, the general tendency was however towards the resistant parent; a 1:2:1 ratio was predominant showing thus that the resistance of M23 and Alpha was controlled by a single dominant major gene. In the cross between the suceptible parents, all the progenies showed susceptible reactions to P. graminea, a cumulative effect of two genes was observed (9:6:1 ratio). The resistant by resistant parent gave in general resistant progenies and two dominant genes with no cumulative effect (15:1 ratio).

Profiling of Gene Expression in the Incompatible Interaction between Barley and the Fungus Pyrenophora teres
(f. teres and f. maculata)

P. Bogacki1,2, O. Oldach2, W. Knogge1,2 and K. J. Williams1,3

1Molecular Plant Breeding CRC, University of Adelaide, Glen Osmond, SA 5064, Australia,
E-mail: paul.bogacki@adelaide.edu.au;
2Department of Plant and Pest Science, University of Adelaide, Glen Osmond, SA 5064, Australia;
3South Australian Research and Development Institute, Adelaide, SA 5001, Australia

Net blotch disease of barley (Hordeum vulgare L.) is caused by the necrotrophic fungus Pyrenophora teres. The two types of leaf symptoms associated with net blotch disease are caused by the two formae of P. teres, with P. teres f. teres causing the net form and P. teres f. maculata responsible for the spot form. We have used the method of suppression subtractive hybridisation to identify differentially expressed genes in the early stages of both incompatible interactions, with the aim of finding defence response genes specific to each pathogen and common to both. Two cDNA subtraction libraries were generated and through cDNA dot blot analysis we were able to distinguish between genes of high and low abundance. A total of 450 randomly selected clones have been sequenced and work is in progress to organise their corresponding genes into putative functional groups. A preliminary overview of the data shows several genes that have previously been implicated in the infection process and a high proportion of genes that have no known function. We aim to further characterise a subset of these genes using a combination of Northern Blot analysis and real time PCR.

Geographic Distribution of Rhynchosporium secalis Populations
in Tunisia

A. Bouajila1, A. Yahyaoui2, A. Ibiyemi2, S. Haouas1, S. Rezgui3, M. Fakhfakh4
and H. Harzallah1

1University of Tunis, 1060 El Manar, Tunisia, E-mail: a.yahyaoui@cgiar.org; 2International Center for Agricultural Research in the Dry Areas (ICARDA), 5466 Aleppo, Syria; 3European Space Agency (ESA), 1121 Mograne, Tunisia; 4CTC, 120 Bousalem, Tunisia

Rhynchosporium secalis (Oud.) Davis causes scald disease of barley and occurs throughout the barley growing areas in Tunisia, where it can cause economically important yield loss. As part of an ongoing study to determine the distribution of R. secalis populations in Tunisia, scald populations were sampled from farmers fields in different agroecological zones using a GPS receiver to record the locations of each collection site. Scald populations were found to be genetically diverse and highly variable in virulence. More than 100 phenotypes have been characterized based on the reaction of isolates on 14 barley differential cultivars. Genetic characterization of the scald populations may provide a genetic definition for the phenotype variation observed in pathogenicity assays. Genetic markers have proved to be valuable tools for detecting variation within pathogen species, and would provide complementary information on the population structure of R. secalis and could also give useful insights into the pathotypic distribution of scald populations within the barley growing areas in Tunisia. Correlation of GPS information with the results of the pathotypic and genotypic diversity in R. secalis enabled us to develop a composite geographic map showing the distribution of the pathogen in Tunisia. The geographic map of scald distribution using GIS is proposed.

Leaf Stripe Resistance in Barley: Marker Assisted Selection
and Fine Mapping of the Resistance Gene Rdg2a

D. Bulgarelli, A. Tantillo, G. Tacconi, E. Dallaglio, G. Tumino, A. M. Stanca
and G. P. Vale

Experimental Institute for Cereal Research, 29017 Fiorenzuola dArda (PC), Italy,
E-mail: gp.vale@iol.it

A barley gene conferring resistance to the leaf stripe agent has been mapped on the chromosome arm 7HS. This resistance gene, named as Rdg2a, confers resistance towards several isolates having therefore a useful range of activity. To verify the reliability of a PCR-based marker (MWG2018) associated to the resistance gene to assess the leaf stripe resistant phenotype in barley breeding programs, several resistant lines obtained from several crosses were tested for the allelic composition at the MWG2018 locus. The results showed that the resistant phenotype of the lines was always associated with the resistant allele of the molecular marker, evidentiating the reliability of this marker to select for leaf stripe resistance; this marker is routinely used in practical breeding. To saturate the Rdg2a chromosomal region with molecular markers, two approaches have substantially been used: (1) several RGAs have been tested for co-segregation with Rdg2a; (2) by exploiting the syntenic relationships between the telomeric regions of barley chromosome 7H and rice chromosome 6, rice ESTs informations have been used to generate PCR-based markers then mapped in the Rdg2a mapping population. By using these approaches, we have observed tight association of RGAs with Rdg2a and conservation of syntenic relationships between the telomeric regions of barley chromosome 7H and rice chromosome 6 for the Rdg2a chromosomal region.

Identification of a New Adult Plant Resistance Gene for Scald (Rhynchosporium secalis) in Barley

M. Cakir1,5, H. Wallwork2,5, S. Gupta1,5, D. B. Moody3,5, K. Williams2,5 and C. D. LI4,5

1Western Australian State Agricultural Biotechnology Centre, Murdoch University, Murdoch,
WA 6150, Australia, E-mail: mcakir@central.murdoch.edu.au;
2South Australian Research and Development Institute, Urrbrae, SA 5064, Australia; 3Victorian Institute for Dryland Agriculture, Horsham, Vic 3401, Australia; 4Crop Improvement Institute, Department
of Agriculture, Bentley Delivery Centre, WA 6983, Australia; 5Molecular Plant Breeding CRC,
University of Adelaide, Glen Osmond, SA 5064, Australia

The identification and deployment of disease resistance genes are key objectives of Australian barley breeding programs. A doubled haploid (DH) population derived from the cross VB9104 × Dash was used to identify markers for resistance to scald (Rhynchosporium secalis). The map comprised of 205 markers including SSRs and AFLPs. The population was assessed for severity of scald during grain fill in a field trial in South Australia. Marker analysis was performed using the software packages Mapmanager and Qgene. QTL analysis identified a region on chromosome 3H, associated with scald resistance in a number of studies, and a region on 4H which has not previously been associated with scald resistance. R2 values for the 3H and 4H chromosome regions were 29% and 22%, respectively. Multiple regression analysis of these two QTLs explained 42% of the variation. There are a number of markers showing strong associations with the resistance in these regions. These markers present an opportunity for marker assisted selection of lines with resistance to scald in barley breeding programs.

Pyramiding Quantitative and Qualitative Resistance
to Barley Stripe Rust

A. Castro1,2, F. Capetini3, A. E. Corey2, T. Filichkin2, P. M. Hayes2, J. S. Sandoval-Islas4
and H. Vivar3

1Faculty of Agronomy, Universidad De la Republica, Paysandu 60000, Uruguay; 2Department of Crop
and Soil Science, Oregon State University, Corvallis, OR 97331, USA,
E-mail: patrick.m.hayes@oregonstate.ed; 3ICARDA/CIMMYT Latin American Regional Program,
006600 Mexico, D.F, Mexico; 4Instituto de Fitosanidad, Colegio de Postgraduados, Chapingo, México

Barley stripe rust (caused by Puccinia hordei f.sp. hordei) is an important disease of barley. Qualitatively and quantitatively inherited resistance loci are distributed throughout the genome, allowing pyramiding of multiple alleles in single genotypes. For the past ten years we have been detecting, mapping, combining and exploiting different sources of resistance to barley stripe rust. Using three quantitative resistance loci mapped in two ICARDA/CIMMYT accessions Cali-sib (on chromosomes 4H and 5H) and Shyri (on chromosome 1H) and an adult plant Mendelian resistance gene mapped in CI10587 (on chromosome 7H), we developed pyramids of both types of resistance. In the first stage we used a complex cross to combine alleles from the the three QTL. Lines with resistance alleles at these QTL had lower disease severities, confirming the additive effect of the QTL, and showing that pyramiding resistance QTL is effective. In the next step we combined the QTL resistance alleles with the qualitative resistance allele. The results show that this combination of alleles is also effective in significantly reducing disease severity, and preliminary studies suggested that the effectiveness is maintained even when challenged with a new pathotype.

Resistance to European Isolates of Blumeria graminis f.sp. hordei in Selections from Barley Landraces Collected in Israel

J. H. Czembor1, H. J. Czembor1 and L. J. M. van Soest2

1Plant Breeding and Genetics Department, Plant Breeding and Acclimatization Institute,
IHAR Radzików, 05-870 Błonie, Poland,
E-mail: j.h.czembor@ihar.edu.pl;
2Centre for Genetic Resources the Netherlands (CGN), 6700 AA Wageningen, The Netherlands

Seed samples of 22 barley landraces were used for screening for resistance to powdery mildew. These landraces were collected in Israel and originated from Centre for Genetic Resources the Netherlands (CGN). The infection types were scored according to a 04 scale and the cultivar Manchuria (CI 2330) was used as a susceptible control. In preliminary study, about 30 plants per landrace were evaluated in greenhouse with isolate 33. Isolate 33 represented the most avirulent isolate available allowing the expression of maximum number of resistance genes. The 14 landraces tested showed powdery mildew resistance reaction and 14 single plant lines were selected. These lines were tested in seedling stage with 21 differential isolates of powdery mildew. The isolates were chosen according to their virulence spectra on the Pallas isolines differential set and 7 additional differential cultivars. These isolates had virulences corresponding to all major resistance genes used in Europe. Twelve tested lines were resistant to all solates used. The results showed that barley landraces collected from Israel are very valuable source of resistance to powdery mildew. Twelve highly resistant lines identified in this study should be used in barley breeding.

Two-Rowed and Six-Rowed Varieties Resistant to Barley Leaf Stripe Developed Using Conventional and Non Conventional (MAS) Selection Methods

G. Delogu and G. P. Vale

Experimental Institute for Cereal Research, 29017 Fiorenzuola dArda (PC), Italy,
E-mail g.delogu@iol.it

Pyrenophora graminea Ito and Kuribayashi (anamorph Drechslera graminea) is a seed-borne pathogen causing barley leaf stripe. The disease is widely distributed in most barley growing areas, where it causes serious damages and yield losses. Several sources of resistance to P. graminea were reported in the literature and based on polygenic partial resistance genes or on single gene factors conferring complete resistance. The programs started in 1987 using as source of complete resistance to P. graminea the cultivars Alpha, Tipper (two rowed type) (unknown gene) and Thibaut (six rowed type) and later the cultivar Rebelle (six rowed type). The last two genotypes both carrying Rdg2 gene. These cultivars have been crossed with susceptible advanced lines and high yielding varieties. Since 1989 selection in F2 generation had been carried out using pedigree methods integrated by artificial infection in the field with spreader of natural population of P. graminea (cvs Perga and Express). After identifications of the ipervirulent isolate Dg2, the pedigree scheme has been modified by screening in glasshouse with isolate Dg2 (Sandwich test). Recently the identification of a based marker linked the Rdg2 gene, called MWG2018, offers the possibility to integrate MAS into the pedigree selection. Practical results have been reached by integrating conventional and non conventional breeding procedure to incorporate single resistant gene as well as poligenic resistant genes. Aiace, Auriga and Vela, are the varieties recently released for the seed companies.

Positional Cloning of the Rph15 Disease Resistance Gene

A. Falk

University of Agricultural Sciences, Department of Plant Biology and Forest Genetics,
750 07 Uppsala, Sweden,
E-mail: anders.falk@vbsg.slu.se

The Rph15 gene confers resistance to most virulent races of the barley leaf rust pathogen, Puccinia hordei Otth. The Rph15 gene was mapped using AFLP and microsatellite markers on chromosome 2HS. Linked AFLP markers were identified by a bulked segregant procedure. High-resolution mapping of Rph15 was done in a population consisting of 3,000 susceptible F2 plants, selected from about 12,000 F2 segregants. In this mapping population, AFLP marker P13M40 cosegregated with Rph15, whereas AFLP marker P22M63 mapped at 1.6 cM proximal to Rph15. The two AFLP markers were used to identify Morex BAC clones closely linked to Rph15. The markers identified partly the same BAC clones. Complete BAC clone sequencing revealed that the cosegregating marker P13M40 is positioned just 3,000 bp from the end of the selected BAC clone, whereas the marker P22M63 is positioned in the middle of the same BAC clone. To further extend the sequence telomeric from P13M40, additional BAC clones were analyzed, extending the sequence 15,000 bp distal to P13M40. The sequence of the BAC clones confirms the finding that most genomic DNA in barley consists of retrotransposons. No obvious resistance gene like sequences have so far been identified in the sequenced region. Additional markers will be developed from the genomic sequence for more fine-scaled mapping. The sequence will be further extended distal to P13M40 by additional BAC clone sequencing.

QTL for Drechslera teres-Resistance in Barley

A. Gay and J. Leon

Department of Crop Science and Plant Breeding, University of Bonn, D-53115 Bonn, Germany,
E-mail: j.leon@uni-bonn.de

In many countries of the world the pathogen of net blotch disease, Drechslera teres, is gaining economic importance in the group of leave-diseases of barley. In some areas yield losses up to 30% have been reported. We screened several cultivars and H. v. spontaneum accessions for their resistance against D. teres and found one nearly resistant spontaneum line, which thereafter was crossed onto a susceptible cultivar. Within this project we used F2 of a second backcross generation with 635 individuals as a basis of a QTL-analysis. These plants were tested for their resistance. A fraction of 10% of the resistant progenies and a fraction of 10% from the susceptible progenies were selected to perform a bulk segregant analysis. All plant of these fractions were genotyped using SSR markers. From this analysis we detected four different QTL regions. For this putative QTL regions a QTL-analysis using the whole population of 635 individuals was performed. Analysing the whole population we founded a slightly different pattern. While three of the putative QTL were verified, one QTL did not show an effect, but was very important in combination with another QTL (epistatic effect). We are just testing these QTL in three validation populations.

Gene Distribution and SSR Markers Linked with Net Type
Net Blotch Resistance in Barley

S. Gupta1,2, C. Wielinga1, C. D. Li2, M. Cakir1, G. Platz3, R. Loughman2, R. Lance2
and R. Appels1,2

1Division of Science and Engineering, WA State Agricultural Biotechnology Centre, Murdoch University, Perth, WA 6150, Australia, E-mail: sanjiv@central.murdoch.edu.au; 2Bentley Delivery Centre, Department of Agriculture, Crop Improvement Institute, WA 6983, Australia; 3Hermitage Research Station, Queensland Department of Primary Industries, Warwick, Q 4370, Australia

Net type net blotch caused by Pyrenophora teres f. teres is a major disease in Western Australia which reduces significant barley production around the world. Studies were focussed on four resistant lines to identify microsatellites linked with the resistance. The four lines, WA 4794 (103 IBON 91) (Pedigree: Arupo S × 2/3/PI 2325/Maf 102//Cossack), Pompadour (Pedigree: FDO192/Patty), CI 9214 (Pedigree: Collected from South Korea) and WPG 8412-9-2-1 (Pedigree: Bowman//Ellice/TR451) were crossed with Stirling (Pedigree: Dampier//Prior/Ymer/3/Piroline), a susceptible but well adapted cultivar in Western Australia. Doubled haploid (DH) populations were generated through anther culture. In case of WA4794, two genes were mapped on 4H and 6H using the microsatellite markers GMS089, Bmag0384 for 4H, and Ebmac0874 for 6H. In Pompadour population, two NNB resistance genes were mapped on 3H and 6H using the microsatellites Bmac0209 and Bmag0173 respectively. In CI 9214, Bmac0218 was linked with the resistance for 2H, Ebmac0871 with 3H, suite of microsatellites Ebmac0635, Ebmac0701 and Ebmac0788 with 4H, and similarly Bmag0173, Bmgtttttt1, Ebmac0874 and HVM74 with 6H. In case of WPG 8412/Stirling, single gene was mapped on 6H using the microsatellite Bmag0173. The R2 value ranged up to 0.80 for the linked microsatellites and some are closely mapped to the resistance genes.

Mapping of Quantitative Genes in Barley that Determine
the Resistance to the Heterologous Wheat Leaf Rust Fungus
(Puccinia triticina)

H. Jafary and R. E. Niks

Laboratory of Plant Breeding, Wageningen University and Research Center,
6700 AJ Wageningen, The Netherlands; E-mail: hossein.jafary@wur.nl

Resistance of an individual plant to an attacking pathogen may be due to nonhost resistance when the plant belongs to a species to which the pathogen is not adapted. Barley is nonhost to some rust species such as the rye leaf rust fungus. However, some barley lines are in the seedling stage somewhat susceptible to heterologous rust fungi such as wheat and wall barley leaf rust fungi. Host range quantification of barley showed even the most susceptible barley accession was not as fully susceptible as the susceptible host plants. Therefore, the level of susceptibility of barley to heterologous rust species may not be high enough to allow a study of the underlying genetics of this resistance. Recently a research line of barley, named SusPtrit has been developed that is fully susceptible to wheat leaf rust (P. triticina). For the development of mapping populations, SusPtrit (as a susceptible parent) has been crossed with Vada and Cebada Capa. Several QTLs for partial resistance have been mapped in Vada as partially resistant parent. Cebada Capa possesses the major gene Pa7 for hypersensitive resistance to P. hordei and in addition, Cebada Capa and Vada carry QTLs for partial resistance to P. hordei. Mapping of genes for nonhost resistance to P. triticina and several other heterologous rust species will be possible, and will show whether the genes for resistance to P. hordei also play a role in resistance to heterologous rusts.

Evaluation and Mapping of a Leaf Rust Resistance Gene Derived
from Hordeum vulgare spp. spontaneum

D. Kopahnke1, M. Nachtigall2, F. Ordon1 and B. J. Steffenson3

1Institute of Epidemiology and Resistance and 2Institute of Resistance Research and Pathogen Diagnostics, Federal Centre for Breeding Research on Cultivated Plants (BAZ), D-06449 Aschersleben, Germany,
E-mail: d.kopahnke@bafz.de; 3Department of Plant Pathology, University of Minnesota,
1991 Upper Buford Circle, USA

The use of resistant cultivars is an efficient means of controlling leaf rust in barley. The basis for breeding resistant cultivars is the availability of effective resistance genes. Because all resistance genes identified in H. vulgare spp. vulgare have been overcome by the fungus meanwhile, the evaluation work was continued in H. vulgare spp. spontaneum accessions are screened for resistance. Genetic studies were performed on a doubled haploid population derived from the cross of a highly resistant line of H. vulgare spp. spontaneum 677 × Krona. It turned out, that the resistance is inherited in a single dominant manner. Bulk segregant analysis using amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) was conducted to identify and map DNA markers associated with this leaf rust resistance gene. By this approach the resistance gene was located on barley chromosome 2H. Respective markers will be useful for marker-assisted selection and gene pyramiding in breeding programs for leaf rust resistance.

Detection and Localisation of Resistance Genes against
Powdery Mildew and Leaf Rust Introgressed from Wild Barley
(H. vulgare ssp. spontaneum)

M. v. Korff, H. Wang, J. Leon and K. Pillen

Department of Crop Science & Plant Breeding, University of Bonn, D-53115 Bonn, Germany,
E-mail: k.pillen@uni-bonn.de

The objective of this study is to map new resistance genes against powdery mildew (Blumeria graminis f. sp. hordei L.) and leaf rust (Puccinia hordei L.) in a BC2DH population derived from a cross between the spring barley cultivar Scarlett and the wild barley accession ISR42-8 (H. v. ssp. spontaneum). Using field scored data of disease severity under natural infestation, we detected eight QTL for powdery mildew and seven QTL for leaf rust resistance. The QTL for powdery mildew resistance were distributed over all chromosomes with the exception of 5H. The QTL for leaf rust resistance were located on 2H, 3H, 4H and 7H and the exotic allele reduced disease severity in all cases. Some of the detected QTL may correspond to previously identified qualitative (i.e. Mla) and to quantitative resistance genes, others may be newly identified resistance genes against powdery mildew and leaf rust. For the majority of resistance QTL the wild barley contributed the favourable allele demonstrating the usefulness of wild barley in the quest for resistant cultivars.

German Network for the Evaluation of Cereals for Disease Resistance (Eva II)

A. Kusterer1, S. Harrer2, F. Ordon1 and E. Schliephake1

1Institute of Epidemiology and Resistance, Federal Centre for Breeding Research on Cultivated Plants (BAZ), D-06449 Aschersleben, Germany, E-mail: a.kusterer@bafz.de;
2German Centre for Documentation and Information in Agriculture, Information Centre for Biological Diversity (IBV), D-53177 Bonn, Germany

EVA II aims to facilitate a more effective use of genetic resources in barley and other cereals resistance breeding. A network of private German plant breeders and research institutes will jointly evaluate germplasm (gene bank material, domestic or foreign varieties, and actual breeding material) of barley and wheat, that is pre-selected according to interesting resistances. The nurseries are screened in multi-site field trials for resistance to most important fungal and viral pathogens. Besides vertical resistance, horizontal resistance is searched for by repeated scoring. To characterise infestation conditions, resistant and susceptible standards are included. Commonly used evaluation methods are refined to be simultaneously applicable to several cereal diseases. Based on field observations respective germplasms are analysed for known resistance genes by PCR markers. An information system for an effective data management is developed by IGR. The acquired results will be shared first of all amongst the project partners for direct use in the respective breeding programs. It is intended to collect experience and develop expertise to build up similar systems for other species. Overall goal of the project is the establishment of a national evaluation program, the results of which will become freely accessible in the medium term.

Variability of Rhynchosporium secalis (Oud.) J.J. Davis Populations in Morphological Characteristics, Isozymes and Fungicide Resistance Markers in the Czech Republic

L. Lebedeva1 and L. Tvaruzek2

1Department of Plant Resistance to Diseases, All-Russian Institute of Plant Protection, St-Petersburg-Pushkin, Russia; 2Department of Integrated Plant Protection, Agricultural Research
Institute Kromeriz, Ltd., 767 01 Kromeriz, Czech Republic
E-mail: tvaruzek@vukrom.cz

The aim of our research was to study the diversity of the Rhynchosporium secalis population in the Czech Republic using morphological (colony colors), biochemical (esterase, -esterase, superoxide-
dismutase, aspartataminotransferase) and fungicide resistance markers. A total of 128 isolates (one isolate from one scald lesion) from five sampling sites of the Czech Republic were studied. Single-spore cultures were divided by color into five groups (from black to beige). The majority of the single-spore cultures (89.8%) kept their colors during the whole period of growth. Most single-spore cultures were genetically homogeneous in the studied trait. Four enzymes of the fungus were studied esterase, -esterase, superoxidedismutase (SOD), aspartataminotransferase (AAT) by using vertical slab polyacrylamide gel electrophoresis. A minimum of three replicates were examined for each isolate. All investigated enzymes of R. secalis were polymorphic. A total of nine patterns of SOD, fifteen esterase, three -esterase and two AAT were obtained. Almost every studied site had the certain major type of polymorphism in esterases and SOD. Unique patterns were identified in certain regions of the Czech Republic. The in vitro reaction to some widely used fungicides was assessed. There were found significant differences between particular isolates and their LD50 levels.

Possibilities of Pyrenophora teres Detection in Barley Leaf Tissue

L. Leisova1, V. Minarikova2, L. Kucera1 and J. Ovesna1

1Research Institute of Crop Production, 161 06 Prague-Ruzyne, Czech Republic, E-mail: leisova@vurv.cz; 2Agricultural Research Institute, 767 01 Kromeriz, Czech Republic, E-mail: minarikova@vukrom.cz

Specific polymerase chain reaction (PCR) primers were developed from AFLP bands of DNA of Pyrenophora teres, the causal agent of net blotch on barley leaves. The primers were designed to specifically amplify DNA from P. teres f.sp. teres and allow its differentiation from P. teres f.sp. maculata, which is morphologically very similar to P. teres f.sp. teres in culture. The PCR amplification was carried out successfully from DNA extracted from fungi mycelium. The PCR assay was validated with 60 samples from 10 barley hosts originating from several regions across the Czech Republic. No cross reaction was observed with DNA of several other species like P. tritici repentis, P. graminea and Helminthosporium sativum. This method is prepared to be used to detect the pathogen from environmental samples for survey and management purposes.

Molecular Dissection of a QTL Region for Partial Resistance
to Barley Leaf Rust

T. C. Marcel and R. E. Niks

Laboratory of Plant Breeding, Wageningen University and Research Center, 6700 AJ Wageningen,
The Netherlands,
E-mail: thierry.marcel@wur.nl

The partial resistance to leaf rust (Puccinia hordei) in barley is a quantitative resistance that is not based on hypersensitivity. This resistance is prehaustorial and characterized by a long latency period in greenhouse tests. Six quantitative trait loci (QTLs) have been mapped on a population of 103 recombinant inbred lines obtained from susceptible parent L94 × partially resistant parent Vada (Qi et al. 1996). The most consistent QTLs Rphq-2, Rphq-3 and Rphq-4 have been incorporated into L94 background to obtain near isogenic lines (NILs) (Berloo et al. 2001). Effect of Rphq-2 NIL has been clearly demonstrated on seedlings and adult plants while Rphq-3 and Rphq-4 NILs only have a clear effect on adult plants. The development of flanking PCR markers, based on mapped RFLP sequences, allowed placing Rphq-2, Rphq-3 and Rphq-4 in physical regions of high (1.1 Mb/cM), suppressed (> 4.4 Mb/cM) and very high (0.2 Mb/cM) recombination respectively (Künzel et al. 2000). Based on those results Rphq-2 seems to be the best candidate gene for cloning. Fine-mapping the Rphq-2 region should open the way towards cloning the first gene for partial resistance to a pathogen.

TILLING for Detection of Single Nucleotide Polymorphism
in Resistance Genes in Barley

N. Mejlhede, Z. Kyjovska, G. Backes and A. Jahoor

Plant Research Department, Risoe National Laboratory, DK-4000 Roskilde, Denmark,
E-mail: nina.mejlhede.jensen@risoe.dk

TILLING (Targeting Induced Local Lesions IN Genomes) is a new reverse genetic strategy that combines random chemical mutagenesis with PCR-based screening of gene regions of interest. Here we have used TILLING to screen for single nucleotide polymorphism in resistance genes for powdery mildew in barley (mlo and mla). For these two genes we have identified gene regions that are most suitable for TILLING, designed optimal PCR primers for mutational screening and analyzed mutants in mla and mlo.

Genetic Variability in Ethiopian, Jordanian and Syrian Populations of the Scald Pathogen (Rhynchosporium secalis)

K. Meles1, S. M. Udupa2, H. Abu-Blan3, M. Baum2 and A. Yahyaoui2

1Tigrai Research Institute, Mekele, Ethiopia, E-mail: kirosm62@yahoo.com;
2International Centre for Agricultural Research in the Dry Areas (ICARDA), Aleppo, Syria,
E-mail: a.yahyaoui@cgiar.org; 3University of Jordan, Amman, Jordan

Samples of Rhynchosporium secalis (Oud.) J. J. Davis were collected from fields of local cultivated barley cultivars in Ethiopia, Jordan and Syria using hierarchical sampling method, during 2002 and 2003 crop seasons. The genetic variation with in and between these field populations of Rhynchosporium secalis was compared using amplified fragment length polymorphism-(AFLP) markers. Genotype diversity, spatial distribution of genotypes within populations, allele frequencies and gametic disequilibrium were determined. High degree of genetic variability exists within populations, among populations within a country and among populations of different country of origin. Ethiopian field populations had relatively higher level of variation than populations from Jordan and Syria. Populations from Syria and Jordan showed a high degree of similarity as indicated by relatively low value of genetic distance. However, the genetic distance for Ethiopian populations was relatively higher as indicated by the difference in the number of genotypes. The observed difference in allele frequencies and level of population differentiation suggests that there is no gene flow between Ethiopian R. secalis populations, and Jordanian and Syrian populations.

Disease Resistance Mapping in Spring Barley

A. C. Newton1, R. C. Meyer1, G. R. Young1, P. E. Lawrence1, J. R. Russell1, A. Booth1,
L. Ramsay1, R. K. Webster2, B. J. Steffenson3 and W. T. B. Thomas1

1Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, UK,
E-mail: wthoma@scri.sari.ac.uk;
2Department of Plant Pathology, University of California-Davis, Davis, CA 95616, USA,
3Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, USA

We used scores obtained from barley mapping populations grown in scald nurseries to show that the main partial resistance loci detected were co-incident with known dwarfing gene loci and other QTL detected for height variation in the same cross. We therefore utilised a detached leaf test to measure scald infection on the same mapping population, conducting the test with several isolates and with leaves of varying ages from GS13 to 33. The detached leaf data showed that, whilst there was significant genetic variation, there was a very large environmental and genotype × environment effects. We detected QTLs representing genuine partial resistance effects in several of the assays and consider that these represent loci that should be explored for increasing the expression of potentially non-specific scald resistance. The same mapping population was scored for expression of resistance to the leaf-spotting complex and Rice Blast. For the former, early spotting was considered to be due to physiological spotting and post GS68 spotting to infection by Ramularia collo-cygni. QTLs were detected for all three with early and late spotting being independent. Most of the QTL were located in the region of other disease resistance loci.

Mapping and Dissession of Barley Stripe Rust Resistance

K. L. Richardson1, F. Capettini2, X. Chen3, A. E. Corey1, P. M. Hayes1, M. Johnston4,
C. Mundt1, S. Sandoval-Islas5 and M. I. Vales1

1Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331, USA,
E-mail: kelley.richardson@oregonstate.edu; 2ICARDA/CIMMYT Barley Program, México, DF México;
3US Department of Agriculture, Agricultural Research Service, Washington State University, Pullman, WA 99164, USA; 4Department of Plant Science and Plant Pathology, Montana State University, Bozeman, MT 59717, USA; 5Instituto de Fitosanidad, Colegio de Postgraduados, Montecillo, Texcoco, México

Barley stripe rust (BSR), caused by Puccinia striiformis f.sp. hordei, is an important fungal disease of barley in the Americas. Genetic resistance to BSR can be qualitatively or quantitatively inherited. Qualitative resistance alone is risky due to evidence that pathogen virulence can evolve faster than breeders can release new resistant varieties. Pyramiding of resistance QTL and combining quantitative and qualitative sources of resistance are effective strategies for lowering disease severity. The goal of this project is to identify genetic factors that determine BSR resistance and to measure the effects and interactions of each resistance factor. A large doubled haploid population was developed from the cross of BCD47 × Baronesse. We have identified QTL on chromosomes 3H, 4H, 5H and 6H where the resistant parent (BCD47) contributed favorable alleles, and QTL on chromosomes 2H and 7H where the susceptible parent (Baronesse) contributed favorable alleles. Currently, quantitative and qualitative resistance genes are deployed in complex genetic backgrounds involving multiple donors. A set of backcross near-isogenic lines (BISONs) was created to allow measurement of resistance allele effects in the same genetic background and the systematic analysis of resistance allele interactions. The BISON lines represent the quantitative resistance alleles on chromosomes 4H and 5H from BCD47, a quantitative resistance allele on chromosome 1H from BCD12 and a qualitative resistance allele on chromosome 7H from D3-6/B23 introgressed, separately, into a Baronesse background.

Introgression and Mapping of Novel Resistance Genes from
the Secondary Genepool of Barley, Hordeum bulbosum

B. Ruge1, A. Linz1, A. Habekuss2, K. Flath3 and P. Wehling1

1Institute of Agricultural Crops, Federal Centre for Breeding Research on Cultivated Plants (BAZ),
D-18190 Gross Lüsewitz, Germany, E-mail: b.ruge@bafz.de; 2Institute of Epidemiology and Resistance, Federal Centre for Breeding Research on Cultivated Plants (BAZ), D-06449 Aschersleben, Germany;
3Institute for Plant Protection in Field Crops and Grassland, Federal Biological Research Centre
for Agriculture and Forestry (BBA), D-14532 Kleinmachnow, Germany

Hordeum bulbosum represents the secondary gene pool of barley and is a potential source of desirable agronomic-trait genes. Despite of crossing barriers, recombination events between the two Hordeum genomes lead to introgressions of H. bulbosum segments which carry novel major resistance genes. Telomeric introgressions on chromosomes 6HS, 2HS and 2HL confer resistance to the soil-borne virus complex (BaMMV, BaYMV-1, -2) as well as to leaf rust and powdery mildew, respectively. Based on the genetic distances in the barley consensus map the introgression sizes were estimated at 13 cM for a 6HS and 35 cM for a 2HL H. bulbosum segment, the latter of which carries multiple resistances. Molecular markers allow the identification of recombination events within the introgression that lead to reduced H. bulbosum segments. In addition, informative markers (cDNA-AFLP) prove to be an efficient tool for the identification of resistance alleles in barley backcross programmes. As an example, the STS marker Xiac500 is cosegregating with the dominant virus resistance gene Rym14Hb that is located on chromosome 6HS.

Fungicidal Effect of Plant Extracts from Some Medicinal Plants against Powdery Mildew on Barley (Blumeria graminis f.sp. hordei)

Z. Tvaruzkova

Gymnazium Kromeriz, 767 01 Kromeriz, Czech Republic
E-mail: zuzana_tvaruzkova@post.cz

The objectives of this work were to detect fungicidal effects in some plant extracts and their mixtures against powdery mildew on barley in glasshouse conditions, to test various extraction methods, to determine optimum concentration of such extracts, interactions between the effect and environmental conditions, particularly temperature, and if it affects different phytopathogenic fungi. I tested 16 extracts obtained from frozen plants occurring in our country and 4 extracts from dried plants delivered from South-East Asia, Mediterranean area and Western part of Africa. All of them preliminary showed high fungicidal effectivity in vitro cultures of Microdochium nivale Fr. Samuels, I.C. Hallet (the pathogen of snow mould). The highest fungicidal effect showed plant extracts of Abies balsamea (L.) Mill., Stellaria graminea L. (Lavandula officinalis CHAIX et KITT.), and Ptelea trifoliata L. The mixture consisted of extracts of wild garlic (Alllium ursinum L.), forest pine (Pinus nigra Arnold), Szechuan lovage root (Ligusticum chanxiong Hort) and schisandra (Schisandra chinensis (Turcz)) showed the highest fungicidal effect against powdery mildew on spring barley. The effectivity of treatment was significantly increased by the adition of surface activator GREEMAX or olive oil to the plant extract solution. Possibility to use plant extracts for effective control of powdery mildew of barley is discussed.

Chemical Induced Resistance (CIR) and Detection of QTL
for Resistance against Rhynchosporium secalis in Barley
(Hordeum vulgare L.)

C. Wagner1, M. Kraemer1, A. G. Badani1, W. Friedt1 and F. Ordon2

1Institute of Crop Science and Plant Breeding I, Justus-Liebig-University Giessen, D-35392 Giessen, Germany; 2Institute of Epidemiology and Resistance, Federal Centre for Breeding Research on Cultivated Plants (BAZ), D-06449 Aschersleben, Germany, E-mail: f.ordon@bafz.de

Scald, caused be the fungus Rhynchosporium secalis (Oud.) J.J. Davis, is an important disease of barley (Hordeum vulgare L.) world wide. Various major resistance genes against scald are known but have been overcome, already. Another approach to reduce yield losses caused by R. secalis may be the use of Chemical Induced Resistance (CIR) in combination with R-genes. Therefore, studies were carried out in order to identify QTL for the effectiveness of CIR against R. secalis. 60 DH lines derived from the cross Igri (rh; two-rowed) × Triton (Rh; six-rowed) were analysed in pot and field experiments for quantitative scald resistance after artificial infection with a mixture of pathotypes overcoming Rh in three variants, i.e. healthy control, artificially infected, DCINA/ASM treated and artificially infected. Regarding the effects of treatment with the chemical inducer DCINA (dichlorisonicotinic acid) and ASM (acetylsalicylmethylester), a genotype specific response was observed but could not be reproduced in different experiments may be due environmental factors. Consequently, no QTL for this trait could be identified based on these phenotypic data and a skeleton map of 163 RAPD-, AFLP and SSR markers comprising 1,344 cM. However, for R. secalis resistance 6 QTL could be detected on chromosomes 1H, 3H and 7H. Further studies now aim at confirming these QTL by enlargement of the mapping population to about 120 DH-lines. Based on these data cDNA-AFLP using RNA isolated during early stages of infection, i.e. forming of papillae and development of subcuticular hyphae will be carried out on lines with positive and negative alleles at respective QTL in order to identify differentiating fragments which will be sequenced and remapped. By this approach ESTs involved in R. secalis resistance will identified and mapped.

Resistance to Scald Identifying Using Differential Isolates

H. Wallwork, L. Scott and K. Williams

Molecular Plant Breeding CRC, South Australian Research and Development Institute, Urrbrae,
SA 5064, Australia, E-mail: wallwork.hugh@saugov.sa.gov.au

The presence of specific scald resistance genes in a wide variety of barley germplasm is being identified through the use of single spore derived differential isolates of Rhynchosporium secalis. Using highly controlled growth conditions and stable isolates, seedling tests have been found to be more reliable than previous reports have suggested. Specific isolates are being repeatably used to detect the presence of two of the most widely distributed genes, Rrs1 and Rrs2, either separately or in combination. Further isolates, virulent on Osiris and other varieties or germplasm with different alleles or genes, are being used to resolve the genetic control of resistance in these lines and to identify the diversity of resistance currently available in barley collections. New sources of seedling resistance can be detected very readily by comparing resistance spectra across a small number of isolates. Where potential new resistance sources are identified, molecular markers are being used to rapidly identify the location of each gene. This system is also being used for confirming the presence of gene pyramids transferred into hosts using marker assisted breeding methods. Detection of adult plant resistance (APR) is not possible in most instances, although where some of these genes occur in combination then increased seedling resistance can be detected.

Determining the Genetics of Leaf Scald and Spot Form
of Net Blotch Resistance Using Molecular Markers

K. Williams, J. Cheong, L. Scott, M. Butt and H. Wallwork

Molecular Plant Breeding CRC, South Australian Research and Development Institute,
Urrbrae, SA 5064, Australia, E-mail: williams.kevin@saugov.sa.au

Leaf scald (caused by Rhynchosporium secalis) and spot form of net blotch (SFNB) (caused by Pyrenophora teres f. maculata) are economically damaging foliar diseases of barley. Our objective has been to identify, and tag with molecular markers, loci providing resistance to these diseases. Genetic mapping and bulked-segregant analysis of doubled-haploid populations were used to identify loci for seedling and adult plant resistance to these pathogens in twelve genotypes. A high level of co-location of resistance genes was observed. Loci for seedling resistance to leaf scald in five lines mapped to the Rrs1 locus previously identified on chromosome 3H. One line has a quantitative trait locus (QTL) for adult plant resistance on chromosome 6H. A limited number of loci have also been observed for resistance to SFNB, with five lines having a seedling resistance gene at the Rpt4 locus on chromosome 7H. Markers linked to Rpt4 explained a large part of the seedling variation for SFNB, but little of the adult plant resistance (APR). In two mapped populations, major QTLs for APR were identified near Rpt4 on chromosome 7H. QTL contributing to APR on chromosomes 4H or 5H were also identified in each population.

Improved Farmer Practices Reduce Impact of Barley Leaf Blight Diseases in Eritrea

A. Yahyaoui1, A. Jahoor2, W. Asmelash3, M. Hovmoller4, Z. Alamdar1 and N. Bereket3

1International Center for Agricultural Research in the Dry Areas (ICARDA), Aleppo, Syria,
E-mail: a,yahyaoui@cgriar.org; 2Plant Research Department, Risoe National Laboratory, DK-4000 Roskilde, Denmark; 3Research Centre Flakkebjerg, Danish Institute of Agricultural Sciences (DIAS),
DK-4200 Slagelse, Denmark; 4Department of Agricultural Research and Human Resource Development (DARHRD), Ministry of Agriculture, Eritrea

In Eritrea, leaf blight diseases are widely spread within the barley landrace cultivars and have evolved to epidemic levels. Management practices combining cultural approaches and the selection of resistant cultivars are necessary to cope with the problem of these diseases. Integrated disease control options were tested. High infection levels of leaf blight diseases are common in farmers fields. Hence, to alleviate the impact of the leaf blotch diseases on barley, farmers have adopted mixtures of wheat and barley, known as Hanfetse. This practice is common in much of the cereal growing areas and is one means the farmers use to reduce disease epidemics that are common on both wheat and barley. However, the benefits of Hanfetse in reducing disease severity, is often lost due to the inadequate combination of the crop species. An improved Hanfetse was developed and tested. Levels of disease infection and grain yield under artificial inoculation and at disease hot spots in farmers fields were assessed. Mixture of barley accessions extracted from widely distinct landrace populations showed adequate tolerance levels to net blotch disease and the yield of the mixture was relatively higher than individual accessions as well as the local population land race mixtures.

Molecular Marker Development for Scald Resistance
in Seebe Barley

J. L. Zantinge, B. J. RuseLl, K. Xi, J. H. Helm and J. M. Nyachiro
Food and Rural Development, Field Crop Development Centre, Alberta Agriculture, Lacombe,
AB T4L 1W8, Canada, E-mail: jennifer.zantinge@gov.ab.ca

Scald of barley caused by the fungus Rhynchosporium secalis is prevalent in central Alberta, Canada and causes considerable yield and quality losses. Developing durable resistance in barley is needed to combat the scald pathogen that has varied in virulence. Previous studies have shown that the cv. Seebe carries a more durable genetic resistance however, breeders have found this trait difficult to transfer into new barley lines. Therefore, we are trying to develop molecular markers for scald resistance from cv. Seebe. Recombinant inbred lines were created from the cross of cvs. Harrington (scald susceptible) and Seebe (scald resistant). Progeny of about 175 individual F2 seedlings were advanced by single-seed descent to the F8 generation. Scald reactions were phenotyped at the seedling stage with a major scald race. By utilizing bulked segregant analysis, resistant and susceptible pooled populations were compared by AFLP analysis. A total of 255 AFLP primer combinations were used to analyze the genetic population and several EcoRI-MseI and PstI-MseI fragments were found linked to scald resistance. These AFLP fragments identified are currently being verified, sequenced and transformed into site specific markers. AFLP and SSR markers are also being used to map the scald resistance genomic location. Results of these studies will be presented.

Breeding Barley for Multiple Disease Resistance in the Upper Midwest Region of the USA

B. J. Steffenson1 and K. P. Smith2

1Department of Plant Pathology and 2Department of Agronomy and Plant Genetics,
University of Minnesota, St. Paul, MN 55108, USA, E-mail: bsteffen@umn.edu

The Upper Midwest is one of the largest barley production areas in the USA. In this region, diseases can markedly reduce both the yield and quality of the crop. Molecular and classical breeding techniques are being employed to develop cultivars with resistance to stem rust, spot blotch, Fusarium head blight (FHB), net blotch, and Septoria speckled leaf blotch (SSLB) in the Minnesota barley program. Stem rust and spot blotch have been successfully controlled for many years through the deployment of the major gene Rpg1 and a major effect QTL, respectively. A SCAR marker developed from the sequence of Rpg1 has made marker-assisted selection (MAS) for stem rust resistance highly effective. Work is underway to develop markers for the spot blotch resistance QTL and study its expression in six- and two-rowed backgrounds. The onset of FHB in 1993 led to major changes in the breeding program. Significant resources have been expended to develop populations for mapping resistance QTL and identify closely linked markers for MAS. This is a difficult challenge because FHB resistance is controlled by many QTL with small effects. Sources of resistance to net blotch and SSLB have been identified in a number of barley accessions. The resistances are conferred by a few genes and are being introgressed into elite lines via MAS.

Inheritance of the Fusarium Head Blight Resistance in Barley

K. Takeda

Barley Germplasm Center, Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan,
E-mail: takeda@rib.okayama-u.ae.jp

Cultivated barley was introduced to Japan more than 2,500 years before and it has been adapted to high humidity conditions by obtaining tolerances to wet injury. The scab disease caused by Fusarium ssp. is one of the serious wet injuries in Japan because it spread severely by high humidity conditions during the ripening period. The present studies on the scab disease resistance are summarized as follows: (1) A total of 104 Fusarium strains were inoculated on the different sources of barley varieties and showed no host-parasite interaction on the disease development. (2) Resistance reaction in more than 4,000 barley accessions was evaluated by cut-spike inoculation method to find 23 highly resistant accessions, which has two-rowed caryopsis without exception. (3) The mode of inheritance for the resistance was analyzed using diallel crosses and single crosses whose parents had different level of disease resistance. The resistance score showed a quantitative inheritance with a moderate heritability. In the segregating populations for the disease resistance and row-types, two-rowed plants were more resistant than six-rowed ones suggesting resistance was controlled by the pleiotropic effect of the row type gene. (4) QTL analysis of resistance was conducted in Russia 6 (highly resistant) × HES 4 (highly susceptible) recombinant inbred lines with a linkage map of 1,255 DNA markers. Two putative loci were allotted on the chromosome 2H and one locus was on the chromosome 5H. These three QTLs determined about 40% of the total phenotypic variation. One of the loci on the chromosome 2H coincided with the gene controlling the row type (vrs1) indicating the strong genetic relationship between the resistance and the row type.