[Show abstract][Hide abstract] ABSTRACT: With 1 figure
The Taiwanese barley (Hordeum vulgare L.) cultivar ‘Taihoku A’, which has been described as resistant to Barley mild mosaic virus (BaMMV), Barley yellow mosaic virus (BaYMV) and BaYMV-2, contains the BaMMV resistance gene rym13 located on chromosome 4HL. Furthermore, ‘Taihoku A’ shows resistance to the newly detected virus strain BaMMV-Teik, which is able to overcome the resistance gene rym5. By analysing a set of 154 DH-lines of the cross ‘Taihoku A’ x ‘Plaisant’ it turned out that resistance to BaMMV-Teik is inherited in a monogenic manner, the gene located on chromosome 4HL. Resistance to BaMMV-Teik is also encoded by rym13 or an additional gene being closer linked to rym13 than 0.65 centiMorgan (cM). Using bulked segregant analysis employing Simple sequence repeats (SSRs) and Amplified fragment length polymorphisms (AFLPs), a map comprising 39.1 cM was constructed with the closest marker linked to the BaMMV/BaMMV-Teik resistance at a distance of 1 cM. Respective markers are useful tools to introduce resistance to BaMMV-Teik into adapted breeding lines carrying other resistance genes, which are not effective against all BaMMV/BaYMV strains known in Europe, e.g. rym4, rym5.
[Show abstract][Hide abstract] ABSTRACT: Soil-borne barley yellow mosaic virus disease--caused by a complex of at least three viruses, i.e. Barley mild mosaic virus (BaMMV), Barley yellow mosaic virus (BaYMV) and BaYMV-2--is one of the most important diseases of winter barley in Europe. The two genes rym4, effective against BaMMV and BaYMV, and rym5, additionally effective against BaYMV-2, comprise a complex locus on chromosome 3HL, which is of special importance to European barley breeding. To provide the genetic basis for positional cloning of the Rym4/Rym5 locus, two high-resolution maps were constructed based on co-dominant flanking markers (MWG838/Y57c10 - MWG010/Bmac29). Mapping at a resolution of about 0.05% rec., rym4 has been located 1.07% recombination distal of marker MWG838 and 1.21% recombination proximal to marker MWG010. Based on a population size of 3,884 F2 plants (0.013% recombination) the interval harbouring rym5 was delimited to 1.49+/-0.14% recombination. By testing segmental recombinant inbred lines (RILs) for reaction to the different viruses at a resolution of 0.05% rec. (rym4) and 0.019% rec. (rym5), no segregation concerning the reaction to the different viruses could be observed. AFLP-based marker saturation for rym4, using 932 PstI+2/MseI+3 primer combinations only resulted in three markers with the closest one linked at 0.9% recombination to the gene. Two of these markers detected epialleles arising from the differential cytosine methylation of PstI sites. Regarding rym5, profiling of 1,200 RAPD primers (about 18,000 loci) and 2,048 EcoRI+3/MseI+3 AFLP primer combinations (about 205,000 loci) resulted in one RAPD marker and seven AFLP markers tightly linked to the resistance gene. Flanking markers with the closest linkage to rym5 (0.05% and 0.88% recombination) were converted into STS markers. These markers provide a starting point for chromosomal walking and may be exploited in marker-assisted selection for virus resistance based on rym5.
[Show abstract][Hide abstract] ABSTRACT: Barley yellow mosaic virus disease - caused by barley mild mosaic virus (BaMMV), barley yellow mosaic virus (BaYMV) and BaYMV-2-has to be considered as one of the most important diseases of winter barley in Europe. Due to transmission by the soil-borne fungus Polymyxa graminis, chemical measures against the disease are neither efficient nor economic. Therefore, breeding for resistance to this disease is of special importance. By segregation analysis followed by the application of molecular techniques, like RFLPs, RAPDs, SSRs and AFLPs, different resistance genes have been integrated into the RFLP-map of barley and PCR-based markers have been developed for these genes (ym4, ym5, ym9, ym11). These markers are useful tools in barley breeding today as they can be used in marker-based selection procedures, marker-assisted backcrossing programmes and in order to combine different resistance genes in one genotype ('pyramiding'), thereby facilitating efficient breeding of resistant lines.
[Show abstract][Hide abstract] ABSTRACT: The genetic structure of the rym5 locus was studied in a population comprising 391 doubled-haploid lines that were evaluated for resistance to two strains
of Barley Yellow Mosaic Virus (BaYMV-1, 2) and to Barley Mild Mosaic Virus (BaMMV). The absence of recombinants that are able
to differentiate between the reaction to these different bymoviruses provides evidence that rym5 is a complex locus, which is either composed of several closely linked genes or of an allelic series of a single gene. For
marker-assisted introgression of this locus into adapted barley germplasm, a CAPS (cleaved amplified polymorphic sequence)
and a microsatellite marker were developed that flank the gene at distances of 0.8 and 1.3% recombination, respectively.
[Show abstract][Hide abstract] ABSTRACT: In the present study three novel genes from barley accessions 10247 (ym8), Bulgarian 347 (ym9), and Russia 57 (ym11), which confer resistance to Barley Mild Mosaic Virus (BaMMV), were mapped using molecular markers. Bulked segregant analysis
of four progenies segregating for resistance to BaMMV was followed by fine-scale mapping of the resistance genes using individual
F2 or BC1F2 plants. The resistance genes are inherited recessively and are located on the long arm of barley chromosome 4HL. A series
of closely linked molecular markers are available for marker-assisted breeding programs. A marker (MWG2134) linked with resistance
gene ym11 from Russia 57 was identified, which is diagnostic for the resistance gene.
[Show abstract][Hide abstract] ABSTRACT: Thirty-six Hordeum vulgare varieties and 12 H. spontaneum germplasms originating from different parts of the world and showing different reactions to the barley yellow mosaic virus
complex (BaMMV, BaYMV, BaYMV-2) were analyzed for genetic similarity using RAPDs. On the basis of an analysis of 20 selected
RAPD-primers corresponding to 544 bands genetic similarity according to Nei and Li (1979) was estimated to be between 0.685
and 0.964. Associations between the 48 genotypes were calculated using UPGMA-clustering and principal coordinate analysis.
By applying these methods we were able to separate H. spontaneum accessions from H. vulgare varieties, and within these groups all the genotypes were clustered correctly according to their origin. Consequently, RAPD
analysis can be considered a very useful and efficient tool for the fast estimation of genetic relationships in barley. The
correlation between genetic similarity with respect to German varieties and adaptation of exotic barley varieties to German
growing conditions is discussed.