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specific markers and on the other hand to the
identification of new and perhaps more efficient
alleles in TILLING populations or in germplasm
collections, by allele mining.
bined using new advances in gene technology
like zinc-finger-nucleases (Shukla et al. 2009).
In summary, it may be concluded that based
on the classical genetic and molecular marker
analyses that resulted in mapping of many dif-
ferent virus resistance genes in barley, genomic
tools available today and the complete sequence
of barley that will be available in the near future,
efficient breeding for virus resistance on the
allele level will be facilitated, thereby broaden-
ing the genetic base of virus resistance in barley.
Allele Mining and Future Prospects
Nowadays, the exploration of allelic diversity
at the molecular level and the utilization of
novel superior alleles using targeted molecular
breeding (“precision breeding”; McCouch 2004)
are of prime interest with respect to enhanc-
ing virus resistance. The analysis of natural or
induced allelic variation and the identification of
unknown valuable alleles at a locus of known
function are called “allele mining” (Kaur et al.
2008). Usually, plant accessions from wild or
locally adapted landrace gene pools contain a
rich repertoire of alleles that have been left
behind by the selective processes of domesti-
cation, selection, and cross-breeding that paved
the way to today's elite cultivars. Allele mining
involves the assembly of a germplasm collec-
tion or screening of a TILLING population for
sequence variation in the target gene. Using this
approach, 47 different alleles have been identi-
fied at the Rym4/Rym5 locus in a barley world
collection of about 1,000 genotypes (Hofinger
et al. 2009, 2011). Respective studies can be con-
ducted for all loci involved in virus resistance in
barley (Table 5.1) as soon as respective genes
have been isolated. The isolation of these virus
resistance genes will transfer breeding to the
allele level, facilitating the identification of novel
alleles and their directed use in molecular breed-
ing strategies (see above) in order to enhance
virus resistance. The use of these alleles mainly
derived from exotic germplasm can be fostered
by marker-assisted backcrossing for the gene of
interest simultaneously with the enhanced elim-
ination of the donor background by genotyp-
ing using high-throughput SNP technologies, for
example, the 9k iSelect chip in barley. How-
ever, respective alleles may also be transferred
directly to high-yielding cultivars or be com-
References
Abrouk M, Murat F, Pont C, Messing J, Jackson S, Faraut T,
Tannier E, Plomion C, Cooke R, Feuillet C, Salse J, 2010.
Palaeogenomics of plants: synteny-based modelling of
extinct ansecstors. Trends Plant Sci 15:479-487.
Adams MJ, Swaby AG, Jones P, 1988. Confirmation of the
transmission of barley yellow mosaic virus (BaYMV) by
the fungus Polymyxa graminis . Ann Appl Biol 112:133-
141.
Anonymous, 2011. Polymyxa graminis. In: CABI/EPPO (ed)
Distribution Maps of Plant Diseases No 1108, Walling-
ford, UK.
Arumuganathan K, Earle ED, 1991. Nuclear DNA content of
some important plant species. Plant Mol Biol Rep 9:208-
218.
Badr A, Muller K, Schafer-Pregl R, El Rabey H, Effgen S,
Ibrahim HH, Pozzi C, Rohde W, Salamini F, 2000. On
the origin and domestication history of barley ( Hordeum
vulgare ). Molecular Biology and Evolution 17:499-510.
Bauer E, Weyen J, Schiemann A, Graner A, Ordon F, 1997.
Molecular mapping of novel resistance genes against
Barley Mild Mosaic Virus (BaMMV). Theoretical and
Applied Genetics 95:1263-1269.
Benito MC, Sanchez M, Shin JS, Blake T, 1988. A map of
barley chromoome-2 using isozymic and morphological
markers. Biochemical Genetics 26:387-394.
Bolot S, Abrouk M, Masood-Quraishi U, Stein N, Messing J,
Feuillet C, Salse J, 2009. The 'inner circle' of the cereal
genomes. Curr Opin Plant Biol 12:119-125.
Bossolini E, Wicker T, Knobel PA, Keller B, 2007. Com-
parison of orthologous loci from small grass genomes
Brachypodium and rice: implications for wheat genomics
and grass genome annotation. Plant J 49:704-717.
Bukvayova N, Henselova M, Vajcikova V, Kormanova T,
2006. Occurrence of dwarf virus of winter wheat and
barley in several regions of Slovakia during the growing
seasons 2001-2004. Plant Soil Environ 9: 292-401.
Catherall J, Hayes JD, 1970. Inheritance and effectiveness of
genes in barley that condition tolerance to Barley yellow
dwarf virus . Annals of Applied Biology 65:153-161.
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