Agriculture Reference
In-Depth Information
disease pressure on resistance is high, it could be a valuable component of disease
management enabling the dependence on fungicides to be reduced.
The above strategy is based on fi rst understanding the mechanisms of tolerance and
the role of particular traits and then exploring the genetics of the traits to aid selection in
breeding. The reverse, but complementary, approach is to make use of the existing data
bases and genotyping platforms to identify possible associations between tolerance and
genetic markers in a large proportion of the current germplasm. The underlying mecha-
nisms can then be investigated on a subset of genotypes to provide information on how
best to deploy and manage the tolerance. Genotyping platforms are now available for
high-throughput SNP (single nucleotide polymorphism)-genotyping and these genotyping
resources are being associated with detailed phenotype data in public databases (i.e. asso-
ciation genetics). By calculating putative tolerance indices from robust and reliable multi-
site fi eld trial data such as that used to compile the UK's CEL (Crop Evaluation Limited)
Recommended List, genomic regions and linked markers can be associated with tolerance
measures. Co-location of other phenotypic traits will indicate the possible sub-traits that
confer the tolerance for further evaluation. If the variance in tolerance accounted for is
suffi ciently great, then such markers may be used for selection in breeding programmes.
The advantage of this approach is that it represents an effi cient use of resources since it
harnesses information from a vast number of genotypes in extant databases. Its weakness,
however, is that tolerance is a complex character and it may not be possible to generate
a reliable index of tolerance from information on yield responses to fungicide treatment
in variety trials. Therefore, a combination of both approaches would seem to offer the
best prospects for understanding and improving the disease tolerance of important crop
species in the future.
7.9
Acknowledgements
Scottish Agricultural College and Scottish Crop Research Institute receive fi nancial support
from the Rural and Environment Research Analysis Directorate of the Scottish Executive.
7.10
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References
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