Physically mapping quantitative traits for stress-resistance in the forage grasses |
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Authors: | Humphreys M; Pasakinskiene I; James A; Thomas H |
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Institution: | Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion, SY23 3EB, UK; Lithuanian Institute of Agriculture, Dotnuva-Akademija, 5051 Kedainiai, Lithuania; Corresponding author |
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Abstract: | Recent advances in cytogenetics of the Lolium/Festuca
complex provide new opportunities for understanding and manipulating
physiological mechanisms in complex quantitative traits such as stress
resistance. The complex provides a valuable reserve for research and
breeding since (a) it includes a wide range of valuable agronomic
characters, (b) it has the capacity for intergeneric hybridization with
promiscuous recombination, and its genomes, despite their close homology,
have sufficient structural heterogeneity to allow
Lolium and Festuca chromosomes to
be discriminated using genomic in situ hybridization
(GISH).Two alternative procedures are used to 'dissect' stress-resistance
traits into their individual components both to determine their function
and to physically map the relevant QTL(s) onto chromosome arms: (a)
Festuca genes are introgessed into
Lolium to improve stress resistance, (b)
Lolium genes are introgressed into
Festuca to reduce stress resistance. Whichever
approach is used, alien introgressions can be detected by GISH and assigned
to chromosome arms to create a physical map. Genes of interest may then be
located more accurately following further recombination events which reduce
the size of the relevant alien introgression.It has become obvious during
the past years that genetic and physical maps are not directly comparable
as chiasmata are not evenly distributed along the chromosome axis. By
integrating physical maps created by GISH and genetic linkage-maps, the
precise site of genes on a chromosome arm may be determined, and markers
found which are tightly linked to the genes of interests, for future use in
breeding programmes.Key words: Genomic in situ
hybridization (GISH), physical mapping, Lolium/Festuca
complex, stress resistance.
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