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3. Fine mapping and diversity organisation at major QTL


The fine mapping of QTLs was carried out by analysing of a large number of recombinants or by association studies.

vgt1 region - The distribution of the early allele fits with the environmental conditions and thus, reinforces the role of this locus in adaptation to the temperate area (Ducrocq et al.,2008, Genetics).

ZmCCT - A major QTL was localised near ZmCCT (170 kb) in an hypo-recombinating region (Ducrocq et al.  2009, Genetics) and its effect on earliness was later confirmed by other colleagues. This locus displays a limited number of haplotypes (fewer than for vgt1 locus), the effects of which were confirmed using near isogenic lines.

Tga1 and Su1 - A QTL affecting different agronomic traits was mapped in the region of Tga1 (involved in the domestication process) and Su1 (carbohydrate metabolism) on chromosome 4. Both genes show a strong decrease of nucleotidic diversity compared to teosinte.

Zcn8 and genome wide studies - Association genetics conducted with the 50k SNP chip highlighted a major effect of Zcn8 locus, which most likely corresponds to QTL vgt2 (Bouchet et al., 2013, Plos One).  This contributes to deciphering the major contribution of the vgt1 - vgt2 region to flowering time variation in maize.