The total linkage drag (combined homozygous and heterozygous types) was 8.53%, which is more than half of the total donor component on carrier chromosomes (Table 3).
If linkage drag among QTLs appears to be caused by a QTL cluster, the Q-TARO database could be used to illustrate the position of the cluster.
The linkage drag also decreased from ~71 in BC1 to ~37 cM in BC4.
Possible linkage drag effects associated to the specific introgressed regions were observed.
The presence of these regions could be ascribed to linkage drag effect specifically associated with the markers employed for the introgression of each QTL.
The magnitudes of donor genome contributions and linkage drags for N = 500 were greater than for N = 1000 due to the lower number of recombinations occurring.
A comparable linkage drag effect observed in the two genetic backgrounds suggests that it might be specifically associated with the markers employed for introgressing the QTL.
Although there was no significant difference between linkage drags across the different heritabilities and frequencies of the favourable QTL allele in the donor line, there was a trend for a lower linkage drag when the frequency of the favourable QTL allele in the donor was reduced.
Second, introducing target genes through MAS can result in linkage drags.
Therefore, selection based on functional markers alone does not guarantee linkage drag-free progeny.
