The length was estimated of the chromosome segment with the desired marker gene introgressed from a donor by backcrossing into a recurrent parent. It was found that, for instance, for a chromosome with a length of 100 cM the length of the segment is 32 cM in BC6.
These estimates were compared with those made by Hanson (1959). Two corrections proved to be necessary.
The implications for breeders and researchers are discussed. Differences between two near-isogenic lines often ascribed to the difference in genotype at the marker locus, may also be caused by genes linked to the marker gene and ‘dragged’ into the backcross product.
Backcrossnear-isogenic linelength of donor chromosome segment