QTL Mapping using Intervarietal Substitution Lines in Rapeseed (Brassica napus L.)

Intervarietal substitution lines (ISLs) having one or a few defined segments of a donor genome in the common genetic background of a recurrent parent can be used to search the genome for donor alleles affecting traits. A complementary set of substitution lines represents ideally the whole donor genome divided into a limited number of distinct segments, each carried by a different line. ISLs were suggested as an alternative to a segregating population for QTL mapping. An ISL population can be used to overcome the limitations of a segregating population in the accuracy of QTL localization. With overlapping donor segments in different substitution lines and their respective phenotypic values, QTL positions can be narrowed down to a few centimorgan (cM), allowing a high precision of QTL localization.

The main objectives of this study were:

- To develop set of intervarietal substitution lines (ISL) from the cross of ¿Express¿ x resynthesized line ¿RS239¿;

- To map QTL for some agronomically important traits in two sets of ISL populations developed from the crosses of ¿Mansholt¿ x ¿Samourai¿ and ¿Express¿ x resynthesized line ¿RS239¿;

- To compare QTL results mapped in the ISL population with QTL mapped in an earlier generation (F1DH population) developed from the cross ¿Mansholt¿ x ¿Samourai¿;

For this, a set of ISLs was developed from a cross between the spring type resynthesized rapeseed line ¿RS239¿ and the winter rapeseed variety ¿Express¿ (¿ExRS239¿). A second set, developed from a cross between doubled haploid lines of the two winter rapeseed varieties ¿Mansholt¿ and ¿Samourai (¿MxS¿), was available from earlier work. The ISLs were developed through five backcross generations. Using marker assisted selection with AFLP markers, lines carrying a complementary set of donor segments were selected.