Investigate large gaps and improve genetic map in narrow-leafed lupin ( Lupinus angustifolius L.)

Genetic map is of vital importance to plant molecular genetic studies. It has been used for QTL mapping, gene cloning, and physical map construction. One common issue for construction of genetic maps is that one chromosome is divided into two or more groups based on low LOD values between each group. In this study, we constructed a genetic map from a F 8 RIL population derived from two domesticated narrow-leafed lupin cultivars Uncrop and Tanjil. In the first round of analysis, 37 linkage subgroups were constructed for the 20 chromosomes. The number of subgroups was greater than the number of chromosomes. And then we merged the linkage subgroups belonging to the same chromosomes based on physical maps and other genetic maps constructed from different mapping populations. The DNA variations between the parents revealed that variation density was highly consistent with marker density in the genetic map, and that the large gaps (> 15 cM) in the same linkage groups resulted from the low DNA variations density in the large regions. Furthermore, the regions with less DNA variations between the two parents will facilitate the screening of the candidate genes located in the region. A single major QTL for grey leaf spot was identified on chromosome 19 from this mapping population.