Genetic variation and inheritance of phytosterol and oil content in a doubled haploid population derived from the winter oilseed rape Sansibar × Oase cross

KEY MESSAGE: Identification of QTL for phytosterol content, oil content, fatty acids content, protein content of defatted meal, and seed weight by multiple interval mapping in aBrassica napusDH population. ABSTRACT: Phytosterols are minor seed constituents in oilseed rape which have recently drawn wide-interest from the food and nutrition industry due to their health benefit in lowering LDL cholesterol in humans. To understand the genetic basis of phytosterol content and its relationship with other seed quality traits in oilseed rape, QTL mapping was performed in a segregating DH population derived from the cross of two winter oilseed rape varieties, Sansibar and Oase, termed SODH population. Both parental lines are of canola quality which differ in phytosterol and oil content in seed. A genetic map was constructed for SODH population based on a total of 1638 markers organized in 23 linkage groups and covering a map length of 2350 cM with a mean marker interval of 2.0 cM. The SODH population and the parental lines were cultivated at six environments in Europe and were phenotyped for phytosterol content, oil content, fatty acids content, protein content of the defatted meal, and seed weight. Multiple interval mapping identified between one and six QTL for nine phytosterol traits, between two and six QTL for four fatty acids, five QTL for oil content, four QTL for protein content of defatted meal, and three QTL for seed weight. Colocalizations of QTL for different traits were more frequently observed than individual isolated QTL. Major QTL (R(2) ≥ 25 %) were all located in the A genome, and the possible candidate genes were investigated by physical localization of the QTL to the reference genome sequence of Brassica rapa. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00122-015-2621-y) contains supplementary material, which is available to authorized users.