Analysis of the genetic basis of heterosis in oilseed rape (Brassica napus) via comparative QTL mapping and expression QTL analysis

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The overall aim of this project is a comparative analysis of the genetic control of heterosis in oilseed rape (Brassica napus L.) by QTL mapping of heterosis-relevant loci in different B. napus mapping populations. In the Gießen project a doubled haploid (DH) mapping population that has been generated in preliminary work from a cross between two lines with high and low general combining ability, respectively, will be used for construction of a genome map containing a set of consensus SSR markers that also slow polymorphisms in another population segregating for heterotic effects, to be constructed by the University of Göttingen in a closely-integrated parallel project. Field trials of test hybrids from crosses between the individual DH lines of the respective populations with common male-sterile tester lines will enable the identification and dissection of QTL that correspond to the expression of heterosis. By using common markers it will be possible to align the genetic maps from the two populations, meaning that the positions, effects and interactions of the respective heterosisrelevant QTL identified in the two populations can be aligned and compared. Based on the results of the respective mapping experiments, the genetic control of heterosis in the two populations will be studied and compared. This will bring important information regarding the following to date unanswered questions: a) Are the same loci involved in the expression of heterosis in different oilseed rape populations, and if so which loci are involved and to what extend? b) What is the respective contribution of different genetic mechanism (dominance, overdominance or epistasis) to heterosis in oilseed rape, and is the genetic basis the same in different populations?