Abstracts Biological Sciences

Inheritance and genetic variation of shoot elongation before winter in oilseed rape (Brassica napus L.)

by Mohammad Ghanbari

Oilseed rape (Brassica napus L.) is a major oilseed in many parts of the world with well adaptation to cold, dry and moist growing conditions. Despite large adaptation, winter survival is a major limiting factor to success of the crop in the regions with extreme freezing temperatures. Selection for improved winter hardiness is a difficult task, because firstly, efficient selection can only be performed in extreme winters, which in principle are not accessible and predictable in all regions. Secondly, winter hardiness is a complex trait, which consists of other interacting stresses. Cessation of shoot elongation before and during winter, has been considered one of the main requirements for successful overwintering in winter plants. Therefore, shoot length before and during winter is particularly considered by oilseed rape breeders as a contributing trait for selection of winter-hardy genotypes. Vernalization requirement, also, is a main winter survival mechanism that reduces the rate of shoot development and extend the vegetative phase to prevent frost damage by prohibiting floral transition during long warm periods before and during winter. To analyze the genetic variation for shoot elongation before winter and vernalization requirement, field experiments were performed with a set of 19 European winter oilseed rape genotypes. Moreover, to understand the genetic architecture of shoot elongation before winter and its correlation with vernalization requirement in winter oilseed rape, QTL mapping was implemented in two bi-parental doubled haploid (DH) populations of Brassica napus (DHLE and DHSO). The DHLE population consists of 151 doubled haploid lines, derived from a cross between the resynthesized line L16 and the winter oilseed rape line Express617. The DHSO population consists of 226 doubled haploid lines, derived from a cross between the two winter oilseed rape cultivars Sansibar and Oase. The two DH populations and the parental lines were phenotypically characterized in series field and greenhouse experiments. The two field environments included the normal sowing time at end of August/beginning of September, called autumn sown environment, and the spring sowing time at end of March/ beginning of April, called spring sown environment. Since the greenhouse, autumn and spring sown experiments represented very different environments; they were called three mega environments. Shoot length, shoot diameter were measured around three months after sowing time in the all three environments. In addition, data from flowering time, plant height, and seed quality traits were used to study their phenotypic and genetic association with the studied traits in the two DH populations. In the set of 19 European winter oilseed rape genotypes, results showed large phenotypic variation with significant genotypic variance components for shoot length in the autumn sown and spring sown environment. Broad sense heritability was high for shoot length in the spring sown environment (h2=97%) while medium heritability (h2=62%) was… Advisors/Committee Members: Möllers, Christian (advisor), Krutovsky, Konstantin (referee), Ecke, Wolfgang (referee).