QTL Mapping of Flowering Time in Brassica napus: A Study on the Interplay between Temperature and Day Length after Vernalization

Eva Heinrich ^1* Antje Schierholt ² Christian Möllers ¹

• ¹ Department of Crop Science, Division of Crop Plant Genetics, Faculty of Agricultural Sciences, University of Göttingen, Göttingen, Lower Saxony, Germany
• ² Department of Crop Science, Division of Plant Breeding Methodology, Faculty of Agricultural Sciences, University of Göttingen, Göttingen, Lower Saxony, Germany

Flowering is a critical life stage for plants and the regulation of flowering is heavily influenced by environmental factors and genetically very complex. In oilseed rape (Brassica napus L.), a major oil crop, yield is heavily dependent on successful flowering. Up until now, the influences of day length and temperature on flowering time have mostly been studied in spring-type rape, though they also affect flowering in winter oilseed rape after vernalization and changing climate conditions alter spring time temperatures. In this study, a doubled haploid population derived from a cross between a winter and a spring-type oilseed rape was examined for the effect of cool and warm temperatures (11°C and 22°C) in combination with long and short days (8/16 hours light) on flowering time after vernalization. QTL analysis revealed major QTL for flowering time in two homologous regions on chromosomes C06 and A07, which were found to interact epistatically. We found that temperature can either delay or promote flowering depending on day length and genotype, highlighting the complex interplay between these factors. Our study provides new insights into the genetic basis of flowering time regulation in B. napus, especially after vernalization, and highlights the importance of considering the interplay between temperature and day length in breeding programs for this crop, particularly in the context of climate change.