Assessment of genotype-specific responses to early flooding stress in winter oilseed rape

Excess water availability and transient flooding during early developmental stages can severely impair establishment, growth and yield in winter oilseed rape (Brassica napus L., WOSR). Although its importance is growing under changing precipitation regimes, the genetic variation for flooding tolerance in WOSR is still not well understood. This study seeks to assess genotype-specific responses to early flooding stress in a diverse panel of 40 WOSR genotypes, employing high-throughput phenotyping under semi-controlled, field-like conditions. Plants are cultivated in the DroughtSpotter XXL precision phenotyping facility of the Justus Liebig University Giessen, where they are grown as microplots in 120 L containers filled with arable soil to ensure high comparability with field conditions. Flooding stress is applied after vernalization during early vegetative development, by controlled waterlogging, while a well-drained control treatment is maintained simultaneously. Automated irrigation allows precise control of water levels, and real-time gravimetric monitoring at 5 minute intervals facilitates continuous quantification of water input, soil water status and water use from juvenile stage until maturity. Multidimensional phenotyping via automated multispectral 3D imaging is conducted throughout stress imposition until harvest, capturing temporal dynamics in morphological and spectral traits in a non-destructive manner. Traits assessed include digital biomass, canopy architecture, leaf area development and vegetation indices, enabling high-resolution monitoring of growth responses to flooding stress. The experimental design is intended to quantify genotype-by-environment interactions associated with early flooding stress and subsequent recovery. The resulting phenotypic dataset will provide a comprehensive trait catalogue describing early flooding responses in WOSR and will form the basis for subsequent integration with yield-related traits, transcriptome, metabolome and breeding data. Ultimately, this study aims to support the identification of robust phenotypic and/or metabolic indicators for flooding tolerance and contribute to breeding strategies targeting increasing climatic variability.