*Article* **Oilseed Rape Cultivars Show Diversity of Root Morphologies with the Potential for Better Capture of Nitrogen**

**László Kupcsik 1, Claudia Chiodi 1, Taraka Ramji Moturu 1, Hugues De Gernier 1,†, Loïc Haelterman 1, Julien Louvieaux 1,2, Pascal Tillard 3, Craig J. Sturrock 4, Malcolm Bennett 4, Philippe Nacry <sup>3</sup> and Christian Hermans 1,\***


**Abstract:** The worldwide demand for vegetable oils is rising. Oilseed rape (*Brassica napus*) diversifies cereal dominated crop rotations but requires important nitrogen input. Yet, the root organ is offering an untapped opportunity to improve the nitrogen capture in soil. This study evaluates three culture systems in controlled environment, to observe root morphology and to identify root attributes for superior biomass production and nitrogen use. The phenotypic diversity in a panel of 55 modern winter oilseed rape cultivars was screened in response to two divergent nitrate supplies. Upon in vitro and hydroponic cultures, a large variability for root morphologies was observed. Root biomass and morphological traits positively correlated with shoot biomass or leaf area. The activities of high-affinity nitrate transport systems correlated negatively with the leaf area, while the combined high- and low-affinity systems positively with the total root length. The X-ray computed tomography permitted to visualize the root system in pipes filled with soil. The in vitro root phenotype at germination stage was indicative of lateral root deployment in soil-grown plants. This study highlights great genetic potential in oilseed rape, which could be manipulated to optimize crop root characteristics and nitrogen capture with substantial implications for agricultural production.

**Keywords:** *Brassica napus*; natural variation; nitrogen nutrition; root system architecture
