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

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.

Deciphering the Genetic Basis of Root and Biomass Traits in Rapeseed (Brassica napus L.) through the Integration of GWAS and RNA-Seq under Nitrogen Stress

“…The significant variations were observed for different root and biomass traits among the genotypes of the association panel due to their diverse genetic background and wide geographical distributions. In agreement with the previous studies [ 26 , 42 ], seedlings grown under LN conditions showed reduced SFW and TFW but increased RSRF, SDW, and RSRD than seedlings grown under control (CK) conditions. This finding shows that N-deficient plants transport more carbon in order to promote root development and, hence, mine the substrate for more nitrogen [ 12 ].…”

Genetic control of root morphology in response to nitrogen across rapeseed diversity

“…Across N levels, the biomass and morphological traits of roots positively correlated with shoot biomass (Figure S3). These observations complement previous reports indicating no trade‐off between root and shoot biomass production in rapeseed seedlings (Thomas et al, 2016b; Louvieaux et al, 2018; Louvieaux et al, 2020a; Kupcsik et al, 2021). This opens prospects to breed for a larger root system without sacrificing above‐ground biomass production.…”

“…Such two‐dimensional root analysis at an early growth stage could be a reliable indicator of later development in the soil (Louvieaux et al, 2020b; Kupcsik et al, 2021) and of seed yield and quality (Koscielny & Gulden, 2012; Louvieaux et al, 2020a). It is common knowledge that large seeds tend to produce more vigorous seedlings with better field performance (Ambika et al, 2014).…”

“…The allelic frequencies for the two DNA bulks are then estimated. The application of genetic studies to rapeseed root traits relies on a phenotyping procedure, which requires growing plants on agar-based medium (Shi et al, 2012;Kiran et al, 2019;Kupcsik et al, 2021), in hydroponics (Zhang et al, 2016;Wang et al, 2017a) or in soil (Arifuzzaman et al, 2016(Arifuzzaman et al, , 2019Louvieaux et al, 2020a).…”

“…Therefore, ameliorating NUE is essential to ensure the economic and environmental sustainability of that crop. The following findings indicate that N uptake improvement could be achieved by targeting root traits in rapeseed: (i) a substantial variety of root phenotypes exists (Fletcher et al, 2015; Thomas et al, 2016a; Zhang et al, 2016; Kiran et al, 2019; Qin et al, 2019; Louvieaux et al 2020a), (ii) N‐efficient cultivars have large root system sizes (Kamh et al, 2005; Berry et al, 2010; Ulas et al, 2012), (iii) nitrate uptake activities positively correlate with root surface (Kupcsik et al, 2021), and (iv) some genetic loci shaping root morphology and controlling NUE co‐localize (Wang et al, 2017a).…”