Genetic Dissection of Root Morphological Traits Related to Nitrogen Use Efficiency in Brassica napus L. under Two Contrasting Nitrogen Conditions.

Jie Wang,Guihua Liu,Xinfa Wang,Jiaqin Shi,Hanzhong Wang,Xiaoling Dun

doi:10.3389/fpls.2017.01709

Abstract

As the major determinant for nutrient uptake, root system architecture (RSA) has a massive impact on nitrogen use efficiency (NUE). However, little is known the molecular control of RSA as related to NUE in rapeseed. Here, a rapeseed recombinant inbred line population (BnaZNRIL) was used to investigate root morphology (RM, an important component for RSA) and NUE-related traits under high-nitrogen (HN) and low-nitrogen (LN) conditions by hydroponics. Data analysis suggested that RM-related traits, particularly root size had significantly phenotypic correlations with plant dry biomass and N uptake irrespective of N levels, but no or little correlation with N utilization efficiency (NUtE), providing the potential to identify QTLs with pleiotropy or specificity for RM- and NUE-related traits. A total of 129 QTLs (including 23 stable QTLs, which were repeatedly detected at least two environments or different N levels) were identified and 83 of them were integrated into 22 pleiotropic QTL clusters. Five RM-NUE, ten RM-specific and three NUE-specific QTL clusters with same directions of additive-effect implied two NUE-improving approaches (RM-based and N utilization-based directly) and provided valuable genomic regions for NUE improvement in rapeseed. Importantly, all of four major QTLs and most of stable QTLs (20 out of 23) detected here were related to RM traits under HN and/or LN levels, suggested that regulating RM to improve NUE would be more feasible than regulating N efficiency directly. These results provided the promising genomic regions for marker-assisted selection on RM-based NUE improvement in rapeseed.

Highlights

As the key element of protein, nucleic acid etc., nitrogen (N) is one of the essential mineral nutrients for crop growth and development
The heritability (h2) of NUErelated traits was moderate except shoot N concentration (SNC) and N utilization efficiency (NUtE), ranging from 0.23 to 0.48 under HN and from 0.26 to 0.59 under LN condition (Table 2)
Four root morphology (RM)-nitrogen use efficiency (NUE) QTL clusters were overlapped between RM and N uptake traits (NU) traits; two were between RM and dry biomass traits (DB) and others were between RM and N concentration (NC), but no were between RM and NUtE. These results indicated that the co-localization of RM-related traits and NUE-related traits was existed under both HN and LN conditions, while RM-related traits were closely related with plant N uptake instead of N utilization efficiency

Summary

Introduction

As the key element of protein, nucleic acid etc., nitrogen (N) is one of the essential mineral nutrients for crop growth and development. Root system is the key place for nutrient and water acquisition and its ability on soil exploring is the major determinant of N uptake efficiency (Li X. et al, 2016). Root system architecture (RSA), often defined as the spatial configuration and distribution of root system in the growth medium, determines the soil exploration in time and space (Lynch, 1995). Considerable researches have shown that RSA was closely related with N uptake, for example, plants with a steeper and deeper root can absorbs N more efficiently in deep soil layers (Lynch, 2013; Trachsel et al, 2013; Zhan and Lynch, 2015). Heterogeneity of N supply permits plants to optimize N acquisition from growth medium by modulating their root morphology (Linkohr et al, 2002; Walch-Liu et al, 2006; Yu et al, 2014; Li P. et al, 2016)

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