Identification of traits for nitrogen use efficiency in oilseed rape (Brassica Napus L.)

Abstract

Oilseed rape (Brassica napus L.) receives high inputs of Nitrogen (N) fertiliser while N uptake and N harvest index are low. This results in high residual soil N which leaches to water bodies and contributes to greenhouse emissions. Such negative environmental impact could be reduced by better understanding the genetic basis of N metabolism in oilseed rape and designating relevant traits for varietal selection towards high nitrogen use efficiency (NUE) at low N fertiliser inputs. In this study the doubled haploid population (TNDH) from a cross between the Chinese semi-winter variety Ningyou7 and the UK winter variety Tapidor was analysed for N physiology and Quantitative Trait Locus (QTL) mapped for relevant traits. Quantitative Trait Loci were mapped in two N treatments over two consecutive field trials for architectural traits such as plant height, foot length, pod number and chlorophyll content in bracts and leaves; yield and yield component traits such as plant biomass, seed yield, harvest index and N metabolism (seed, plant and total N concentration, N uptake, utilisation and use efficiencies and N harvest index). A larger number of QTL were detected at High N than at Low N. In total 49 QTL were detected at High N versus 44 in Low N during 2005/06, while in 2007/07, 72 versus 62 QTL were detected at High and Low N respectively. Most QTL for different traits were treatment specific. Novel QTL for agronomic traits specific at Low N were identified. The correlations between traits were also studied through QTL co-localisations, particularly for relationships between seed yield, N uptake and N use efficiency. Seven chromosomal regions are discussed for potential candidate genes. Additionally, QTL reproducibility, interval mapping and composite interval mapping, QTL x environment interactions and phenotypic plasticity in oilseed rape are also discussed.