Influence of the Semi-dwarf Growth Type on Nitrogen Use Efficiency in Winter Oilseed Rape

Abstract

A higher nitrogen (N) use efficiency is an important breeding goal in crops such as oilseed rape (Brassica napus L.) that are considered less N efficient compared with crops like wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.). Changes in the plant ideotype, such as reduced plant height of semi-dwarf hybrids, are said to result in an increased harvest index and N harvest index. This could lead to a higher N efficiency, especially when N availability is restricted. A double haploid population was developed that was segregating for the bzh dwarf locus, with 54 dwarf and 54 normal-type lines. By crossing with a normal-type tester, 108 testcrosses were produced with 54 hybrids each of semi-dwarf and normal types. They were evaluated for seed yield, straw yield, and N content under zero and high N fertilization in six and four trials, respectively, in the years 2010 to 2013. Quantitative trait loci were estimated for N-related traits across environments. Semi-dwarf hybrids showed a significantly higher N harvest index, N uptake efficiency, N utilization efficiency, and N use efficiency compared with normal-type hybrids at N deficiency. The relative contribution of N uptake efficiency to the total genetic variation in N use efficiency was higher in semi-dwarf genotypes than in normal-type hybrids at both N levels. Quantitative trait loci of five and two N-related traits under zero and high N fertilization, respectively, cosegregated with the bzh-locus on linkage group A06, indicating that the semi-dwarf growth type has a high influence on N efficiency. We conclude that semi-dwarf hybrids are better adapted to N deficiency.