Georg-August Universität Göttingen, Department of Crop Sciences, Göttingen, Germany.
Metalloid Transport Group, Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany.
Ann Bot. 2019 Nov 27;124(6):891-901. doi: 10.1093/aob/mcy197.
In oilseed rape (Brassica napus) semi-dwarf hybrid varieties from crosses between bzh dwarf and normal-type lines are of increasing interest. They have improved nitrogen (N) uptake, N-utilization and N-use efficiency compared to normal types. This study aimed to elucidate whether these N-related effects can be explained by the bzh shoot growth-type alone or also by differences in root traits.
Root system size was measured using root electrical capacitance (EC) in field trials with two N levels in two sets of genotypes segregating for the bzh-locus: (1) 108 doubled haploid (DH) test hybrids in two seasons, 2010-2012, and (2) 16 near-isogenic hybrids in the 2016-17 season. Quantitative trait loci (QTL) for root EC were estimated in DH test hybrids. Seedling root architecture parameters were monitored in vitro.
In vitro root growth showed a higher root: shoot ratio in bzh semi-dwarf hybrids. Root EC in field trials was higher at high N supply than at zero N fertilization. In most trials semi-dwarf hybrids had higher EC than normal-type hybrids, but they reduced root EC in response to N limitation more than normal types. Root EC was more heritable at the end of flowering (h2 = 0.73) than at the beginning of flowering (h2 = 0.36) in near-isogenic hybrids and had a lower heritability in trials of DH test hybrids (h2 = 0.27). A QTL for root EC in the genomic region of the bzh-locus on linkage group A06 was significant at zero N fertilization.
Root EC proved to be a meaningful method in oilseed rape breeding programmes targeting root system size. The greater reduction of semi-dwarf root EC compared to the normal type under low N supply with simultaneous increase in N efficiency implies that in roots it is not a question of 'the more the merrier' and that the bzh root system reacts highly economically when N is scarce.
在油菜（甘蓝型油菜）半矮秆杂交品种中，来自 bzh 矮秆和普通型品系杂交的品种越来越受到关注。与普通型相比，它们提高了氮（N）的吸收、利用和利用效率。本研究旨在阐明这些与 N 相关的效应是否仅由 bzh 茎生长型单独解释，还是也由根性状的差异解释。
在两个 N 水平的田间试验中，使用根电容量（EC）测量根系大小，这两个试验是在两个分离 bzh 基因座的基因型组中进行的：（1）2010-2012 年两个季节的 108 个加倍单倍体（DH）测试杂种，以及（2）2016-17 年的 16 个近等基因杂种。在 DH 测试杂种中估计了根 EC 的数量性状基因座（QTL）。在体外监测幼苗根结构参数。
体外根生长显示 bzh 半矮秆杂种的根：茎比更高。田间试验中，高氮供应下的根 EC 高于零氮施肥。在大多数试验中，半矮秆杂种的 EC 高于普通型杂种，但它们对氮限制的反应比普通型杂种减少根 EC。近等基因杂种开花末期（h2 = 0.73）的根 EC 比开花初期（h2 = 0.36）更具遗传性，DH 测试杂种试验中的根 EC 遗传性较低（h2 = 0.27）。在连锁群 A06 的 bzh 基因座基因组区域中，一个根 EC 的 QTL 在零氮施肥时是显著的。
根 EC 被证明是油菜根系大小育种计划的一种有意义的方法。与低氮供应下普通型相比，半矮秆根 EC 的减少更大，同时氮效率增加，这意味着在根系中，不是‘越多越好’的问题，bzh 根系在氮稀缺时反应非常经济。
