Unlocking the genetic potential of the root system, rhizosheath mucilage and microbiome of wheat (Triticum aestivum L.)

全球人口不断增加，气候预测将挑战足够的作物生产，以及化肥和农药的有害使用，这意味着我们需要在对环境影响最小的情况下提高目前耕地的生产力。小麦是全球作物产量的第二大贡献者，在两个半球的一系列纬度地区种植。小麦根系是植物性能的关键决定因素，但由于研究地下器官的挑战，根系在育种中被忽视。来自文献的证据表明，在高产和压力环境中，水和养分的吸收往往不是最佳的。促进将根系特征纳入育种计划，并制定增强根系功能的作物管理策略，可能是提高产量潜力和稳定性，同时最大限度地减少投入的关键。为填补根系-根际-产量相互作用的知识空白，本研究将福尔斯划分为三个战略领域：根系结构（RSA）、根系分泌物和根际微生物组。1）在Avalon x Cadenza双单倍体（AxC）作图群体中进行RSA的遗传作图，确定了幼苗种子根角度、长度和生长速率的数量性状位点（QTL）。可复制QTL与根角相关，定位在3A和4D染色体上，解释了7%的表型变异。经过广泛的根表型，尾巴显示表型在人口分布的极端进行了田间试验。幼苗根系表型与田间成熟植株根系和冠层表型之间的相关性进行了计算。2）根系分泌物代表了植物固定碳的显著损失，但它们被认为对植物水分状况、营养、盐胁迫、微生物相互作用和根鞘发育具有益处。酶联免疫吸附测定（ELISA）用于定量AxC尾根鞘中高分子量多糖的量，确定基因型对分泌的影响，并研究与RSA的潜在相互作用。3）AxC尾根鞘内微生物种群的宏基因组学研究揭示了相同物种品系之间微生物群落组成的差异。根据表型（分泌水平、RSA、产量）分组的品系表明，高产品系的微生物组不同于低产品系。总的来说，这项研究提出了一种新的，多方面的研究根系，从幼苗到成熟的植物在田间，作为一个整体的方法来改善作物比不太可能发现的“银子弹”更强大。

An increasing global population, projections of climates that will challenge sufficient crop production, and a detrimental use of fertiliser and pesticides mean that we need to increase the productivity of land currently under cultivation with minimal impact on the environment. Wheat is the second largest contributor to global crop production and is cultivated across a range of latitudes across both hemispheres. The wheat root system is a crucial determinant of plant performance, yet roots are overlooked in breeding due to the challenge of studying organs below ground. Evidence from the literature indicate that water and nutrient uptake are often suboptimal in high yielding and stressed environments. Facilitating the incorporation of root system characteristics into breeding programmes and developing crop management strategies that enhance root function could be key to increasing yield potential and stability, while minimising inputs. To fill the knowledge gap on root-rhizosphere-yield interactions the research presented here falls into three strategic areas: root system architecture (RSA), root secretions and the rhizosphere microbiome.1) Genetic mapping of RSA in the Avalon x Cadenza Doubled Haploid (AxC) mapping population identified quantitative trait loci (QTL) for seedling seminal root angle, length and growth rate. Replicable QTLs were associated with root angle and mapped to chromosomes 3A and 4D, explaining 7% of phenotypic variation. After extensive root phenotyping, the tails displaying phenotypes at the extremes of the population distribution were taken forward for field trials. Correlations between seedling root phenotypes and the root and canopy phenotypes of mature plants grown in the field were calculated.2) Root secretions represent a significant loss of fixed carbon from the plant, yet they are thought to confer benefits in relation to plant water status, nutrition, salinity stress, microbial interactions and the development of the rhizosheath. Enzyme-linked immunosorbent assays (ELISAs) were used to quantify the amount of high molecular weight polysaccharides in the rhizosheath of AxC tails, determine the influence of genotype on secretion and investigate potential interactions with RSA.3) A metagenomics study of the microbial population within the rhizosheath of AxC tails uncovered differences in microbial community composition between lines of the same species. Lines grouped according to phenotype (level of secretion, RSA, yield) showed that the microbiome of high-yielding lines differed from that of low-yielding lines. The level of secreted polysaccharides was associated with differences in the microbiome.Overall, this research presents a novel, multi-faceted study of the root system, from seedling to mature plant in the field, as a holistic approach to crop improvement is more robust than the unlikely discovery of a "silver bullet".