An Integrated Phenomics Approach to Identifying the Genetic Basis for Maize Root Structure and Control of Plant Nutrient Relations

在不断变化的气候中提高作物产量和作物生产的可持续性是我们这个时代最重要的挑战之一。玉米是美国最重要的农作物，但尽管玉米产量稳步增加，预计产量仍达不到需求。此外，石油基氮肥已被确定为美国和全球主要水道污染的主要驱动因素。这个项目的重点是植物的“隐藏的一半”根系，它负责所有的水、氮和其他养分的获取。它利用先进的成像技术来分析根系的结构，其中一些技术是在医学和工业研究部门开发的。氮素吸收能力较强的玉米品种的根系结构将与劣势品种进行比较，并确定控制根系与氮素相互作用的基因。这将通过识别控制根生长和有效获得氮素的基因，直接使玉米和其他作物育种者受益，从而使美国农业的一个主要部门受益。另一个目标是通过为中学生到本科生建立课外和暑期教育计划来培养下一代科学家。这些学员将获得使用3D打印机和负担得起的微处理器构建、编程和使用植物成像系统的第一手经验。实现根系在压力下提高和稳定作物产量以及减少不可持续的化肥使用水平的巨大潜力，将需要彻底了解它们的遗传学和生理学。基于图像的表型分析已经实现了对根的高通量和准确测量，但尽管有许多新的和有前途的方法，每一种方法都有内在的权衡，限制了它们的个人能力。该项目采用了一种综合的根系表观和生理特征分析方法来解决玉米根系构型的遗传基础和功能后果。它将以四种互补的方式描绘两个玉米种群的根构型：在凝胶系统中对幼苗进行3D/4D成像，对从田间挖掘出来的根冠进行光学和X射线成像，以及对田间土壤剖面上生长的根部进行微型加速器成像。这些方法中的每一种的定量遗传分析都将允许识别控制这些特征的基因。此外，这种对相同基因类型的综合分析将产生迄今为止最全面的根表型方法比较。一个群体将在项目的头两年从NAM亲本品系的筛选中选出，另一个群体将是伊利诺伊州蛋白品系重组近交系(IPSRIs)。在五年的时间里，这一方法将解决以下目标：1.确定控制根构型表型变异的基因；2.寻找控制根构型可塑性对氮素供应的基因；3.确定根构型对植物氮素状况、元素含量和种子品质的功能影响。

Increasing the yield and sustainability of crop production in a changing climate is one of the foremost challenges of our time. Corn is the most important crop in the United States, but despite steady increases in corn production, projected yields fall short of demands. Furthermore, petroleum-based nitrogen fertilizers have been identified as a primary driver of pollution of major waterways in the U.S. and globally. This project focuses on root systems, the "hidden-half" of plants, that are responsible for all of the water, nitrogen, and other nutrient acquisition. It leverages advanced imaging techniques, some of which were developed in the medical and industrial research sectors, to analyze the structure of root systems. Root structures from corn varieties that are known to be superior in nitrogen acquisition will be compared those that are inferior, and the genes that control root-nitrogen interactions will be identified. This will directly benefit corn and other crop breeders, and thus a major sector of U.S. agriculture, through identification of genes that control root growth and efficient nitrogen acquisition. An additional objective is to train the next generation of scientists by establishing after-school and summer educational programs for middle-school to undergraduate students. These trainees will gain first-hand experience building, programming, and employing plant imaging systems using 3D printers and affordable microprocessors.Realizing the enormous potential of root systems to boost and stabilize crop yields under stress and to reduce unsustainable levels of fertilizer use will require a thorough understanding of their genetics and physiology. Image-based phenotyping has enabled high-throughput and accurate measurements of roots, but despite many new and promising methods, each has inherent tradeoffs that limit their individual power. This project employs an integrated root phenomic and physiological profiling approach to resolve the genetic basis and functional consequences of maize root architecture. It will profile the root architecture of two maize populations in four complementary ways: 3D/4D imaging of young plants in a gel based system, optical and X-ray based imaging of root crowns excavated from the field, and minirhizotron imaging of roots growing across the soil profile in the field. Quantitative genetic analyses from each of these methods will allow identification of the genes controlling these traits. Additionally, this integrated analysis of identical genotypes will generate the most comprehensive comparison of root phenotyping methods to date. One population will be selected from screening of the NAM parent lines in the first two years of the project, the other population will be the Illinois Protein Strain Recombinant Inbreds (IPSRIs). Over five years, this approach will address the following aims: 1. Identify genes driving phenotypic variation of root architecture, 2. Identify genes controlling phenotypic plasticity of root architecture to nitrogen supply, 3. Determine the functional impacts of root architecture on plant nitrogen status, elemental content and seed quality.