Rhizo-Rice: a novel ideotype for deeper roots and improved drought tolerance

大米是全球粮食安全的支柱。干旱胁迫是水稻产量的主要限制因素，由于全球气候变化的影响，预计未来还会恶化。因此，培育抗旱性更好的水稻品种是全球粮食安全的重要战略目标。该项目通过开发根状水稻来满足这一需求，根状水稻是一种新的水稻品系，具有根部特征，使它们在干旱条件下既能更好地探索土壤，又能更有效地集水。根稻品系将有1)更陡峭的根生长角，2)更少的主根，3)更多的根在深层土壤中的分枝，4)根空气空间(通风组织)的形成，这降低了根组织的成本，以及5)更小的导水管(木质部)，这迫使植物更少地利用土壤水分。据推测，这些特征组合在一起的价值将比从它们单独的影响预测的要大得多。该项目将评估根型水稻品系的田间效益和计算机模拟模型，并将发现控制根型水稻根系特征的遗传因素。此外，我们将评估泰国正在使用的水稻育种系的这些根性状，并将培训泰国科学家将根性状纳入水稻育种计划的方法。该项目汇集了泰国领先的水稻研究人员和育种者，英国和菲律宾国际水稻研究所的领先作物生理学家，以及英国领先的根系模型建模者。我们将通过测量不同条件下生长的水稻植株的根系特征来研究不同的根构型和干旱条件对水稻生长的影响。通过记录不同类型根的数量、长度和角度，并拍摄根结构的显微镜图像，我们将测试这些特征如何影响抗旱性。这些测量将得到计算模型的补充，这将使我们能够测试许多不同的根系结构和干旱条件。我们之前已经开发了计算模型来模拟玉米、大麦、菜豆、羽扇豆根和南瓜的根生长。我们将采用这些模型来模拟水稻的根生长，这将使我们能够预测最好的根生长类型，以在干旱条件下最大限度地吸收水分。最后，我们将确定哪些基因负责创造理想的根结构。我们将使用最近开发的技术来分析许多不同水稻品种的基因和根系结构，这将使我们能够识别出适合最大限度地提高抗旱性的品种。该项目将产生几种工具，以促进培育更耐旱的水稻品系。它将验证特定的根性状作为水稻育种的选择目标；将发现这些性状的遗传标记；将在水稻种质中确定理想的根性状来源，并将增强泰国科学家创建一支培育具有优越根性状的水稻品系的能力。

Rice is a mainstay of global food security. Drought stress is a primary limitation to rice yields and is projected to worsen in the future due to the effects of global climate change. The development of rice cultivars with better drought tolerance is therefore an important strategic goal for global food security. This project addresses this need by developing Rhizo-rice, new rice lines that have root traits that permit them to have both improved soil exploration and more efficient water capture under drought conditions. Rhizo-rice lines will have 1) steeper root growth angles, 2) fewer major roots, 3) greater root branching in deep soil, 4) increased formation of root air spaces (aerenchyma), which reduces the cost of root tissue, and 5) smaller water conductance vessels (xylem), which forces the plant to use soil water more sparingly. It is hypothesized that these traits will have much more value in combination than would be predicted from their isolated effects. This project will evaluate the benefits of Rhizo-rice lines in the field and computer simulation modelling and will discover genetic elements controlling Rhizo-rice root traits. Furthermore, we will evaluate these root traits in rice breeding lines in use in Thailand and will train Thai scientists in methods to incorporate root traits in rice breeding programs.This project integrates leading rice researchers and breeders in Thailand, leading crop physiologists in the UK and at the International Rice Research Institute in the Philippines, and leading root modelers in the UK. We will investigate how different root architectures and drought conditions affect rice growth by measuring features of the root system in rice plants grown in different conditions. By recording the number, length and angle of different types of roots and taking microscopy images of the root structures, we will test how these features affect drought tolerance. These measurements will be complemented by computational modelling, which will enable us to test many different root structures and drought conditions. We have previously developed computational models to simulate root growth in maize, barley, common bean, lupin and squash. We will adapt these models to simulate rice root growth, which will enable us to predict the best type of root growth to maximise water uptake in drought conditions. Finally, we will determine which genes are responsible for creating the desirable root structures. We will use recently developed techniques to analyse the genes and root structures in many different varieties of rice, which will enable us to identify suitable varieties for maximising drought tolerance. This project will generate several tools to facilitate the breeding of more drought tolerant rice lines. It will validate specific root traits as selection targets in rice breeding; will discover genetic markers for these traits; will identify sources for desirable root traits in rice germplasm, and will enhance the ability of Thai scientists to create a team for breeding rice lines with superior root traits.