Accelerated breeding of black rot resistant brassicas for the benefit of east African smallholders

植物抗病基因可以保护作物免受具有相应无毒基因的病原菌的侵害。在许多情况下，由单一的、通常是显性的抗病（R）基因赋予的保护是短暂的，因为病原体菌株可以通过突变和选择而进化，有利于具有改变的或缺失的avr基因的菌株，从而能够引起疾病。广谱抗病性是数量上的，涉及几个基因，通常预计更持久。然而，这种抗性在育种计划中更难利用。这种植物防御战略的基础目前尚不清楚。我们选择了油菜对野油菜黄单胞菌致病变种（Xcc）的数量抗性作为研究模型。十字花科植物黑腐病。这种种子传播的疾病是世界范围内油菜最重要的疾病之一。在以前的芸苔属研究中，我们已经确定了良好的抗性来源，并绘制了主要遗传成分的位置。在这个项目中，我们将利用芜菁基因组学的令人兴奋的新发展和新出现的信息，芸苔属和拟南芥基因组的密切相关性，以确定抗性和识别相关基因。在拟议的项目中，上述资源的组合将使我们能够提供关于作物物种定量抗病性基本基础的新颖和令人兴奋的信息。这项工作的关键实际成果将是具有紧密连锁的分子标记的抗性植物材料和关于芸苔属基因组抗性的自然变异程度的信息，这些信息可用于植物育种，以提供对非常重要的病原体的持久抗性。

Plant disease resistance genes can protect crops against pathogens that have the corresponding avirulence (avr) genes. In many cases, the protection conferred by single, generally dominant, disease resistance (R) genes is short lived as the pathogen strains can evolve through mutation and selection, favouring strains with altered or missing avr genes that are therefore able to cause disease. Broad spectrum disease resistance that is quantitative, involving several genes, is generally expected to be more durable. However, this kind of resistance is more difficult to exploit in breeding programmes. The basis of this plant defence strategy is currently unknown. We have chosen quantitative resistance to Xanthomonas campestris pv campestris (Xcc) in Brassica rapa as a model for investigation. Xcc causes black rot of crucifers. This seed-borne disease is one of the most important diseases of Brassicas worldwide. In previous Brassica research at WHRI we have identified good sources of resistance and mapped the location of the major genetic components. In this project we will exploit the exciting new developments in Brassica rapa genomics and emerging information on the close relatedness of the Brassica and Arabidopsis genomes to characterise the resistance and identify the genes involved. The combination of the above resources in the proposed project will allow us to deliver novel and exciting information on the fundamental basis of quantitative disease resistance in a crop species. Key practical outcomes of this work will be resistant plant material with tightly linked molecular markers and information on the extent of natural variation for resistance in Brassica genomes that could be exploited in plant breeding to provide durable resistance to a very significant pathogen.