Apple Replant Disease (ARD) Evolution and Rootstock Interaction (ARDERI)

再植病害是苹果和其他蔷薇科物种（如樱桃、李子、草莓和玫瑰）中广泛认识到的问题。苹果再植病（英语：Apple replant disease，ARD）是指新的苹果树在以前生长的土壤中种植时无法茁壮成长的问题。从历史上看，人们提出了许多原因来解释这种疾病，例如农药的积累和分解根部释放的挥发性毒素。然而，目前的科学共识集中在一种混合的专业根腐烂病原微生物，包括真菌样的“水霉菌”和真正的真菌（降解根组织）和微观线虫（提供容易感染的地方，当他们喂养）。幸存的受影响的树木通常在生命后期结果实，并且在其一生中，产生较少的质量降低的果实。这些复合效应导致商业果园利润损失高达50%。现代生产系统涉及更高的树木密度（高达30倍）和更快的更换周期，加剧了ARD问题。此外，洪水等极端环境事件往往导致树木死亡，需要在幼龄果园中重新种植。ARD对于培育树木的苗圃来说是一个更重要的问题，影响了他们的砧木（商业树木的根系）生产以及在嫁接结果品种（接穗）后成品树的健康。选择商业砧木品种主要是因为它们对树势和早熟的影响。它们还影响果园在特定土壤类型上的表现以及对包括ARD在内的病虫害的抗性，但是对于砧木对再植的敏感性差异以及不同砧木基因型对随后的ARD严重性的遗留效应的根本原因知之甚少。化学品登记程序和环境污染法规继续减少传统上有效控制化学品的选择用于管理ARD。这意味着种植者将依赖更昂贵的管理方案，包括用蒸汽对土壤进行消毒（目前不经济），与核果树或其他无关作物轮作，或通过向土壤中添加各种堆肥类调理剂来鼓励有益的土壤微生物。明确掌握ARD中涉及的微生物及其常见的致病机制对于制定经济上可行的管理策略至关重要。砧木的选择将成为一个越来越重要的组成部分，一个综合的方法，农业和农村发展，因此，更好地了解砧木和微生物种群之间的相互作用，在不同的土壤类型的农业和农村发展是迫切需要的。东马岭研究所（EMR）在苹果砧木的开发和特性鉴定方面享有世界声誉。在与英国，荷兰和比利时的树木苗圃，苹果育种家和英国苹果种植者的合作，我们建议提供苹果种植业与砧木，土壤和微生物之间的相互作用的详细信息，这将使新的管理策略的发展ARD和直接未来的砧木育种计划，以提高耐ARD。主要的科学发现将是1）ARD组分的相对丰度与土壤性质、微生物种群和砧木的关系，2）阐明砧木-土壤生物群相互作用及其对根和芽结构和生长的影响，以及3）阐明不同砧木基因型对ARD的遗传效应。这将有利于英国的主要园艺产业之一，为疾病管理提供新的机会，以提高产量效率和减少农场粮食浪费。因此，英国消费者将继续享受我们最受欢迎的国产水果之一所带来的健康益处。

Replant disease is a widely recognized problem in apples and other rosaceous species, such as cherries, plums, strawberries and roses. Apple replant disease (ARD) is the problem of new apple trees failing to thrive when planted in soil where apples have previously grown. Historically, many causes have been proposed to explain this disorder such as accumulation of pesticides and the release of volatile toxins from decomposing roots. However, current scientific consensus focuses on a mix of specialist root-rotting pathogenic microorganisms, comprised of fungus-like "water moulds" and true fungi (degrading root tissues) and microscopic eelworms (providing easy points of infection when they feed). Surviving affected trees typically fruit later in life and, over their lifetime, produce less fruit of reduced quality. These compound effects result in a loss of profitability of up to 50% in commercial orchards. Modern production systems involve much higher tree density (up to 30x greater) and faster replacement cycles exacerbating the ARD problem. Furthermore, extreme environmental events such as flooding often lead to tree death requiring gaps to be replanted in young orchards. ARD is an even more significant problem for the nurseries that raise the trees, affecting their production of rootstocks (root system in a commercial tree) as well as the health of the finished tree, after the fruit-bearing variety (scion) is grafted. Commercial rootstock varieties are selected mainly for their effects on tree vigour and precocity. They also affect orchard performance on particular soil types and resistance to pests and diseases including ARD but the underlying reasons for differences in rootstock susceptibility to replant and the legacy effect of different rootstock genotypes on the subsequent severity of ARD are poorly understood.On-going changes to agri-chemical registration procedures and environmental pollution regulations continue to reduce the options for effective chemical control traditionally used to manage ARD. This means that growers will be reliant on more costly management options including sterilization of soil with steam (currently uneconomical), rotation with stone fruit trees or other unrelated crops or encouraging beneficial soil microbes by adding various compost-like conditioners to soil. A clear grasp on the organisms involved in ARD and their common pathogenic mechanisms is essential to develop financially-viable management strategies. Rootstock choice will become an increasingly important component of an integrated approach to ARD management; thus better understanding of the interactions between rootstocks and the microbe populations across different soil types in relation to ARD development is urgently needed. East Malling Research (EMR) has a worldwide reputation for the development and characterisation of apple rootstocks. In collaboration with UK, Dutch and Belgian tree nurseries, apple breeders, and UK apple growers, we propose to provide the apple growing industry with detailed information about the interactions between rootstocks, soil and microorganisms that will enable development of new management strategies for ARD and direct future rootstock breeding programmes for improved tolerance to ARD. The main scientific discoveries will be 1) relationship of the relative abundance of ARD components with soil properties, microbial population and rootstocks, 2) Elucidation of rootstock - soil biota interactions and their effects on root and shoot architecture and growth in terms of ARD development, and 3) clarification of the legacy effect of different rootstock genotypes on ARD. This will benefit one of the UK's major horticultural industries by providing new opportunities for disease management to increase yield efficiency and reduce on-farm food wastage. As a result, the UK consumers will continue to enjoy the health benefits conferred by one of our most popular home-produced fruits.