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

再植病害是苹果和樱桃、李子、草莓和玫瑰等其他玫瑰科植物普遍存在的问题。苹果再植病(ARD)是指在以前种植苹果的土壤中种植的新苹果树不能茁壮成长的问题。从历史上看，人们提出了许多原因来解释这种疾病，如杀虫剂的积累和腐烂的根部释放挥发性毒素。然而，目前的科学共识集中在专业的根腐病病原微生物的混合上，包括类似真菌的“水霉”和真正的真菌(降解根组织)和微小的鳗鱼(它们在觅食时提供容易感染的点)。幸存下来的受影响的树木通常会在生命的后期结果，而且在他们的一生中，产生的果实更少，质量下降。这些复合效应导致商业果园的盈利能力损失高达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，这加剧了ARD问题。此外，洪水等极端环境事件往往会导致树木死亡，需要在幼小的果园中重新种植林隙。对于培育树木的苗圃来说，ARD是一个更严重的问题，在嫁接结果品种(接穗)后，会影响他们的砧木生产(商业树木的根系)以及完成的树木的健康。商业砧木品种的选择主要是因为它们对树木活力和早熟的影响。它们还影响果园在特定土壤类型上的表现和对病虫害的抗性，包括ARD，但对不同砧木再植敏感性差异的根本原因以及不同砧木基因型对随后ARD严重程度的遗传影响尚不清楚。农用化学品登记程序和环境污染法规的不断变化继续减少了传统上用于管理ARD的有效化学防治的选择。这意味着种植者将依赖于更昂贵的管理选择，包括用蒸汽对土壤进行灭菌(目前不经济)，与石果树或其他无关作物轮作，或者通过在土壤中添加各种堆肥类调理剂来鼓励有益的土壤微生物。对ARD所涉及的生物体及其常见致病机制的清楚把握对于制定经济上可行的管理策略是至关重要的。砧木选择将成为抗逆转录病毒病综合管理方法的一个越来越重要的组成部分；因此，迫切需要更好地了解不同土壤类型的根癌与微生物种群之间的相互作用与抗病发展的关系。东马林研究公司(EMR)在苹果砧木的开发和特性方面享誉全球。我们建议与英国、荷兰和比利时的苗圃、苹果育种者和英国的苹果种植者合作，为苹果种植业提供有关砧木、土壤和微生物之间相互作用的详细信息，以帮助制定新的ARD管理策略，并指导未来的砧木育种计划，以提高对ARD的耐受性。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)从ARD发育的角度阐明根茎-土壤生物群的相互作用及其对根和地上部构型和生长的影响，以及3)阐明不同的砧木基因对ARD的遗传效应。这将使英国的主要园艺行业之一受益，因为它为疾病管理提供了新的机会，以提高产量效率和减少农场食物浪费。因此，英国消费者将继续享受我们最受欢迎的自制水果之一带来的健康益处。

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.