Horticulture: Seeking new tools to manipulate soil and root microbiology for biocontrol of soft fruit Phytophthora diseases

全球数据估计，每年高达40%的农作物产量因病虫害而损失。树莓疫霉根腐病是由土传疫霉引起的一种树莓根腐病。原生侵染是当红星病菌的游动水生孢子被生长的根尖吸引时开始的，它们感染并传播到整个根系，破坏组织，阻止营养和水分的吸收，杀死植物。每次感染都会释放游动孢子，然后游动孢子传播到其他植物。红色疫霉可能已经存在于种植地点，因为孢子可能会持续多年，对极端环境和许多杀虫剂具有抵抗力。或者，新的感染可以到达受感染的植物上，或者通过经过受污染土壤的灌溉水到达。最初的运动传播阶段(游动孢子)依赖于土壤自由水。英国软果业遭受根腐病的重创，迫使种植者在基质中使用盆栽系统生产80%的树莓，以避免与受污染的田间土壤接触。然而，根腐病仍然是一个巨大的问题，因为导致这种疾病的疫霉存在于繁殖种群中，并可以在灌溉水中局部传播。为了保护树莓产业，必须确定持久和有效的病原菌控制的新的、更可持续的方法。事实上，为了满足英国政府的净零战略，需要在可持续性、弹性和资源利用效率方面进行改进，该战略打算在大约十年内将英国的净排放量减半，并在2050年之前消除这些净排放量。新的可持续基质的潜力是这一战略的一部分，目前正在开发新的可持续基质更有效地管理水并结合新的IPM工具来控制疾病，这些基质在控制根病方面有很大潜力。在一些有机覆盖物中发现的微生物活性已被证明能导致疫霉菌丝细胞壁的破裂。木霉是一种重要的自由生活真菌属，由许多菌株组成，它们可以直接与根相互作用，促进植物生长，增强对疾病的抗性，并增加对非生物胁迫的耐受性。许多木霉菌株以其对真菌病原体的直接拮抗活性而闻名，并可能通过竞争资源、抗生素、真菌寄生、菌丝相互作用和分泌酶等一系列机制来减轻病原体引起的疾病症状。在这里，我们将调查这些潜在的好处，树莓作为模式木本植物，有潜力帮助控制过多的其他经济和环境意义重大的疫霉疾病。我们已经建立了一个免费的团队来筛选几种木霉真菌，以确定它们作为土壤和树莓栽培品种基质添加剂的适宜性。它们对卵菌群体生长的直接影响将被进行，一项基于盆栽的研究将评估木质模式树莓在可持续底物中存在木霉对致病疫霉引起的疾病的发展的健康和韧性。非化学方法抑制疫霉根腐病的目标是病原体生活史的不同阶段。已经开发了新的基质，限制了自由水的可获得性，从而降低了游动孢子传播的能力，防止了新的感染。疫霉根腐病的生物防治包括添加对疫霉有拮抗作用的生物体，或通过竞争营养物质、产生抑制化合物或直接通过寄生来间接防治疫霉。综合有效的控制是可能的。

Worldwide figures estimate that up to 40% of crop yields are lost to pest and diseases each year. Phytophthora root rot of Raspberry is caused by the soilborne pathogen Phytophthora rubi. Primary infection is initiated when motile water-borne zoospores of P. rubi are attracted to growing root tips, which they infect and spread through the whole root system destroying tissue and preventing nutrient and water uptake, killing the plant. Each infection releases zoospores which then spread to other plants. Phytophthora rubi may already be present on planting sites, as spores may persist for many years, being resistant to environmental extremes and many pesticides. Alternatively new infections can arrive on infected plants, or via irrigation water which has passed through contaminated soil. The initial motile spreading phase (zoospores) are reliant on free soil water. The UK soft fruit industry has been devastated by root rot disease that forced growers to produce 80% of UK raspberries using pot-based systems in substrate to avoid contact with contaminated field soil. However, root rot is still a huge problem as the Phytophthora pathogen responsible for the disease is present in propagation stocks and can spread locally in irrigation water. To protect the raspberry industry, it is imperative that new, more sustainable methods of durable and effective pathogen control are identified. Indeed, improvements in sustainability, resilience and resource-use efficiency are required to meet the UK Government's Net Zero Strategy, that intends to halve UK net emissions in around a decade and eliminate them by 2050. The potential for new sustainable substrates that manage water more efficiently in combination with novel IPM tools to control disease are part of this strategy and are currently under development and there is great potential for these to manage root diseasesDisease suppressive cultural practices such as the use of organic mulches including sawdust, compost or bark can help to suppress soil pathogen populations. The microbial activity found in some organic mulches have been shown to cause breakdown of cell walls of Phytophthora hyphae. Trichoderma is an important free-living fungal genus comprising many strains that can interact directly with roots, promote plant growth, boost resistance to diseases, and increase tolerance to abiotic stresses. Many Trichoderma strains are known for their direct antagonistic activity against fungal pathogens and potential to reduce disease symptoms caused by pathogens by a range of mechanisms such as competition for resources, antibiosis, mycoparasitism, hyphal interactions, and secreted enzymes. Here we will investigate these potential benefits to raspberry as a model woody species with potential to help control a plethora of other economically and environmentally significant Phytophthora diseases. We have established a complimentary team to screen several Trichoderma fungal species for their suitability as an additive to soil and substrates in a range of Raspberry cultivars. Their direct impact on oomycete colony growth will be performed and a pot-based study will provide an assessment of health and resilience of the woody model host raspberry in presence of Trichoderma in sustainable substrate on the development of disease caused by pathogenic Phytophthora.Non-chemical approaches for suppression of Phytophthora root rots target different phases of the life cycle of the pathogen. New substrates have been developed which limited the availability of free-water and hence reduce the ability of the motile zoospores to spread preventing new infections. Biocontrol of Phytophthora root rot involves the addition of organisms which are antagonistic to Phytophthora, either indirectly via competition for nutrients, production of suppressive compounds, or directly via parasitism. Combined effective control may be possible.