Apple replant disease (ARD) causes significant economic losses across all major apple growing regions worldwide. The disease etiology is not well defined and expresses as the poor growth of newly planted trees. This problem is exacerbated in Europe by the removal of several effective chemical soil fumigants and many modern cultivars lacking resistance to other pathogens such as European Canker (Neonectria ditissima). Recent results at NIAB EMR suggested that ARD is likely to be caused by several organisms: lack of specific beneficial microbes (particularly bacteria), fungal and oomycetes pathogens, and exacerbated by nematodes. Thus, in absence of broad-spectrum fumigants, reducing ARD requires careful soil management to improve soil structure (particularly microbiota), especially in nurseries where young trees are grown in a high density. Furthermore, empirical evidence on the rapid development of apple canker symptoms at specific planting sites also suggested that certain soil conditions are likely to affect canker development in new plantings.
This project aims to understand how various soil management practices (including amending soils with specific microbes) will impact soil quality in terms of ARD and canker development.
We will investigate temporal dynamics of the soil microbial community, changes in specific beneficial microbes (e.g. arbuscular mycorrhizal fungi, known biocontrol microbes of plant diseases, and plant growth promoting rhizobacteria) and candidate ARD pathogens in response to soil amendments. Such microbial dynamics will also be studied under a few climate change scenarios: combination of elevated CO2 x temperature x water potential stress. Both traditional and modern DNA sequencing technologies will be used to quantify microbial changes. Short and medium term experiments under several climate change scenarios will be conducted at the newly purpose-built AgriTech Centre (CHAP) at Cranfield University. The central hypothesis is that by improving tree health in nurseries we can improve tree establishment when planted in conjunction with appropriate management (irrigation, soil amendment etc.).