HORTICULTURE: Biological control of potato scab using natural Pseudomonas strains

Lead Research Organisation: John Innes Centre
Department Name: Molecular Microbiology


Plant diseases cause significant crop losses in both the field and in storage, particularly within the processing sector. While some diseases can be controlled by chemical pesticides, these can be very damaging to the environment, causing massive losses in biodiversity and significant contributions to carbon emissions. Many pesticides are being withdrawn from the market on environmental grounds, and few products exist to take their place. For a growing number of crop diseases, few if any effective pesticides are available. There is therefore an urgent need to develop sustainable methods to control crop pathogens.

A promising source of treatments for crop pathogens are a group of naturally-occurring bacteria called Pseudomonas that live in the soil surrounding plant roots. These plant-associated, friendly bacteria can suppress pathogens and fight plant infections by producing an array of bioactive molecules, a process called biocontrol. Soil Pseudomonas bacteria and the secreted molecules they produce have great potential for use in sustainable control of crop diseases. To this end, we recently conducted an extensive study of the biocontrol bacteria associated with potato field soil, and identified several Pseudomonas strains that could effectively suppress the potato disease Common Scab in greenhouse experiments.

Our biocontrol bugs are promising candidates for an effective, environmentally friendly treatment for common scab. However, to use them effectively we first need to understand whether our greenhouse biocontrol results will translate into effective disease suppression in a field environment. To ensure that our Pseudomonas biocontrol strains represent an environmentally sustainable option for crop protection, it is also important to examine how the native microbial community associated with potato field soil responds to the addition of a biocontrol bacterial treatment. We anticipate that our strains will disrupt the soil microbiome much less than conventional chemical pesticides, but this remains to be proven.

In partnership with the major potato grower Branston and the agricultural biotechnology company B-hive, we will carry out field trials with our most promising biocontrol Pseudomonas strains to assess their ability to prevent the yield and crop quality losses associated with Common Scab. In parallel, we will sample the soil surrounding our growing potato plants, and use a sequencing based method to determine how biocontrol strain treatments affect the microbiology of the field soil. Finally, we will extend our study of Pseudomonas biocontrol from the field to crop storage. We will treat harvested potato crops with our biocontrol Pseudomonas strains, and assess their ability to prevent yield losses in stored potatoes over an extended period.

The results of this study will support our ongoing efforts to develop effective, environmentally friendly alternatives to crop pesticide treatments, and will advance our understanding of how the soil microbial community responds to plant growth and the introduction of new microbial species.

Technical Summary

Potato common scab is a soil-borne disease that infects root vegetables and causes scabby lesions on their surfaces. Common scab reduces crop value and marketable yields, and limited treatment options are available. Our research into the microbiology of potato field soil identified several bioactive Pseudomonas isolates that effectively suppress scab symptoms in greenhouse grown potatoes. We seek to build on this work to test the ability of our strains to control potato diseases in agriculturally relevant settings.

We will conduct field trials to test whether our Pseudomonas strains can suppress potato common scab in untreated field sites. Pseudomonas biocontrol strains will be used to treat potato plants grown in unirrigated fields on sandy loam soils in Norfolk. These sites are managed by Branston, who will conduct these trials with strains supplied by JIC. Post-treatment and harvest, potatoes will be scored for scab symptoms alongside symptoms of other diseases, plant weight and crop yield.

In parallel, we will analyse how the potato rhizosphere microbiome differs between soils subject to biocontrol strain applications. Amplicon sequencing and qPCR on selected bacterial loci will be used to ascertain microbial community composition and species abundance in treated and untreated soil samples. We will examine the statistical relationships between biocontrol effectiveness, crop yield, plant health phenotypes and microbial abundance, and use these to identify potential links between microbiome composition and plant health.

Finally, we will measure the ability of Pseudomonas strains to prevent pathogen-induced losses during extended storage. Potatoes will be sprayed post-harvest with selected Pseudomonas bacterial suspensions and placed in Branston's commercial storage facilities. Potatoes will be checked weekly for visible disease symptoms and cumulative yield and quality losses, and the capacity of our strains to prevent these will be recorded over time.


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