How do bacteria affect plant health?

It’s Plant Health Week 2022 and we are celebrating the benefits of healthy plants. An important part of keeping plants healthy is understanding the relationships between plants and bacteria to help manage bacterial diseases.

Plants have a microbiome too

Just like in the human gut, plants have a microbiome – a community of micro-organisms including bacteria that live on and around them. Many of these microbes are beneficial but sometimes, as in humans, a particular combination of plant, bacteria and environment causes disease. These diseases have various symptoms including small spots, dead-looking areas, yellowing leaves, wilting, galls, and cankers. Bacterial plant diseases can damage or destroy crops, trees and other plants in orchards, forests, and gardens. They can also have an impact on wild plant populations (although we often don’t notice it). In some cases, bacterial disease outbreaks will be sporadic whilst in others, diseases will affect plants year after year. Generally, bacterial diseases are more common when temperatures rise, and humidity is high. This means climate change might increase the spread and establishment of some diseases.

Bacterial plant diseases are particularly challenging

Controlling bacterial diseases is difficult. Unlike with fungal diseases, chemical control options are limited, often ineffective and can cause more problems than they solve. Antimicrobial resistance is already a huge challenge so spraying antibiotics into the environment is irresponsible. Currently, the most effective approach is to avoid introducing infected plants or seeds in the first place.

The Bacterial Plant Diseases Programme was initiated to develop cutting edge approaches to understanding and managing plant bacterial diseases, identifying new control solutions, predicting new threats and developing diagnostics to identify disease outbreaks. The programme’s projects target a range of important plant pathogens that currently impact UK crops or might threaten some plants or trees if introduced. Researching the diversity of bacterial plant pathogens, their biology and interactions with plant hosts, and the microbiome as well as methods of early detection is fundamental to devising new ways to manage and control these diseases.

Planning for emerging threats

Our projects are studying a range of different plant/bacteria combinations. Xylella fastidiosa, which is not currently present in the UK, can affect many different plant hosts including cherry, olive, oak, maple, lavender, rosemary, blueberry, and grapes. The risk of introduction and spread of Xylella fastidiosa in UK has been reduced following research into the trade routes and markets, potential insect vectors and early diagnosis strategies. Another disease of concern, although it is not currently causing major problems in the UK, is caused by Candidatus Liberibacter, which can infect carrots. Our researchers are trying to understand (and stop) spread from non-food plants on field margins.

Better management of existing diseases

We are also extending our knowledge of bacterial diseases like blackleg of potato, bacterial canker of cherry and black rot of brassicas (e.g., cabbage, broccoli) which are regularly causing problems in the UK. This will help develop tools for farmers, agronomists and policymakers. It could also lead to the identification of plants that are more disease-resistant and therefore reduce losses.

Harnessing the microbiome

Microbiome studies are helping us understand, not just particular bacteria of concern, but also the entire community of micro-organisms found on a plant and how imbalances can lead to disease. Studying the microbiome of oak trees will give us more information on acute oak decline to help develop disease management strategies to protect oaks in our forests. In the future we might use beneficial bacteria mixtures – synthetic microbiomes – to protect plants. It’s a bit like us taking a probiotic drink to help our gut health.

Alternative control methods

Other projects are developing new methods to minimise the impact of bacterial diseases including using bacteriophages (viruses that attack bacteria) to control brown rot of tomato and potato, and developing synthetic microbial populations that might help control root mat disease of tomato plants.

Taking part in Plant Health Week

During #PlantHeathWeek members of our community will be taking part in social media campaigns to highlight how plants make life better and what we are doing to help keep plants healthy. We are also hosting a on ‘Innovative approaches to controlling bacterial plant diseases’ on Wednesday 11 May at 1pm – register here. We hope you will get involved on social media or by coming to the webinar to help us celebrate the benefits of healthy plants.