Plants have good bacteria too!

A new study of the role microbial communities play on the leaves of plants (reported in Current Biology), suggests that fertilising crops may make them more susceptible to disease.

The natural microbiome (organisms) living on the root of the plant (its rhizosphere) impacts on its health and so does the microbiome on the plant’s surface (its phyllosphere) protect the plant against harmful organisms.

For the new study, researchers examined how the phyllosphere of tomato plants interacted with Pseudomonas syringae bacteria, which cause tomato speck, a major problem that is treated with pesticides. They found that the normal bacterial population on the plant prevented Pseudomonas infections. However, when plants were sprayed with fertiliser, this protective effect disappeared.

The working theory to explain this is that the nutrients in fertiliser keep all the microbes happy and remove the need for the good microbes to out-compete the bad microbes.

Further research into fertiliser use and overall plant health is currently underway.