New technology protects crops by testing the air for DNA of plant diseases

Plant infections can now be detected in our crops before they become visible.

By identifying DNA from spores floating in the air, it is hoped that a new technology called AirSeq can help farmers deal with crop diseases more effectively while using fewer chemicals.

Air DNA may be important to protecting our food security.

Every year, up to 40% of the world’s crops are lost to pests and diseases, costing farmers hundreds of billions of pounds. More than 4 million tons of pesticides are used worldwide every year to try and suppress these threats, which destroy the soil, water and even us.

In most cases, pesticides have little effect on stopping the infestation. Many diseases are detected as soon as the plants start to show symptoms, and it is often too late to save them.

Now, researchers at the Natural History Museum and the Earlham Institute have developed a new method to detect this infection before it becomes a problem. Known as AirSeq, the device absorbs thousands of liters of air to identify DNA fragments of disease-causing fungi.

Tests in the east of England have shown that AirSeq can detect how levels of this DNA change over the course of a year. Dr. Matt Clark, one of the co-authors of the new research, says this could allow farmers to take action when the risk of infection is too high.

“Right now, farmers spray their crops with fungicides to make their plants less susceptible to fungal diseases,” Matt says. “But since different crops are resistant to different types of pathogens, this is not always necessary.”

“AirSeq can detect which pathogens are present and how much they are present, which would allow farmers to see if they need to use fungicides or not. This means that farmers are I successfully spray their crops, saving them money and promoting more sustainable agriculture.”

The findings of the study were published in a journal Current Biology.

Increased risk of fungal infections

A few hundred years ago, agriculture was very different from what it is now. Farmers planted a mixture of different crops in small parts of the world. These types of crops meant that farms could withstand potential diseases but at a lower cost of yield.

Today, most fields are monocultures where farmers plant one variety over a large area. While this makes farming more efficient, it increases the risk of disease. Infections can spread like wildfire through plants, especially plants with very similar genes.

Fungi are one of the major causes of plant infections. Fungal diseases such as rusts and spots kill large numbers of crops, with losses estimated to be enough to feed between 600 million and 4 billion people for an entire year.

These losses are only expected to increase due to climate change, making the fight against fungal disease more important than ever. However, using more chemicals alone is not the solution. Just as bacteria are resistant to antibiotics, fungi can also become resistant to fungicides.

Matt explains: “Some fungicides can also affect the production of hormones in animals, so increasing their use can also be harmful to our health.”

“Some important fungicides are now banned in the EU as a result. Since these chemicals have been phased out, it is even more important to use the remaining options sparingly to prevent fungicide resistance.”

News like this inspired the team to develop AirSeq technology. What began as a project to study how spores travel between fields has evolved into testing crop diseases through their airborne DNA.

What can AirSeq do?

AirSeq works by aspirating air through a series of filters, with airborne particles that end up in a collection fluid. This fluid is then collected and used for DNA extraction and sequencing to determine what was in the air.

To prove it could work, the first team tested AirSeq’s ability to detect the bacterium Bacillus thuringiensis (Bt) in the wind tunnel. The bacteria were released into the air gradually, with increasing levels of Bt DNA picked up by the device and detected in sequence.

Having validated the technology in a controlled environment, it was time to test AirSeq in the field. The device sampled the air around fields of wheat, barley and peas for over a month and a half to see what it could detect.

“Our approach is to sequence everything in the air, rather than focusing on specific genes or sequences,” Matt explains. “If we can only sequence certain genes or species, then it’s possible to miss what we don’t want.”

“This method can detect anything, including new and unexpected types of diseases. In the long term, it can allow us to see how these viruses are evolving.”

The AirSeq test revealed DNA from a wide variety of pathogens, including those caused by fungi and bacteria. These included common wheat diseases in the UK such as powdery mildew and septoria leaf blotch, as well as rare ones such as stem rust.

Fungal levels appear to be linked to weather and climate, with high humidity and rainfall associated with an increase in fungal infections.

The team now hopes to continue improving AirSeq to the point where it can be transferred to farmers around the world. Their main goal is to develop an autonomous device that can constantly monitor the air for signs of disease.

This can help farmers to take measures aimed at reducing crop losses, and reducing world hunger.

This story is reprinted courtesy of the Natural History Museum. Read the original story here.