Environmental-DNA exposes pathogens
It could be that farmers in the future use environmental DNA, or eDNA, to predict when pests arrive. English researchers show in Current Biology that this is a possibility.
Knowing if and when a pest arrives is essential for farmers. Only then can they intervene, preventing pests of getting a foothold. For lots of herbivory insect this is already reality. With help of observations and weather forecasts can be calculated when the next generation will be emerging from its egg, allowing farmers to take measures at exactly that moment.
Bot the even smaller pathogens, like fungi and bacteria, are difficult to recognise in an early stadium. But just as all other living organism they leave traces of DNA behind in the environment. Traces that can betray the pathogens. The researchers decided to test this.
Distinguishing subspecies at the moment is still difficult, because there is not enough known about where they differ in their DNA
Before they starting testing this out in the field they figured out if the traces of fungi and bacterial DNA detected in the air was comparable with their actual presence. In a wind tunnel they released various concentrations of spores from a harmless fungi. The detected amount of fungi DNA increased when there were more fungi spores in the air.
Now the researchers could start collecting samples in the field. After a test for the optimal sampling time, 60 minutes, they researchers started measurements. For one and a half months during the summer they collected three samples each week.
In order to use eDNA for early detection of pathogens, the detected eDNA needs to correspond with the actual organisms present. This turned out to be the case. The researchers found in their samples DNA from the on the field growing crops. But also from pathogens that infect those crops.
There is a good chance that eDNA will be added to the crop protection management kit
Those pathogens, the researchers could distinguish from each other up to species level. The researchers argue that it should even be possible to distinguish up to subspecies level. But, so they also say, then it needs to be known where they differ in their DNA. Something that for lots of subspecies of pathogens is unknown. The distinguishing of subspecies would particularly be useful for farmers that grow crops resistant to one subspecies, but not the other.
To use eDNA as a real predictor, the eDNA present needs to fluctuate in tune with fluctuations of its corresponding organism. This it turned out it did. The researchers had already observed that the amount of detected eDNA of a species changed with each measurement. This corresponded to the observed weather. There was for example more fungi eDNA present when it was humid, but not when it was hot weather. Corresponding to the fungi weather preferences.
There is a good chance that eDNA measurements will be added to the crop protection management kit of a farmer. Al does it need to be said that this study is only a proof-of concept. In addition the researchers say that the same method could also be used for other applications of air eDNA detection.
Literature
Giolai et al., Measuring air metagenomic diversity in an agricultural ecosystem, Current Biology (2024), https://doi.org/10.1016/j.cub.2024.07.030
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