You are reading: Hiding in plain sight – innocent weed or weapon in disguise?

Hiding in plain sight – innocent weed or weapon in disguise?

Driving down a country road you’ll see plenty of innocent plants lining the roadside. But how innocent are they? New research has shown these weeds can act as secondary hosts and harbour pathogens that cause diseases detrimental to crops in the adjacent paddocks. Author: Rachel Clarke May 19, 2021 Read Time: 2 minutes

In a recently published CCDM study, our researchers now have a better understanding of which plant pathogens are present in the fungal community of commonly found weed species adjacent to cropping fields, thanks to cutting edge comparative genomic technique called “metagenomics”.

Lead author, Dr Pippa Michael, said these crop-zone weeds are host to a wide range of plant-associated fungi, including fungi responsible for diseases such as rusts, blackleg, sclerotinia rots, powdery mildew, leaf blight and crown rot.

“We recommend controlling these weeds to prevent the harbouring of fungal pathogens that can contribute to crop disease load both in the current cropping season and the following season,” Pippa said. 

How they did it

The CCDM research into weed hosts, which began in 2016, included samples from capeweed, wild oats, annual ryegrass, wild radish, brome grass, erodium, flatweed, Patterson’s curse, double gee, barley grass, soursob and silver grass.

Samples were collected in autumn from road verges adjacent to cropping paddocks from 15 different wheatbelt locations including Badgingarra, Borden, Buntine, Harrismith, Hyden, Kalannie, Kojonup, Morawa, Mullewa, Newdegate, Nungarin, Pingelly, Toodyay, Walebing and Yoting.

These locations reported a difference in weed fungal community composition due to location and climatic factors.

So what?

According to Pippa, the difference in latitude or climate zones appeared to influence the distributions of fungal pathogenic species more so than the types of weeds that were present, with the exception of Brassicaceae host family (eg. Wild radish).

“This new information on weed host-specific or region-specific association with pathogen species may become an increasingly important factor in developing new methods for crop disease management in the future,” Pippa said.

CCDM Director, Professor Mark Gibberd, said this study establishes the potential role of metagenomics as an early warning system for biosecurity and for monitoring populations of plant pathogens within the landscape.

“The use of ‘untargeted’ surveys of pathogens through metagenomics can be a useful approach to enable researchers to be watchful for emerging diseases and to understand the role of climate on pathogen distribution,” Mark said.

“This is a powerful technique that allows us to understand the ecology and dynamics of pathogen distribution in areas that occur alongside crops.  By doing so we can effectively monitor not just current disease-causing organisms but also for fungal species that may be closely related to current crop pathogens, or species that could be pathogens of future crops not yet grown in the area. 

“Collectively, this allows us to use metagenomics to predict future disease outbreaks and to act as early warning system,” he said. 

For the paper, Crop-Zone Weed Mycobiomes of the South-Western Australian Grain Belt, click here (

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