Research trials have consistently conformed that blackgrass thrives on heavy land, particularly where drainage is poor.
Herbicide-resistant blackgrass has represented a significant challenge for the tillage sector in the UK for a number of years and more recently, in Ireland.
Blackgrass is one of the most problematic and damaging agricultural weeds for winter wheat in western Europe.
Severe infestations can result in yield loses of up to 70%, squeezing farm productivity and ultimately, imperilling our food security.
As few as 12 plants/m2 could reduce crop yield by 5%.
Now, a new study has shown that this problematic weed uses specific adaptations to flourish, even when soil is totally saturated for up to three weeks.
Blackgrass
The data shows that when waterlogged, blackgrass plants grow bigger than their well-drained counterparts, while wheat growth under the same conditions was significantly reduced.
The research also examined different populations of blackgrass and showed that the more herbicide resistant the population was, the more waterlogging tolerant it was too.
Other studies have shown that weed competition early in crop development has the greatest impact on yield.
These findings suggest fields infested with herbicide resistant blackgrass are going to be badly affected by autumn waterlogging.
The results also help to explain why blackgrass tends to form patches in areas of the field where the soil is good at holding onto water.
Rothamsted’s Dr. Dana MacGregor, who led the research, said: “This is an important step forward in our understanding of what makes blackgrass so resilient.
“We are getting closer to pinpointing the physical and genetic mechanisms that makes blackgrass such a formidable foe for cereal farmers.”
Study
For the study, seedlings of wheat and blackgrass were flooded for up to 21 days in pots in the greenhouse.
During this time, the size of the plant was measured and plant tissues were collected and analysed.
The plants’ roots were carefully examined under the microscope to see if structural changes could be identified.
Dr. MacGregor explained: “We knew that wheat plants alter their root structure in response to waterlogging, making drinking-straw-like structures called aerenchyma that increase gas exchange from the unflooded tissues down into the flooded roots.
“Although this survival response helps, renovating roots takes time and energy. What we were surprised to see, is that blackgrass always had these structures even in the well-drained conditions.
“In other words, blackgrass is ‘ready to go’ when fields are flooded, whilst wheat and other crops, must remake their roots to survive.”
Molecular analyses also showed that wheat changes gene expression and metabolite concentrations when waterlogged, turning on pathways that will help it to survive or using up stress-relieving metabolites.
Blackgrass on the other hand, showed minimal responses, behaving almost as if it was oblivious to the waterlogging.
Despite the small response, the transcriptomic and metabolomic profiles of these two species were different.
These differences could not only help shape potential control strategies for this pernicious weed, but may also identify new physical, genetic or metabolic traits that may be helpful in future-proofing climate stressed crops.
“Blackgrass is incredibly resilient and will probably do pretty well even in the face of climate change,” Dr. MacGregor added.
“If we want to future-proof our crops, studying how this weed survives today’s challenges could help us to identify new or useful traits that could be used in tomorrow’s crops.”