Over the years, breeders concentration on increasing wheat varieties harvest index may unwittingly have made the crop more susceptible to black-grass competition.

That is according to researcher Jed Clark, who is halfway through a four-year AHDB-funded PhD study.

He is currently conducting research to identify wheat varieties that are more competitive against black-grass.

He says: Previously, certain above ground traits have been described as conveying competitiveness against black-grass, but very little is known regarding below-ground interactions.

Our aim is to identify certain traits in wheat, with a focus on roots, which convey a competitive advantage over black-grass and then screen and identify possible competitive lines to be added to the Recommended List for combating the weed.

The research mainly consists of growing plants in the laboratory under controlled glasshouse conditions and in the field and outdoor containers at ADAS Boxworth.

Six winter wheat varieties and one hybrid barley are being examined (see panel, left).

Comparisons We grow plants individually to allow comparisons over time between different lines, explains Mr Clark.

And we grow different plants together, for example wheat and black-grass, to compare the competitive effects they have on one another under different conditions.

Over their lifespan we assess growth stages, tiller numbers and biomass to allow us to create a workable dataset for statistical analysis.

In the laboratory the plants are grown in pots of soil as well as hydroponically in water and in rhizoboxes, the latter two options allowing root growths to be seen and measured.

Barriers through which chemicals can pass without the roots touching are also used to see how neighbouring plants detect and interact with each other.

Chemical signalling and growth inhibition are clearly involved.

Both wheat and black-grass grow better alone than when growing side by side in containers with the barriers, says Mr Clark.

We have a container trial underway which consists of 92 x 20-litre pots containing different crop lines with theoretically different root traits, in competition with different black-grass densities.

This trial is looked after by staff at ADAS and I have visited several times throughout the year to aid in key data collection.

Well continue to work with ADAS, with container and field trials due to commence in the next winter growing season.

Mr Clark outlines some key findings to date.

Barley grows better roots than elite wheats and so is less affected by black-grass.

Competition Root growth in black-grass is better than in wheat.

The question is, does this difference in root growth result in a crop winning or losing in competition with black-grass? Black-grass gains its competitive advantage over wheat due to its faster growth in winter conditions, increased ‘investment in its root system and a prolonged period in which to build its root system.

These allow it to dominate the underground space and resources by spring.

The weed doesnt have the same advantages in spring sowings.

We hope that by identifying traits and lines that are more competitive well be able to give growers another factor to consider when choosing which varieties to sow, says Mr Clark.

He also hopes that the results may influence the direction of crop breeding, with an emphasis on root traits for multiple benefits.

Overall, we want to help reduce the impact of black-grass.

As herbicide resistance continues to increase in black grass and other grass-weeds, farmers are looking for as many other options as possible to aid control, says ADAS weed biologist Lynn Tatnell.

This is a really exciting project as it will be generating new data to help us understand whether some cereal varieties really can suppress black-grass better than others.

The importance of good integrated pest management strategies, in this case for grass-weed control, is at the forefront of peoples minds now, and these include using as many cultural control options as possible.

Understanding Variety choice is a great cultural control tool and an improved understanding of the competitive effects against black-grass should further enhance farmers choices.

Understanding specifically the root aspects of black-grass suppression is exploring areas where less research has been done in the past.

Work has already shown the beneficial effect of hybrid barley against grass-weeds, mainly due to its overall competitive and vigorous growth habit.

So, focusing on the rooting aspects is generating new knowledge.

The detailed genetic studies at Leeds University partnered with the applied experiments at ADAS will hopefully result in a really practical outcome in terms of understanding the root competitive effects between the cereal varieties tested and black-grass.

If this could be the start of introducing this characteristic into future Recommended Lists then that would be really beneficial to farmers and widen the choices available.