The 20:20 wheat project unveiled by Rothamsted Research last month aims to provide the knowledge base and tools for UK wheat yields to hit 20t/ha in the next 20 years, members of the Rothamsted Research Association (RRA) were told at a meeting last week.

Malcolm Hawkesford, of Rothamsted Research, outlined the first part of the ambitious programme, which starts in April 2012 and will run for five years.

“The three challenges are to increase yield potential, while maintaining quality, to minimise the gap between yield potential and on-farm yields and to maximise the efficiency of input use,” he said. “These will be tackled by four packages of research.” (see box)

The average wheat yield in the UK is currently 8.4t/ha, he continued. “That compares well with the world average of 2.8t/ha.”

Contrary to reports that farm yields have stagnated in recent years, plant breeding and agronomic efforts have resulted in an annual increase in wheat yields of 1%, he noted.

However, hitting the 20t/ha target would need this to rise to 2.5%, as yields would have to go up by 0.4t/ha every year, RRA members pointed out.

Mikhail Semenov, of Rothamsted Research, responded to that challenge. “Certainly, to reach 20t/ha, a 10% increase in light conversion efficiency by the wheat plant will be needed.

“But that can be done, through wide germplasm crossing and the optimisation of the photosynthetic mechanism. That’s why this programme is so important.”

He pointed out that the world wheat yield record of 15.636t/ha was set in New Zealand in 2010. “So we’re not that far away. In Scotland in 1981, some 13.99t/ha was achieved.”

A model developed at Rothamsted Research has allowed his team to evaluate wheat performance under climate change. “It shows us that we can expect significant yield loss from drought just once every 20 years.”

However, bringing the maturity date of wheat forward by three weeks will avoid the worst effects of drought stress, continued Dr Semenov. “It is difficult to know which characteristic we should breed for – drought or heat tolerance.”

Heat stress reduces grain numbers, he explained, but the wheat plant can compensate by producing larger grains.

“But if the heat stress occurs after anthesis, it can limit potential grain size. So it is a threat. Short periods of heat stress, which is when temperatures are above 27C, can cause male sterility.”

However, tolerance to post-anthesis heat stress is cultivar specific, he reported. “So it is something which we might be able to breed for, to try and avoid yield loss.”

Reaching 20t/ha: Where is it going to come from?

The four research packages referred to go some of the way to explaining how the extra yield will be achieved. But funding for the programme has only been confirmed for the first five years, prompting some concern that such a long-term programme may prove difficult to maintain.

1. Maximising Yield Potential – making genotype improvements which improve crop biomass and yield through improved photosynthetic efficiency, altered canopy and root architecture, modified seed development and enhanced nutrient utilisation efficiency.

2. Protecting Yield Potential – mitigating losses through pests and diseases, with particular focus on Septoria tritici, fusarium ear blight and take-all. Solutions could contribute 5-10% average yield increases.

3. Determining Soil Resource Interactions – how soil properties and root characteristics interact to determine water uptake and nutrient acquisition. Expected to make a 10-18% yield contribution.

4. Using Systems Approaches to Crop Improvement – developing crop models based on physiological and environmental parameters to explore wheat performance under climate change.

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