Varietal testing, carried out by the Department of Agriculture, Food and the Marine (DAFM), has confirmed a plateau in modern wheat yields.
Meanwhile, it has been previously identified that feed wheat crops have the potential to produce 20t/ha, a target that remains well outside the wherewithal of cereal growers to achieve.
Recent work carried out at Rothamsted Research, however, has indicated that significant reductions in the numbers of root-promoting bacteria, found in association with modern wheat varieties, could help unlock this yield conundrum.
This is specifically the case if wheat is grown within lower crop input systems.
Modern wheat varieties grown with inorganic fertiliser show markedly fewer beneficial root bacteria compared to their unfertilised counterparts.
In contrast, ancestral wheats show no such reduction, whether fertilised or not. This suggests modern cultivars have been bred to rely on nutritional inputs to maintain yields, a practice which reduces soil health.
Modern wheat yields
Significantly, a recent Rothamsted study highlights the potential of harnessing beneficial microbes and plant genetics to transition to lower-input farming systems.
Modern wheats have complex genomes with either four (tetraploid) or six (hexaploid) sets of chromosomes due to extensive crossing and interbreeding.
Ancestral varieties, however, have simpler genomes with only two (diploid) sets of chromosomes.
The Rothamsted research team performed controlled experiments to compare growth-promoting root bacteria (plant growth-promoting rhizobacteria or PGPR) associated with diploid, tetraploid, and hexaploid wheats grown in both fertilised and unfertilised soil, resulting in the isolation of over 14,000 bacterial isolates.
“Modern wheat varieties have been bred to thrive in high-input systems,” Dr. Tessa Reid, the study’s lead researcher said.
“This appears to have greatly reduced the numbers of beneficial bacteria living on or around their root system.
“If we are to move to lower input systems, we will need to work out how to boost the abundance of beneficial soil microbes, so that they provide the nutritional benefits currently delivered by inorganic fertilisers.”
Significantly, the Rothamsted team found that fertiliser application reduced the abundance of PGPR in polyploid wheats by 45%, making their levels no higher than in unplanted soil.
This reduction was not observed in diploid wild wheats, the ancestors of modern varieties.
Additional analysis has revealed this was largely driven by a reduced selection of beneficial root bacteria in modern wheats.
Future work could involve performing microbiome transplants, whereby, beneficial root microbes reduced through domestication, will be supplemented to modern wheat varieties.
Alternatively, reintroducing key genetic traits to modern wheat, from their ancestors, to boost root colonisation of beneficial soil bacteria is another promising strategy.
