As featured in Arable Farming Magazine
Exploring environmental effects on bread wheat quality
by Arable Farming Magazine May issue
Achieving a better understanding of what drives wheat breadmaking quality is the aim of an AHDB-funded PhD studentship project
In theory, new varieties and processing advances mean the UK could grow all its own breadmaking wheat, according to Prof Peter Shewry, research professor at Rothamsted Research.
However, the industry faces two challenges, says Prof Shewry.
“The first is growers’ reliance on high levels of nitrogen fertiliser to achieve the required protein content.
“Secondly, the environment strongly affects quality.
This means that year-to-year variations linked to climate change are increasingly affecting the UK wheat crop’s suitability for breadmaking.”
High grain protein content can substitute for low protein quality, but only to a limited extent, he adds.
Rohan Richard’s PhD project, which Prof Shewry supervises, is focused on strategies to increase grain protein content and understanding environmental effects on processing quality.
“We’re taking a genetic approach with studies exploiting the variation in a cross between the good, but currently outclassed, breadmaking quality varieties Malacca and Hereward.”
The cross was made by RAGT Seeds as part of HGCA Project FQS 23 ‘Improving wheat functionality through breeding and end use’, he adds.
The project exploits the phenomenon known as ‘grain protein deviation’ (GPD) to try to reduce the need for high nitrogen applications.
Grain protein content “Analyses of field trials data of varieties grown under various conditions show a clear inverse relationship between grain yield and grain protein content, allowing a regression line to be drawn,” says Prof Shewry.
However, some varieties consistently have higher grain protein content than expected – which being above the regression line is known as GPD.
The importance of GPD in determining good breadmaking quality under conditions of low nitrogen fertilisation was recently demonstrated by the AHDB/ Biotechnology and Biological Sciences Research Council (BBSRC) LINK Project ‘Low Protein Wheat for Breadmaking’ (AHDB project report No 621).
Work in this latest project, and in a previous BBSRC Industrial Partnership project, found that GPD is shown by Hereward but not by Malacca, which falls on or only slightly above the regression line.
So, a Malacca/Hereward cross is being used to identify the genetic areas responsible for GPD, explains Prof Shewry.
It involves analysing a population of about 100 lines grown in replicated trials at Rothamsted Research and the University of Reading experimental farm.
Detailed genetic maps for the lines, based on almost 30,000 molecular markers, should allow the genetic areas and ‘candidate genes’ in them to be pinpointed and so help breeders select for GPD in their breeding programmes.
GPD data for two field trials has been collected and several genetic areas have been identified for protein content, grain yield and GPD, adds Mr Richard.
The underlying molecular mechanism behind GPD is also being explored by recording the rate at which the lines senesce.
“This is important as a substantial proportion of the nitrogen in the mature grain is transferred from the leaves during this phase,” Prof Shewry says.
The field experiments are being carried out at the University of Reading, with senescence measured using Phenobike – a modified bicycle with a sensor to measure the crop’s greenness.
The second part of the project is using pairs of lines which differ in single genetic loci for breadmaking quality.
Some novel quantitative trait loci (QTLs) for breadmaking quality were identified in the Malacca cross Hereward population in the HGCA project.
Effects “Simon Griffiths and colleagues at the John Innes Centre have since developed sets of lines which differ only in single loci, by backcrossing to either Hereward or Malacca,” says Prof Shewry.
“These sets of lines allow us to determine the effects of the individual loci in near-identical genetic backgrounds.”
Six sets are being compared in the project, by growing them and analysing their flour for protein composition, metabolite profiles, dough elasticity and extensibility and breadmaking performance.
“The individual loci are also being combined in various combinations which will allow us to determine additive effects.”
The loci which have significant effects on breadmaking quality will be delivered to breeders together with molecular markers to allow their selection in breeding programmes.
“This work should contribute to the development of wheat lines which perform better under varying environmental conditions, by conferring higher intrinsic quality.
“The biochemical basis for the differences in quality controlled by the loci is also being explored, by comparing the composition and properties of the gluten proteins which are the main determinants of breadmaking quality.”
Extreme weather The work has been challenging due to extreme weather and working under Covid-19-safe conditions, he adds.
“We’ll only be able to draw firm conclusions when the field trials are complete, and all the material has been analysed.”
Project is pushing the boundaries
Global population growth and greenhouse gas emissions mean there is a need for more efficient, higher yielding crops but yield and wheat protein quantity are on a collision course, says Mervin Poole, who is responsible for technical and business development at flour miller Heygates.
The firm has 10 mills on four sites producing more than 10,000 tonnes of flour a week.
Mr Poole says: “The work in this project is pushing the boundaries of more than 10,000 years of wheat breeding.”
Wheat grains are simply stores of carbon from the atmosphere as starch and nitrogen from the soil as protein, he adds.
Nitrogen balance “However, the total carbon to nitrogen balance in plants is difficult to change.
“Wheat differs from other cereals in how the proteins contribute to nutritional quality and the strength and flexibility of bubbles in baked goods.
“Grain protein deviation [GDP] is seen as a route to maintaining wheat qualities while achieving higher yields.
“Consistent improvements in GDP should support farm efficiency, reduce greenhouse gas emissions and improve the UK crop’s performance in delivering the required strength, flexibility, volume and nutritional properties of bakery products.
“Most importantly, those improvements should begin to support the consistent availability of the UK crop of the correct quality for food applications and can help reduce our reliance on imports.”