Breaking the yield barrier

9 Apr 2015

Soon the agricultural magazines will be featuring farmers who are striving for higher wheat yields and even trying to break the UK or world record. This leads to a healthy debate and it is interesting to read the various approaches that they are adopting. For some it is better plant nutrition and for others it is improved soil management etc. However, I remain sceptical that these welcome initiatives will lead to a significant break in the plateau of wheat yields that we have been on for the last twenty years or so.

By the mid-1990s we had nearly all the technology that we have today. Admittedly, since that time, we have seen the introduction of the strobilurin and SDHI fungicides and the steady increase in yield potential of new varieties. However, these have not produced the increase in average yields that might have been expected. There has been much debate about why this has not occurred.

There is much talk about trying to grab back the world yield record from New Zealand. I do not think that is possible because NZ has more sunlight (solar radiation), despite similar temperatures, during their growing season (see diagram). However, their average yields are similar to ours because natural rainfall typically limits their yields more than in the UK. Southland at the bottom of the South Island in NZ has more rainfall than the other arable areas and that is where the world record yield was grown. Further north, in the Canterbury Plain, even higher yields have been achieved with irrigation towards the end of their season.  

The rapid increase in UK wheat yields in the last quarter of the 20th century was due to the exploitation of current technologies by the industry. In particular, improved pesticides increased field yields but they are now subject to growing levels of resistance and legislation. All in all, this provides an unstable background to the attempts to increase yields further.

It is clear to me that we need a new technology or at least a significant shift in current technologies in order to break out of the yield plateau. I have been looking around and my current favourite is close to home.

Today’s wheat varieties all stem back to a freakish cross that occurred around 10,000 years ago between emmer wheat (a relative of durum wheat) and a wild goat grass. This produced the hexaploid wheat that we know so well.  It has a huge genome when compared to other crops and also when compared to many animals. In fact the wheat genome is five times larger than that of a human being. This ensured that breeders had plenty to work on and increasing yield potential is still possible, even after many years of scientifically based crossing and selection.

It is critically important to remember that the genetic base for all wheat breeding goes back to that one freak cross. It is both logical and perhaps essential to repeat that freak cross with a range of parents in order to bring more genetic diversity into wheat. This is what is being researched at NIAB and the early evidence is that such an approach could lead to a very significant breakthrough in yield potential.

This was part of a display by NIAB at the Cambridge Science Festival (see script of the display board). Let us hope that this promise will be delivered into practice but it will not happen overnight. The display also included how light drives plant cells and also the identification of genetic markers for the genes that influence the flowering date of wheat. NIAB has a good record on communicating science to the public at the annual Cambridge Science Festival and the researchers who volunteer for the festival hope that they will inspire the next generation of plant breeders.