Ug99: a wheat fungus that is threatening the world's food supply

Virtually all wheat breeding during the past 100 years has employed single-gene (i.e., vertical) resistances which usually provide a complete protection, but which are liable to break down to new strains of wheat parasites. One of the worst diseases of wheat is caused by a fungus called ‘stem rust’ (Puccinia graminis) and much of the world’s wheat is protected against it by a resistance gene called Sr24.

In 1999, a new 'strain' (i.e., vertical pathotype) of the stem rust fungus was identified in Uganda and it is now known as Ug99. This strain is particularly dangerous because it can match Sr24 and, as a consequence, much of the world’s wheat is in grave danger. During the past few years, this rust spread to Kenya, Ethiopia, and the Yemen. It has now been recorded in Iran, and it is thought to have reached Pakistan. This is bad news indeed because it is only a matter of time before it reaches the Punjab and the ‘bread basket’ of Asia.

There is an urgent need for horizontal resistance breeding against wheat parasites but none of the professional wheat breeders seem prepared to tackle this. This reluctance to test anything new, and to stick with old concepts and techniques, is known as ‘scientific fundamentalism’, and it is much more common than most people realise. One of the more important objectives of the Open Plant Breeding Foundation is to promote horizontal resistance and to demonstrate just how easy horizontal resistance is to work with, and just how effective it can be.

Wheat is not the easiest crop to breed and it is not normally recommended for breeding clubs made up of amateurs. But it is a suitable project for university breeding clubs which are backed up by the university resources and expertise.

We beg agricultural colleges and universities in the countries where Ug99 is already present to establish wheat breeding clubs working with horizontal resistance to all the locally important wheat parasites. This may well prove to be the only means of overcoming the scientific fundamentalism within wheat breeding.

Wheat Breeding

Breeding wheat for horizontal resistance is becoming an urgent necessity for the world's food supply. Almost all wheat breeding during the last century has worked with single-gene vertical resistances. These can provide protection for some time, but they almost inevitably break down to new strains of diseases and parasites.

One of the worst diseases of wheat is stem rust, caused by the Puccinia graminis fungus. Most of the world’s wheat is protected against this fungus by a resistance gene called Sr24, and this gene has allowed wheat to be grown in relative safety from stem rust.  But in 1999, a new strain of Puccinia graminis was discovered in Uganda which breaks down the Sr24 resistance. And this new strain of fungus is already spreading.