Yellow rust

The fungus Puccinia striiformis f. sp. sp. tritici is responsible for the wheat yellow rust, whose name is due to the yellow color and the distribution of the fungus’ uredinia in the leaves, arranged in long linear striations parallel to the direction of the leaf veins. The symptoms of the disease can manifest at any stage of crop development, but the yellowish color of the leaves is the most characteristic.

There are few studies on the occurrence, epidemiology, damage and control of yellow rust, but the few data released reveal that the disease causes losses in wheat crops that can vary between 5 and 50%.

With a simple propagation capacity, wheat yellow rust spores spread through the wind, easily crossing borders and reaching other countries. New aggressive strains of the yellow rust fungus have emerged since the turn of the century, reaching some countries, including Portugal in 2013 and 2014. According to data released by INIAV in 2015, the new yellow rust strain (called Warrior) that affected the wheat crops in Portugal in these years “combines a broad spectrum of virulence that allows it to attack both common wheat and durum wheat, and triticale”, a hybrid cereal resulting from the crossing of wheat with rye.

The introduction of resistant genes in plants, the reduction of primary sources of dissemination and the spraying with specific fungicides are the disease control measures currently available on the market, but they have proved to be ineffective.

It should be noted that wheat is the second largest cereal crop in the world (after maize) and a staple food, used to make flour and bread, used as animal feed and as an ingredient in beer production.