Pathogens which threaten food security: Puccinia striiformis, the wheat stripe rust pathogen

Stripe rust, caused by Puccinia striiformis, is an important disease of wheat worldwide. The disease is old, but often appears as a re-emerging problem and also expands to new areas. Large-scale stripe rust epidemics occur when new races overcoming specific resistance genes develop in the pathogen population and/or when extreme disease-favourable weather conditions occur. Research progress has been made in the understanding of the biology, genomics, and evolution of the pathogen; host-pathogen interaction; and epidemiology and management of the disease. Despite its importance, the complete life cycle of this important pathogen was not known until very recently. The pathogen is now known to have a heteroecious macrocyclic lifecycle, but whether sexual reproduction on alternate hosts plays an important role in generating diverse races and increasing epidemics on crops is largely unknown. The pathogen has a large number of host species in the grass family, but the role of grass hosts in crop epidemics is not clear in many regions of the world. The disease can be controlled by growing resistant cultivars, appropriate use of fungicide, and suitable cultural practices. However, greater effort are needed to develop more cultivars with durable, high level resistance, develop accurate forecast models, and monitor the disease and pathogen virulence for more effective, profitable, and sustainable control of stripe rust.