Recent epidemics of yellow rust on wheat and barley and how they should be controlled

摘要

In the last twenty years yellow rust on wheat, caused by Puccinia striiformis f.sp tritici, has spread to Australia, (1979), New Zealand (1980) and South Africa (1996) and caused some epidemics. Recently there have also been severe epidemics in several middle eastern countries, including Iran and Pakistan. These have been due to cultivation of susceptible wheats, often associated with spread of new races of the pathogen. Imprtant sources of durable resistance to yellow rust include wheats with Yr18,common in CEVIMYT wheats, and European wheats such as Hybride de Bersee, with resistance carried by several chromosomes including the 5BS-7BS translocated chromosome. Alone, neither Yr18, nor 5BS-7BS and the resistance-carrying 5BS-7BS might provide durable resistance to yellow rust in most environments, including some where their performance alone is inadequate. In 1975, P. striiformis f.sp. hordei, the barley-attacking strain, reached South America. Since then it has spread to the north of North America, during which it caused several epidemics on barleys that never bred for resistance to it. In Europe, most barley cultivars have durable resistance, and there are few races of the pathogen. Despite reports of numerous races being found in the pacificnorthwest USA, the solution to the problem could be systematic exploitation of resistance from the durably resistant sources from Europe.