From 1984-1999, 239 races of P. triticina were identified among 13,309 single-pustule isolates from eight wheat growing regions of the United States. Most races identified in the U.S. were virulent to Lr1, 3, and 10. Races with virulence to Lr2a and 2c increased in the central U.S. since 1996 in response to increased use of cultivars that have Lr2a as part of their leaf rust resistance. Lr24 and 26 were highly effective as late as 1985, but now provide little protection. Nearly half of the leaf rust isolates collected in the central United States in recent years are virulent to Lr24 and 26. In the past 10 years virulence to Lr9 and 16 has increased where cultivars with these genes have been planted in significant acreage. In the past, virulence to Lr16 had declined when cultivars with Lr16 lost favor and were removed from production, which allowed Lr16 to be recycled in some breeding programs. Virulence to Lr11 was common throughout the United States and was identified in 50% or more of the rust collections from 1990-1999. This reflects a selective advantage of this virulence due to an increase in the acreage of cultivars with Lr11. Since 1996 cultivars with Lr17 have gained popularity, which was followed by a corresponding increase in virulence from 1996 to the present. The history of breeding for leaf rust resistance, especially in winter wheats, has shown that it is a never ending battle. With the release of each new resistance gene, a new virulence can be expected to emerge not far in the future.
|Original language||English (US)|
|Number of pages||5|
|Journal||Acta Phytopathologica et Entomologica Hungarica|
|State||Published - Dec 1 2000|
- Puccinia triticina
- Wheat leaf rust