Occurrence And Virulence Of Wheat Yellow Rust In Central And Western Asia

Amor Yahyaoui and Munzer El-Naimi
ICARDA, P.O. Box 5466, Aleppo, Syria.
E-mail: A.Yahyaoui@cgiar.org

Abstract

Wheat yellow rust, caused by Puccinia striiformis west f.s.p. tritici is a major disease problem that affects wheat production in many countries in Central and Western Asia (CWA). Occurrence of yellow rust became more frequent in the last two decades and the disease caused great yield losses that reached up to 30% in Lebanon in 1994. High yield losses were also recorded in Turkey in 1991, Iran in 1993 and 1995, Yemen in 1988 and Azerbaijan in 1998. Wheat cultivars grown in CWA were resistant to the pathogen populations. Occurrence of new virulence types of P. striiformis f.s.p. tritici, and break down of resistance genes in many common cultivars were observed. Effective resistance genes were characterized and new sources of resistance were identified. Multi-location testing of yellow rust trap nurseries and germplasm pools has revealed the variability in yellow rust pathotypes and their distribution in CWA. The effectiveness/ineffectiveness of the resistance genes was determined at each testing site in CWA. Yellow rust physiologic races are annually analyzed in Syria. Studies of yellow rust population dynamics using DNA finger printing are being conducted in CWA. Knowledge of yellow rust population dynamics and its virulence types will enable researchers to better manage the resistance sources and the deployment of resistance genes.