Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

(Ahmed et al., 1991). Earlier, epiphytotics were recorded in the same region in
1983. In 1993 and 1995, yellow rust epidemics occurred in most of the wheatgrowing
areas of Iran and caused over 30% crop loss. Estimated grain losses
were of the order of 1.5 million tonne in 1993 and 1 million tonne in 1995
(Torabi et al., 1995). In Turkey, wheat cv. Gerek 79, grown on more than
one million hectare, suffered losses of 26.5% due to the yellow rust epidemic in
1991 (Braun and Saari, 1992), and over 50% in 1998. In the Cukurova area of
Turkey, a loss of over 500 000 tonne was recorded in Turkey, due to epidemics
of yellow rust on cv. Seri 82 (Dusunceli et al., 1996). In Syria, several epidemics
have occurred over the last three decades, the most serious one being in 1988,
which devastated wheat areas planted to the susceptible cv. Mexipak. In
experimental trials, Mexipak showed a loss of 29% in grain yield at a severe
infection level (75S). In the Jezireh area alone, Syria experienced an estimated
loss of over 100 000 tonne of wheat grain (Mamluk et al., 1989; Mamluk and El-
Naimi, 1992). Epidemics caused losses of 30% in national grain production in
1994, when cvs Seri 82 and Mexipak were widely grown. In Ethiopia, yellow
rust epiphytotics were recorded in 1977, 1980–1983, 1986, 1988 and 1990. Yield
losses in 1988 were severe in bread wheat, and were as high as 58% on cv.
Dashen (Badebo and Bayu, 1992). Ethiopia and Yemen form an ecological unit
with respect to yellow rust epidemiology and may have an important impact
on inoculum development and the evolution of virulence in the Central and
West Asia (CWA) region. In Egypt, major epiphytotics were recorded at least
once in each decade since the 1960s, with the most recent reported in the Delta
region in 1995. The average grain yield loss ranged from 14 to 26% in the Delta
region, while the national loss was about 10% (El-Daoudi et al., 1996). Yellow
rust epidemics and significant yield losses in 1996 were observed in
Azerbaijan. In 1997, the wheat crop in Tajikistan suffered over 60% loss due to
yellow rust. During a survey in May 1998, yellow rust was considered a major
wheat disease in the country. In Uzbekistan over 60% of the wheat area is
spayed annually to control yellow and leaf rusts.
Past studies in Central and Western Asia and North Africa (CWANA) have
been sporadic and localized. There is an urgent need to gain a more
comprehensive understanding of pathotype variation. Such studies should be
complemented with epidemiological investigations of pathogen movement in
order to determine the origin of new pathotypes and thus provide an early
warning system for farmers growing potentially susceptible cultivars.
Furthermore, knowledge of effective Yr resistance genes in the region will
enable breeders to incorporate these genes in elite wheat germplasm, thus
helping the development of cultivars with durable disease resistance.
Current research in CWANA focuses primarily on field evaluation of
germplasm and varieties. In Pakistan, systematic but limited studies have
provided useful information on pathogen virulence. In Egypt and Iran,
greenhouse studies on pathogen virulence have been initiated. Similar studies
have been initiated in other countries of the CWANA region, using trap
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